!2891 CacheOp phase 1

Merge pull request !2891 from Jamie/CacheOp_dev

mindspore/ccsrc/dataset/CMakeLists.txt

@@ -47,6 +47,8 @@ include_directories(${CMAKE_SOURCE_DIR}/mindspore/ccsrc/dataset/include)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wl,-rpath,$ORIGIN:$ORIGIN/lib")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility=default")
 
+ms_build_flatbuffers("engine/cache/de_tensor.fbs" ${CMAKE_CURRENT_SOURCE_DIR} generated_engine_files ${CMAKE_BINARY_DIR})
+
 ################## Include sub-modules ###############################
 add_subdirectory(util)
 add_subdirectory(core)
@@ -55,7 +57,7 @@ add_subdirectory(engine)
 add_subdirectory(api)
 add_subdirectory(text)
 ######################################################################
-add_dependencies(core utils)
+add_dependencies(utils core)
 add_dependencies(kernels-image core)
 add_dependencies(kernels-data core)
 add_dependencies(kernels core)
@@ -89,6 +91,8 @@ set(submodules
     $<TARGET_OBJECTS:engine-perf>
     $<TARGET_OBJECTS:engine-datasetops>
     $<TARGET_OBJECTS:engine-opt>
+    $<TARGET_OBJECTS:engine-cache-client>
+    $<TARGET_OBJECTS:engine-cache-server>
     $<TARGET_OBJECTS:engine>
     $<TARGET_OBJECTS:text>
     $<TARGET_OBJECTS:text-kernels>
@@ -106,6 +110,8 @@ else ()
     add_library(_c_dataengine SHARED ${submodules})
 endif ()
 
+add_dependencies(_c_dataengine generated_engine_files)
+
 set_target_properties(_c_dataengine PROPERTIES
     PREFIX "${PYTHON_MODULE_PREFIX}"
     SUFFIX "${PYTHON_MODULE_EXTENSION}"

mindspore/ccsrc/dataset/api/de_pipeline.cc

@@ -21,8 +21,10 @@
 
 #include "common/utils.h"
 #include "dataset/core/tensor.h"
+#include "dataset/engine/cache/cache_client.h"
 #include "dataset/engine/dataset_iterator.h"
 #include "dataset/engine/datasetops/bucket_batch_by_length_op.h"
+#include "dataset/engine/datasetops/cache_op.h"
 #include "dataset/engine/datasetops/filter_op.h"
 #include "dataset/engine/datasetops/source/celeba_op.h"
 #include "dataset/engine/datasetops/source/cifar_op.h"
@@ -34,6 +36,7 @@
 #include "dataset/engine/datasetops/source/random_data_op.h"
 #include "dataset/engine/datasetops/source/text_file_op.h"
 #include "dataset/engine/datasetops/source/voc_op.h"
+#include "dataset/engine/datasetops/source/sampler/sequential_sampler.h"
 #include "dataset/kernels/py_func_op.h"
 #include "dataset/util/random.h"
 #include "dataset/util/status.h"
@@ -441,6 +444,8 @@ Status DEPipeline::ParseMapOp(const py::dict &args, std::shared_ptr<DatasetOp> *
   MapOp::Builder map_builder;
   std::vector<std::shared_ptr<TensorOp>> tensor_op_list;
   std::vector<std::string> project_columns;
+  std::shared_ptr<CacheClient> cache_client = nullptr;
+  int num_workers = 0;
 
   if (args["operations"].is_none()) RETURN_STATUS_UNEXPECTED("Error: 'operations' is not set. \n");
 
@@ -456,7 +461,8 @@ Status DEPipeline::ParseMapOp(const py::dict &args, std::shared_ptr<DatasetOp> *
       } else if (key == "columns_order") {
         project_columns = ToStringVector(value);
       } else if (key == "num_parallel_workers") {
-        (void)map_builder.SetNumWorkers(ToInt(value));
+        num_workers = ToInt(value);
+        (void)map_builder.SetNumWorkers(num_workers);
       } else if (key == "prefetch_size") {
         (void)map_builder.SetOpConnectorSize(ToInt(value));
       } else if (key == "operations") {
@@ -477,6 +483,8 @@ Status DEPipeline::ParseMapOp(const py::dict &args, std::shared_ptr<DatasetOp> *
         }
         if (tensor_op_list.empty()) RETURN_STATUS_UNEXPECTED("Error: tensor_op is invalid or not set.");
         (void)map_builder.SetTensorFuncs(std::move(tensor_op_list));
+      } else if (key == "cache") {
+        cache_client = value.cast<std::shared_ptr<CacheClient>>();
       } else {
         RETURN_STATUS_UNEXPECTED("Error: Unhandled key: " + key);
       }
@@ -499,6 +507,15 @@ Status DEPipeline::ParseMapOp(const py::dict &args, std::shared_ptr<DatasetOp> *
     *bottom = map_op;
   }
 
+  // Additionally, add a cache if required.  This will go over top of the project op if one
+  // was created, otherwise it goes over top of the map op
+  if (cache_client) {
+    std::shared_ptr<DatasetOp> cache_op = nullptr;
+    RETURN_IF_NOT_OK(AddCacheOp(cache_client, num_workers, *top, &cache_op));
+    *top = cache_op;
+    *bottom = map_op;
+  }
+
   return Status::OK();
 }
 
@@ -809,6 +826,9 @@ Status DEPipeline::ParseTFReaderOp(const py::dict &args, std::shared_ptr<Dataset
                                    std::shared_ptr<DatasetOp> *bottom) {
   // Required arguments
   std::vector<std::string> files_list;
+  std::shared_ptr<CacheClient> cache_client = nullptr;
+  std::shared_ptr<Sampler> sampler = nullptr;
+  int num_workers = 0;
   std::shared_ptr<TFReaderOp::Builder> builder = std::make_shared<TFReaderOp::Builder>();
   if (!args["dataset_files"].is_none()) {
     files_list = ToStringVector(args["dataset_files"]);
@@ -828,7 +848,8 @@ Status DEPipeline::ParseTFReaderOp(const py::dict &args, std::shared_ptr<Dataset
     py::handle value = arg.second;
     if (!value.is_none()) {
       if (key == "num_parallel_workers") {
-        (void)builder->SetNumWorkers(ToInt(value));
+        num_workers = ToInt(value);
+        (void)builder->SetNumWorkers(num_workers);
       } else if (key == "columns_list") {
         columns_to_load = ToStringVector(value);
         (void)builder->SetColumnsToLoad(columns_to_load);
@@ -848,6 +869,11 @@ Status DEPipeline::ParseTFReaderOp(const py::dict &args, std::shared_ptr<Dataset
         (void)builder->SetDeviceId(ToInt(value));
       } else if (key == "shard_equal_rows") {
         (void)builder->SetShardEqualRows(ToBool(value));
+      } else if (key == "cache") {
+        cache_client = value.cast<std::shared_ptr<CacheClient>>();
+      } else if (key == "sampler") {
+        auto create = py::reinterpret_borrow<py::object>(value).attr("create");
+        sampler = create().cast<std::shared_ptr<Sampler>>();
       }
     }
   }
@@ -860,12 +886,27 @@ Status DEPipeline::ParseTFReaderOp(const py::dict &args, std::shared_ptr<Dataset
     }
     (void)builder->SetDataSchema(std::move(schema));
   }
+
+  // If the user gave a sampler, but they did not ask for a cache, then by itself this is not allowed
+  // because TFReaderOp is a non-mappable dataset that does not support sampling.
+  // However, if a cache operator is injected at some other place higher in the tree, that cache can
+  // inherit this sampler from the leaf, providing sampling support from the caching layer.
+  // That is why we save the sampler here in a leaf node that does not use sampling.
+  if (sampler) {
+    (void)builder->SetSampler(std::move(sampler));
+  } else if (cache_client) {
+    int64_t num_samples = 0;
+    int64_t start_index = 0;
+    sampler = std::make_shared<SequentialSampler>(num_samples, start_index);
+    (void)builder->SetSampler(std::move(sampler));
+  }
+
   std::shared_ptr<TFReaderOp> tf_op;
   RETURN_IF_NOT_OK(builder->Build(&tf_op));
   RETURN_IF_NOT_OK(tree_->AssociateNode(tf_op));
   *top = tf_op;
 
-  if (shuffle_required) {
+  if (!cache_client && shuffle_required) {
     const boolean estimate = true;
     const int64_t workers = 8;
     std::shared_ptr<DatasetOp> shuffle_op = nullptr;
@@ -882,6 +923,15 @@ Status DEPipeline::ParseTFReaderOp(const py::dict &args, std::shared_ptr<Dataset
     *bottom = tf_op;
   }
 
+  // Add a cache op over this op if required and update the output subtree (top/bottom)
+  if (cache_client) {
+    // Note, it is not allowed to have both shuffle and cache
+    std::shared_ptr<DatasetOp> cache_op = nullptr;
+    RETURN_IF_NOT_OK(AddCacheOp(cache_client, num_workers, tf_op, &cache_op));
+    *top = cache_op;
+    *bottom = tf_op;
+  }
+
   return Status::OK();
 }
 
@@ -906,6 +956,8 @@ Status DEPipeline::ParseImageFolderOp(const py::dict &args, std::shared_ptr<Data
     std::string err_msg = "Error: No dataset path specified";
     RETURN_STATUS_UNEXPECTED(err_msg);
   }
+  int num_workers = 0;
+  std::shared_ptr<CacheClient> cache_client = nullptr;
   std::shared_ptr<ImageFolderOp::Builder> builder = std::make_shared<ImageFolderOp::Builder>();
   (void)builder->SetImageFolderDir(ToString(args["dataset_dir"]));
 
@@ -915,7 +967,8 @@ Status DEPipeline::ParseImageFolderOp(const py::dict &args, std::shared_ptr<Data
     py::handle value = arg.second;
     if (!value.is_none()) {
       if (key == "num_parallel_workers") {
-        (void)builder->SetNumWorkers(ToInt(value));
+        num_workers = ToInt(value);
+        (void)builder->SetNumWorkers(num_workers);
       } else if (key == "sampler") {
         auto create = py::reinterpret_borrow<py::object>(value).attr("create");
         std::shared_ptr<Sampler> sampler = create().cast<std::shared_ptr<Sampler>>();
@@ -926,12 +979,27 @@ Status DEPipeline::ParseImageFolderOp(const py::dict &args, std::shared_ptr<Data
         (void)builder->SetClassIndex(ToStringMap(value));
       } else if (key == "decode") {
         (void)builder->SetDecode(ToBool(value));
+      } else if (key == "cache") {
+        cache_client = value.cast<std::shared_ptr<CacheClient>>();
       }
     }
   }
-  std::shared_ptr<ImageFolderOp> op;
-  RETURN_IF_NOT_OK(builder->Build(&op));
-  *top = op;
+  std::shared_ptr<ImageFolderOp> if_op;
+  RETURN_IF_NOT_OK(builder->Build(&if_op));
+  RETURN_IF_NOT_OK(tree_->AssociateNode(if_op));
+  *top = if_op;
+
+  // Additionally, add a cache if required.
+  // Note that this cache op is only acting as a place holder for the caching position
+  // within the tree.  Later, a pre-pass will execute a tree transform to set up the actual
+  // caching logic in the tree.
+  if (cache_client) {
+    std::shared_ptr<DatasetOp> cache_op = nullptr;
+    RETURN_IF_NOT_OK(AddCacheOp(cache_client, num_workers, if_op, &cache_op));
+    *top = cache_op;
+    *bottom = if_op;
+  }
+
   return Status::OK();
 }
 
@@ -1130,9 +1198,12 @@ Status DEPipeline::ParseRandomDataOp(const py::dict &args, std::shared_ptr<Datas
                                      std::shared_ptr<DatasetOp> *bottom) {
   // Required arguments
   RandomDataOp::Builder builder;
+  std::shared_ptr<CacheClient> cache_client = nullptr;
+  std::shared_ptr<Sampler> sampler = nullptr;
+  int num_workers = 0;
 
-  if (args["num_samples"].is_none()) {
-    std::string err_msg = "Error: num_samples is a required argument";
+  if (args["total_rows"].is_none()) {
+    std::string err_msg = "Error: total_rows is a required argument";
     RETURN_STATUS_UNEXPECTED(err_msg);
   }
   std::vector<std::string> columns_to_load;
@@ -1141,16 +1212,23 @@ Status DEPipeline::ParseRandomDataOp(const py::dict &args, std::shared_ptr<Datas
   for (auto arg : args) {
     std::string key = py::str(arg.first);
     py::handle value = arg.second;
-    if (key == "num_parallel_workers") {
-      (void)builder.SetNumWorkers(ToInt(value));
-    } else if (key == "schema_file_path" || key == "schema_json_string") {
-      schema_exists = true;
-    } else if (key == "columns_list") {
-      columns_to_load = ToStringVector(value);
-    } else if (key == "num_samples") {
-      // This is not sampling here. The random data op needs to know how much data to
-      // generate. It does not currently support sampling.
-      (void)builder.SetTotalRows(ToInt(value));
+    if (!value.is_none()) {
+      if (key == "num_parallel_workers") {
+        num_workers = ToInt(value);
+        (void)builder.SetNumWorkers(num_workers);
+      } else if (key == "schema_file_path" || key == "schema_json_string") {
+        schema_exists = true;
+      } else if (key == "columns_list") {
+        columns_to_load = ToStringVector(value);
+      } else if (key == "total_rows") {
+        // This is not sampling here. The random data op needs to know how much data to generate.
+        (void)builder.SetTotalRows(ToInt(value));
+      } else if (key == "cache") {
+        cache_client = value.cast<std::shared_ptr<CacheClient>>();
+      } else if (key == "sampler") {
+        auto create = py::reinterpret_borrow<py::object>(value).attr("create");
+        sampler = create().cast<std::shared_ptr<Sampler>>();
+      }
     }
   }
   if (schema_exists) {
@@ -1162,9 +1240,34 @@ Status DEPipeline::ParseRandomDataOp(const py::dict &args, std::shared_ptr<Datas
     }
     (void)builder.SetDataSchema(std::move(schema));
   }
-  std::shared_ptr<RandomDataOp> op;
-  RETURN_IF_NOT_OK(builder.Build(&op));
-  *top = op;
+
+  // If the user gave a sampler, but they did not ask for a cache, then by itself this is not allowed
+  // because RandomDataOp is a non-mappable dataset that does not support sampling.
+  // However, if a cache operator is injected at some other place higher in the tree, that cache can
+  // inherit this sampler from the leaf, providing sampling support from the caching layer.
+  // That is why we save the sampler here in a leaf node that does not use sampling.
+  if (sampler) {
+    (void)builder.SetSampler(std::move(sampler));
+  } else if (cache_client) {
+    int64_t num_samples = 0;
+    int64_t start_index = 0;
+    sampler = std::make_shared<SequentialSampler>(num_samples, start_index);
+    (void)builder.SetSampler(std::move(sampler));
+  }
+
+  std::shared_ptr<RandomDataOp> random_op = nullptr;
+  RETURN_IF_NOT_OK(builder.Build(&random_op));
+  RETURN_IF_NOT_OK(tree_->AssociateNode(random_op));
+  *top = random_op;
+
+  // Add a cache op over this op if required and update the output subtree (top/bottom)
+  if (cache_client) {
+    std::shared_ptr<DatasetOp> cache_op = nullptr;
+    RETURN_IF_NOT_OK(AddCacheOp(cache_client, num_workers, random_op, &cache_op));
+    *top = cache_op;
+    *bottom = random_op;
+  }
+
   return Status::OK();
 }
 
@@ -1425,6 +1528,31 @@ Status DEPipeline::ParseClueOp(const py::dict &args, std::shared_ptr<DatasetOp>
   return Status::OK();
 }
 
+// Helper function to inject the cache operator over top of the current operation being built.
+Status DEPipeline::AddCacheOp(std::shared_ptr<CacheClient> cache_client, int num_workers,
+                              std::shared_ptr<DatasetOp> input_op, std::shared_ptr<DatasetOp> *cache_op) {
+  std::shared_ptr<CacheOp> new_cache_op = nullptr;
+  CacheOp::Builder cache_builder;
+  // use the same number of workers as the leaf. We need some optimization here, the user does not
+  // give the cache op number of workers directly.
+  if (num_workers != 0) {
+    (void)cache_builder.SetNumWorkers(num_workers);
+  }
+  (void)cache_builder.SetClient(cache_client);
+  RETURN_IF_NOT_OK(cache_builder.Build(&new_cache_op));
+  RETURN_IF_NOT_OK(tree_->AssociateNode(new_cache_op));
+  RETURN_IF_NOT_OK(new_cache_op->AddChild(input_op));
+  // We have now created:
+  //
+  // CacheOp
+  //   |
+  // input_op
+  //
+  *cache_op = new_cache_op;
+
+  return Status::OK();
+}
+
 // Helper function to inject a shuffle operator over top of the current operation being built.
 Status DEPipeline::AddShuffleOp(int64_t shuffle_size, std::shared_ptr<DatasetOp> input_op,
                                 std::shared_ptr<DatasetOp> *shuffle_op) {

mindspore/ccsrc/dataset/api/de_pipeline.h

@@ -35,6 +35,8 @@ namespace mindspore {
 namespace dataset {
 using DsOpPtr = std::shared_ptr<DatasetOp>;
 
+class CacheClient;
+
 // enum for the dataset operator names
 enum OpName {
   kShuffle,
@@ -181,6 +183,16 @@ class DEPipeline {
 
   static Status ParsePadInfo(py::handle value, PadInfo *pad_info);
 
+  /// \brief Helper function to inject a cache operator over top of the current operation being built.
+  /// \param[in] cache_client The client to use for caching
+  /// \param[in] num_workers The number of workers to use in the cache op
+  /// \param[in] input_op The operator to build the cache on top of
+  /// \param[out] cache_op The top node of the created subtree (subtree contains two nodes). In this case it will be
+  ///     the cache operator
+  /// \return Status return code
+  Status AddCacheOp(std::shared_ptr<CacheClient> cache_client, int num_workers, std::shared_ptr<DatasetOp> input_op,
+                    std::shared_ptr<DatasetOp> *cache_op);
+
   /// \brief Helper function to inject a shuffle operator over top of the current operation being built.
   /// \param[in] shuffle_size The size to use in the shuffle buffer
   /// \param[in] input_op The operator to build shuffle on top of

mindspore/ccsrc/dataset/api/python_bindings.cc

@@ -35,6 +35,7 @@
 #include "dataset/engine/datasetops/source/text_file_op.h"
 #include "dataset/engine/datasetops/source/tf_reader_op.h"
 #include "dataset/engine/datasetops/source/voc_op.h"
+#include "dataset/engine/cache/cache_client.h"
 #include "dataset/engine/gnn/graph.h"
 #include "dataset/engine/jagged_connector.h"
 #include "dataset/kernels/data/concatenate_op.h"
@@ -768,6 +769,11 @@ void bindInfoObjects(py::module *m) {
     .def("get_batch_num", &BatchOp::CBatchInfo::get_batch_num);
 }
 
+void bindCacheClient(py::module *m) {
+  (void)py::class_<CacheClient, std::shared_ptr<CacheClient>>(*m, "CacheClient")
+    .def(py::init<uint32_t, uint64_t, bool>());
+}
+
 void bindVocabObjects(py::module *m) {
   (void)py::class_<Vocab, std::shared_ptr<Vocab>>(*m, "Vocab")
     .def(py::init<>())
@@ -939,6 +945,7 @@ PYBIND11_MODULE(_c_dataengine, m) {
   bindSamplerOps(&m);
   bindDatasetOps(&m);
   bindInfoObjects(&m);
+  bindCacheClient(&m);
   bindVocabObjects(&m);
   bindGraphData(&m);
   bindDependIcuTokenizerOps(&m);

mindspore/ccsrc/dataset/engine/CMakeLists.txt

@@ -2,6 +2,7 @@ add_subdirectory(datasetops)
 add_subdirectory(opt)
 add_subdirectory(gnn)
 add_subdirectory(perf)
+add_subdirectory(cache)
 if (ENABLE_TDTQUE)
   add_subdirectory(tdt)
 endif ()
@@ -17,7 +18,9 @@ add_library(engine OBJECT
 target_include_directories(engine PRIVATE ${pybind11_INCLUDE_DIRS})
 
 if (ENABLE_TDTQUE)
-  add_dependencies(engine engine-datasetops engine-datasetops-source engine-tdt engine-opt engine-gnn engine-perf)
-else()
-  add_dependencies(engine engine-datasetops engine-datasetops-source engine-opt engine-gnn engine-perf)
+  add_dependencies(engine engine-datasetops engine-datasetops-source engine-tdt engine-opt engine-gnn engine-perf
+                   engine-cache-client engine-cache-server)
+else ()
+  add_dependencies(engine engine-datasetops engine-datasetops-source engine-opt engine-gnn engine-perf
+                   engine-cache-client engine-cache-server)
 endif ()

mindspore/ccsrc/dataset/engine/cache/CMakeLists.txt

@@ -0,0 +1,8 @@
+file(GLOB_RECURSE _CURRENT_SRC_FILES RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "*.cc")
+set_property(SOURCE ${_CURRENT_SRC_FILES} PROPERTY COMPILE_DEFINITIONS SUBMODULE_ID=mindspore::SubModuleId::SM_MD)
+add_library(engine-cache-client OBJECT
+    cache_client.cc
+    cache_request.cc)
+add_library(engine-cache-server OBJECT
+    cache_service.cc
+    cache_server.cc)

mindspore/ccsrc/dataset/engine/cache/cache_client.cc

@@ -0,0 +1,208 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <iomanip>
+#include "dataset/engine/cache/cache_client.h"
+#include "dataset/engine/cache/cache_request.h"
+#include "dataset/util/bit.h"
+
+namespace mindspore {
+namespace dataset {
+
+// Constructor
+CacheClient::CacheClient(uint32_t session_id, uint64_t cache_mem_sz, bool spill)
+    : server_connection_id_(0), session_id_(session_id), cache_crc_(0), cache_mem_sz_(cache_mem_sz), spill_(spill) {}
+
+// print method for display cache details
+void CacheClient::Print(std::ostream &out) const {
+  out << "  Session id: " << session_id_ << "\n  Cache crc: " << cache_crc_
+      << "\n  Server cache id: " << server_connection_id_ << "\n  Cache mem size: " << cache_mem_sz_
+      << "\n  Spilling: " << std::boolalpha << spill_;
+}
+
+Status CacheClient::WriteRow(const TensorRow &row, row_id_type *row_id_from_server) const {
+  CacheRowRequest rq(server_connection_id_, cookie());
+  RETURN_IF_NOT_OK(rq.SerializeCacheRowRequest(row));
+  RETURN_IF_NOT_OK(CacheServer::GetInstance().PushRequest(&rq));
+  RETURN_IF_NOT_OK(rq.Wait());
+  if (row_id_from_server != nullptr) {
+    *row_id_from_server = rq.GetRowIdAfterCache();
+  }
+  return Status::OK();
+}
+
+Status CacheClient::WriteBuffer(std::unique_ptr<DataBuffer> &&in) const {
+  std::unique_ptr<DataBuffer> db_ptr = std::move(in);
+  auto num_rows = db_ptr->NumRows();
+  std::vector<TensorRow> all_rows;
+  if (num_rows > 0) {
+    all_rows.reserve(num_rows);
+    // Break down the DataBuffer into TensorRow. We will send the requests async
+    // and then do a final wait.
+    MemGuard<CacheRowRequest> rq_arr;
+    RETURN_IF_NOT_OK(rq_arr.allocate(num_rows, server_connection_id_, cookie()));
+    CacheServer &cs = CacheServer::GetInstance();
+    for (auto i = 0; i < num_rows; ++i) {
+      TensorRow row;
+      auto rq = rq_arr[i];
+      RETURN_IF_NOT_OK(db_ptr->PopRow(&row));
+      RETURN_IF_NOT_OK(rq->SerializeCacheRowRequest(row));
+      RETURN_IF_NOT_OK(cs.PushRequest(rq));
+      // We can't let row go out of scope. Otherwise it will free all the tensor memory.
+      // So park it in the vector. When this function go out of scope, its memory
+      // will be freed.
+      all_rows.push_back(std::move(row));
+    }
+    // Now we wait for the requests to be done.
+    for (auto i = 0; i < num_rows; ++i) {
+      auto rq = rq_arr[i];
+      RETURN_IF_NOT_OK(rq->Wait());
+    }
+  }
+  return Status::OK();
+}
+
+Status CacheClient::GetRows(const std::vector<row_id_type> &row_id, TensorTable *out) const {
+  RETURN_UNEXPECTED_IF_NULL(out);
+  BatchFetchRequest rq(server_connection_id_, row_id);
+  RETURN_IF_NOT_OK(CacheServer::GetInstance().PushRequest(&rq));
+  RETURN_IF_NOT_OK(rq.Wait());
+  RETURN_IF_NOT_OK(rq.RestoreRows(out));
+  return Status::OK();
+}
+
+Status CacheClient::CreateCache(uint32_t tree_crc, bool generate_id) {
+  UniqueLock lck(&mux_);
+  // To create a cache, we identify ourself at the client by:
+  // - the shared session id
+  // - a crc for the tree nodes from the cache downward
+  // Pack these 2 into a single 64 bit request id
+  //
+  // Consider this example:
+  // tree1: tfreader --> map(decode) --> cache (session id = 1, crc = 123) --> batch
+  // tree2: cifar10 --> map(rotate) --> cache (session id = 1, crc = 456) --> batch
+  // These are different trees in a single session, but the user wants to share the cache.
+  // This is not allowed because the data of these caches are different.
+  //
+  // Consider this example:
+  // tree1: tfreader --> map(decode) --> cache (session id = 1, crc = 123) --> batch
+  // tree2: tfreader --> map(decode) --> cache (session id = 1, crc = 123) --> map(rotate) --> batch
+  // These are different trees in the same session, but the cached data is the same, so it is okay
+  // to allow the sharing of this cache between these pipelines.
+
+  // The CRC is computed by the tree prepare phase and passed to this function when creating the cache.
+  // If we already have a server_connection_id_, then it means this same cache client has already been used
+  // to create a cache and some other tree is trying to use the same cache.
+  // That is allowed, however the crc better match!
+  if (server_connection_id_) {
+    if (cache_crc_ != tree_crc) {
+      RETURN_STATUS_UNEXPECTED("Attempt to re-use a cache for a different tree!");
+    }
+    // Check the state of the server. For non-mappable case where there is a build phase and a fetch phase, we should
+    // skip the build phase.
+    lck.Unlock();  // GetStat will grab the mutex again. So unlock it to prevent deadlock.
+    CacheClient::ServiceStat stat{};
+    RETURN_IF_NOT_OK(GetStat(&stat));
+    if (stat.cache_service_state == static_cast<uint8_t>(CacheService::State::kFetchPhase)) {
+      return Status(StatusCode::kDuplicateKey, __LINE__, __FILE__, "Not an error and we should bypass the build phase");
+    }
+  } else {
+    cache_crc_ = tree_crc;  // It's really a new cache we're creating so save our crc in the client
+    // Combine the session and crc.  This will form our client cache identifier.
+    connection_id_type connection_identification = (static_cast<uint64_t>(session_id_) << 32) | cache_crc_;
+    // Now execute the cache create request using this identifier and other configs
+    BaseRequest::CreateCacheFlag createFlag = BaseRequest::CreateCacheFlag::kNone;
+    if (spill_) {
+      createFlag |= BaseRequest::CreateCacheFlag::kSpillToDisk;
+    }
+    if (generate_id) {
+      createFlag |= BaseRequest::CreateCacheFlag::kGenerateRowId;
+    }
+    CreationCacheRequest rq(connection_identification, cache_mem_sz_, createFlag);
+    RETURN_IF_NOT_OK(CacheServer::GetInstance().PushRequest(&rq));
+    Status rc = rq.Wait();
+    if (rc.IsOk() || rc.get_code() == StatusCode::kDuplicateKey) {
+      server_connection_id_ = rq.GetServerConnectionId();
+      if (rc.IsOk()) {
+        // The 1st guy creating the cache will get a cookie back.
+        // But this object may be shared among pipelines and we don't want
+        // overwrite it.
+        cookie_ = rq.cookie();
+      }
+    }
+    // We are not resetting the Duplicate key return code. We are passing it back to the CacheOp. This will tell the
+    // CacheOp to bypass the build phase.
+    return rc;
+  }
+  return Status::OK();
+}
+
+Status CacheClient::PurgeCache() {
+  UniqueLock lck(&mux_);
+  PurgeCacheRequest rq(server_connection_id_);
+  RETURN_IF_NOT_OK(CacheServer::GetInstance().PushRequest(&rq));
+  return rq.Wait();
+}
+
+Status CacheClient::DestroyCache() {
+  UniqueLock lck(&mux_);
+  DestroyCacheRequest rq(server_connection_id_);
+  RETURN_IF_NOT_OK(CacheServer::GetInstance().PushRequest(&rq));
+  return rq.Wait();
+}
+
+Status CacheClient::GetStat(ServiceStat *stat) {
+  SharedLock lck(&mux_);
+  RETURN_UNEXPECTED_IF_NULL(stat);
+  GetStatRequest rq(server_connection_id_);
+  RETURN_IF_NOT_OK(CacheServer::GetInstance().PushRequest(&rq));
+  RETURN_IF_NOT_OK(rq.Wait());
+  stat->num_disk_cached = rq.GetNumDiskCached();
+  stat->num_mem_cached = rq.GetNumMemCached();
+  stat->min_row_id = rq.GetMinRowId();
+  stat->max_row_id = rq.GetMaxRowId();
+  stat->cache_service_state = rq.GetState();
+  return Status::OK();
+}
+
+Status CacheClient::CacheSchema(const std::unordered_map<std::string, int32_t> &map) {
+  SharedLock lck(&mux_);
+  CacheSchemaRequest rq(server_connection_id_);
+  RETURN_IF_NOT_OK(rq.SerializeCacheSchemaRequest(map));
+  RETURN_IF_NOT_OK(CacheServer::GetInstance().PushRequest(&rq));
+  RETURN_IF_NOT_OK(rq.Wait());
+  return Status::OK();
+}
+
+Status CacheClient::FetchSchema(std::unordered_map<std::string, int32_t> *map) {
+  SharedLock lck(&mux_);
+  RETURN_UNEXPECTED_IF_NULL(map);
+  FetchSchemaRequest rq(server_connection_id_);
+  RETURN_IF_NOT_OK(CacheServer::GetInstance().PushRequest(&rq));
+  RETURN_IF_NOT_OK(rq.Wait());
+  *map = rq.GetColumnMap();
+  return Status::OK();
+}
+
+Status CacheClient::BuildPhaseDone() const {
+  SharedLock lck(&mux_);
+  BuildPhaseDoneRequest rq(server_connection_id_, cookie());
+  RETURN_IF_NOT_OK(CacheServer::GetInstance().PushRequest(&rq));
+  RETURN_IF_NOT_OK(rq.Wait());
+  return Status::OK();
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/cache/cache_client.h

@@ -0,0 +1,141 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef DATASET_ENGINE_CACHE_CLIENT_H_
+#define DATASET_ENGINE_CACHE_CLIENT_H_
+
+#include <iostream>
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+#include "./de_tensor_generated.h"
+#include "dataset/engine/data_buffer.h"
+#include "dataset/engine/cache/cache_server.h"
+#include "dataset/util/lock.h"
+
+namespace mindspore {
+namespace dataset {
+/// \brief A CacheClient is a bridge between a DatasetOp and a CacheServer. All communications are through
+/// a CacheClient. Typical tasks including like creating a cache service, cache a data buffer, restore a previously
+/// rows, etc.
+class CacheClient {
+ public:
+  /// \brief Constructor
+  /// \param session_id A user assigned session id for the current pipeline
+  /// \param cache_mem_sz Size of the memory set aside for the row caching. 0 for unlimited
+  /// \param spill Spill to disk if out of memory
+  CacheClient(uint32_t session_id, uint64_t cache_mem_sz, bool spill);
+
+  /// \brief Destructor
+  ~CacheClient() = default;
+
+  /// \brief Getter function for returning the current session id
+  /// \return session id
+  uint64_t session_id() const { return session_id_; }
+
+  /// \brief Send a TensorRow to the cache server
+  /// \param[in] row
+  /// \param[out] row_id_from_server Optional. The row id assigned by the server for non-mappable dataset
+  /// \return return code
+  Status WriteRow(const TensorRow &row, row_id_type *row_id_from_server = nullptr) const;
+
+  /// \brief Send a DataBuffer to the cache server
+  /// \param in Unique pointer of the DataBuffer to be cached
+  /// \return return code
+  Status WriteBuffer(std::unique_ptr<DataBuffer> &&in) const;
+
+  /// \brief Fetch a list of rows from the cache server. An empty TensorRow will be returned if there is
+  /// any cache miss
+  /// \param row_id A vector of row id's
+  /// \param out A TensorTable of TensorRows.
+  /// \return return code
+  Status GetRows(const std::vector<row_id_type> &row_id, TensorTable *out) const;
+
+  /// \brief Create a cache.
+  /// \param tree_crc  A crc that was generated during tree prepare phase
+  /// \param generate_id Let the cache service generate row id
+  /// \return Status object
+  Status CreateCache(uint32_t tree_crc, bool generate_id);
+
+  /// \brief Purge a cache. Cache can be reused after reset.
+  /// \return Status object
+  Status PurgeCache();
+
+  /// \brief Destroy a cache. Like Purge but the cache is deleted and can't be reused.
+  /// \return Status object
+  Status DestroyCache();
+
+  /// \brief Get the statistics from a cache.
+  /// \param[in/out] Pointer to a pre-allocated ServiceStat object
+  /// \return Status object
+  struct ServiceStat {
+    int64_t num_mem_cached;
+    int64_t num_disk_cached;
+    row_id_type min_row_id;
+    row_id_type max_row_id;
+    int8_t cache_service_state;
+  };
+  Status GetStat(ServiceStat *);
+
+  /// \brief Cache the schema at the cache server
+  /// \param map The unordered map of the schema
+  /// \return Status object
+  Status CacheSchema(const std::unordered_map<std::string, int32_t> &map);
+
+  /// \brief Fetch the schema from the cache server
+  /// \param map Pointer to pre-allocated map object
+  /// \return Status object.
+  Status FetchSchema(std::unordered_map<std::string, int32_t> *map);
+
+  /// \brief Change the state from build phase to read phase. Applicable to non-mappable dataset only. Only the cache
+  /// client that holds cookie can be allowed to make this request
+  /// \return Status object
+  Status BuildPhaseDone() const;
+
+  /// \brief A print method typically used for debugging
+  /// \param out The output stream to write output to
+  void Print(std::ostream &out) const;
+
+  /// \brief Stream output operator overload
+  /// \return the output stream must be returned
+  friend std::ostream &operator<<(std::ostream &out, const CacheClient &cc) {
+    cc.Print(out);
+    return out;
+  }
+
+  /// \brief Every cache server has a cookie which uniquely identifies the CacheClient that creates it.
+  /// \return Cookie
+  std::string cookie() const { return cookie_; }
+
+ private:
+  mutable RWLock mux_;
+  uint64_t cache_mem_sz_;
+  bool spill_;
+  // The session_id_ and cache_crc_ work together to uniquely identify this particular cache and allow
+  // sharing of the cache.
+  uint32_t session_id_;
+  uint32_t cache_crc_;
+  // The server_connection_id_ is the actual id we use for operations after the cache is built
+  connection_id_type server_connection_id_;
+  // Some magic cookie returned from the cache server.
+  std::string cookie_;
+};
+}  // namespace dataset
+}  // namespace mindspore
+
+#endif  // DATASET_ENGINE_CACHE_CLIENT_H_

mindspore/ccsrc/dataset/engine/cache/cache_request.cc

@@ -0,0 +1,223 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+*/
+#include "dataset/engine/cache/cache_request.h"
+
+namespace mindspore {
+namespace dataset {
+
+Status CacheRowRequest::SerializeCacheRowRequest(const TensorRow &row) {
+  buffers_.reserve(row.size() + 1);
+  RETURN_IF_NOT_OK(SerializeTensorRowHeader(row));
+  buffers_.push_back(fbb_->GetBufferPointer());
+  for (const auto &ts : row) {
+    buffers_.push_back(ts->GetBuffer());
+  }
+  return Status::OK();
+}
+
+Status CacheRowRequest::SerializeTensorRowHeader(const TensorRow &row) {
+  try {
+    fbb_ = std::make_shared<flatbuffers::FlatBufferBuilder>();
+    std::vector<flatbuffers::Offset<TensorMetaMsg>> v;
+    std::vector<int64_t> tensor_sz;
+    v.reserve(row.size());
+    tensor_sz.reserve(row.size());
+    // We will go through each column in the row.
+    for (const std::shared_ptr<Tensor> &ts_ptr : row) {
+      flatbuffers::Offset<TensorMetaMsg> ts_off;
+      RETURN_IF_NOT_OK(SerializeOneTensorMeta(ts_ptr, &ts_off));
+      v.push_back(ts_off);
+      tensor_sz.push_back(ts_ptr->SizeInBytes());
+    }
+    auto column_off = fbb_->CreateVector(v);
+    auto data_sz_off = fbb_->CreateVector(tensor_sz);
+    TensorRowHeaderMsgBuilder row_builder(*fbb_);
+    row_builder.add_column(column_off);
+    row_builder.add_data_sz(data_sz_off);
+    // Pass the row_id even if it may not be known.
+    row_builder.add_row_id(row.getId());
+    row_builder.add_size_of_this(-1);  // fill in later after we call Finish.
+    auto out = row_builder.Finish();
+    fbb_->Finish(out);
+    // Now go back to fill in size_of_this in the flat buffer.
+    auto msg = GetMutableTensorRowHeaderMsg(fbb_->GetBufferPointer());
+    auto success = msg->mutate_size_of_this(fbb_->GetSize());
+    if (!success) {
+      RETURN_STATUS_UNEXPECTED("Unable to set size_of_this");
+    }
+    return Status::OK();
+  } catch (const std::bad_alloc &e) {
+    return Status(StatusCode::kOutOfMemory, __LINE__, __FILE__);
+  }
+}
+
+Status CacheRowRequest::SerializeOneTensorMeta(const std::shared_ptr<Tensor> &ts_ptr,
+                                               flatbuffers::Offset<TensorMetaMsg> *out_off) {
+  RETURN_UNEXPECTED_IF_NULL(out_off);
+  const Tensor *ts = ts_ptr.get();
+  auto shape_off = fbb_->CreateVector(ts->shape().AsVector());
+  const auto ptr = ts->GetBuffer();
+  if (ptr == nullptr) {
+    RETURN_STATUS_UNEXPECTED("Tensor buffer is null");
+  }
+  auto src = ts->type().value();
+  TensorType dest;
+#define CASE(t)                        \
+  case DataType::t:                    \
+    dest = TensorType::TensorType_##t; \
+    break
+  // Map the type to fill in the flat buffer.
+  switch (src) {
+    CASE(DE_BOOL);
+    CASE(DE_INT8);
+    CASE(DE_UINT8);
+    CASE(DE_INT16);
+    CASE(DE_UINT16);
+    CASE(DE_INT32);
+    CASE(DE_UINT32);
+    CASE(DE_INT64);
+    CASE(DE_UINT64);
+    CASE(DE_FLOAT16);
+    CASE(DE_FLOAT32);
+    CASE(DE_FLOAT64);
+    CASE(DE_STRING);
+    default:
+      MS_LOG(ERROR) << "Unknown tensor. Dumping content:\n" << *ts;
+      RETURN_STATUS_UNEXPECTED("Unknown type");
+  }
+#undef CASE
+
+  TensorMetaMsgBuilder ts_builder(*fbb_);
+  ts_builder.add_dims(shape_off);
+  ts_builder.add_type(dest);
+  auto ts_off = ts_builder.Finish();
+  *out_off = ts_off;
+  return Status::OK();
+}
+
+Status BatchFetchRequest::RestoreOneTensor(const TensorMetaMsg *col_ts, const ReadableSlice &data,
+                                           std::shared_ptr<Tensor> *out) {
+  RETURN_UNEXPECTED_IF_NULL(col_ts);
+  auto shape_in = col_ts->dims();
+  auto type_in = col_ts->type();
+  std::vector<dsize_t> v;
+  v.reserve(shape_in->size());
+  v.assign(shape_in->begin(), shape_in->end());
+  TensorShape shape(v);
+  DataType::Type dest = DataType::DE_UNKNOWN;
+#define CASE(t)               \
+  case TensorType_##t:        \
+    dest = DataType::Type::t; \
+    break
+
+  switch (type_in) {
+    CASE(DE_BOOL);
+    CASE(DE_INT8);
+    CASE(DE_UINT8);
+    CASE(DE_INT16);
+    CASE(DE_UINT16);
+    CASE(DE_INT32);
+    CASE(DE_UINT32);
+    CASE(DE_INT64);
+    CASE(DE_UINT64);
+    CASE(DE_FLOAT16);
+    CASE(DE_FLOAT32);
+    CASE(DE_FLOAT64);
+    CASE(DE_STRING);
+  }
+#undef CASE
+
+  DataType type(dest);
+  std::shared_ptr<Tensor> ts =
+    std::make_shared<Tensor>(shape, type, static_cast<const unsigned char *>(data.GetPointer()), data.GetSize());
+  // Next we restore the real data which can be embedded or stored separately.
+  if (ts->SizeInBytes() != data.GetSize()) {
+    MS_LOG(ERROR) << "Unexpected length. Read " << data.GetSize() << ". Expected " << ts->SizeInBytes() << ".\n"
+                  << "Dumping tensor\n"
+                  << *ts << "\n";
+    RETURN_STATUS_UNEXPECTED("Length mismatch. See log file for details.");
+  }
+  *out = std::move(ts);
+  return Status::OK();
+}
+
+Status BatchFetchRequest::RestoreRows(TensorTable *out) {
+  RETURN_UNEXPECTED_IF_NULL(out);
+  auto num_elements = row_id_.size();
+  auto *offset_array = reinterpret_cast<const int64_t *>(mem_.GetPointer());
+  TensorTable tbl;
+  tbl.reserve(num_elements);
+  ReadableSlice all(mem_.GetPointer(), mem_.GetSizeInBytes());
+  for (auto i = 0; i < num_elements; ++i) {
+    auto len = offset_array[i + 1] - offset_array[i];
+    TensorRow row;
+    row.setId(row_id_.at(i));
+    if (len > 0) {
+      ReadableSlice row_data(all, offset_array[i], len);
+      // Next we de-serialize flat buffer to get back each column
+      auto msg = GetTensorRowHeaderMsg(row_data.GetPointer());
+      auto msg_sz = msg->size_of_this();
+      // Start of the tensor data
+      auto ts_offset = msg_sz;
+      row.reserve(msg->column()->size());
+      for (auto k = 0; k < msg->column()->size(); ++k) {
+        auto col_ts = msg->column()->Get(k);
+        std::shared_ptr<Tensor> ts;
+        ReadableSlice data(row_data, ts_offset, msg->data_sz()->Get(k));
+        RETURN_IF_NOT_OK(RestoreOneTensor(col_ts, data, &ts));
+        row.push_back(ts);
+        ts_offset += data.GetSize();
+      }
+    }
+    tbl.push_back(std::move(row));
+  }
+  *out = std::move(tbl);
+  return Status::OK();
+}
+
+Status CacheSchemaRequest::SerializeCacheSchemaRequest(const std::unordered_map<std::string, int32_t> &map) {
+  try {
+    fbb_ = std::make_shared<flatbuffers::FlatBufferBuilder>();
+    std::vector<flatbuffers::Offset<ColumnNameMsg>> v;
+    v.reserve(map.size());
+    for (auto &column : map) {
+      auto c = CreateColumnNameMsg(*fbb_, fbb_->CreateString(column.first), column.second);
+      v.push_back(c);
+    }
+    auto v_off = fbb_->CreateVector(v);
+    auto final_off = CreateSchemaMsg(*fbb_, v_off);
+    fbb_->Finish(final_off);
+    buf_ = fbb_->GetBufferPointer();
+    len_of_buf_ = fbb_->GetSize();
+    return Status::OK();
+  } catch (const std::bad_alloc &e) {
+    return Status(StatusCode::kOutOfMemory, __LINE__, __FILE__);
+  }
+}
+
+std::unordered_map<std::string, int32_t> FetchSchemaRequest::GetColumnMap() {
+  if (column_name_id_map_.empty()) {
+    auto *map_msg = flatbuffers::GetRoot<SchemaMsg>(mem_.GetPointer());
+    auto v = map_msg->column();
+    for (auto i = 0; i < v->size(); ++i) {
+      auto col = map_msg->column()->Get(i);
+      column_name_id_map_.emplace(col->name()->str(), col->id());
+    }
+  }
+  return column_name_id_map_;
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/cache/cache_request.h

@@ -0,0 +1,225 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+*/
+#ifndef DATASET_ENGINE_CACHE_REQ_H_
+#define DATASET_ENGINE_CACHE_REQ_H_
+
+#include <algorithm>
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+#include "./de_tensor_generated.h"
+#include "dataset/core/tensor_row.h"
+#include "dataset/util/slice.h"
+#include "dataset/util/wait_post.h"
+
+namespace mindspore {
+namespace dataset {
+/// \brief CacheClient communicates with CacheServer using Requests.
+class BaseRequest {
+ public:
+  // Request types
+  enum class RequestType : int16_t {
+    kCacheRow = 0,
+    kBatchFetchRows = 1,
+    kCreateCache = 2,
+    kPurgeCache = 3,
+    kDestroyCache = 4,
+    kGetStat = 5,
+    kCacheSchema = 6,
+    kFetchSchema = 7,
+    kBuildPhaseDone = 8,
+    // Add new request before it.
+    kRequestUnknown = 32767
+  };
+  // For kCreateCache
+  enum class CreateCacheFlag : uint32_t { kNone = 0, kSpillToDisk = 1, kGenerateRowId = 1u << 1L };
+  friend class CacheServer;
+  /// \brief Base class of a cache server request
+  /// \param connection_id A combination of session id and crc that uniquely identifies a connection.
+  /// \param type Type of the request
+  explicit BaseRequest(connection_id_type connection_id, RequestType type)
+      : type_(type), connection_id_(connection_id) {}
+  virtual ~BaseRequest() = default;
+  /// \brief Wait for the completion of a request
+  /// \return Status returned from the cache server
+  Status Wait() {
+    RETURN_IF_NOT_OK(wp_.Wait());
+    return rc_;
+  }
+
+  /// \brief Getter function of the current connection id
+  /// \return Connection id
+  connection_id_type GetServerConnectionId() const { return connection_id_; }
+
+ private:
+  RequestType type_;
+  connection_id_type connection_id_;
+  Status rc_;
+  WaitPost wp_;
+};
+/// \brief Request to cache a single TensorRow
+class CacheRowRequest : public BaseRequest {
+ public:
+  friend class CacheServer;
+  explicit CacheRowRequest(connection_id_type connection_id, const std::string &cookie)
+      : BaseRequest(connection_id, RequestType::kCacheRow), row_id_from_server_(-1), cookie_(cookie) {}
+  ~CacheRowRequest() = default;
+
+  /// \brief Serialize a TensorRow for streaming to the cache server
+  /// \param row TensorRow
+  /// \return Status object
+  Status SerializeCacheRowRequest(const TensorRow &row);
+  /// \brief Return the row id assigned to this row for non-mappable dataset
+  /// \return row id of the cached row
+  row_id_type GetRowIdAfterCache() { return row_id_from_server_; }
+
+ private:
+  std::shared_ptr<flatbuffers::FlatBufferBuilder> fbb_;
+  row_id_type row_id_from_server_;
+  std::vector<const void *> buffers_;
+  std::string cookie_;
+
+  /// \brief Private function to serialize one TensorRow
+  /// \param row TensorRow
+  /// \return Status object
+  Status SerializeTensorRowHeader(const TensorRow &row);
+  /// \brief Private function to serialize one Tensor
+  /// \param ts_ptr Tensor
+  /// \return Status object
+  Status SerializeOneTensorMeta(const std::shared_ptr<Tensor> &ts_ptr, flatbuffers::Offset<TensorMetaMsg> *out_off);
+};
+/// \brief Request to fetch rows in batch
+class BatchFetchRequest : public BaseRequest {
+ public:
+  friend class CacheServer;
+  friend class CacheService;
+  BatchFetchRequest(connection_id_type connection_id, const std::vector<row_id_type> &row_id)
+      : BaseRequest(connection_id, RequestType::kBatchFetchRows), row_id_(row_id) {}
+  Status RestoreRows(TensorTable *out);
+
+ private:
+  std::vector<row_id_type> row_id_;
+  MemGuard<uint8_t> mem_;
+  Status RestoreOneTensor(const TensorMetaMsg *col_ts, const ReadableSlice &data, std::shared_ptr<Tensor> *out);
+};
+/// \brief Request to create a cache for the current connection
+class CreationCacheRequest : public BaseRequest {
+ public:
+  friend class CacheServer;
+  /// \brief Constructor
+  /// \param connection_id
+  /// \param cache_mem_sz Maximum memory assigned for this connection. 0 means unlimited
+  /// \param flag Attributes of the cache.
+  explicit CreationCacheRequest(connection_id_type connection_id, uint64_t cache_mem_sz,
+                                CreateCacheFlag flag = CreateCacheFlag::kNone)
+      : BaseRequest(connection_id, RequestType::kCreateCache), cache_mem_sz(cache_mem_sz), flag_(flag) {}
+
+  std::string cookie() const { return cookie_; }
+
+ private:
+  uint64_t cache_mem_sz;
+  CreateCacheFlag flag_;
+  std::string cookie_;
+};
+/// \brief Request to purge a cache.
+class PurgeCacheRequest : public BaseRequest {
+ public:
+  friend class CacheServer;
+  explicit PurgeCacheRequest(connection_id_type connection_id) : BaseRequest(connection_id, RequestType::kPurgeCache) {}
+};
+/// \brief Request to destroy a cache
+class DestroyCacheRequest : public BaseRequest {
+ public:
+  friend class CacheServer;
+  explicit DestroyCacheRequest(connection_id_type connection_id)
+      : BaseRequest(connection_id, RequestType::kDestroyCache) {}
+};
+/// \brief Obtain the statistics of the current connection
+class GetStatRequest : public BaseRequest {
+ public:
+  friend class CacheServer;
+  friend class CacheService;
+  explicit GetStatRequest(connection_id_type connection_id) : BaseRequest(connection_id, RequestType::kGetStat) {}
+  row_id_type GetMinRowId() const {
+    auto *msg = flatbuffers::GetRoot<ServiceStatMsg>(mem_.GetPointer());
+    return msg->min_row_id();
+  }
+  row_id_type GetMaxRowId() const {
+    auto *msg = flatbuffers::GetRoot<ServiceStatMsg>(mem_.GetPointer());
+    return msg->max_row_id();
+  }
+  int64_t GetNumMemCached() const {
+    auto *msg = flatbuffers::GetRoot<ServiceStatMsg>(mem_.GetPointer());
+    return msg->num_mem_cached();
+  }
+  int64_t GetNumDiskCached() const {
+    auto *msg = flatbuffers::GetRoot<ServiceStatMsg>(mem_.GetPointer());
+    return msg->num_disk_cached();
+  }
+  uint8_t GetState() const {
+    auto *msg = flatbuffers::GetRoot<ServiceStatMsg>(mem_.GetPointer());
+    return msg->state();
+  }
+
+ private:
+  MemGuard<uint8_t> mem_;
+};
+/// \brief Request to cache a schema
+class CacheSchemaRequest : public BaseRequest {
+ public:
+  friend class CacheServer;
+  explicit CacheSchemaRequest(connection_id_type connection_id)
+      : BaseRequest(connection_id, RequestType::kCacheSchema), buf_(nullptr), len_of_buf_(0) {}
+  ~CacheSchemaRequest() = default;
+
+  Status SerializeCacheSchemaRequest(const std::unordered_map<std::string, int32_t> &map);
+  const void *GetBuffer() const { return buf_; }
+
+ private:
+  std::shared_ptr<flatbuffers::FlatBufferBuilder> fbb_;
+  const void *buf_;
+  int64_t len_of_buf_;
+};
+/// \brief Request to fetch a schema
+class FetchSchemaRequest : public BaseRequest {
+ public:
+  friend class CacheServer;
+  explicit FetchSchemaRequest(connection_id_type connection_id)
+      : BaseRequest(connection_id, RequestType::kFetchSchema) {}
+  ~FetchSchemaRequest() = default;
+
+  std::unordered_map<std::string, int32_t> GetColumnMap();
+
+ private:
+  MemGuard<uint8_t> mem_;
+  std::unordered_map<std::string, int32_t> column_name_id_map_;
+};
+/// \brief Request to change a cache from build phase to read phase. Applies to non-mappable cache only.
+class BuildPhaseDoneRequest : public BaseRequest {
+ public:
+  friend class CacheServer;
+  BuildPhaseDoneRequest(connection_id_type connection_id, const std::string &cookie)
+      : BaseRequest(connection_id, RequestType::kBuildPhaseDone), cookie_(cookie) {}
+
+ private:
+  std::string cookie_;
+};
+}  // namespace dataset
+}  // namespace mindspore
+#endif  // DATASET_ENGINE_CACHE_SERVICE_H_

mindspore/ccsrc/dataset/engine/cache/cache_server.cc

@@ -0,0 +1,252 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+*/
+#include "dataset/engine/cache/cache_server.h"
+#include "dataset/engine/cache/cache_service.h"
+#include "dataset/engine/cache/cache_request.h"
+#include "dataset/util/bit.h"
+
+namespace mindspore {
+namespace dataset {
+Status CacheServer::DoServiceStart() {
+  if (!top_.empty()) {
+    Path spill(top_);
+    RETURN_IF_NOT_OK(spill.CreateDirectories());
+    MS_LOG(INFO) << "CacheServer will use disk folder: " << top_;
+  }
+  RETURN_IF_NOT_OK(vg_.ServiceStart());
+  cache_q_ = std::make_shared<Queue<BaseRequest *>>(1024);
+  RETURN_IF_NOT_OK(cache_q_->Register(&vg_));
+  auto f = std::bind(&CacheServer::ServerRequest, this);
+  // Spawn a a few threads to serve the request.
+  for (auto i = 0; i < num_workers_; ++i) {
+    RETURN_IF_NOT_OK(vg_.CreateAsyncTask("Cache server", f));
+  }
+  return Status::OK();
+}
+
+Status CacheServer::DoServiceStop() {
+  Status rc;
+  Status rc2;
+  // First stop all the threads.
+  RETURN_IF_NOT_OK(vg_.ServiceStop());
+  // Clean up all the caches if any.
+  UniqueLock lck(&rwLock_);
+  auto it = all_caches_.begin();
+  while (it != all_caches_.end()) {
+    auto cs = std::move(it->second);
+    rc2 = cs->ServiceStop();
+    if (rc2.IsError()) {
+      rc = rc2;
+    }
+    ++it;
+  }
+  return rc;
+}
+
+CacheService *CacheServer::GetService(connection_id_type id) const {
+  SharedLock lck(&rwLock_);
+  auto it = all_caches_.find(id);
+  if (it != all_caches_.end()) {
+    return it->second.get();
+  }
+  return nullptr;
+}
+
+Status CacheServer::CreateService(connection_id_type connection_id, uint64_t cache_mem_sz,
+                                  BaseRequest::CreateCacheFlag flag, std::string *out_cookie) {
+  // We can't do spilling unless this server is setup with a spill path in the first place
+  bool spill = (flag & BaseRequest::CreateCacheFlag::kSpillToDisk) == BaseRequest::CreateCacheFlag::kSpillToDisk;
+  bool generate_id =
+    (flag & BaseRequest::CreateCacheFlag::kGenerateRowId) == BaseRequest::CreateCacheFlag::kGenerateRowId;
+  if (spill && top_.empty()) {
+    RETURN_STATUS_UNEXPECTED("Server is not set up with spill support.");
+  }
+  RETURN_UNEXPECTED_IF_NULL(out_cookie);
+  *out_cookie = "";
+  // Before creating the cache, first check if this is a request for a shared usage of an existing cache
+  // If two CreateService come in with identical connection_id, we need to serialize the create.
+  // The first create will be successful and be given a special cookie.
+  UniqueLock lck(&rwLock_);
+  auto end = all_caches_.end();
+  auto it = all_caches_.find(connection_id);
+  if (it == end) {
+    std::unique_ptr<CacheService> cs;
+    try {
+      cs = std::make_unique<CacheService>(cache_mem_sz, spill ? top_ : "", generate_id);
+      RETURN_IF_NOT_OK(cs->ServiceStart());
+      *out_cookie = cs->cookie();
+      all_caches_.emplace(connection_id, std::move(cs));
+    } catch (const std::bad_alloc &e) {
+      return Status(StatusCode::kOutOfMemory);
+    }
+  } else {
+    MS_LOG(INFO) << "Duplicate request for " + std::to_string(connection_id) + " to create cache service";
+    // We can return OK but we will return a duplicate key so user can act accordingly to either ignore it
+    // treat it as OK.
+    return Status(StatusCode::kDuplicateKey);
+  }
+  return Status::OK();
+}
+
+/// This is the main loop the cache server thread(s) are running.
+/// Each thread will pop a request and save the result in the same request.
+/// The sender will wait on the wait post in the request. Once the request
+/// is fulfilled, the server thread will do a post signalling the request is
+/// is processed.
+/// \return
+Status CacheServer::ServerRequest() {
+  TaskManager::FindMe()->Post();
+  // Loop forever until we are interrupted.
+  while (true) {
+    BaseRequest *base_rq = nullptr;
+    RETURN_IF_NOT_OK(cache_q_->PopFront(&base_rq));
+    auto cs = GetService(base_rq->connection_id_);
+    // Except for creating a new session, we expect cs is not null.
+    switch (base_rq->type_) {
+      case BaseRequest::RequestType::kCacheRow: {
+        if (cs == nullptr) {
+          std::string errMsg = "Cache id " + std::to_string(base_rq->connection_id_) + " not found";
+          base_rq->rc_ = Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, errMsg);
+        } else {
+          auto *rq = reinterpret_cast<CacheRowRequest *>(base_rq);
+          // Only if the cookie matches, we can accept insert into this cache that has a build phase
+          if (!cs->HasBuildPhase() || rq->cookie_ == cs->cookie()) {
+            rq->rc_ = cs->CacheRow(rq->buffers_, &rq->row_id_from_server_);
+          } else {
+            return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, "Cookie mismatch");
+          }
+        }
+        break;
+      }
+      case BaseRequest::RequestType::kBatchFetchRows: {
+        if (cs == nullptr) {
+          std::string errMsg = "Cache id " + std::to_string(base_rq->connection_id_) + " not found";
+          base_rq->rc_ = Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, errMsg);
+        } else {
+          auto *rq = reinterpret_cast<BatchFetchRequest *>(base_rq);
+          rq->rc_ = cs->BatchFetch(rq->row_id_, &rq->mem_);
+        }
+        break;
+      }
+      case BaseRequest::RequestType::kCreateCache: {
+        // If the cache is already created we still need to run the creation so that we do sanity checks on the
+        // client id and return the cache id back to the user.
+        auto *rq = reinterpret_cast<CreationCacheRequest *>(base_rq);
+        rq->rc_ = CreateService(rq->connection_id_, rq->cache_mem_sz, rq->flag_, &rq->cookie_);
+        break;
+      }
+      case BaseRequest::RequestType::kPurgeCache: {
+        if (cs != nullptr) {
+          base_rq->rc_ = cs->Purge();
+        } else {
+          // it is already purged. Ignore it.
+          base_rq->rc_ = Status::OK();
+        }
+        break;
+      }
+      case BaseRequest::RequestType::kDestroyCache: {
+        if (cs != nullptr) {
+          // We need a strong lock to protect the map.
+          connection_id_type id = base_rq->connection_id_;
+          UniqueLock lck(&rwLock_);
+          // std::map will invoke the constructor of CacheService. So we don't need to do anything here.
+          auto n = all_caches_.erase(id);
+          if (n == 0) {
+            // It has been destroyed by another duplicate request.
+            MS_LOG(INFO) << "Duplicate request for " + std::to_string(id) + " to create cache service";
+          }
+          base_rq->rc_ = Status::OK();
+        } else {
+          // it is already destroyed. Ignore it.
+          base_rq->rc_ = Status::OK();
+        }
+        break;
+      }
+      case BaseRequest::RequestType::kGetStat: {
+        if (cs == nullptr) {
+          std::string errMsg = "Session " + std::to_string(base_rq->connection_id_) + " not found";
+          base_rq->rc_ = Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, errMsg);
+        } else {
+          auto *rq = reinterpret_cast<GetStatRequest *>(base_rq);
+          CacheService::ServiceStat svc_stat;
+          rq->rc_ = cs->GetStat(&svc_stat);
+          if (rq->rc_.IsOk()) {
+            flatbuffers::FlatBufferBuilder fbb;
+            ServiceStatMsgBuilder bld(fbb);
+            bld.add_num_disk_cached(svc_stat.stat_.num_disk_cached);
+            bld.add_num_mem_cached(svc_stat.stat_.num_mem_cached);
+            bld.add_max_row_id(svc_stat.max_);
+            bld.add_min_row_id(svc_stat.min_);
+            bld.add_state(svc_stat.state_);
+            auto offset = bld.Finish();
+            fbb.Finish(offset);
+            rq->rc_ = rq->mem_.allocate(fbb.GetSize());
+            if (rq->rc_.IsOk()) {
+              WritableSlice dest(rq->mem_.GetMutablePointer(), fbb.GetSize());
+              ReadableSlice src(fbb.GetBufferPointer(), fbb.GetSize());
+              RETURN_IF_NOT_OK(WritableSlice::Copy(&dest, src));
+            }
+          }
+        }
+        break;
+      }
+      case BaseRequest::RequestType::kCacheSchema: {
+        if (cs == nullptr) {
+          std::string errMsg = "Session " + std::to_string(base_rq->connection_id_) + " not found";
+          base_rq->rc_ = Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, errMsg);
+        } else {
+          auto *rq = reinterpret_cast<CacheSchemaRequest *>(base_rq);
+          rq->rc_ = cs->CacheSchema(rq->buf_, rq->len_of_buf_);
+        }
+        break;
+      }
+      case BaseRequest::RequestType::kFetchSchema: {
+        if (cs == nullptr) {
+          std::string errMsg = "Session " + std::to_string(base_rq->connection_id_) + " not found";
+          base_rq->rc_ = Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, errMsg);
+        } else {
+          auto *rq = reinterpret_cast<FetchSchemaRequest *>(base_rq);
+          rq->rc_ = cs->FetchSchema(&rq->mem_);
+        }
+        break;
+      }
+      case BaseRequest::RequestType::kBuildPhaseDone: {
+        if (cs == nullptr) {
+          std::string errMsg = "Session " + std::to_string(base_rq->connection_id_) + " not found";
+          base_rq->rc_ = Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, errMsg);
+        } else {
+          auto *rq = reinterpret_cast<BuildPhaseDoneRequest *>(base_rq);
+          // We can only allow to switch phase is the cookie match.
+          if (rq->cookie_ == cs->cookie()) {
+            rq->rc_ = cs->BuildPhaseDone();
+          } else {
+            return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, "Cookie mismatch");
+          }
+        }
+        break;
+      }
+      default:
+        base_rq->rc_ = Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, "Unknown request type");
+    }
+    // Notify it is done, and move on to the next request.
+    base_rq->wp_.Set();
+  }
+  return Status::OK();
+}
+CacheServer::CacheServer(const std::string &spill_path, int32_t num_workers)
+    : top_(spill_path), num_workers_(num_workers) {}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/cache/cache_server.h

@@ -0,0 +1,98 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+*/
+
+#ifndef DATASET_ENGINE_CACHE_SERVER_H_
+#define DATASET_ENGINE_CACHE_SERVER_H_
+
+#include <algorithm>
+#include <atomic>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+#include <map>
+#include "dataset/engine/cache/cache_service.h"
+#include "dataset/core/tensor.h"
+#include "dataset/util/arena.h"
+#include "dataset/util/cache_pool.h"
+#include "dataset/util/lock.h"
+#include "dataset/util/service.h"
+#include "dataset/util/services.h"
+#include "dataset/util/system_pool.h"
+#include "dataset/util/queue.h"
+#include "dataset/util/task_manager.h"
+
+namespace mindspore {
+namespace dataset {
+class BaseRequest;
+/// \brief A server which provides CacheService services.
+class CacheServer : public Service {
+ public:
+  friend class Services;
+  using cache_index = std::map<connection_id_type, std::unique_ptr<CacheService>>;
+
+  CacheServer(const CacheServer &) = delete;
+  CacheServer &operator=(const CacheServer &) = delete;
+  CacheServer(CacheServer &&) = delete;
+  CacheServer &operator=(CacheServer &) = delete;
+  static CacheServer &GetInstance() noexcept { return Services::getCacheServer(); }
+  Status DoServiceStart() override;
+  Status DoServiceStop() override;
+  ~CacheServer() { (void)ServiceStop(); }
+
+  /// \brief For the current demonstration, a cache client contacts cache server using a Queue.
+  /// \param rq
+  /// \return Status object
+  Status PushRequest(BaseRequest *rq) {
+    RETURN_UNEXPECTED_IF_NULL(rq);
+    RETURN_IF_NOT_OK(cache_q_->Add(rq));
+    return Status::OK();
+  }
+
+ private:
+  mutable RWLock rwLock_;
+  std::string top_;
+  cache_index all_caches_;
+  std::shared_ptr<Queue<BaseRequest *>> cache_q_;
+  TaskGroup vg_;
+  int32_t num_workers_;
+
+  /// \brief Constructor
+  /// \param spill_path Top directory for spilling buffers to.
+  /// \param num_workers Number of threads for handling requests.
+  explicit CacheServer(const std::string &spill_path, int32_t num_workers = 3);
+
+  /// \brief Locate a cache service from connection id.
+  /// \return Pointer to cache service. Null if not found
+  CacheService *GetService(connection_id_type id) const;
+
+  /// \brief Create a cache service. We allow multiple clients to create the same cache service.
+  /// Subsequent duplicate requests are ignored. The first cache client to create the service will be given
+  /// a special unique cookie.
+  /// \param[in] connection_id This is from a Cache client.
+  /// \param[in] cache_mem_sz
+  /// \param[in] flag
+  /// \param[out] out_cookie Only the first cache client will be given a special cookie to identify the creator
+  /// \return Status object
+  Status CreateService(connection_id_type connection_id, uint64_t cache_mem_sz, BaseRequest::CreateCacheFlag flag,
+                       std::string *out_cookie);
+
+  /// \brief Entry point for all server threads.
+  Status ServerRequest();
+};
+}  // namespace dataset
+}  // namespace mindspore
+#endif  // DATASET_CORE_CACHE_TENSOR_H_

mindspore/ccsrc/dataset/engine/cache/cache_service.cc

@@ -0,0 +1,265 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+*/
+#include "dataset/engine/cache/cache_service.h"
+#include "dataset/util/slice.h"
+
+namespace mindspore {
+namespace dataset {
+CacheService::CacheService(uint64_t mem_sz, const std::string &root, bool generate_id)
+    : root_(root),
+      cache_mem_sz_(mem_sz),
+      cp_(nullptr),
+      map_(nullptr),
+      next_id_(0),
+      generate_id_(generate_id),
+      schema_key_(-1),
+      st_(generate_id ? State::kBuildPhase : State::kNone) {}
+CacheService::~CacheService() { (void)ServiceStop(); }
+bool CacheService::UseArena() {
+  // If fixed size, use Arena instead of the pool from global context.
+  return (cache_mem_sz_ > 0);
+}
+Status CacheService::DoServiceStart() {
+  std::shared_ptr<MemoryPool> mp_;
+  if (UseArena()) {
+    // Create a fixed size arena based on the parameter.
+    std::shared_ptr<Arena> arena;
+    RETURN_IF_NOT_OK(Arena::CreateArena(&arena, cache_mem_sz_));
+    mp_ = std::move(arena);
+  } else {
+    // Unlimited size. Simply use a system pool. Another choice is CircularPool.
+    mp_ = std::make_shared<SystemPool>();
+  }
+  // Put together a CachePool for backing up the Tensor
+  cp_ = std::make_shared<CachePool>(CachePool::value_allocator(mp_), root_);
+  RETURN_IF_NOT_OK(cp_->ServiceStart());
+  // Set up the B+ tree as well. But use the system pool instead.
+  map_ = std::make_shared<row_map>();
+  // Assign a name to this cache. Used for exclusive connection. But we can just use CachePool's name.
+  cookie_ = cp_->MyName();
+  return Status::OK();
+}
+Status CacheService::DoServiceStop() {
+  if (cp_ != nullptr) {
+    RETURN_IF_NOT_OK(cp_->ServiceStop());
+  }
+  return Status::OK();
+}
+Status CacheService::CacheRow(const std::vector<const void *> &buf, row_id_type *row_id_generated) {
+  SharedLock rw(&rw_lock_);
+  RETURN_UNEXPECTED_IF_NULL(row_id_generated);
+  if (st_ == State::kFetchPhase) {
+    // For this kind of cache service, once we are done with the build phase into fetch phase, we can't
+    // allow other to cache more rows.
+    RETURN_STATUS_UNEXPECTED("Can't accept cache request in fetch phase");
+  }
+  try {
+    // The first buffer is a flatbuffer which describes the rest of the buffers follow
+    auto fb = buf.front();
+    RETURN_UNEXPECTED_IF_NULL(fb);
+    auto msg = GetTensorRowHeaderMsg(fb);
+    // If the server side is designed to ignore incoming row id, we generate row id.
+    if (generate_id_) {
+      *row_id_generated = GetNextRowId();
+      // Some debug information on how many rows we have generated so far.
+      if ((*row_id_generated) % 1000 == 0) {
+        MS_LOG(DEBUG) << "Number of rows cached: " << *row_id_generated;
+      }
+    } else {
+      if (msg->row_id() < 0) {
+        std::string errMsg = "Expect positive row id: " + std::to_string(msg->row_id());
+        RETURN_STATUS_UNEXPECTED(errMsg);
+      }
+      *row_id_generated = msg->row_id();
+    }
+    auto size_of_this = msg->size_of_this();
+    auto column_hdr = msg->column();
+    // Number of tensor buffer should match the number of columns plus one.
+    if (buf.size() != column_hdr->size() + 1) {
+      std::string errMsg = "Column count does not match. Expect " + std::to_string(column_hdr->size() + 1) +
+                           " but get " + std::to_string(buf.size());
+      RETURN_STATUS_UNEXPECTED(errMsg);
+    }
+    // Next we store in either memory or on disk. Low level code will consolidate everything in one piece.
+    std::vector<ReadableSlice> all_data;
+    all_data.reserve(column_hdr->size() + 1);
+    all_data.emplace_back(fb, size_of_this);
+    for (auto i = 0; i < column_hdr->size(); ++i) {
+      all_data.emplace_back(buf.at(i + 1), msg->data_sz()->Get(i));
+    }
+    // Now we cache the flat buffer.
+    CachePool::key_type key;
+    RETURN_IF_NOT_OK(cp_->Insert(all_data, &key));
+    Status rc = map_->DoInsert(*row_id_generated, key);
+    if (rc == Status(StatusCode::kDuplicateKey)) {
+      MS_LOG(DEBUG) << "Ignoring duplicate key";
+    } else {
+      RETURN_IF_NOT_OK(rc);
+    }
+    return Status::OK();
+  } catch (const std::exception &e) {
+    RETURN_STATUS_UNEXPECTED(e.what());
+  }
+}
+std::ostream &operator<<(std::ostream &out, const CacheService &cs) {
+  // Then show any custom derived-internal stuff
+  out << "\nCache memory size: " << cs.cache_mem_sz_;
+  out << "\nSpill path: ";
+  if (cs.root_.empty()) {
+    out << "None";
+  } else {
+    out << cs.GetSpillPath();
+  }
+  return out;
+}
+Path CacheService::GetSpillPath() const { return cp_->GetSpillPath(); }
+Status CacheService::Purge() {
+  // First we must lock exclusively. No one else can cache/restore anything.
+  UniqueLock rw(&rw_lock_);
+  RETURN_IF_NOT_OK(cp_->ServiceStop());
+  auto new_map = std::make_shared<row_map>();
+  map_.reset();
+  map_ = std::move(new_map);
+  next_id_ = 0;
+  RETURN_IF_NOT_OK(cp_->ServiceStart());
+  return Status::OK();
+}
+Status CacheService::GetStat(CacheService::ServiceStat *out) {
+  SharedLock rw(&rw_lock_);
+  RETURN_UNEXPECTED_IF_NULL(out);
+  if (st_ == State::kNone || st_ == State::kFetchPhase) {
+    out->stat_ = cp_->GetStat();
+    out->state_ = static_cast<ServiceStat::state_type>(st_);
+    auto it = map_->begin();
+    if (it != map_->end()) {
+      out->min_ = it.key();
+      auto end_it = map_->end();
+      --end_it;
+      out->max_ = end_it.key();
+    }
+  } else {
+    out->state_ = static_cast<ServiceStat::state_type>(st_);
+  }
+  return Status::OK();
+}
+Status CacheService::BatchFetch(const std::vector<row_id_type> &v, MemGuard<uint8_t> *out) const {
+  RETURN_UNEXPECTED_IF_NULL(out);
+  SharedLock rw(&rw_lock_);
+  if (st_ == State::kBuildPhase) {
+    // For this kind of cache service, we can't fetch yet until we are done with caching all the rows.
+    RETURN_STATUS_UNEXPECTED("Can't accept cache request in fetch phase");
+  }
+  const auto num_elements = v.size();
+  int64_t mem_sz = (num_elements + 1) * sizeof(int64_t);
+  int64_t data_offset = mem_sz;
+  std::vector<int64_t> sz_v;
+  std::vector<CachePool::key_type> keys;
+  sz_v.reserve(num_elements);
+  keys.reserve(num_elements);
+  for (auto row_id : v) {
+    auto r = map_->Search(row_id);
+    if (r.second) {
+      auto &it = r.first;
+      CachePool::key_type key = it.value();
+      auto sz = cp_->GetSize(key);
+      if (sz == 0) {
+        std::string errMsg = "Key not found: ";
+        errMsg += std::to_string(key);
+        RETURN_STATUS_UNEXPECTED(errMsg);
+      }
+      keys.push_back(key);
+      sz_v.push_back(sz);
+      mem_sz += sz;
+    } else {
+      keys.push_back(-1);
+      sz_v.push_back(0);
+    }
+  }
+  MemGuard<uint8_t> mem;
+  RETURN_IF_NOT_OK(mem.allocate(mem_sz));
+  auto *offset_array = reinterpret_cast<int64_t *>(mem.GetMutablePointer());
+  offset_array[0] = data_offset;
+  WritableSlice all(mem.GetMutablePointer(), mem.GetSizeInBytes());
+  for (auto i = 0; i < num_elements; ++i) {
+    auto sz = sz_v.at(i);
+    offset_array[i + 1] = offset_array[i] + sz;
+    if (sz > 0) {
+      WritableSlice row_data(all, offset_array[i], sz);
+      auto key = keys.at(i);
+      size_t bytesRead = 0;
+      RETURN_IF_NOT_OK(cp_->Read(key, &row_data, &bytesRead));
+      if (bytesRead != sz) {
+        MS_LOG(ERROR) << "Unexpected length. Read " << bytesRead << ". Expected " << sz << "."
+                      << " Internal key: " << key << "\n";
+        RETURN_STATUS_UNEXPECTED("Length mismatch. See log file for details.");
+      }
+    }
+  }
+  *out = std::move(mem);
+  return Status::OK();
+}
+Status CacheService::CacheSchema(const void *buf, int64_t len) {
+  SharedLock rw(&rw_lock_);
+  if (st_ == State::kFetchPhase) {
+    // For this kind of cache service, once we are done with the build phase into fetch phase, we can't
+    // allow other to cache more rows.
+    RETURN_STATUS_UNEXPECTED("Can't accept cache request in fetch phase");
+  }
+  // This is a special request and we need to remember where we store it.
+  // In case we are calling the same function from multiple threads, only
+  // the first one is considered. Rest is ignored.
+  CachePool::key_type cur_key = schema_key_;
+  CachePool::key_type key;
+  if (cur_key < 0) {
+    RETURN_IF_NOT_OK(cp_->Insert({ReadableSlice(buf, len)}, &key));
+    auto result = std::atomic_compare_exchange_strong(&schema_key_, &cur_key, key);
+    MS_LOG(DEBUG) << "Caching Schema. Result = " << result;
+  } else {
+    MS_LOG(DEBUG) << "Caching Schema already done";
+  }
+  return Status::OK();
+}
+Status CacheService::FetchSchema(MemGuard<uint8_t> *out) const {
+  SharedLock rw(&rw_lock_);
+  if (st_ == State::kBuildPhase) {
+    // For this kind of cache service, we can't fetch yet until we are done with caching all the rows.
+    RETURN_STATUS_UNEXPECTED("Can't accept cache request in fetch phase");
+  }
+  RETURN_UNEXPECTED_IF_NULL(out);
+  MemGuard<uint8_t> mem;
+  if (schema_key_ >= 0) {
+    auto len = cp_->GetSize(schema_key_);
+    RETURN_IF_NOT_OK(mem.allocate(len));
+    auto slice = WritableSlice(mem.GetMutablePointer(), len);
+    RETURN_IF_NOT_OK(cp_->Read(schema_key_, &slice));
+    *out = std::move(mem);
+  } else {
+    return Status(StatusCode::kFileNotExist, __LINE__, __FILE__, "No schema has been cached");
+  }
+  return Status::OK();
+}
+Status CacheService::BuildPhaseDone() {
+  if (HasBuildPhase()) {
+    // Exclusive lock to switch phase
+    UniqueLock rw(&rw_lock_);
+    st_ = State::kFetchPhase;
+    return Status::OK();
+  } else {
+    RETURN_STATUS_UNEXPECTED("Not a cache that has a build phase");
+  }
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/cache/cache_service.h

@@ -0,0 +1,143 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+
+ * http://www.apache.org/licenses/LICENSE-2.0
+
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+*/
+
+#ifndef DATASET_ENGINE_CACHE_SERVICE_H_
+#define DATASET_ENGINE_CACHE_SERVICE_H_
+
+#include <algorithm>
+#include <atomic>
+#include <memory>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "./de_tensor_generated.h"
+#include "dataset/core/global_context.h"
+#include "dataset/core/tensor.h"
+#include "dataset/engine/cache/cache_request.h"
+#include "dataset/util/arena.h"
+#include "dataset/util/btree.h"
+#include "dataset/util/cache_pool.h"
+#include "dataset/util/service.h"
+#include "dataset/util/services.h"
+#include "dataset/util/system_pool.h"
+
+namespace mindspore {
+namespace dataset {
+struct CacheStat;
+/// \brief A cache service for storing/fetching buffers to in memory cache and may spill to disk the cache service is
+/// created to support spilling
+class CacheService : public Service {
+ public:
+  friend class CacheServer;
+  using row_map = BPlusTree<row_id_type, CachePool::key_type>;
+
+  enum class State : uint8_t { kNone = 0, kBuildPhase, kFetchPhase };
+
+  /// \brief Constructor
+  /// \param mem_sz Memory size to be set aside for the in memory cache. 0 means unlimited
+  /// \param root Spill path. Empty string means no spilling
+  /// \param generate_id If the cache service should generate row id for buffer that is cached.
+  /// For non-mappable dataset, this should be set to true.
+  CacheService(uint64_t mem_sz, const std::string &root, bool generate_id);
+  ~CacheService();
+
+  /// \brief For fixed size memory, we will create an Arena.
+  /// \return false if unlimited memory.
+  bool UseArena();
+
+  Status DoServiceStart() override;
+  Status DoServiceStop() override;
+
+  /// \brief Main function to cache a row which is in form a series of buffers.
+  /// The first buffer is a Google flatbuffer which describes the rest of the buffers followed.
+  /// \param[in] buf Vector of buffer
+  /// \param[out] row_id_generated The row id assigned to this row if any
+  /// \return Status object
+  Status CacheRow(const std::vector<const void *> &buf, row_id_type *row_id_generated);
+  /// \brief Main function to fetch rows in batch. The output is a contiguous memory which will be decoded
+  /// by the CacheClient. Cache miss is not an error, and will be coded in the output to mark an empty row.
+  /// \param[in] v A vector of row id.
+  /// \param[out] out A contiguous memory buffer that holds the requested rows.
+  /// \return Status object
+  Status BatchFetch(const std::vector<row_id_type> &v, MemGuard<uint8_t> *out) const;
+
+  /// \brief Getter function
+  /// \return Spilling path
+  Path GetSpillPath() const;
+  /// \brief A structure returned from the cache server for statistics request.
+  class ServiceStat {
+   public:
+    using state_type = std::underlying_type<State>::type;
+    ServiceStat() : min_(0), max_(0), state_(0) {}
+    CachePool::CacheStat stat_{};
+    row_id_type min_;
+    row_id_type max_;
+    state_type state_;
+  };
+  /// \brief Statistics for the current service
+  /// \param[in/out] A pointer to a pre-allocated ServiceStat structure
+  /// \return Status Object
+  Status GetStat(ServiceStat *);
+  /// \brief Cache schema
+  /// \param buf A Google Flatbuffer that contains the schema
+  /// \param len size of the buffer
+  /// \return Status object
+  Status CacheSchema(const void *buf, int64_t len);
+  /// \brief Fetch schema
+  /// \param out A contiguous memory that contains the serialized form of schema.
+  /// \return Status object
+  Status FetchSchema(MemGuard<uint8_t> *out) const;
+  /// \brief Purge the content of a cache
+  /// \return Status object
+  Status Purge();
+  /// \brief Overload the << operator to print a cache service
+  /// \param out std::ostream
+  /// \param cs A cache service
+  /// \return std::ostream
+  friend std::ostream &operator<<(std::ostream &out, const CacheService &cs);
+  /// \brief Every cache service has a cookie. If the cookie of a CacheClient matches this cookie, this CacheClient
+  /// is the creator
+  /// \return Cookie
+  std::string cookie() const { return cookie_; }
+  /// \brief If this cache service generates row id for buffer cached, it is divided into two phases, a build phase and
+  /// a read phase.
+  /// \return True if has two phases.
+  bool HasBuildPhase() const { return generate_id_; }
+  /// \brief Change from write phase to read phase. Only the creator of this service is allowed to make this call.
+  /// \return Status object
+  Status BuildPhaseDone();
+
+ private:
+  mutable RWLock rw_lock_;
+  std::string root_;
+  uint64_t cache_mem_sz_;
+  std::shared_ptr<CachePool> cp_;
+  std::shared_ptr<row_map> map_;
+  std::atomic<row_id_type> next_id_;
+  bool generate_id_;
+  std::atomic<CachePool::key_type> schema_key_;
+  std::string cookie_;
+  State st_;
+
+  /// \brief Private function to generate a row id
+  /// \return Row id assigned.
+  row_id_type GetNextRowId() { return next_id_.fetch_add(1); }
+};
+}  // namespace dataset
+}  // namespace mindspore
+#endif  // DATASET_ENGINE_CACHE_SERVICE_H_

mindspore/ccsrc/dataset/engine/cache/de_tensor.fbs

@@ -0,0 +1,81 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+namespace mindspore.dataset;
+
+/// Type of a Tensor
+enum TensorType : byte {
+    DE_UNKNOWN = 0,
+    DE_BOOL = 1,
+    DE_INT8 = 2,
+    DE_UINT8 = 3,
+    DE_INT16 = 4,
+    DE_UINT16 = 5,
+    DE_INT32 = 6,
+    DE_UINT32 = 7,
+    DE_INT64 = 8,
+    DE_UINT64 = 9,
+    DE_FLOAT16 = 10,
+    DE_FLOAT32 = 11,
+    DE_FLOAT64 = 12,
+    DE_STRING = 13
+}
+
+/// The meta information of a Tensor
+/// \note Only the type and shape are considered meta information. Tensor data is excluded.
+table TensorMetaMsg {
+    dims:[int64] (required);
+    type:TensorType;
+}
+
+/// This is the first buffer that is sent to a Cache server when a TensorRow is serialized.
+/// \param row_id is the row id of the TensorRow.
+/// \param column The meta information of each Tensor in the row
+/// \param size of this serialized buffer
+/// \param size of each tensor data buffer that follows
+table TensorRowHeaderMsg {
+    row_id:int64;
+    column:[TensorMetaMsg] (required);
+    size_of_this:int64;
+    data_sz:[int64] (required);
+}
+
+root_type TensorRowHeaderMsg;
+
+/// A row of row id's
+table TensorRowIds {
+    row_id:[int64] (required);
+}
+
+/// Statistics returned from each cache service
+/// \note It must match CacheService::ServiceStat
+table ServiceStatMsg {
+    num_mem_cached:int64;
+    num_disk_cached:int64;
+    min_row_id:int64;
+    max_row_id:int64;
+    state:int8;
+}
+
+/// Column description of each column in a schema
+table ColumnNameMsg {
+    name:string;
+    id:int32;
+}
+
+/// Serialized form of a schema
+table SchemaMsg {
+    column:[ColumnNameMsg];
+}

mindspore/ccsrc/dataset/engine/data_buffer.cc

@@ -24,10 +24,8 @@ namespace dataset {
 // Description: This is the main constructor that is used for making a buffer
 DataBuffer::DataBuffer(int32_t id, BufferFlags flags) : buffer_id_(id), tensor_table_(nullptr), buffer_flags_(flags) {}
 
-// Name: print()
-// Description: A function that prints info about the DataBuffer (base class version)
-void DataBuffer::Print(std::ostream &out,      // In: The output stream to print to
-                       bool show_all) const {  // In: T/F if it should show everything
+// A method for debug printing of the buffer
+void DataBuffer::Print(std::ostream &out, bool show_all) const {
   out << "bufferId: " << buffer_id_ << "\nflags: " << std::hex << buffer_flags_ << std::dec << "\n";
 
   // If the column counts are set then it means that data has been set into
@@ -46,11 +44,6 @@ void DataBuffer::Print(std::ostream &out,      // In: The output stream to print
   }
 }
 
-Status DataBuffer::Load() {
-  std::string err_msg = "Base class load called, but it does not have an implementation!";
-  RETURN_STATUS_UNEXPECTED(err_msg);
-}
-
 // Remove me!! Callers should fetch rows via pop
 Status DataBuffer::GetTensor(std::shared_ptr<Tensor> *ptr, int32_t row_id, int32_t col_id) const {
   if (row_id < tensor_table_->size() && col_id < tensor_table_->at(row_id).size()) {
@@ -92,8 +85,5 @@ Status DataBuffer::SliceOff(int64_t number_of_rows) {
 
   return Status::OK();
 }
-
-// Destructor
-DataBuffer::~DataBuffer() {}
 }  // namespace dataset
 }  // namespace mindspore

mindspore/ccsrc/dataset/engine/data_buffer.h

@@ -29,11 +29,9 @@
 
 namespace mindspore {
 namespace dataset {
-// The DataBuffer class is a base class that will represent the data for n values based
-// on a unique row id for each row of data.
-// There can be different types of DataBuffers to abstract over how the data is stored
-// in memory and acquired from storage.
-// Each buffer holds a range of consecutive row id's.
+/// \brief The DataBuffer class is a container of tensor data and is the unit of transmission between
+///     connectors of dataset operators.  Inside the buffer, tensors are organized into a table-like format
+///     where n TensorRows may consist of m tensors (columns).
 class DataBuffer {
  public:
   // Buffer flags
@@ -47,13 +45,13 @@ class DataBuffer {
   // Description: This is the main constructor that is used for making a buffer
   DataBuffer(int32_t id, BufferFlags flags);
 
-  // Destructor
-  virtual ~DataBuffer();
+  /// \brief default destructor
+  ~DataBuffer() = default;
 
-  // Name: print()
-  // Description: A function that prints info about the DataBuffer (base class version)
-  virtual void Print(std::ostream &out,     // In: The output stream to print to
-                     bool show_all) const;  // In: T/F if it should show everything
+  /// \brief A method for debug printing of the buffer
+  /// \param[inout] out The stream to write to
+  /// \param[in] show_all A boolean to toggle between details and summary printing
+  void Print(std::ostream &out, bool show_all) const;
 
   // Provide stream operator for displaying it
   friend std::ostream &operator<<(std::ostream &out, const DataBuffer &cb) {
@@ -61,10 +59,6 @@ class DataBuffer {
     return out;
   }
 
-  // Name: load()
-  // Description: populates the DataBuffer with data based on it's id
-  virtual Status Load();
-
   // Convenience getter functions for flag checking
   bool eof() const { return (static_cast<uint32_t>(buffer_flags_) & static_cast<uint32_t>(kDeBFlagEOF)); }
 

mindspore/ccsrc/dataset/engine/datasetops/CMakeLists.txt

@@ -17,7 +17,11 @@ set(DATASET_ENGINE_DATASETOPS_SRC_FILES
     take_op.cc
     shuffle_op.cc
     zip_op.cc
-    concat_op.cc 
+    concat_op.cc
+    cache_base_op.cc
+    cache_lookup_op.cc
+    cache_op.cc
+    cache_merge_op.cc
     )
 
 if (ENABLE_PYTHON)

mindspore/ccsrc/dataset/engine/datasetops/cache_base_op.cc

@@ -0,0 +1,185 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "dataset/engine/datasetops/cache_base_op.h"
+#include <iomanip>
+#include <iostream>
+#include "dataset/engine/execution_tree.h"
+
+namespace mindspore {
+namespace dataset {
+// A print method typically used for debugging
+void CacheBase::Print(std::ostream &out, bool show_all) const {
+  // Always show the id and name as first line regardless if this summary or detailed print
+  out << "(" << std::setw(2) << operator_id_ << ") <" << Name() << ">:";
+  if (!show_all) {
+    // Call the super class for displaying any common 1-liner info
+    ParallelOp::Print(out, show_all);
+    out << "\n";
+  } else {
+    // Call the super class for displaying any common detailed info
+    ParallelOp::Print(out, show_all);
+    // Then show any custom derived-internal stuff
+    out << "\nCache client:\n" << *cache_client_ << "\n\n";
+  }
+}
+// Overrides base class reset method.  When an operator does a reset, it cleans up any state
+// info from it's previous execution and then initializes itself so that it can be executed
+// again.
+Status CacheBase::Reset() {
+  if (sampler_ != nullptr) {
+    RETURN_IF_NOT_OK(sampler_->ResetSampler());
+  }
+  // Wake up the workers to get them going again in a new epoch
+  MS_LOG(DEBUG) << Name() << " resetting.";
+  epoch_sync_.Set();
+  return Status::OK();
+}
+CacheBase::CacheBase(int32_t num_workers, int32_t op_connector_size, int32_t rows_per_buf,
+                     std::shared_ptr<CacheClient> cache_client, std::shared_ptr<Sampler> sampler)
+    : ParallelOp(num_workers, op_connector_size, sampler),
+      cache_client_(cache_client),
+      rows_per_buffer_(rows_per_buf),
+      // We can cause deadlock if this internal Connector size is too small.
+      keys_miss_(num_workers_, 1, 1024) {
+  io_block_queues_.Init(num_workers, op_connector_size);
+}
+// Common function to fetch samples from the sampler and send them using the io_block_queues to
+// the parallel workers
+Status CacheBase::FetchSamplesToWorkers() {
+  int64_t buf_cnt = 0;
+  int64_t wait_cnt = 0;
+  do {
+    epoch_sync_.Clear();
+    std::vector<row_id_type> keys;
+    int64_t row_cnt = 0;
+    keys.reserve(rows_per_buffer_);
+    std::unique_ptr<DataBuffer> sampler_buffer;
+    RETURN_IF_NOT_OK(sampler_->GetNextSample(&sampler_buffer));
+    while (!sampler_buffer->eoe()) {
+      TensorRow sample_row;
+      RETURN_IF_NOT_OK(sampler_buffer->PopRow(&sample_row));
+      std::shared_ptr<Tensor> sample_ids = sample_row[0];
+      for (auto itr = sample_ids->begin<int64_t>(); itr != sample_ids->end<int64_t>(); itr++) {
+        keys.push_back(*itr);
+        ++row_cnt;
+        if (row_cnt % rows_per_buffer_ == 0) {
+          auto blk = std::make_unique<IOBlock>(IOBlock(keys, IOBlock::kDeIoBlockNone));
+          RETURN_IF_NOT_OK(io_block_queues_[buf_cnt++ % num_workers_]->Add(std::move(blk)));
+          keys.clear();
+        }
+      }
+      RETURN_IF_NOT_OK(sampler_->GetNextSample(&sampler_buffer));
+    }
+    if (!keys.empty()) {
+      auto blk = std::make_unique<IOBlock>(IOBlock(keys, IOBlock::kDeIoBlockNone));
+      RETURN_IF_NOT_OK(io_block_queues_[buf_cnt++ % num_workers_]->Add(std::move(blk)));
+    }
+    // send the eoe
+    RETURN_IF_NOT_OK(
+      io_block_queues_[(buf_cnt++) % num_workers_]->Add(std::make_unique<IOBlock>(IOBlock::kDeIoBlockFlagEoe)));
+    // If repeat but the not last repeat, wait for reset.
+    if (BitTest(op_ctrl_flags_, kDeOpRepeated) && !BitTest(op_ctrl_flags_, kDeOpLastRepeat)) {
+      MS_LOG(DEBUG) << Name() << " Waiting for reset. Count " << ++wait_cnt << " Buffer sent " << buf_cnt;
+      RETURN_IF_NOT_OK(epoch_sync_.Wait());
+    } else {
+      // We can break out from the loop.
+      break;
+    }
+  } while (true);
+  // Flow the eof before exit
+  RETURN_IF_NOT_OK(
+    io_block_queues_[(buf_cnt++) % num_workers_]->Add(std::make_unique<IOBlock>(IOBlock::kDeIoBlockFlagEof)));
+  // Ask all the workers to quit.
+  for (int32_t i = 0; i < num_workers_; i++) {
+    RETURN_IF_NOT_OK(
+      io_block_queues_[i]->Add(std::make_unique<IOBlock>(std::vector<int64_t>(), IOBlock::kDeIoBlockNone)));
+  }
+  return Status::OK();
+}
+Status CacheBase::FetchFromCache(int32_t worker_id) {
+  int64_t buffer_id = worker_id;
+  std::unique_ptr<IOBlock> blk;
+  do {
+    RETURN_IF_NOT_OK(io_block_queues_[worker_id]->PopFront(&blk));
+    if (blk->eof()) {
+      RETURN_IF_NOT_OK(out_connector_->Add(worker_id, std::make_unique<DataBuffer>(0, DataBuffer::kDeBFlagEOF)));
+    } else if (blk->eoe()) {
+      if (AllowCacheMiss()) {
+        // This code path is for CacheLookupOp acting as a sampler. If we get a eoe from
+        // a sampler, send a eoe to physical leaf op as well.
+        std::vector<row_id_type> eoe;
+        eoe.push_back(eoe_row_id);
+        RETURN_IF_NOT_OK(keys_miss_.Push(worker_id, eoe));
+      }
+      RETURN_IF_NOT_OK(out_connector_->Add(worker_id, std::make_unique<DataBuffer>(0, DataBuffer::kDeBFlagEOE)));
+    } else {
+      std::vector<int64_t> keys;
+      RETURN_IF_NOT_OK(blk->GetKeys(&keys));
+      if (keys.empty()) {
+        // empty key is a quit signal for workers
+        break;
+      }
+      std::unique_ptr<DataBuffer> db = std::make_unique<DataBuffer>(buffer_id, DataBuffer::kDeBFlagNone);
+      std::unique_ptr<TensorQTable> que = std::make_unique<TensorQTable>();
+      TensorTable ttbl;
+      RETURN_IF_NOT_OK(cache_client_->GetRows(keys, &ttbl));
+      auto row_it = ttbl.begin();
+      std::vector<row_id_type> cache_miss;
+      cache_miss.reserve(keys.size());
+      for (auto row_id : keys) {
+        auto &row = *row_it;
+        if (row.empty()) {
+          if (AllowCacheMiss()) {
+            cache_miss.push_back(row_id);
+          } else {
+            std::string errMsg = "Row id " + std::to_string(row_id) + " not found.";
+            RETURN_STATUS_UNEXPECTED(errMsg);
+          }
+        }
+        que->push_back(std::move(row));
+        ++row_it;
+      }
+      db->set_tensor_table(std::move(que));
+      if (AllowCacheMiss()) {
+        // Because of the way connector works, we push unconditionally even cache_miss can be empty.
+        RETURN_IF_NOT_OK(keys_miss_.Push(worker_id, cache_miss));
+      }
+      RETURN_IF_NOT_OK(out_connector_->Add(worker_id, std::move(db)));
+      buffer_id += num_workers_;
+    }
+  } while (true);
+  return Status::OK();
+}
+Status CacheBase::RegisterResources() {
+  RETURN_IF_NOT_OK(epoch_sync_.Register(tree_->AllTasks()));
+  RETURN_IF_NOT_OK(io_block_queues_.Register(tree_->AllTasks()));
+  return Status::OK();
+}
+CacheBase::~CacheBase() {}
+Status CacheBase::UpdateColumnMapFromCache() {
+  Status rc;
+  // Get the schema from the server. It may not be there yet. So tolerate the error.
+  if (column_name_id_map_.empty()) {
+    rc = cache_client_->FetchSchema(&column_name_id_map_);
+    if (rc == Status(StatusCode::kFileNotExist)) {
+      MS_LOG(DEBUG) << "Schema not in the server yet.";
+      rc = Status::OK();
+    }
+  }
+  return rc;
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/datasetops/cache_base_op.h

@@ -0,0 +1,108 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef DATASET_ENGINE_DATASETOPS_CACHE_BASE_OP_H_
+#define DATASET_ENGINE_DATASETOPS_CACHE_BASE_OP_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+#include "dataset/engine/cache/cache_client.h"
+#include "dataset/engine/cache/cache_service.h"
+#include "dataset/engine/datasetops/parallel_op.h"
+#include "dataset/engine/datasetops/repeat_op.h"
+#include "dataset/engine/datasetops/source/io_block.h"
+#include "dataset/engine/datasetops/source/sampler/sampler.h"
+#include "dataset/engine/datasetops/source/sampler/sequential_sampler.h"
+#include "dataset/util/queue.h"
+#include "dataset/util/wait_post.h"
+#include "dataset/engine/datasetops/cache_base_op.h"
+namespace mindspore {
+namespace dataset {
+/// \brief This is the base class for CacheOp and CacheLookupOp which share many similarities.
+/// \see CacheOp
+/// \see CacheLookupOp
+class CacheBase : public ParallelOp {
+ public:
+  /// \brief Base class constructor
+  /// \param num_workers Number of parallel workers
+  /// \param op_connector_size Connector size
+  /// \param rows_per_buf Number of rows per buffer
+  /// \param cache_client CacheClient for communication to the CacheServer
+  /// \param sampler Sampler which is mandatory
+  CacheBase(int32_t num_workers, int32_t op_connector_size, int32_t rows_per_buf,
+            std::shared_ptr<CacheClient> cache_client, std::shared_ptr<Sampler> sampler);
+  /// \brief Destructor
+  ~CacheBase();
+
+  constexpr static int eoe_row_id = -1;
+
+  /// \brief Overrides base class reset method.  When an operator does a reset, it cleans up any state
+  /// info from it's previous execution and then initializes itself so that it can be executed
+  /// again.
+  /// \return Status - The error code return
+  Status Reset() override;
+
+  /// \brief A print method typically used for debugging
+  /// \param out The output stream to write output to
+  /// \param show_all A bool to control if you want to show all info or just a summary
+  void Print(std::ostream &out, bool show_all) const override;
+
+  /// \brief << Stream output operator overload
+  /// \notes This allows you to write the debug print info using stream operators
+  /// \param out reference to the output stream being overloaded
+  /// \param mo reference to the CacheOp to display
+  /// \return the output stream must be returned
+  friend std::ostream &operator<<(std::ostream &out, const CacheBase &mo) {
+    mo.Print(out, false);
+    return out;
+  }
+
+  /// \brief Getter for the cache client
+  /// \return shared ptr to the cache client
+  std::shared_ptr<CacheClient> cache_client() { return cache_client_; }
+  /// \brief Setter for the cache client
+  void SetCacheClient(std::shared_ptr<CacheClient> cache_client) { cache_client_ = std::move(cache_client); }
+  /// \brief Derived class must implement this method if a cache miss is treated as error
+  virtual bool AllowCacheMiss() = 0;
+
+ protected:
+  std::shared_ptr<CacheClient> cache_client_;
+  WaitPost epoch_sync_;
+  int32_t rows_per_buffer_;
+  Connector<std::vector<row_id_type>> keys_miss_;
+
+  /// \brief Common function to register resources for interrupt
+  /// \note Derived should override this function for extra resources to be registered
+  virtual Status RegisterResources();
+  /// \brief This function is called by main thread to send samples to the worker thread.
+  /// \note It is a non-virtual function
+  /// \return Status object
+  Status FetchSamplesToWorkers();
+  /// \brief This function is called by each worker to fetch rows from the cache server for a given set of
+  /// sample row id's
+  /// \return Status object
+  Status FetchFromCache(int32_t worker_id);
+  /// \brief Get the column map from cache server
+  Status UpdateColumnMapFromCache();
+
+ private:
+  QueueList<std::unique_ptr<IOBlock>> io_block_queues_;
+};
+}  // namespace dataset
+}  // namespace mindspore
+
+#endif  // DATASET_ENGINE_DATASETOPS_CACHE_BASE_OP_H_

mindspore/ccsrc/dataset/engine/datasetops/cache_lookup_op.cc

@@ -0,0 +1,130 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "dataset/engine/datasetops/cache_lookup_op.h"
+#include "dataset/engine/opt/pass.h"
+#include "dataset/core/config_manager.h"
+#include "dataset/core/constants.h"
+#include "dataset/core/global_context.h"
+#include "dataset/engine/execution_tree.h"
+#include "utils/log_adapter.h"
+#include "utils/system/crc32c.h"
+
+namespace mindspore {
+namespace dataset {
+// Builder constructor. Creates the builder object.
+CacheLookupOp::Builder::Builder() : build_cache_client_(nullptr), build_sampler_(nullptr) {
+  std::shared_ptr<ConfigManager> cfg = GlobalContext::config_manager();
+  build_num_workers_ = cfg->num_parallel_workers();
+  rows_per_buffer_ = cfg->rows_per_buffer();
+  build_op_connector_size_ = cfg->op_connector_size();
+}
+
+// Check if the required parameters are set by the builder.
+Status CacheLookupOp::Builder::SanityCheck() const {
+  if (build_cache_client_ == nullptr) {
+    return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, "CacheLookupOp requires a CacheClient");
+  }
+  // Make sure the cache client has a valid session
+  if (!build_cache_client_->session_id()) {
+    return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__,
+                  "Cache client for CacheLookupOp is missing session id");
+  }
+  return Status::OK();
+}
+
+// The builder "build" method creates the final object and does some init on it
+Status CacheLookupOp::Builder::Build(std::shared_ptr<CacheLookupOp> *ptr) {
+  RETURN_IF_NOT_OK(SanityCheck());
+  *ptr = std::make_shared<CacheLookupOp>(build_num_workers_, build_op_connector_size_, rows_per_buffer_,
+                                         build_cache_client_, build_sampler_);
+  return Status::OK();
+}
+Status CacheLookupOp::operator()() {
+  if (!sampler_) {
+    return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__,
+                  "CacheLookupOp requires a sampler before it can be executed!");
+  }
+  RETURN_IF_NOT_OK(RegisterResources());
+  // Kick off the workers
+  RETURN_IF_NOT_OK(
+    tree_->LaunchWorkers(num_workers_, std::bind(&CacheLookupOp::WorkerEntry, this, std::placeholders::_1)));
+  // required task group sync after launching workers
+  TaskManager::FindMe()->Post();
+  // We have to wait until the leaf op has handshake with us.
+  RETURN_IF_NOT_OK(leaf_op_wp_.Wait());
+  RETURN_IF_NOT_OK(FetchSamplesToWorkers());
+  return Status::OK();
+}
+Status CacheLookupOp::WorkerEntry(int32_t worker_id) {
+  TaskManager::FindMe()->Post();
+  RETURN_IF_NOT_OK(FetchFromCache(worker_id));
+  return Status::OK();
+}
+Status CacheLookupOp::ResetSampler() { return Status::OK(); }
+Status CacheLookupOp::HandshakeRandomAccessOp(const RandomAccessOp *op) {
+  // We act like a sampler and as a dataset op. During handshake with leaf op,
+  // We must wait until the leaf op has indexed everything.
+  RETURN_IF_NOT_OK(sampler_->HandshakeRandomAccessOp(op));
+  // Now we notify the main thread handshake has finished.
+  leaf_op_wp_.Set();
+  return Status::OK();
+}
+Status CacheLookupOp::InitSampler() { return Sampler::InitSampler(); }
+void CacheLookupOp::Print(std::ostream &out, bool show_all) const { CacheBase::Print(out, show_all); }
+Status CacheLookupOp::GetNextSample(std::unique_ptr<DataBuffer> *out_buffer) {
+  std::vector<row_id_type> cache_miss;
+  RETURN_IF_NOT_OK(keys_miss_.Pop(0, &cache_miss));
+  // Ignore the case we have no cache miss, we can't return empty samples.
+  while (cache_miss.empty()) {
+    RETURN_IF_NOT_OK(keys_miss_.Pop(0, &cache_miss));
+  }
+  // Special code for eoe
+  if (cache_miss.at(0) == eoe_row_id) {
+    *out_buffer = std::make_unique<DataBuffer>(0, DataBuffer::kDeBFlagEOE);
+  } else {
+    std::shared_ptr<Tensor> sample_ts;
+    RETURN_IF_NOT_OK(CreateSamplerTensor(&sample_ts, cache_miss.size()));
+    (*out_buffer) = std::make_unique<DataBuffer>(0, DataBuffer::kDeBFlagNone);
+    auto idPtr = sample_ts->begin<int64_t>();
+    for (auto i = 0; i < cache_miss.size(); ++i) {
+      *idPtr = cache_miss.at(i);
+      ++idPtr;
+    }
+    TensorRow row;
+    row.push_back(sample_ts);
+    (*out_buffer)->set_tensor_table(std::make_unique<TensorQTable>(1, row));
+  }
+  return Status::OK();
+}
+Status CacheLookupOp::RegisterResources() {
+  RETURN_IF_NOT_OK(CacheBase::RegisterResources());
+  RETURN_IF_NOT_OK(leaf_op_wp_.Register(tree_->AllTasks()));
+  return Status::OK();
+}
+Status CacheLookupOp::ComputeColMap() {
+  // We don't know the column map at this point unless we contact the cache server
+  // to fetch the schema but the cache server may not have it at this point either.
+  // So we will just return OK and let MergeOp (our parent) to handle it.
+  return Status::OK();
+}
+
+// Visitor accept method for NodePass
+Status CacheLookupOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<CacheLookupOp>(), modified);
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/datasetops/cache_lookup_op.h

@@ -0,0 +1,122 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef DATASET_ENGINE_DATASETOPS_CACHE_LOOKUP_OP_H_
+#define DATASET_ENGINE_DATASETOPS_CACHE_LOOKUP_OP_H_
+
+#include <atomic>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+#include "dataset/engine/datasetops/cache_base_op.h"
+
+namespace mindspore {
+namespace dataset {
+/// \brief provides a memory/disk cache that acts as a save-point within a mappable dataset.
+/// \note For non-mappable dataset, please see CacheOp
+/// \see CacheOp
+class CacheLookupOp : public CacheBase, public Sampler {
+ public:
+  class Builder {
+   public:
+    /// \brief Builder constructor. Creates the builder object.
+    /// \note No default args
+    Builder();
+
+    /// Default destructor
+    ~Builder() = default;
+
+    /// Setter method.
+    /// \treturn Builder setter method returns reference to the builder.
+    Builder &SetNumWorkers(int32_t num_workers) {
+      build_num_workers_ = num_workers;
+      return *this;
+    }
+
+    /// Setter method.
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetOpConnectorSize(int32_t connector_size) {
+      build_op_connector_size_ = connector_size;
+      return *this;
+    }
+
+    /// Setter method.
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetClient(std::shared_ptr<CacheClient> cache_client) {
+      build_cache_client_ = cache_client;
+      return *this;
+    }
+
+    /// \brief Setter method.
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetSampler(std::shared_ptr<Sampler> sampler) {
+      build_sampler_ = std::move(sampler);
+      return *this;
+    }
+
+    /// \brief The builder "build" method creates the final object and does some init on it.
+    /// \param ptr The shared_ptr to the new CacheLookupOp object
+    /// \return Status
+    Status Build(std::shared_ptr<CacheLookupOp> *ptr);
+
+   private:
+    int32_t build_num_workers_;
+    int32_t rows_per_buffer_;
+    int32_t build_op_connector_size_;
+    std::shared_ptr<CacheClient> build_cache_client_;
+    std::shared_ptr<Sampler> build_sampler_;
+
+    // Check if the required parameters are set by the builder.
+    // \return Status The error code return
+    Status SanityCheck() const;
+  };
+  /// \brief Constructor
+  /// \note It takes the same argument as the base class.
+  /// \see CacheBase
+  CacheLookupOp(int32_t num_workers, int32_t op_connector_size, int32_t rows_per_buf,
+                std::shared_ptr<CacheClient> cache_client, std::shared_ptr<Sampler> sampler)
+      : CacheBase(num_workers, op_connector_size, rows_per_buf, cache_client, sampler), Sampler(*(sampler.get())) {}
+  ~CacheLookupOp() = default;
+  // As a parallel op, we override these two functions
+  Status operator()() override;
+  Status WorkerEntry(int32_t worker_id) override;
+  // As a sampler, we override the following functions
+  Status ResetSampler() override;
+  Status HandshakeRandomAccessOp(const RandomAccessOp *op) override;
+  Status InitSampler() override;
+  Status GetNextSample(std::unique_ptr<DataBuffer> *out_buffer) override;
+  void Print(std::ostream &out, bool show_all) const override;
+  bool AllowCacheMiss() override { return true; }
+  std::string Name() const override { return "CacheLookupOp"; }
+
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p The node to visit
+  /// \param[out] modified Indicator if the node was modified
+  /// \return Status of the node visit
+  Status Accept(NodePass *p, bool *modified) override;
+
+ protected:
+  Status ComputeColMap() override;
+
+ private:
+  WaitPost leaf_op_wp_;
+
+  Status RegisterResources() override;
+};
+}  // namespace dataset
+}  // namespace mindspore
+
+#endif  // DATASET_ENGINE_DATASETOPS_CACHE_LOOKUP_OP_H_

mindspore/ccsrc/dataset/engine/datasetops/cache_merge_op.cc

@@ -0,0 +1,301 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <algorithm>
+#include <functional>
+#include <iomanip>
+#include "dataset/core/config_manager.h"
+#include "dataset/core/constants.h"
+#include "dataset/core/global_context.h"
+#include "dataset/engine/datasetops/cache_merge_op.h"
+#include "dataset/engine/opt/pass.h"
+#include "dataset/engine/execution_tree.h"
+#include "dataset/util/task_manager.h"
+
+namespace mindspore {
+namespace dataset {
+CacheMergeOp::~CacheMergeOp() = default;
+void CacheMergeOp::Print(std::ostream &out, bool show_all)
+  const {  // Always show the id and name as first line regardless if this is summary or detailed print
+  out << "(" << std::setw(2) << operator_id_ << ") <CacheMergeOp>:";
+  if (!show_all) {
+    // Call the super class for displaying any common 1-liner info
+    ParallelOp::Print(out, show_all);
+    // Then show any custom derived-internal 1-liner info for this op
+    out << "\n";
+  } else {
+    // Call the super class for displaying any common detailed info
+    ParallelOp::Print(out, show_all);
+    // Then show any custom derived-internal stuff
+    out << "\n\n";
+  }
+}
+CacheMergeOp::CacheMergeOp(int32_t numWorkers, int32_t opConnectorSize, int32_t numCleaners,
+                           std::shared_ptr<CacheClient> cache_client, const std::shared_ptr<Sampler> &sampler)
+    : ParallelOp(numWorkers, opConnectorSize, sampler), num_cleaners_(numCleaners), cache_client_(cache_client) {}
+Status CacheMergeOp::operator()() {
+  // A queue of row id to let cleaner send cache miss rows to the cache server
+  // We don't want a small queue as this will block the parallel op workers.
+  // A row id is 8 byte integer. So bigger size doesn't consume a lot of memory.
+  io_que_ = std::make_unique<Queue<row_id_type>>(512);
+  RETURN_IF_NOT_OK(io_que_->Register(tree_->AllTasks()));
+  RETURN_IF_NOT_OK(
+    tree_->LaunchWorkers(num_workers_, std::bind(&CacheMergeOp::WorkerEntry, this, std::placeholders::_1)));
+  RETURN_IF_NOT_OK(
+    tree_->LaunchWorkers(num_workers_, std::bind(&CacheMergeOp::CacheMissWorkerEntry, this, std::placeholders::_1)));
+  // One dedicated thread to move TensorRow from the pool to the cache server
+  for (auto i = 0; i < num_cleaners_; ++i) {
+    RETURN_IF_NOT_OK(tree_->AllTasks()->CreateAsyncTask("Cleaner", std::bind(&CacheMergeOp::Cleaner, this)));
+  }
+  TaskManager::FindMe()->Post();
+  return Status::OK();
+}
+// Each parallel worker will pop from the CacheHit stream. If there is a missing TensorRow, we will wait
+// until it shows up in the pool.
+Status CacheMergeOp::WorkerEntry(int32_t worker_id) {
+  TaskManager::FindMe()->Post();
+  std::shared_ptr<DatasetOp> cache_hit_stream = child_[kCacheHitChildIdx];
+  std::unique_ptr<DataBuffer> db_ptr;
+  RETURN_IF_NOT_OK(cache_hit_stream->GetNextBuffer(&db_ptr, worker_id));
+  while (!db_ptr->eof()) {
+    if (db_ptr->eoe()) {
+      RETURN_IF_NOT_OK(EoeReceived(worker_id));
+      db_ptr.reset();
+      RETURN_IF_NOT_OK(cache_hit_stream->GetNextBuffer(&db_ptr, worker_id));
+    } else {
+      // See if there is any missing row
+      auto tbl = std::make_unique<TensorQTable>();
+      while (db_ptr->NumRows() > 0) {
+        TensorRow row;
+        RETURN_IF_NOT_OK(db_ptr->PopRow(&row));
+        if (row.empty()) {
+          auto row_id = row.getId();
+          TensorRowRequest *rq = nullptr;
+          RETURN_IF_NOT_OK(GetRq(row_id, &rq));
+          // Block until the row shows up in the pool.
+          RETURN_IF_NOT_OK(rq->Wait(&row));
+        }
+        tbl->push_back(std::move(row));
+      }
+      db_ptr->set_tensor_table(std::move(tbl));
+      RETURN_IF_NOT_OK(out_connector_->Add(worker_id, std::move(db_ptr)));
+      RETURN_IF_NOT_OK(cache_hit_stream->GetNextBuffer(&db_ptr, worker_id));
+    }
+  }
+  RETURN_IF_NOT_OK(out_connector_->Add(worker_id, std::move(db_ptr)));
+  return Status::OK();
+}
+Status CacheMergeOp::CacheMissWorkerEntry(int32_t workerId) {
+  TaskManager::FindMe()->Post();
+  // We will simply pop TensorRow from the stream and insert them into the pool and
+  // wake up any worker that is awaiting on the missing TensorRow.
+  // If we see an eoe, ignore it. For eof, we exit.
+  std::shared_ptr<DatasetOp> cache_missing_stream = child_[kCacheMissChildIdx];
+  // Before we start, cache the schema at the server. Pick one of the workers
+  // do it. The schema should have been done at prepare time.
+  if (workerId == 0) {
+    RETURN_IF_NOT_OK(cache_client_->CacheSchema(column_name_id_map()));
+  }
+  std::unique_ptr<DataBuffer> db_ptr;
+  RETURN_IF_NOT_OK(cache_missing_stream->GetNextBuffer(&db_ptr, workerId));
+  while (!db_ptr->eof()) {
+    if (db_ptr->eoe()) {
+      // Ignore it.
+      MS_LOG(DEBUG) << "Ignore eoe";
+    } else {
+      while (db_ptr->NumRows() > 0) {
+        TensorRow row;
+        RETURN_IF_NOT_OK(db_ptr->PopRow(&row));
+        row_id_type row_id = row.getId();
+        if (row_id < 0) {
+          std::string errMsg = "Expect positive row id: " + std::to_string(row_id);
+          RETURN_STATUS_UNEXPECTED(errMsg);
+        }
+        TensorRowRequest *rq = nullptr;
+        RETURN_IF_NOT_OK(GetRq(row_id, &rq));
+        rq->WakeUpAny(std::move(row));
+        // Let the cleaner to flush out this row (async) to the cache server.
+        RETURN_IF_NOT_OK(io_que_->EmplaceBack(row_id));
+      }
+    }
+    RETURN_IF_NOT_OK(cache_missing_stream->GetNextBuffer(&db_ptr, workerId));
+  }
+  return Status::OK();
+}
+Status CacheMergeOp::Cleaner() {
+  TaskManager::FindMe()->Post();
+  while (true) {
+    row_id_type row_id;
+    RETURN_IF_NOT_OK(io_que_->PopFront(&row_id));
+    if (row_id < 0) {
+      break;
+    }
+    TensorRowRequest *rq = nullptr;
+    RETURN_IF_NOT_OK(GetRq(row_id, &rq));
+    if (rq->GetState() == TensorRowRequest::State::kClean) {
+      // If already flushed, move on to the next one.
+      continue;
+    }
+    TensorRow row;
+    RETURN_IF_NOT_OK(rq->Release(&row));
+    CHECK_FAIL_RETURN_UNEXPECTED(!row.empty(), "Programming error");
+    Status rc = cache_client_->WriteRow(row);
+    // Bad rc should not bring down the pipeline
+    if (rc.IsError()) {
+      MS_LOG(WARNING) << "Cache not successful." << rc.ToString();
+    }
+    rq->SetState(TensorRowRequest::State::kClean);
+  }
+  return Status::OK();
+}
+
+Status CacheMergeOp::GetRq(row_id_type row_id, CacheMergeOp::TensorRowRequest **out) {
+  RETURN_UNEXPECTED_IF_NULL(out);
+  std::unique_lock<std::mutex> lck(mux_);
+  auto it = cache_miss_map_.find(row_id);
+  if (it != cache_miss_map_.end()) {
+    *out = it->second.GetMutablePointer();
+  } else {
+    // We will create a new one.
+    auto alloc = Services::GetAllocator<TensorRowRequest>();
+    auto r = cache_miss_map_.emplace(row_id, MemGuard<TensorRowRequest, Allocator<TensorRowRequest>>(alloc));
+    if (r.second) {
+      auto &mem = r.first->second;
+      RETURN_IF_NOT_OK(mem.allocate(1, row_id));
+      *out = mem.GetMutablePointer();
+    } else {
+      RETURN_STATUS_UNEXPECTED("Map insert fail.");
+    }
+  }
+  return Status::OK();
+}
+Status CacheMergeOp::PrepareNodePostAction() {  // Run any common code from super class first before adding our own
+                                                // specific logic
+  CHECK_FAIL_RETURN_UNEXPECTED(child_.size() == 2, "Incorrect number of children");
+  RETURN_IF_NOT_OK(ParallelOp::PrepareNodePostAction());
+  // Get the computed check sum from all ops in the cache miss class
+  uint32_t cache_crc = DatasetOp::GenerateCRC(child_[kCacheMissChildIdx]);
+  // This is a mappable cache op so the id's need to be generated.
+  // Construct the cache
+  const bool generate_ids = false;
+  Status rc = cache_client_->CreateCache(cache_crc, generate_ids);
+  if (rc.get_code() == StatusCode::kDuplicateKey) {
+    // We are told the cache has been created already.
+    MS_LOG(INFO) << "Cache created already";
+    rc = Status::OK();
+  }
+  RETURN_IF_NOT_OK(rc);
+  return Status::OK();
+}
+Status CacheMergeOp::ComputeColMap() {
+  CHECK_FAIL_RETURN_UNEXPECTED(child_[kCacheMissChildIdx] != nullptr, "Cache miss stream empty");
+  if (column_name_id_map().empty()) {
+    column_name_id_map_ = child_[kCacheMissChildIdx]->column_name_id_map();
+  }
+  CHECK_FAIL_RETURN_UNEXPECTED(!column_name_id_map().empty(), "No column map detected");
+  return Status::OK();
+}
+Status CacheMergeOp::TensorRowRequest::Wait(TensorRow *out) {
+  RETURN_UNEXPECTED_IF_NULL(out);
+  // Block until the missing row is in the pool.
+  RETURN_IF_NOT_OK(use_count_.P());
+  std::unique_lock<std::mutex> lck(dq_mux_);
+  CHECK_FAIL_RETURN_UNEXPECTED(!row_.empty(), "Programming error");
+  *out = std::move(row_.front());
+  row_.pop_front();
+  return Status::OK();
+}
+void CacheMergeOp::TensorRowRequest::WakeUpAny(TensorRow &&row) {
+  std::unique_lock<std::mutex> lck(dq_mux_);
+  // Technically number of this row shows up in the cache miss stream is equal to the number
+  // of P() call. However the cleaner wants it too. So we need an extra copy.
+  if (GetState() == State::kEmpty) {
+    // We will do a deep copy
+    for (auto &ts : row) {
+      auto out_ts = std::make_shared<Tensor>(ts->shape(), ts->type(), ts->GetBuffer(), ts->SizeInBytes());
+      cleaner_copy_.push_back(out_ts);
+    }
+    cleaner_copy_.setId(row.getId());
+    // Change the state to dirty
+    SetState(State::kDirty);
+  }
+  row_.push_back(std::move(row));
+  // Bump up the use count by 1. This wake up any parallel worker which is waiting
+  // for this row.
+  use_count_.V();
+}
+Status CacheMergeOp::TensorRowRequest::Release(TensorRow *out) {
+  RETURN_UNEXPECTED_IF_NULL(out);
+  // We are not holding any mutex here because the cleaner isn't really touching the deque row_.
+  // In case we have multiple cleaners and they all see the copy, only one of them will
+  // get it.
+  auto expected = State::kDirty;
+  if (st_.compare_exchange_strong(expected, State::kClean)) {
+    *out = std::move(cleaner_copy_);
+  }
+  return Status::OK();
+}
+// Builder constructor. Creates the builder object.
+CacheMergeOp::Builder::Builder() : build_cache_client_(nullptr), build_sampler_(nullptr) {
+  std::shared_ptr<ConfigManager> cfg = GlobalContext::config_manager();
+  build_num_workers_ = cfg->num_parallel_workers();
+  build_op_connector_size_ = cfg->op_connector_size();
+  build_num_cleaners_ = 1;
+}
+
+// Check if the required parameters are set by the builder.
+Status CacheMergeOp::Builder::SanityCheck() const {
+  if (build_cache_client_ == nullptr) {
+    return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, "CacheMergeOp requires a CacheClient");
+  }
+  // Make sure the cache client has a valid session
+  if (!build_cache_client_->session_id()) {
+    return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__,
+                  "Cache client for CacheMergeOp is missing session id");
+  }
+  return Status::OK();
+}
+
+// The builder "build" method creates the final object and does some init on it
+Status CacheMergeOp::Builder::Build(std::shared_ptr<CacheMergeOp> *ptr) {
+  RETURN_IF_NOT_OK(SanityCheck());
+  *ptr = std::make_shared<CacheMergeOp>(build_num_workers_, build_op_connector_size_, build_num_cleaners_,
+                                        build_cache_client_, build_sampler_);
+  return Status::OK();
+}
+
+// Pre-Visitor accept method for NodePass
+Status CacheMergeOp::PreAccept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call the pre-visitation
+  return p->PreRunOnNode(shared_from_base<CacheMergeOp>(), modified);
+}
+
+// Visitor accept method for NodePass
+Status CacheMergeOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<CacheMergeOp>(), modified);
+}
+
+Status CacheMergeOp::EoeReceived(int32_t worker_id) {
+  // If we are in a repeat path, send the eoe up.
+  // Otherwise ignore it.
+  if (BitTest(op_ctrl_flags_, kDeOpRepeated)) {
+    return DatasetOp::EoeReceived(worker_id);
+  }
+  return Status::OK();
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/datasetops/cache_merge_op.h

@@ -0,0 +1,196 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef DATASET_ENGINE_DATASETOPS_CACHE_MERGE_OP_H_
+#define DATASET_ENGINE_DATASETOPS_CACHE_MERGE_OP_H_
+
+#include <atomic>
+#include <deque>
+#include <map>
+#include <memory>
+#include <mutex>
+#include <string>
+#include <utility>
+#include "dataset/core/tensor_row.h"
+#include "dataset/engine/cache/cache_client.h"
+#include "dataset/engine/datasetops/parallel_op.h"
+#include "dataset/engine/dataset_iterator.h"
+#include "dataset/util/queue.h"
+#include "dataset/util/semaphore.h"
+
+namespace mindspore {
+namespace dataset {
+/// \brief Provides method to merge two streams (one from CacheLookup and one from cache miss stream) into one single
+/// stream
+class CacheMergeOp : public ParallelOp {
+ public:
+  // Some handshake structures among the main thread, cleaner threads and parallel op threads.
+  class TensorRowRequest {
+   public:
+    enum class State : uint8_t {
+      kEmpty = 0,  // No row in the deque
+      kDirty = 1,  // Cleaner hasn't flushed it to the cache server yet.
+      kClean = 2   // The row has been flushed already.
+    };
+    explicit TensorRowRequest(row_id_type id) : st_(State::kEmpty), use_count_(0) {}
+    ~TensorRowRequest() = default;
+    State GetState() const { return st_; }
+    void SetState(State newState) { st_ = newState; }
+    Status Wait(TensorRow *out);
+    void WakeUpAny(TensorRow &&row);
+    Status Release(TensorRow *out);
+
+   private:
+    std::mutex dq_mux_;
+    std::atomic<State> st_;
+    Semaphore use_count_;
+    std::deque<TensorRow> row_;
+    TensorRow cleaner_copy_;
+  };
+
+  constexpr static int kCacheHitChildIdx = 0;   // Cache hit stream
+  constexpr static int kCacheMissChildIdx = 1;  // Cache miss stream
+
+  /// \brief The nested builder class inside of the CacheMergeOp is used to help manage all of
+  /// the arguments for constructing it.  Use the builder by setting each argument
+  /// with the provided set methods, and then finally call the build method to execute
+  /// the actual construction.
+  class Builder {
+   public:
+    /// Builder constructor. Creates the builder object.
+    /// \note No default args
+    Builder();
+
+    /// Default destructor
+    ~Builder() = default;
+
+    /// Setter method.
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetNumWorkers(int32_t num_workers) {
+      build_num_workers_ = num_workers;
+      return *this;
+    }
+
+    /// Setter method.
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetOpConnectorSize(int32_t connector_size) {
+      build_op_connector_size_ = connector_size;
+      return *this;
+    }
+
+    /// Setter method.
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetClient(std::shared_ptr<CacheClient> cache_client) {
+      build_cache_client_ = cache_client;
+      return *this;
+    }
+
+    /// \brief Setter method
+    /// \param sampler
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetSampler(std::shared_ptr<Sampler> sampler) {
+      build_sampler_ = std::move(sampler);
+      return *this;
+    }
+
+    /// \brief Setter method
+    /// \param num_cleaners
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetNumCleaner(int32_t num_cleaners) {
+      build_num_cleaners_ = num_cleaners;
+      return *this;
+    }
+
+    /// The builder "build" method creates the final object and does some init on it.
+    /// \param ptr The shared_ptr to the new CacheMergeOp object
+    /// \return Status
+    Status Build(std::shared_ptr<CacheMergeOp> *ptr);
+
+   private:
+    int32_t build_num_workers_;
+    int32_t build_op_connector_size_;
+    int32_t build_num_cleaners_;
+    std::shared_ptr<CacheClient> build_cache_client_;
+    std::shared_ptr<Sampler> build_sampler_;
+
+    /// Check if the required parameters are set by the builder.
+    /// \return Status The error code return
+    Status SanityCheck() const;
+  };
+
+  /// \brief Constructor
+  /// \param numWorkers Number of parallel workers as a derived class of ParallelOp
+  /// \param opConnector Size Connector size as a derived class of ParallelOp
+  /// \param numCleaners Number of cleaners to move cache miss rows into the cache server
+  /// \param cache_client CacheClient to commmunicate with the Cache server
+  /// \param sampler as a derived class of ParallelOp
+  CacheMergeOp(int32_t numWorkers, int32_t opConnectorSize, int32_t numCleaners,
+               std::shared_ptr<CacheClient> cache_client, const std::shared_ptr<Sampler> &sampler);
+  ~CacheMergeOp();
+  void Print(std::ostream &out, bool show_all) const override;
+  friend std::ostream &operator<<(std::ostream &out, const CacheMergeOp &mo) {
+    mo.Print(out, false);
+    return out;
+  }
+  /// \brief Master thread responsible to spawn all the necessary worker threads for the two streams and
+  /// the threads for the cleaners.
+  /// \return
+  Status operator()() override;
+  /// \brief Entry function for worker thread that fetch rows from CacheLookupOp
+  /// \param workerId
+  /// \return Status object
+  Status WorkerEntry(int32_t workerId) override;
+  Status PrepareNodePostAction() override;
+  /// \brief Entry function for worker thread that fetch rows from the cache miss stream
+  /// \param workerId
+  /// \return Status object
+  Status CacheMissWorkerEntry(int32_t workerId);
+  Status GetRq(row_id_type row_id, TensorRowRequest **);
+
+  /// \brief Base-class override for NodePass pre-visit acceptor
+  /// \param[in] p The node to visit
+  /// \param[out] modified Indicator if the node was modified
+  /// \return Status of the node visit
+  Status PreAccept(NodePass *p, bool *modified) override;
+
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p The node to visit
+  /// \param[out] modified Indicator if the node was modified
+  /// \return Status of the node visit
+  Status Accept(NodePass *p, bool *modified) override;
+
+  /// \brief Base-class override for eoe handling
+  /// \param worker_id
+  /// \return Status object
+  Status EoeReceived(int32_t worker_id) override;
+
+ protected:
+  Status ComputeColMap() override;
+
+ private:
+  std::mutex mux_;
+  std::map<row_id_type, MemGuard<TensorRowRequest, Allocator<TensorRowRequest>>> cache_miss_map_;
+  std::unique_ptr<Queue<row_id_type>> io_que_;
+  std::shared_ptr<CacheClient> cache_client_;
+  int32_t num_cleaners_;
+
+  /// \brief These are the entry functions for the cleaner threads. Each cleaner is responsible for
+  /// moving cache miss TensorRow into the CacheServer.
+  /// \return Status object
+  Status Cleaner();
+};
+}  // namespace dataset
+}  // namespace mindspore
+#endif  // DATASET_ENGINE_DATASETOPS_CACHE_MERGE_OP_H_

mindspore/ccsrc/dataset/engine/datasetops/cache_op.cc

@@ -0,0 +1,219 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "dataset/engine/datasetops/cache_op.h"
+
+#include <memory>
+#include <vector>
+#include "dataset/core/config_manager.h"
+#include "dataset/core/constants.h"
+#include "dataset/core/global_context.h"
+#include "dataset/engine/datasetops/repeat_op.h"
+#include "dataset/engine/data_buffer.h"
+#include "dataset/engine/execution_tree.h"
+#include "dataset/engine/opt/pass.h"
+#include "dataset/util/task_manager.h"
+#include "utils/log_adapter.h"
+
+namespace mindspore {
+namespace dataset {
+// Builder constructor. Creates the builder object.
+CacheOp::Builder::Builder() : build_cache_client_(nullptr), build_sampler_(nullptr) {
+  std::shared_ptr<ConfigManager> cfg = GlobalContext::config_manager();
+  build_num_workers_ = cfg->num_parallel_workers();
+  rows_per_buffer_ = cfg->rows_per_buffer();
+  build_op_connector_size_ = cfg->op_connector_size();
+}
+
+// Check if the required parameters are set by the builder.
+Status CacheOp::Builder::SanityCheck() const {
+  if (build_cache_client_ == nullptr) {
+    return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, "CacheOp requires a CacheClient");
+  }
+  // Make sure the cache client has a valid session
+  if (!build_cache_client_->session_id()) {
+    return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__, "Cache client for CacheOp is missing session id");
+  }
+  return Status::OK();
+}
+
+// The builder "build" method creates the final object and does some init on it
+Status CacheOp::Builder::Build(std::shared_ptr<CacheOp> *ptr) {
+  RETURN_IF_NOT_OK(SanityCheck());
+  *ptr = std::make_shared<CacheOp>(build_num_workers_, build_op_connector_size_, rows_per_buffer_, build_cache_client_,
+                                   build_sampler_);
+  RETURN_IF_NOT_OK((*ptr)->InitCache());
+
+  return Status::OK();
+}
+
+// Constructor of CacheOp
+CacheOp::CacheOp(int32_t num_workers, int32_t op_connector_size, int32_t rows_per_buf,
+                 std::shared_ptr<CacheClient> cache_client, std::shared_ptr<Sampler> sampler)
+    : CacheBase(num_workers, op_connector_size, rows_per_buf, cache_client, sampler),
+      num_guys_in_(0),
+      phase_(Phase::kBuildPhase) {}
+
+// Destructor
+CacheOp::~CacheOp() = default;
+
+// Private function for cache setup/init work just after construction
+Status CacheOp::InitCache() { return Status::OK(); }
+
+// This class functor will provide the master loop that drives the logic for performing the work
+Status CacheOp::operator()() {
+  if (!sampler_) {
+    return Status(StatusCode::kUnexpectedError, __LINE__, __FILE__,
+                  "CacheOp requires a sampler before it can be executed!");
+  }
+  RETURN_IF_NOT_OK(RegisterResources());
+  // Kick off the workers
+  RETURN_IF_NOT_OK(tree_->LaunchWorkers(num_workers_, std::bind(&CacheOp::WorkerEntry, this, std::placeholders::_1)));
+  // required task group sync after launching workers
+  TaskManager::FindMe()->Post();
+  // Wait for the workers to finish caching the rows.
+  RETURN_IF_NOT_OK(WaitForCachingAllRows());
+  RETURN_IF_NOT_OK(FetchSamplesToWorkers());
+  return Status::OK();
+}
+Status CacheOp::CacheAllRows(int32_t worker_id) {
+  // If the current phase is to fill the cache, do it then.
+  if (phase_ == Phase::kBuildPhase) {
+    // We will take the chance to cache the schema at the server.
+    // Just do it once and pick one worker to do it.
+    if (worker_id == 0) {
+      RETURN_IF_NOT_OK(cache_client_->CacheSchema(column_name_id_map()));
+    }
+    MS_LOG(INFO) << "CacheOp first epoch SAVE mode started. Worker: " << worker_id;
+    // SAVE mode loop
+    std::unique_ptr<DataBuffer> db_ptr;
+    RETURN_IF_NOT_OK(this->GetNextInput(&db_ptr, worker_id, 0));
+    while (!db_ptr->eof()) {
+      if (!db_ptr->eoe()) {
+        RETURN_IF_NOT_OK(cache_client_->WriteBuffer(std::move(db_ptr)));
+      } else {
+        // In a repeat-over-cache scenario, any of the "real" leaf operators below us have been set up
+        // as non-repeating leaf ops.  As such, they only do one epoch and then quit.  Since we got the
+        // the eoe to indicate the end of the epoch, we should next expect to get the eof.
+        // Drain this eof so that we don't leave it sitting there on a connector that we'll never fetch
+        // from again.
+        RETURN_IF_NOT_OK(this->GetNextInput(&db_ptr, worker_id, 0));
+        if (!db_ptr->eof()) {
+          RETURN_STATUS_UNEXPECTED("Cache op expects to get an eof after eoe from child.");
+        }
+      }
+      RETURN_IF_NOT_OK(this->GetNextInput(&db_ptr, worker_id, 0));
+    }
+  }
+  // Let the main guy know we are done.
+  auto last_guy_in = num_guys_in_.fetch_add(1);
+  if ((last_guy_in + 1) == num_workers_) {
+    rows_cache_done_.Set();
+  } else {
+    // Let's do a sync up here.
+    RETURN_IF_NOT_OK(rows_cache_done_.Wait());
+  }
+  return Status::OK();
+}
+Status CacheOp::WaitForCachingAllRows() {
+  // Wait for the workers to finish caching the rows.
+  RETURN_IF_NOT_OK(rows_cache_done_.Wait());
+  // Move from build phase to fetch phase if we are the one to fill the cache
+  if (phase_ == Phase::kBuildPhase) {
+    RETURN_IF_NOT_OK(cache_client_->BuildPhaseDone());
+    // Move to the next phase
+    phase_ = Phase::kFetchPhase;
+  }
+  // Get statistics from the server, and if we are not the one to create the cache,
+  // wait until the state changed from build phase to fetch base.
+  CacheClient::ServiceStat stat{};
+  bool BuildPhaseDone = true;
+  do {
+    RETURN_IF_NOT_OK(cache_client_->GetStat(&stat));
+    BuildPhaseDone = stat.cache_service_state == static_cast<uint8_t>(CacheService::State::kFetchPhase);
+    if (!BuildPhaseDone) {
+      std::this_thread::sleep_for(std::chrono::milliseconds(100));
+    }
+  } while (!BuildPhaseDone);
+  const row_id_type min_key = stat.min_row_id;
+  const row_id_type max_key = stat.max_row_id;
+  num_rows_ = max_key - min_key + 1;
+  MS_LOG(INFO) << "Number of rows cached: " << num_rows_;
+  MS_LOG(INFO) << "Number of rows cached in memory : " << stat.num_mem_cached;
+  MS_LOG(INFO) << "Number of rows spilled to disk : " << stat.num_disk_cached;
+  // Now all rows are cached and we have done a sync point check up. Next phase is
+  // is pick up fetch input from sampler and pass up to the caller.
+  RETURN_IF_NOT_OK(sampler_->HandshakeRandomAccessOp(this));
+  return Status::OK();
+}
+Status CacheOp::WorkerEntry(int32_t worker_id) {
+  TaskManager::FindMe()->Post();
+  RETURN_IF_NOT_OK(CacheAllRows(worker_id));
+  RETURN_IF_NOT_OK(FetchFromCache(worker_id));
+  return Status::OK();
+}
+Status CacheOp::RegisterResources() {
+  RETURN_IF_NOT_OK(CacheBase::RegisterResources());
+  RETURN_IF_NOT_OK(rows_cache_done_.Register(tree_->AllTasks()));
+  RETURN_IF_NOT_OK(keys_miss_.Register(tree_->AllTasks()));
+  return Status::OK();
+}
+
+// Base-class override for setting specific CacheOp configurations. This code will be called
+// during the execution tree prepare phase BEFORE traversing down to child operators.
+uint32_t CacheOp::PrepareFlags() const { return ExecutionTree::kDePrepCache; }
+// Base-class override for special eoe handler.
+// CacheOp must override this because it shall not perform default handling of eoe. Instead
+// the CacheOp manages actions related to the end of the epoch.
+Status CacheOp::EoeReceived(int32_t worker_id) {
+  state_ = OpState::kDeOpIdle;
+  return Status::OK();
+}
+// Base-class override for handling cases when an eof is received.
+Status CacheOp::EofReceived(int32_t worker_id) {
+  // eofReceived is overloaded because we want to manually handle this eof.
+  // Specifically, the default behaviour is to pack it and flow it up to the next connection.
+  // In this case, we want a no-op behaviour so that we can perform correct action.
+  return Status::OK();
+}
+
+// Pre-Visitor accept method for NodePass
+Status CacheOp::PreAccept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call the pre-visitation
+  return p->PreRunOnNode(shared_from_base<CacheOp>(), modified);
+}
+
+// Visitor accept method for NodePass
+Status CacheOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<CacheOp>(), modified);
+}
+
+// A public wrapper for creating the cache through the client
+Status CacheOp::CreateCache(uint32_t cache_crc) {
+  // This is a non-mappable cache op so the id's need to be generated.
+  // Construct the cache
+  const bool generate_ids = true;
+  Status rc = cache_client_->CreateCache(cache_crc, generate_ids);
+  if (rc.get_code() == StatusCode::kDuplicateKey) {
+    // We are told the cache has been created already. So we skip the build phase.
+    phase_ = Phase::kFetchPhase;
+    rc = Status::OK();
+  }
+  RETURN_IF_NOT_OK(rc);
+  return Status::OK();
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/datasetops/cache_op.h

@@ -0,0 +1,168 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef DATASET_ENGINE_DATASETOPS_CACHE_OP_H_
+#define DATASET_ENGINE_DATASETOPS_CACHE_OP_H_
+
+#include <atomic>
+#include <string>
+#include <utility>
+#include <memory>
+#include "dataset/engine/datasetops/cache_base_op.h"
+
+namespace mindspore {
+namespace dataset {
+/// \brief CacheOp provides a memory/disk cache that acts as a save-point within a non-mappable dataset.
+/// \note For mappable dataset, please see CacheLookupOp.
+/// \see CacheLookupOp
+class CacheOp : public CacheBase, public RandomAccessOp {
+ public:
+  // This CacheOp is for non-mappable case where it is divided into two phases.
+  // The first phase is we cache all the rows from the child (and let the cache server
+  // assigns row id). No read access in the first phase. Once the cache is fully built,
+  // we switch to second phase and fetch requests from the sampler.
+  enum class Phase : uint8_t { kBuildPhase = 0, kFetchPhase = 1 };
+
+  /// \brief The nested builder class inside of the CacheOp is used to help manage all of
+  /// the arguments for constructing it.  Use the builder by setting each argument
+  /// with the provided set methods, and then finally call the build method to execute
+  /// the actual construction.
+  class Builder {
+   public:
+    // Builder constructor. Creates the builder object.
+    // @note No default args
+    // @return This is a constructor.
+    Builder();
+
+    // Default destructor
+    ~Builder() = default;
+
+    /// \brief Setter method.
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetNumWorkers(int32_t num_workers) {
+      build_num_workers_ = num_workers;
+      return *this;
+    }
+
+    /// \brief Setter method.
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetOpConnectorSize(int32_t connector_size) {
+      build_op_connector_size_ = connector_size;
+      return *this;
+    }
+
+    /// Setter method.
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetClient(std::shared_ptr<CacheClient> cache_client) {
+      build_cache_client_ = cache_client;
+      return *this;
+    }
+
+    /// \brief Setter method
+    /// \param rows_per_buffer
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetRowsPerBuffer(int32_t rows_per_buffer) {
+      rows_per_buffer_ = rows_per_buffer;
+      return *this;
+    }
+
+    /// \brief Setter method
+    /// \param sampler
+    /// \return Builder setter method returns reference to the builder.
+    Builder &SetSampler(std::shared_ptr<Sampler> sampler) {
+      build_sampler_ = std::move(sampler);
+      return *this;
+    }
+
+    /// \brief The builder "build" method creates the final object and does some init on it.
+    /// \param ptr The shared_ptr to the new CacheOp object
+    /// \return Status
+    Status Build(std::shared_ptr<CacheOp> *ptr);
+
+   private:
+    int32_t build_num_workers_;
+    int32_t rows_per_buffer_;
+    int32_t build_op_connector_size_;
+    std::shared_ptr<CacheClient> build_cache_client_;
+    std::shared_ptr<Sampler> build_sampler_;
+
+    /// \brief Check if the required parameters are set by the builder.
+    /// \return Status The error code return
+    Status SanityCheck() const;
+  };
+
+  /// \brief Constructor of CacheOp
+  /// \note The builder class should be used to call it.
+  /// \param num_workers The number of worker threads.
+  /// \param op_connector_size The size of each queue in the connector.
+  CacheOp(int32_t num_workers, int32_t op_connector_size, int32_t rows_per_buf,
+          std::shared_ptr<CacheClient> cache_client, std::shared_ptr<Sampler> sampler);
+
+  // Destructor
+  ~CacheOp();
+
+  /// \brief Base-class override for setting specific CacheOp configurations. This code will be called
+  /// during the execution tree prepare phase BEFORE traversing down to child operators.
+  uint32_t PrepareFlags() const override;
+  /// \brief Base-class override for special eoe handler.
+  /// CacheOp must override this because it shall not perform default handling of eoe. Instead
+  /// the CacheOp manages actions related to the end of the epoch.
+  /// \return Status - The error code return
+  Status EoeReceived(int32_t worker_id) override;
+  /// \brief Base-class override for NodePass pre-visit acceptor
+  /// \param[in] p The node to visit
+  /// \param[out] modified Indicator if the node was modified
+  /// \return Status of the node visit
+  Status PreAccept(NodePass *p, bool *modified) override;
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p The node to visit
+  /// \param[out] modified Indicator if the node was modified
+  /// \return Status of the node visit
+  Status Accept(NodePass *p, bool *modified) override;
+  /// \brief Base-class override for handling cases when an eof is received.
+  /// \param worker_id - The worker id
+  /// \return Status - The error code return
+  Status EofReceived(int32_t worker_id) override;
+  Status operator()() override;
+  Status WorkerEntry(int32_t worker_id) override;
+  /// \brief Base-class override for handling cases if we allow cache miss
+  bool AllowCacheMiss() override { return false; }
+  /// \brief Base-class override for the name of this operator
+  std::string Name() const override { return "CacheOp"; }
+  /// \brief A public wrapper for creating the cache through the client
+  /// \param[in] cache_crc The crc that identifies the cache
+  /// \see cache_pass.cc
+  /// \return Status return code
+  Status CreateCache(uint32_t cache_crc);
+
+ private:
+  WaitPost rows_cache_done_;
+  std::atomic<int64_t> num_guys_in_;
+  Phase phase_;
+  /// \brief The main thread will wait until all the rows are cached and will start the handshake with the sampler.
+  /// \return Status object
+  Status WaitForCachingAllRows();
+  /// \brief For non-mappable dataset, there is a build phase where we cache all the rows.
+  /// \return Status object
+  Status CacheAllRows(int32_t worker_id);
+  Status RegisterResources() override;
+  /// \brief Private function for cache setup/init work just after construction
+  /// \return Status The error code return
+  Status InitCache();
+};
+}  // namespace dataset
+}  // namespace mindspore
+
+#endif  // DATASET_ENGINE_DATASETOPS_CACHE_OP_H_

mindspore/ccsrc/dataset/engine/datasetops/concat_op.cc

@@ -61,46 +61,39 @@ void ConcatOp::Print(std::ostream &out, bool show_all) const {
 Status ConcatOp::operator()() {
   // The children_num_ parameter needs to be put here
   children_num_ = static_cast<int32_t>(child_.size());
-
   TaskManager::FindMe()->Post();
   std::unique_ptr<DataBuffer> buf;
-  RETURN_IF_NOT_OK(child_[0]->GetNextBuffer(&buf));
-
   int eof_count = 0;
-  while (eof_count != children_num_) {
+  while (eof_count == 0) {
     for (int i = 0; i < children_num_; i++) {
-      // 1. Throw the eof buffer when meet it
-      if (buf->eof() || buf->eoe()) {
-        RETURN_IF_NOT_OK(child_[i]->GetNextBuffer(&buf));
+      // 1. Read the first buffer
+      RETURN_IF_NOT_OK(child_[i]->GetNextBuffer(&buf));
+      if (buf->eof()) {
+        eof_count++;
+        continue;
       }
       // 2. Do verification as for column name, column data type and rank of column data
-      RETURN_IF_NOT_OK(Verify(i, buf));
-
+      if (!buf->eoe()) {
+        RETURN_IF_NOT_OK(Verify(i, buf));
+      }
       // 3. Put the data into output_connector
       while (!buf->eoe() && !buf->eof()) {
         RETURN_IF_NOT_OK(out_connector_->Add(0, std::move(buf)));
         RETURN_IF_NOT_OK(child_[i]->GetNextBuffer(&buf));
       }
-
-      // 4. Throw the eoe buffer when meet it
-      if (buf->eoe() && (!BitTest(op_ctrl_flags_, kDeOpRepeated) || BitTest(op_ctrl_flags_, kDeOpLastRepeat))) {
-        RETURN_IF_NOT_OK(child_[i]->GetNextBuffer(&buf));
-      }
-      // 5. Add eoe buffer after get buffer from all child
-      if (i == (children_num_ - 1)) {
-        auto eoe_buffer = std::make_unique<DataBuffer>(0, DataBuffer::kDeBFlagEOE);
-        RETURN_IF_NOT_OK(out_connector_->Add(0, std::move(eoe_buffer)));
-      }
-      if (buf->eof()) {
-        eof_count++;
-      }
+    }
+    // 4. Add eoe buffer after get buffer from all child
+    if (eof_count == 0) {
+      auto eoe_buffer = std::make_unique<DataBuffer>(0, DataBuffer::kDeBFlagEOE);
+      RETURN_IF_NOT_OK(out_connector_->Add(0, std::move(eoe_buffer)));
     }
   }
-  // 6. Add eof buffer in the end manually
+  CHECK_FAIL_RETURN_UNEXPECTED(eof_count == children_num_,
+                               "Something went wrong, eof count does not match the number of children.");
+  // 5. Add eof buffer in the end manually
   MS_LOG(DEBUG) << "Add the eof buffer manualy in the end.";
   auto eof_buffer = std::make_unique<DataBuffer>(0, DataBuffer::kDeBFlagEOF);
   RETURN_IF_NOT_OK(out_connector_->Add(0, std::move(eof_buffer)));
-
   return Status::OK();
 }
 
@@ -126,12 +119,6 @@ Status ConcatOp::Verify(int32_t id, const std::unique_ptr<DataBuffer> &buf) {
   return Status::OK();
 }
 
-Status ConcatOp::PrepareNodePostAction() {
-  RETURN_IF_NOT_OK(PipelineOp::PrepareNodePostAction());
-  tree_->AddToEOEOpStack(shared_from_this());
-  return Status::OK();
-}
-
 // We need to overwrite the super class ComputeColMap here because the number of children is more than 1.
 Status ConcatOp::ComputeColMap() {
   if (column_name_id_map_.empty()) {

mindspore/ccsrc/dataset/engine/datasetops/concat_op.h

@@ -75,12 +75,6 @@ class ConcatOp : public PipelineOp {
   // @return Status - The error code return
   Status operator()() override;
 
-  // During tree prepare phase, operators may have specific post-operations to perform depending on
-  // their role.
-  // @notes Derived versions of this function should always call it's superclass version first
-  // before providing their own implementations.
-  Status PrepareNodePostAction() override;
-
   // Op name getter
   // @return Name of the current Op
   std::string Name() const override { return "ConcatOp"; }

mindspore/ccsrc/dataset/engine/datasetops/dataset_op.cc

@@ -153,16 +153,38 @@ Status DatasetOp::Remove() {
     }
   }
 
+  // Finally, clear "this" op's parent and child pointers since we have just
+  // disconnected it from the tree and invalidate it's fields.
+  child_.clear();
+  parent_.clear();
+  operator_id_ = kInvalidOperatorId;
+  tree_ = nullptr;
+
   return Status::OK();
 }
 
-// Getter function to get a shared pointer to our childAdds a operator to become our child.
+// Getter function to get a shared pointer to our child
 std::shared_ptr<DatasetOp> DatasetOp::child(int32_t child_index) const {
+  std::shared_ptr<DatasetOp> return_op = nullptr;
+  if (child_.empty()) {
+    return return_op;
+  }
   MS_ASSERT(child_index < static_cast<int>(child_.size()));
   // Return a shared pointer
   return child_[child_index];
 }
 
+// Getter function to get the parent pointer
+void DatasetOp::Parent(DatasetOp **parent, int32_t parent_index) const {
+  if (parent_.empty()) {
+    // common case if this is a root node
+    *parent = nullptr;
+  } else {
+    MS_ASSERT(parent_index < static_cast<int>(parent_.size()));
+    *parent = parent_[parent_index];
+  }
+}
+
 // Creates the connector within this operator
 void DatasetOp::CreateConnector(int32_t num_producers, int32_t num_consumers) {
   MS_LOG(DEBUG) << "Creating connector in tree operator: " << operator_id_ << ". Producer: " << num_producers
@@ -264,19 +286,11 @@ Status DatasetOp::EofReceived(int32_t worker_id) {
 
 // During tree prepare phase, operators may have specific pre-operations to perform depending on
 // their role.
-Status DatasetOp::PrepareNodePreAction() {
-  if (BitTest(tree_->PrepareFlags(), ExecutionTree::kDePrepRepeat)) set_control_flag(kDeOpRepeated);
-  return Status::OK();
-}
+Status DatasetOp::PrepareNodePreAction() { return Status::OK(); }
+
 // During tree prepare phase, operators may have specific post-operations to perform depending on
 // their role.
 Status DatasetOp::PrepareNodePostAction() {
-  // If this op does not have any children and it is in a repeat path of the tree...
-  if (child_.empty() && BitTest(op_ctrl_flags_, kDeOpRepeated)) {
-    // push ourselves onto the eoe operator stack.  Later, a repeat/epoch ctrl operator
-    // above us will consume them.
-    tree_->AddToEOEOpStack(shared_from_this());
-  }
   // Creating Connector object for each op.
   // The consumer of the root node is assumed to be one thread.
   // If multiple threads are consuming from the root node, they will get the ordered data in round robin fashion.
@@ -346,34 +360,13 @@ Status DatasetOp::Accept(NodePass *p, bool *modified) {
   return p->RunOnNode(shared_from_this(), modified);
 }
 
-// A helper function with some common code that leaf nodes can use during
-// prepare phase for checking if they need to assign a sampler to the cache.
-Status DatasetOp::SaveSamplerForCache(bool random_access_op) {
-  // If we are a descendant under a cache op and we have a sampler, then save this sampler
-  // to a stack so that the cache can pick it up during it's processing above us.
-  if (sampler_) {
-    if (BitTest(tree_->PrepareFlags(), ExecutionTree::kDePrepCache)) {
-      // use move semantic to set our sampler_ to null after the move.  This is okay because a sampler is
-      // useless to a random data op.  It was only being used as a temporary holding until the cache can
-      // be created
-      tree_->AddToSamplerStack(sampler_);
-      MS_LOG(INFO) << "Preparing a leaf op: passing sampler up the tree for Cache handling.";
-    } else if (!random_access_op) {
-      // A sampler exists, but we are not in a caching tree and we are not a random access mappable leaf.
-      // This is an error because that type of leaf does not use sampling unless there's a cache to hook it into.
-      RETURN_STATUS_UNEXPECTED(
-        "Non-mappable leaf op has a sampler, but it only supports sampling if there is a cache after it in the tree");
-    }
-  }
-
-  if (!random_access_op) {
-    // Since we don't truly need the sampler for this non-mappable dataset and it's been saved for the cache
-    // we can remove it now from the base.
-    sampler_.reset();
-  }
-
+// Getter for the sampler, and it also removes the sampler from the op
+Status DatasetOp::FetchRemoveSampler(std::shared_ptr<Sampler> *sampler) {
+  *sampler = sampler_;  // It's okay if it sampler_ points to nullptr
+  sampler_.reset();     // clear our member-copy of this pointer.  We no longer have this sampler
   return Status::OK();
 }
+
 uint32_t DatasetOp::GenerateCRC(const std::shared_ptr<DatasetOp> &op) {
   std::stringstream ss;
   op->tree_->Print(ss, op);

mindspore/ccsrc/dataset/engine/datasetops/dataset_op.h

@@ -45,10 +45,10 @@ class DatasetOp : public std::enable_shared_from_this<DatasetOp> {
  public:
   static constexpr int32_t kInvalidOperatorId = -1;
 
-  // Flags that control operator runtime behaviours
+  // Operator control flags
   enum OpControlFlags {
     kDeOpNone = 0,
-    kDeOpRepeated = 1,        // Operator is a leaf node in a repeat path
+    kDeOpRepeated = 1,        // Operator is a node in a repeat path
     kDeOpLastRepeat = 1 << 1  // We are in the last repeat loop
   };
 
@@ -71,17 +71,23 @@ class DatasetOp : public std::enable_shared_from_this<DatasetOp> {
   /// \param child - shared pointer to the child to remove.
   Status RemoveChild(std::shared_ptr<DatasetOp> child);
 
-  /// \brief Removes this node from the tree and connects it's parent/child together.
+  /// \brief Removes this node from the tree and connects it's parent/child together
   /// \return Status eerror code returned
   Status Remove();
 
   /// \brief Getter function to get a shared pointer to our child
-  /// \param child_index - An operator can have n children. Indicates choose which child to return.
+  /// \param[in] child_index An operator can have n children. Indicates which child to return.
+  /// \return The shared pointer to the child.  If there are no children, it returns null regardless of the given index
   std::shared_ptr<DatasetOp> child(int32_t child_index) const;
 
-  /// \brief Inserts a operator as the parent current op.
-  /// Inserted op will become the sole parent of the current op.
-  /// The existing parent of the current op will be transferred to the inserted op.
+  /// \brief Getter function to get the pointer to our parent
+  ///     If there are no parents, it returns null regardless of the given index
+  /// \param[in] parent_index An operator can have n parents. Indicates which parent to return.
+  void Parent(DatasetOp **parent, int32_t parent_index) const;
+
+  // Inserts a operator as the parent current op.
+  // Inserted op will become the sole parent of the current op.
+  // The existing parent of the current op will be transferred to the inserted op.
   Status InsertAsParent(std::shared_ptr<DatasetOp> to_add);
 
   /// \brief Creates the connector within this operator
@@ -161,16 +167,6 @@ class DatasetOp : public std::enable_shared_from_this<DatasetOp> {
   /// \return Status - The error code return
   virtual Status Reset();
 
-  /// \brief This calls the reset function on this subtree in pre-order
-  /// \return Status - The error code return
-  virtual Status ResetSubtree() {
-    RETURN_IF_NOT_OK(Reset());
-    for (const auto &c : child_) {
-      RETURN_IF_NOT_OK(c->ResetSubtree());
-    }
-    return Status::OK();
-  }
-
   /// \brief During tree prepare phase, operators may have specific pre-operations to perform depending on
   /// their role.
   /// \notes Derived versions of this function should always call it's superclass version first
@@ -296,7 +292,12 @@ class DatasetOp : public std::enable_shared_from_this<DatasetOp> {
   /// \return Shared pointer to the sampler (may return nullptr)
   std::shared_ptr<Sampler> sampler() { return sampler_; }
 
-  /// Computes a CRC value for the operator
+  /// \brief Getter for the sampler, and it also removes the sampler from the op
+  /// \param[out] sampler A pointer to the output sampler that was removed
+  /// \return Status error code
+  Status FetchRemoveSampler(std::shared_ptr<Sampler> *sampler);
+
+  // Computes a CRC value for the operator
   static uint32_t GenerateCRC(const std::shared_ptr<DatasetOp> &op);
 
   /// \brief A helper templated function for casting "this" pointer to shared_ptr<derived>
@@ -307,17 +308,24 @@ class DatasetOp : public std::enable_shared_from_this<DatasetOp> {
     return std::static_pointer_cast<Derived>(shared_from_this());
   }
 
- protected:
-  /// Adds a parent operator to this operator
-  /// \notes External callers do not have access to this function.
-  /// \param parent - The parent node to add
-  void AddParent(DatasetOp *parent);
+  /// \brief Setter for the sampler.  Allows you to overwrite a previous sampler with a new one.
+  void SetSampler(std::shared_ptr<Sampler> sampler) { sampler_ = sampler; }
+
+  /// \brief Checks if this is a leaf node (0 children)
+  /// \return boolean returns true if it's a leaf
+  bool IsLeaf() { return (child_.empty()); }
 
-  /// Removes a parent operator from this operator
-  /// \notes External callers do not have access to this function.
-  /// \param parent - The parent node to remove
+ protected:
+  /// \brief Removes a parent operator from this operator
+  /// \notes External callers do not have access to this function
+  /// \param[in] parent The parent node to remove
   void RemoveParent(const DatasetOp *parent);
 
+  /// \brief Adds a parent operator to this operator
+  /// \notes External callers do not have access to this function
+  /// \param[in] parent The parent node to add
+  void AddParent(DatasetOp *parent);
+
   /// Compute the current op's column map using its child's column map.
   /// Get called during the tree post-prepare phase in PrepareNodePostAction.
   /// This base implementation just inherits the map from child 0, and can only be used if the number of children is 1.
@@ -325,12 +333,6 @@ class DatasetOp : public std::enable_shared_from_this<DatasetOp> {
   /// \return - Status
   virtual Status ComputeColMap();
 
-  /// A helper function with some common code that leaf nodes can use during
-  /// pre/pare phase for checking if they need to assign a sampler to the cache.
-  /// \param random_access_op - indicate if this is a mappable random access leaf or not
-  /// \return - Status
-  Status SaveSamplerForCache(bool random_access_op);
-
   std::vector<std::shared_ptr<DatasetOp>> child_;                // Child nodes
   std::vector<DatasetOp *> parent_;                              // Parent nodes. No ownership
   std::shared_ptr<Sampler> sampler_;                             // Some leaf ops might have a sampler

mindspore/ccsrc/dataset/engine/datasetops/repeat_op.cc

@@ -77,26 +77,6 @@ void RepeatOp::Print(std::ostream &out, bool show_all) const {
   }
 }
 
-// Base-class override for executing specific RepeatOp configurations. This code will be called
-// during the execution tree prepare phase when it is visiting this operator.
-Status RepeatOp::PrepareNodePostAction() {
-  // Run any common code from super class first before adding our own specific logic
-  RETURN_IF_NOT_OK(PipelineOp::PrepareNodePostAction());
-  std::shared_ptr<DatasetOp> leaf_op = tree_->PopFromEOEOpStack();
-  while (leaf_op != nullptr) {
-    // Track the leaf operators that are under this repeat op.
-    eoe_ops_.push_back(leaf_op);
-    leaf_op = tree_->PopFromEOEOpStack();
-  }
-  // Push ourselves to the stack in case one of our ascendants is repeat too.
-  tree_->AddToEOEOpStack(shared_from_this());
-  return Status::OK();
-}
-
-// Base-class override for setting specific RepeatOp configurations. This code will be called
-// during the execution tree prepare phase BEFORE traversing down to child operators.
-uint32_t RepeatOp::PrepareFlags() const { return ExecutionTree::kDePrepRepeat; }
-
 // This function returns the buffer that is at the top of our output connector. The caller is
 // typically our parent node, when the parent is asking us to provide the next buffer of data.
 // Since RepeatOp is an inlined op, getting a buffer from us will simply bounce you to get
@@ -130,7 +110,8 @@ Status RepeatOp::GetNextBuffer(std::unique_ptr<DataBuffer> *p_buffer, int32_t wo
 // Base-class override for handling cases when an eoe is received.
 Status RepeatOp::EoeReceived(int32_t worker_id) {
   repeat_count_++;
-  MS_LOG(DEBUG) << "Repeat operator end of epoch message received. Repeat count is now: " << repeat_count_ << ".";
+  MS_LOG(DEBUG) << "Repeat operator (" << operator_id_
+                << ") end of epoch message received. Repeat count is now: " << repeat_count_ << ".";
   bool repeated = BitTest(op_ctrl_flags_, kDeOpRepeated);
   bool last_repeat = BitTest(op_ctrl_flags_, kDeOpLastRepeat);
   // If we've reached the requested repeat count, then flag the eoe nodes
@@ -149,8 +130,12 @@ Status RepeatOp::EoeReceived(int32_t worker_id) {
     return Status::OK();
   }
 
-  //  base-class ResetSubtree
-  return (DatasetOp::ResetSubtree());
+  // Invoke a reset against the eoe nodes only.
+  for (auto &eoe_op : eoe_ops_) {
+    RETURN_IF_NOT_OK(eoe_op->Reset());
+  }
+
+  return Status::OK();
 }
 
 // Class functor operator () override.
@@ -178,6 +163,18 @@ int32_t RepeatOp::num_consumers() const {
   }
 }
 
+// Drive reset actions if needed
+Status RepeatOp::Reset() {
+  // If there's nested repeats, an ascendant repeat may have ourself listed as an eoe op.
+  // In that case, we now have to bounce the reset down to our own eoe ops.
+  MS_LOG(DEBUG) << "Repeat operator (" << operator_id_ << ") reset.";
+  for (auto &eoe_op : eoe_ops_) {
+    RETURN_IF_NOT_OK(eoe_op->Reset());
+  }
+  state_ = OpState::kDeOpRunning;
+  return Status::OK();
+}
+
 int32_t RepeatOp::num_producers() const {
   if (child_.empty() || child_[0] == nullptr) {
     MS_LOG(DEBUG) << "Repeat operator, pointer to child node is null. Returning 0.";
@@ -187,6 +184,12 @@ int32_t RepeatOp::num_producers() const {
   }
 }
 
+// Pre-Visitor accept method for NodePass
+Status RepeatOp::PreAccept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call the pre-visitation
+  return p->PreRunOnNode(shared_from_base<RepeatOp>(), modified);
+}
+
 // Visitor accept method for NodePass
 Status RepeatOp::Accept(NodePass *p, bool *modified) {
   // Downcast shared pointer then call visitor

mindspore/ccsrc/dataset/engine/datasetops/repeat_op.h

@@ -18,6 +18,7 @@
 
 #include <memory>
 #include <string>
+#include <utility>
 #include <vector>
 #include "dataset/engine/datasetops/pipeline_op.h"
 
@@ -82,14 +83,6 @@ class RepeatOp : public PipelineOp {
   // @return Status - The error code return
   Status operator()() override;
 
-  // Base-class override for setting specific RepeatOp configurations. This code will be called
-  // during the execution tree prepare phase BEFORE traversing down to child operators.
-  uint32_t PrepareFlags() const override;
-
-  // Base-class override for executing specific RepeatOp configurations. This code will be called
-  // during the execution tree post-prepare phase when it is visiting this operator.
-  Status PrepareNodePostAction() override;
-
   // This function returns the buffer that is at the top of our output connector. The caller is
   // typically our parent node, when the parent is asking us to provide the next buffer of data.
   // Since RepeatOp is an inlined op, getting a buffer from us will simply bounce you to get
@@ -110,6 +103,10 @@ class RepeatOp : public PipelineOp {
   // @param worker_id - The worker id
   Status EofReceived(int32_t worker_id) override;
 
+  /// \brief reset Op
+  /// \@return Status - The error code return
+  Status Reset() override;
+
   // Base-class override. Return the number of workers in the first parent.
   // @param workerId - The worker id
   int32_t num_consumers() const override;
@@ -118,16 +115,26 @@ class RepeatOp : public PipelineOp {
   // @param workerId - The worker id
   int32_t num_producers() const override;
 
-  // Base-class override for NodePass visitor acceptor.
-  // @param p - Pointer to the NodePass to be accepted.
-  // @param modified - Whether this node visit modified the pipeline.
-  // @return - Status of the node visit.
+  /// \brief Base-class override for NodePass pre-visit acceptor
+  /// \param[in] p The node to visit
+  /// \param[out] modified Indicator if the node was modified
+  /// \return Status of the node visit
+  Status PreAccept(NodePass *p, bool *modified) override;
+
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p The node to visit
+  /// \param[out] modified Indicator if the node was modified
+  /// \return Status of the node visit
   Status Accept(NodePass *p, bool *modified) override;
 
   // Op name getter
   // @return Name of the current Op
   std::string Name() const override { return "RepeatOp"; }
 
+  /// \brief Adds an operator to the repeat ops list of tracked leaf/eoe nodes
+  /// \param[in] eoe_op The input leaf/eoe operator to add to the list
+  void AddToEoeList(std::shared_ptr<DatasetOp> eoe_op) { eoe_ops_.push_back(std::move(eoe_op)); }
+
  private:
   int32_t max_repeats_;                              // The number of repeats that the user requested
   int32_t repeat_count_;                             // A counter for the current number of executed repeats

mindspore/ccsrc/dataset/engine/datasetops/source/celeba_op.cc

@@ -22,6 +22,7 @@
 #include "dataset/engine/datasetops/source/sampler/sequential_sampler.h"
 #include "dataset/engine/data_schema.h"
 #include "dataset/engine/execution_tree.h"
+#include "dataset/engine/opt/pass.h"
 #include "dataset/kernels/image/image_utils.h"
 
 namespace mindspore {
@@ -408,6 +409,12 @@ Status CelebAOp::Reset() {
   return Status::OK();
 }
 
+// Visitor accept method for NodePass
+Status CelebAOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<CelebAOp>(), modified);
+}
+
 Status CelebAOp::ComputeColMap() {
   // Set the column name map (base class field)
   if (column_name_id_map_.empty()) {

mindspore/ccsrc/dataset/engine/datasetops/source/celeba_op.h

@@ -169,6 +169,12 @@ class CelebAOp : public ParallelOp, RandomAccessOp {
   // @return Status - The error code return
   Status AddIOBlock(std::unique_ptr<DataBuffer> *data_buffer);
 
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p Pointer to the NodePass to be accepted
+  /// \param[out] modified Indicator if the node was changed at all
+  /// \return Status of the node visit
+  Status Accept(NodePass *p, bool *modified) override;
+
   // Op name getter
   // @return Name of the current Op
   std::string Name() const { return "CelebAOp"; }

mindspore/ccsrc/dataset/engine/datasetops/source/cifar_op.cc

@@ -26,6 +26,7 @@
 #include "dataset/engine/datasetops/source/sampler/sequential_sampler.h"
 #include "dataset/engine/db_connector.h"
 #include "dataset/engine/execution_tree.h"
+#include "dataset/engine/opt/pass.h"
 
 namespace mindspore {
 namespace dataset {
@@ -450,6 +451,12 @@ Status CifarOp::CountTotalRows(const std::string &dir, bool isCIFAR10, int64_t *
   }
 }
 
+// Visitor accept method for NodePass
+Status CifarOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<CifarOp>(), modified);
+}
+
 Status CifarOp::ComputeColMap() {
   // set the column name map (base class field)
   if (column_name_id_map_.empty()) {

mindspore/ccsrc/dataset/engine/datasetops/source/cifar_op.h

@@ -155,6 +155,12 @@ class CifarOp : public ParallelOp, public RandomAccessOp {
   // @return
   static Status CountTotalRows(const std::string &dir, bool isCIFAR10, int64_t *count);
 
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p Pointer to the NodePass to be accepted
+  /// \param[out] modified Indicator if the node was changed at all
+  /// \return Status of the node visit
+  Status Accept(NodePass *p, bool *modified) override;
+
   // Op name getter
   // @return Name of the current Op
   std::string Name() const override { return "CifarOp"; }

mindspore/ccsrc/dataset/engine/datasetops/source/coco_op.cc

@@ -24,6 +24,7 @@
 #include "dataset/engine/datasetops/source/sampler/sequential_sampler.h"
 #include "dataset/engine/db_connector.h"
 #include "dataset/engine/execution_tree.h"
+#include "dataset/engine/opt/pass.h"
 
 namespace mindspore {
 namespace dataset {
@@ -624,6 +625,12 @@ Status CocoOp::GetClassIndexing(const std::string &dir, const std::string &file,
   return Status::OK();
 }
 
+// Visitor accept method for NodePass
+Status CocoOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<CocoOp>(), modified);
+}
+
 Status CocoOp::ComputeColMap() {
   // Set the column name map (base class field)
   if (column_name_id_map_.empty()) {

mindspore/ccsrc/dataset/engine/datasetops/source/coco_op.h

@@ -200,6 +200,12 @@ class CocoOp : public ParallelOp, public RandomAccessOp {
   static Status GetClassIndexing(const std::string &dir, const std::string &task_type, const std::string &task_mode,
                                  std::vector<std::pair<std::string, std::vector<int32_t>>> *output_class_indexing);
 
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p Pointer to the NodePass to be accepted
+  /// \param[out] modified Indicator if the node was changed at all
+  /// \return Status of the node visit
+  Status Accept(NodePass *p, bool *modified) override;
+
  private:
   // Initialize Sampler, calls sampler->Init() within
   // @return Status - The error code return

mindspore/ccsrc/dataset/engine/datasetops/source/manifest_op.cc

@@ -26,6 +26,7 @@
 #include "dataset/engine/datasetops/source/sampler/sequential_sampler.h"
 #include "dataset/engine/db_connector.h"
 #include "dataset/engine/execution_tree.h"
+#include "dataset/engine/opt/pass.h"
 
 namespace mindspore {
 namespace dataset {
@@ -416,6 +417,12 @@ Status ManifestOp::GetClassIndexing(const std::string &file, const py::dict &dic
   return Status::OK();
 }
 
+// Visitor accept method for NodePass
+Status ManifestOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<ManifestOp>(), modified);
+}
+
 Status ManifestOp::ComputeColMap() {
   // Set the column name map (base class field)
   if (column_name_id_map_.empty()) {

mindspore/ccsrc/dataset/engine/datasetops/source/manifest_op.h

@@ -172,6 +172,12 @@ class ManifestOp : public ParallelOp, public RandomAccessOp {
   static Status GetClassIndexing(const std::string &file, const py::dict &dict, const std::string &usage,
                                  std::map<std::string, int32_t> *output_class_indexing);
 
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p Pointer to the NodePass to be accepted
+  /// \param[out] modified Indicator if the node was changed at all
+  /// \return Status of the node visit
+  Status Accept(NodePass *p, bool *modified) override;
+
   // Op name getter
   // @return Name of the current Op
   std::string Name() const override { return "ManifestOp"; }

mindspore/ccsrc/dataset/engine/datasetops/source/mnist_op.cc

@@ -23,6 +23,7 @@
 #include "dataset/engine/datasetops/source/sampler/sequential_sampler.h"
 #include "dataset/engine/db_connector.h"
 #include "dataset/engine/execution_tree.h"
+#include "dataset/engine/opt/pass.h"
 
 namespace mindspore {
 namespace dataset {
@@ -428,6 +429,12 @@ Status MnistOp::CountTotalRows(const std::string &dir, int64_t *count) {
   return Status::OK();
 }
 
+// Visitor accept method for NodePass
+Status MnistOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<MnistOp>(), modified);
+}
+
 Status MnistOp::ComputeColMap() {
   // set the column name map (base class field)
   if (column_name_id_map_.empty()) {

mindspore/ccsrc/dataset/engine/datasetops/source/mnist_op.h

@@ -152,6 +152,12 @@ class MnistOp : public ParallelOp, public RandomAccessOp {
   // @return
   static Status CountTotalRows(const std::string &dir, int64_t *count);
 
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p Pointer to the NodePass to be accepted
+  /// \param[out] modified Indicator if the node was changed at all
+  /// \return Status of the node visit
+  Status Accept(NodePass *p, bool *modified) override;
+
   // Op name getter
   // @return Name of the current Op
   std::string Name() const override { return "MnistOp"; }

mindspore/ccsrc/dataset/engine/datasetops/source/random_data_op.cc

@@ -22,6 +22,7 @@
 #include "dataset/util/random.h"
 #include "dataset/util/wait_post.h"
 #include "dataset/engine/datasetops/source/sampler/sequential_sampler.h"
+#include "dataset/engine/opt/pass.h"
 
 namespace mindspore {
 namespace dataset {
@@ -406,6 +407,12 @@ Status RandomDataOp::Reset() {
   return Status::OK();
 }
 
+// Visitor accept method for NodePass
+Status RandomDataOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<RandomDataOp>(), modified);
+}
+
 Status RandomDataOp::ComputeColMap() {
   // Extract the column name mapping from the schema and save it in the class.
   if (column_name_id_map_.empty()) {
@@ -415,15 +422,5 @@ Status RandomDataOp::ComputeColMap() {
   }
   return Status::OK();
 }
-
-// During tree prepare phase, operators may have specific post-operations to perform depending on
-// their role.
-Status RandomDataOp::PrepareNodePostAction() {
-  // Run common code from super class before adding RandomDataOp specific handling
-  RETURN_IF_NOT_OK(ParallelOp::PrepareNodePostAction());
-  // Specific handling for this op, we need to do cache op work to assign the sampler to the cache.
-  RETURN_IF_NOT_OK(DatasetOp::SaveSamplerForCache(false));
-  return Status::OK();
-}
 }  // namespace dataset
 }  // namespace mindspore

mindspore/ccsrc/dataset/engine/datasetops/source/random_data_op.h

@@ -203,12 +203,6 @@ class RandomDataOp : public ParallelOp {
   // @return Name of the current Op
   std::string Name() const override { return "RandomDataOp"; }
 
-  // During tree prepare phase, operators may have specific post-operations to perform depending on
-  // their role.
-  // @notes Derived versions of this function should always call it's superclass version first
-  // before providing their own implementations.
-  Status PrepareNodePostAction() override;
-
  private:
   /**
    * The entry point code for when workers are launched
@@ -266,6 +260,12 @@ class RandomDataOp : public ParallelOp {
     return ++buffer_id_;
   }
 
+  // Base-class override for NodePass visitor acceptor.
+  // @param p - Pointer to the NodePass to be accepted.
+  // @param modified - Whether this node visit modified the pipeline.
+  // @return - Status of the node visit.
+  Status Accept(NodePass *p, bool *modified) override;
+
   // Private function for computing the assignment of the column name map.
   // @return - Status
   Status ComputeColMap() override;

mindspore/ccsrc/dataset/engine/datasetops/source/tf_reader_op.cc

@@ -1019,31 +1019,28 @@ Status TFReaderOp::ComputeColMap() {
   return Status::OK();
 }
 
+// Brief If a cache has been added into the ascendant tree over this tf reader, then the cache will be executing
+// a sampler for fetching the data.  As such, any options in the tf reader need to be reset to its defaults so
+// that this tf reader will produce the full set of data into the cache.
+void TFReaderOp::MakeSimpleProducer() {
+  device_id_ = 0;
+  num_devices_ = 1;
+  total_rows_ = 0;
+  shuffle_files_ = false;
+  equal_rows_per_shard_ = false;
+}
+
 // During tree prepare phase, operators may have specific post-operations to perform depending on
 // their role.
 Status TFReaderOp::PrepareNodePostAction() {
   // Run common code from super class before adding TFReaderOp specific handling
   RETURN_IF_NOT_OK(ParallelOp::PrepareNodePostAction());
 
-  // Specific handling for this op, we need to do cache op work so assign the sampler to the cache
-  // TF is a special case because it can support file-based sharding/shuffling, or, if there
-  // is a cache, then it can also do row-based sampler using the sampler on the cache.
-  // Thus, pass true for random access op flag when saving the sampler.  This is a special case,
-  // since usually a non-mappable dataset would pass false here.
-  RETURN_IF_NOT_OK(DatasetOp::SaveSamplerForCache(true));
-
   // Now that the sampler has been saved for the cache, we need to adjust the TFReaderOp to turn it into
   // a simpler producer of all data (no shuffling or sharding or anything)
-  if (BitTest(tree_->PrepareFlags(), ExecutionTree::kDePrepCache)) {
-    device_id_ = 0;
-    num_devices_ = 1;
-    total_rows_ = 0;
-    shuffle_files_ = false;
-    equal_rows_per_shard_ = false;
-    sampler_.reset();  // Normally SaveSampler code did this for us, but we passed in true above (See comment)
-  } else {
+  if (!BitTest(tree_->PrepareFlags(), ExecutionTree::kDePrepCache)) {
     // This sanity check had been delayed until now in the prepare loop.
-    // If we are not in a cache path, then we can validate the the file-based sharding config.
+    // If we are not in a cache path, then we can validate the file-based sharding config.
     // If we are in a cache path, there is no file-based sharding so the check is not correct in that
     // situation.
     if (!equal_rows_per_shard_ && dataset_files_list_.size() < static_cast<uint32_t>(num_devices_)) {

mindspore/ccsrc/dataset/engine/datasetops/source/tf_reader_op.h

@@ -246,6 +246,11 @@ class TFReaderOp : public ParallelOp {
   // @return Vector of the input file names
   std::vector<std::string> FileNames() { return dataset_files_list_; }
 
+  /// \Brief If a cache has been added into the ascendant tree over this tf reader, then the cache will be executing
+  ///     a sampler for fetching the data.  As such, any options in the tf reader need to be reset to its defaults so
+  ///     that this tf reader will produce the full set of data into the cache.
+  void MakeSimpleProducer();
+
   // During tree prepare phase, operators may have specific post-operations to perform depending on
   // their role.
   // @notes Derived versions of this function should always call it's superclass version first

mindspore/ccsrc/dataset/engine/datasetops/source/voc_op.cc

@@ -25,6 +25,7 @@
 #include "dataset/engine/datasetops/source/sampler/sequential_sampler.h"
 #include "dataset/engine/db_connector.h"
 #include "dataset/engine/execution_tree.h"
+#include "dataset/engine/opt/pass.h"
 
 using tinyxml2::XMLDocument;
 using tinyxml2::XMLElement;
@@ -449,6 +450,11 @@ Status VOCOp::GetClassIndexing(const std::string &dir, const std::string &task_t
 
   return Status::OK();
 }
+// Visitor accept method for NodePass
+Status VOCOp::Accept(NodePass *p, bool *modified) {
+  // Downcast shared pointer then call visitor
+  return p->RunOnNode(shared_from_base<VOCOp>(), modified);
+}
 
 Status VOCOp::ComputeColMap() {
   // Set the column name map (base class field)

mindspore/ccsrc/dataset/engine/datasetops/source/voc_op.h

@@ -205,6 +205,12 @@ class VOCOp : public ParallelOp, public RandomAccessOp {
   static Status GetClassIndexing(const std::string &dir, const std::string &task_type, const std::string &task_mode,
                                  const py::dict &dict, std::map<std::string, int32_t> *output_class_indexing);
 
+  /// \brief Base-class override for NodePass visitor acceptor
+  /// \param[in] p Pointer to the NodePass to be accepted
+  /// \param[out] modified Indicator if the node was changed at all
+  /// \return Status of the node visit
+  Status Accept(NodePass *p, bool *modified) override;
+
   // Op name getter
   // @return Name of the current Op
   std::string Name() const override { return "VOCOp"; }

mindspore/ccsrc/dataset/engine/datasetops/take_op.cc

@@ -127,12 +127,6 @@ Status TakeOp::FillBuffer(std::unique_ptr<DataBuffer> *buffer, std::unique_ptr<D
   return Status::OK();
 }
 
-Status TakeOp::PrepareNodePostAction() {
-  RETURN_IF_NOT_OK(PipelineOp::PrepareNodePostAction());
-  tree_->AddToEOEOpStack(shared_from_this());
-  return Status::OK();
-}
-
 // Visitor accept method for NodePass
 Status TakeOp::Accept(NodePass *p, bool *modified) {
   // Downcast shared pointer then call visitor

mindspore/ccsrc/dataset/engine/datasetops/take_op.h

@@ -78,12 +78,6 @@ class TakeOp : public PipelineOp {
   // @return Status - The error code return
   Status operator()() override;
 
-  // During tree prepare phase, operators may have specific post-operations to perform depending on
-  // their role.
-  // @notes Derived versions of this function should always call it's superclass version first
-  // before providing their own implementations.
-  Status PrepareNodePostAction() override;
-
   // Base-class override for NodePass visitor acceptor.
   // @param p - Pointer to the NodePass to be accepted.
   // @param modified - Whether this node visit modified the pipeline.

mindspore/ccsrc/dataset/engine/execution_tree.cc

@@ -21,6 +21,8 @@
 #include "dataset/util/task_manager.h"
 #include "dataset/engine/opt/pass.h"
 #include "dataset/engine/opt/pre/removal_pass.h"
+#include "dataset/engine/opt/pre/cache_transform_pass.h"
+#include "dataset/engine/opt/post/repeat_pass.h"
 #include "dataset/engine/perf/profiling.h"
 #include "dataset/engine/perf/monitor.h"
 
@@ -215,18 +217,33 @@ Status ExecutionTree::PrepareTreePreAction() {
   bool modified = false;
   std::vector<std::unique_ptr<Pass>> pre_actions;
   // Construct pre actions
-  MS_LOG(INFO) << "Running pre pass";
-  pre_actions.push_back(std::make_unique<RemovalPass>(RemovalPass()));
+  MS_LOG(INFO) << "Running pre pass loops.";
+  pre_actions.push_back(std::make_unique<RemovalPass>());
+  pre_actions.push_back(std::make_unique<CacheTransformPass>());
   // Apply pre action passes
   for (auto &pass : pre_actions) {
     RETURN_IF_NOT_OK(pass->Run(this, &modified));
   }
+  MS_LOG(INFO) << "Pre passes complete.";
   return Status::OK();
 }
 
 Status ExecutionTree::PrepareTreePostAction() {
   // The tree is ready to be prepared.
   tree_state_ = kDeTStatePrepare;
+
+  bool modified = false;
+  std::vector<std::unique_ptr<Pass>> post_actions;
+  // Construct pre actions
+  MS_LOG(INFO) << "Running post pass loops.";
+  post_actions.push_back(std::make_unique<RepeatPass>());
+
+  // Apply post action passes
+  for (auto &pass : post_actions) {
+    RETURN_IF_NOT_OK(pass->Run(this, &modified));
+  }
+  MS_LOG(INFO) << "Post passes complete.";
+
   return Status::OK();
 }
 
@@ -280,31 +297,5 @@ Status ExecutionTree::PrepareNode(const std::shared_ptr<DatasetOp> &dataset_op)
 
   return Status::OK();
 }
-
-// Adds an operator to the eoe operator stack during prepare phase.
-void ExecutionTree::AddToEOEOpStack(std::shared_ptr<DatasetOp> dataset_op) { eoe_stack_.push(dataset_op); }
-
-// Pops an operator from the eoe operator stack during prepare phase.
-std::shared_ptr<DatasetOp> ExecutionTree::PopFromEOEOpStack() {
-  std::shared_ptr<DatasetOp> top_op = nullptr;
-  if (!eoe_stack_.empty()) {
-    top_op = eoe_stack_.top();
-    eoe_stack_.pop();
-  }
-  return top_op;
-}
-
-// Adds a sampler to the sampler stack during prepare phase.
-void ExecutionTree::AddToSamplerStack(std::shared_ptr<Sampler> sampler) { sampler_stack_.push(sampler); }
-
-// Pops an operator from the sampler stack during prepare phase.
-std::shared_ptr<Sampler> ExecutionTree::PopFromSamplerStack() {
-  std::shared_ptr<Sampler> top_sampler = nullptr;
-  if (!sampler_stack_.empty()) {
-    top_sampler = sampler_stack_.top();
-    sampler_stack_.pop();
-  }
-  return top_sampler;
-}
 }  // namespace dataset
 }  // namespace mindspore

mindspore/ccsrc/dataset/engine/execution_tree.h

@@ -200,24 +200,6 @@ class ExecutionTree {
   // @return Status - The error code return
   Status PrepareNode(const std::shared_ptr<DatasetOp> &dataset_op);
 
-  /// Adds an operator to the eoe operator stack during prepare phase.
-  /// \param op - The dataset op to work add to eoe stack
-  /// \return Status - The error code return
-  void AddToEOEOpStack(std::shared_ptr<DatasetOp> dataset_op);
-
-  /// Pops an operator from the eoe operator stack during prepare phase.
-  /// \return shared_ptr to the popped operator
-  std::shared_ptr<DatasetOp> PopFromEOEOpStack();
-
-  /// Adds a sampler to the sampler stack during prepare phase.
-  /// \param samplerop - The dataset op to work add to eoe stack
-  /// \return Status - The error code return
-  void AddToSamplerStack(std::shared_ptr<Sampler> sampler);
-
-  /// Pops an operator from the sampler stack during prepare phase.
-  /// \return shared_ptr to the popped operator
-  std::shared_ptr<Sampler> PopFromSamplerStack();
-
   // Return the pointer to the TaskGroup
   // @return raw pointer to the TaskGroup
   TaskGroup *AllTasks() const { return tg_.get(); }
@@ -248,8 +230,6 @@ class ExecutionTree {
   TreeState tree_state_;                                 // Tracking the current tree state
   std::unique_ptr<Monitor> perf_monitor_;                // Performance Monitor
   std::unique_ptr<ProfilingManager> profiling_manager_;  // Profiling manager
-  std::stack<std::shared_ptr<DatasetOp>> eoe_stack_;     // A stack used during prepare phase
-  std::stack<std::shared_ptr<Sampler>> sampler_stack_;   // A stack used during prepare phase
 };
 }  // namespace dataset
 }  // namespace mindspore

mindspore/ccsrc/dataset/engine/opt/CMakeLists.txt

@@ -2,6 +2,9 @@ file(GLOB_RECURSE _CURRENT_SRC_FILES RELATIVE ${CMAKE_CURRENT_SOURCE_DIR} "*.cc"
 set_property(SOURCE ${_CURRENT_SRC_FILES} PROPERTY COMPILE_DEFINITIONS SUBMODULE_ID=mindspore::SubModuleId::SM_MD)
 add_library(engine-opt OBJECT
           pass.cc
+          post/repeat_pass.cc
+          pre/cache_pass.cc
+          pre/cache_transform_pass.cc
           pre/removal_nodes.cc
           pre/removal_pass.cc
           util/printer_pass.cc

mindspore/ccsrc/dataset/engine/opt/pass.cc

@@ -16,6 +16,9 @@
 
 #include "dataset/engine/opt/pass.h"
 #include "dataset/engine/datasetops/batch_op.h"
+#include "dataset/engine/datasetops/cache_op.h"
+#include "dataset/engine/datasetops/cache_merge_op.h"
+#include "dataset/engine/datasetops/cache_lookup_op.h"
 #include "dataset/engine/datasetops/dataset_op.h"
 #include "dataset/engine/datasetops/device_queue_op.h"
 #include "dataset/engine/datasetops/map_op.h"
@@ -24,8 +27,15 @@
 #include "dataset/engine/datasetops/repeat_op.h"
 #include "dataset/engine/datasetops/skip_op.h"
 #include "dataset/engine/datasetops/shuffle_op.h"
+#include "dataset/engine/datasetops/source/celeba_op.h"
+#include "dataset/engine/datasetops/source/cifar_op.h"
+#include "dataset/engine/datasetops/source/coco_op.h"
+#include "dataset/engine/datasetops/source/manifest_op.h"
 #include "dataset/engine/datasetops/source/mindrecord_op.h"
+#include "dataset/engine/datasetops/source/mnist_op.h"
+#include "dataset/engine/datasetops/source/random_data_op.h"
 #include "dataset/engine/datasetops/source/tf_reader_op.h"
+#include "dataset/engine/datasetops/source/voc_op.h"
 #ifdef ENABLE_PYTHON
 #include "dataset/engine/datasetops/filter_op.h"
 #include "dataset/engine/datasetops/source/generator_op.h"
@@ -145,6 +155,11 @@ Status NodePass::RunOnNode(std::shared_ptr<GeneratorOp> node, bool *modified) {
 }
 #endif
 
+Status NodePass::RunOnNode(std::shared_ptr<RandomDataOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
 Status NodePass::RunOnNode(std::shared_ptr<TakeOp> node, bool *modified) {
   // Fallback to base class visitor by default
   return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
@@ -164,5 +179,70 @@ Status NodePass::RunOnNode(std::shared_ptr<ImageFolderOp> node, bool *modified)
   // Fallback to base class visitor by default
   return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
 }
+
+Status NodePass::RunOnNode(std::shared_ptr<CacheOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::RunOnNode(std::shared_ptr<MnistOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::RunOnNode(std::shared_ptr<ManifestOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::RunOnNode(std::shared_ptr<CifarOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::RunOnNode(std::shared_ptr<VOCOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::RunOnNode(std::shared_ptr<CelebAOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::RunOnNode(std::shared_ptr<CocoOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::RunOnNode(std::shared_ptr<RepeatOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::RunOnNode(std::shared_ptr<CacheMergeOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::RunOnNode(std::shared_ptr<CacheLookupOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return RunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::PreRunOnNode(std::shared_ptr<RepeatOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return PreRunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::PreRunOnNode(std::shared_ptr<CacheOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return PreRunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
+
+Status NodePass::PreRunOnNode(std::shared_ptr<CacheMergeOp> node, bool *modified) {
+  // Fallback to base class visitor by default
+  return PreRunOnNode(std::static_pointer_cast<DatasetOp>(node), modified);
+}
 }  // namespace dataset
 }  // namespace mindspore

mindspore/ccsrc/dataset/engine/opt/pass.h

@@ -47,6 +47,10 @@ class FilterOp;
 class GeneratorOp;
 #endif
 
+class RandomDataOp;
+
+class RepeatOp;
+
 class TakeOp;
 
 class ZipOp;
@@ -55,6 +59,24 @@ class DeviceQueueOp;
 
 class ImageFolderOp;
 
+class CacheOp;
+
+class MnistOp;
+
+class ManifestOp;
+
+class CifarOp;
+
+class VOCOp;
+
+class CocoOp;
+
+class CelebAOp;
+
+class CacheMergeOp;
+
+class CacheLookupOp;
+
 // The base class Pass is the basic unit of tree transformation.
 // The actual implementation of the passes will be derived from here.
 class Pass : public std::enable_shared_from_this<Pass> {
@@ -138,14 +160,42 @@ class NodePass : public Pass {
   virtual Status RunOnNode(std::shared_ptr<GeneratorOp> node, bool *modified);
 #endif
 
+  virtual Status RunOnNode(std::shared_ptr<RandomDataOp> node, bool *modified);
+
   virtual Status RunOnNode(std::shared_ptr<TakeOp> node, bool *modified);
 
   virtual Status RunOnNode(std::shared_ptr<ZipOp> node, bool *modified);
 
   virtual Status RunOnNode(std::shared_ptr<DeviceQueueOp> node, bool *modified);
 
+  virtual Status RunOnNode(std::shared_ptr<CacheOp> node, bool *modified);
+
   virtual Status RunOnNode(std::shared_ptr<ImageFolderOp> node, bool *modified);
 
+  virtual Status RunOnNode(std::shared_ptr<MnistOp> node, bool *modified);
+
+  virtual Status RunOnNode(std::shared_ptr<ManifestOp> node, bool *modified);
+
+  virtual Status RunOnNode(std::shared_ptr<CifarOp> node, bool *modified);
+
+  virtual Status RunOnNode(std::shared_ptr<VOCOp> node, bool *modified);
+
+  virtual Status RunOnNode(std::shared_ptr<CocoOp> node, bool *modified);
+
+  virtual Status RunOnNode(std::shared_ptr<CelebAOp> node, bool *modified);
+
+  virtual Status RunOnNode(std::shared_ptr<RepeatOp> node, bool *modified);
+
+  virtual Status RunOnNode(std::shared_ptr<CacheMergeOp> node, bool *modified);
+
+  virtual Status RunOnNode(std::shared_ptr<CacheLookupOp> node, bool *modified);
+
+  virtual Status PreRunOnNode(std::shared_ptr<CacheOp> node, bool *modified);
+
+  virtual Status PreRunOnNode(std::shared_ptr<RepeatOp> node, bool *modified);
+
+  virtual Status PreRunOnNode(std::shared_ptr<CacheMergeOp> node, bool *modified);
+
  private:
   // Helper function to perform DFS visit
   Status DFSNodeVisit(std::shared_ptr<DatasetOp> node, bool *modified);

mindspore/ccsrc/dataset/engine/opt/post/repeat_pass.cc

@@ -0,0 +1,161 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <memory>
+#include "dataset/engine/opt/post/repeat_pass.h"
+#include "dataset/engine/datasetops/repeat_op.h"
+#include "dataset/engine/datasetops/cache_op.h"
+#include "dataset/engine/datasetops/cache_lookup_op.h"
+#include "dataset/engine/datasetops/cache_merge_op.h"
+
+namespace mindspore {
+namespace dataset {
+
+RepeatPass::RepeatPass() : is_repeated_(false), nested_repeats_(0), is_merge_(false), cache_lookup_(nullptr) {}
+
+// Identifies the subtree below this node as being in a repeated path of the tree.
+Status RepeatPass::PreRunOnNode(std::shared_ptr<RepeatOp> node, bool *modified) {
+  // If we are already repeated, then this is a nested repeat.
+  if (is_repeated_) {
+    nested_repeats_++;
+  }
+  is_repeated_ = true;
+  return Status::OK();
+}
+
+// Identifies the subtree below this node as being in a cache merge path
+Status RepeatPass::PreRunOnNode(std::shared_ptr<CacheMergeOp> node, bool *modified) {
+  // Turn on the flag that we're under a merge op
+  is_merge_ = true;
+  return Status::OK();
+}
+
+// Hooks up any identified eoe nodes under this repeat.
+Status RepeatPass::RunOnNode(std::shared_ptr<RepeatOp> node, bool *modified) {
+  // Pop the leaf ops from the save-area stack and add them to the repeat op's eoe node tracking
+  std::shared_ptr<DatasetOp> leaf_op = PopFromEOEOpStack();
+  while (leaf_op != nullptr) {
+    node->AddToEoeList(leaf_op);
+    leaf_op = PopFromEOEOpStack();
+  }
+
+  // We are a repeat op in the descendant tree of a merge op, then we take the saved lookup up
+  // and add it to the list of eoe/leaf ops for the repeat, removing it from the save area.
+  if (is_merge_ && cache_lookup_) {
+    cache_lookup_->set_control_flag(DatasetOp::kDeOpRepeated);
+    node->AddToEoeList(std::move(cache_lookup_));
+  }
+
+  // If we are a nested repeat, then we add ourself to the repeat stack for the next one above us.
+  // A nested repeat acts like an eoe/leaf for the repeat in the ascendant tree.
+  if (nested_repeats_ > 0) {
+    node->set_control_flag(DatasetOp::kDeOpRepeated);
+    AddToEOEOpStack(node);
+    nested_repeats_--;
+  }
+
+  // If we are not nested, or we were the top-most repeat, now we clear the flag
+  if (nested_repeats_ == 0) {
+    is_repeated_ = false;
+  }
+
+  return Status::OK();
+}
+
+// CacheOp removes previous leaf ops and replaces them with itself
+Status RepeatPass::RunOnNode(std::shared_ptr<CacheOp> node, bool *modified) {
+  if (is_repeated_) {
+    node->set_control_flag(DatasetOp::kDeOpRepeated);
+    // if we are a cache within a repeat path of the tree, then there will be
+    // eoe-generating ops in the eoe op stack in the tree.  They are flagged as such so that the
+    // repeat or epoch ctrl operators can work with them for repeat activity during runtime.
+    // However, since a cache is present:
+    // - unflag those ops as being repeated ops
+    // - remove them from the eoe op stack so that repeat op above in the tree won't know about them
+    // - add ourself (the cache op), as an eoe op
+    // We do this so that those old leafs become 1-time use (up to eoe), never repeated.  Instead
+    // the repeating behaviours shall be invoked against the cache op.
+    std::shared_ptr<DatasetOp> leaf_op = PopFromEOEOpStack();
+    while (leaf_op != nullptr) {
+      leaf_op->ClearControlFlag(DatasetOp::kDeOpLastRepeat);
+      leaf_op->ClearControlFlag(DatasetOp::kDeOpRepeated);
+      leaf_op = PopFromEOEOpStack();
+    }
+    AddToEOEOpStack(std::static_pointer_cast<DatasetOp>(node));
+  }
+
+  return Status::OK();
+}
+
+// All operators have a flag that might be set related to the repeat and any leaf nodes need to be set up
+// for use with a controlling repeat above it.
+Status RepeatPass::RunOnNode(std::shared_ptr<DatasetOp> node, bool *modified) {
+  // If we are in a repeat path, then set our repeated flag
+  if (is_repeated_) {
+    node->set_control_flag(DatasetOp::kDeOpRepeated);
+
+    // if we are a leaf node then save ourself in a stack for the repeat operator above us
+    if (node->IsLeaf()) {
+      AddToEOEOpStack(node);
+    }
+  }
+  return Status::OK();
+}
+
+// Turns off the tracking for operations under merge op
+Status RepeatPass::RunOnNode(std::shared_ptr<CacheMergeOp> node, bool *modified) {
+  // Setting the flag is needed since we didn't call the base class DatasetOp version
+  if (is_repeated_) node->set_control_flag(DatasetOp::kDeOpRepeated);
+  is_merge_ = false;
+  cache_lookup_.reset();  // If a repeat op did not consume this then it's no longer needed
+  return Status::OK();
+}
+
+// Saves the lookup up in case it needs to be referenced by a repeat
+Status RepeatPass::RunOnNode(std::shared_ptr<CacheLookupOp> node, bool *modified) {
+  if (!node->IsLeaf()) {
+    // By definition, the CacheLookup must be a leaf op.  Make that clear here.
+    RETURN_STATUS_UNEXPECTED("CacheLookupOp must be a leaf node!");
+  }
+
+  // If we are in a repeat path already, then there must be a repeat above the merge op
+  // In this case, we naturally are a repeating leaf op so add the required setup for leafs under repeat here.
+  if (is_repeated_) {
+    node->set_control_flag(DatasetOp::kDeOpRepeated);
+    AddToEOEOpStack(node);
+  } else {
+    // save the lookup op.  There could be a repeat in the cache miss leg of the merge op, in which case we
+    // may still need to be flagged as a repeating leaf.  We can't decide that here though, so save ourself
+    // into the pass so that the decision can be made during the processing of the cache miss leg of the merge.
+    cache_lookup_ = std::static_pointer_cast<DatasetOp>(node);
+  }
+  return Status::OK();
+}
+
+// Adds an operator to the eoe operator stack save area
+void RepeatPass::AddToEOEOpStack(std::shared_ptr<DatasetOp> dataset_op) { eoe_stack_.push(dataset_op); }
+
+// Pops an operator from the eoe operator stack save area
+std::shared_ptr<DatasetOp> RepeatPass::PopFromEOEOpStack() {
+  std::shared_ptr<DatasetOp> top_op = nullptr;
+  if (!eoe_stack_.empty()) {
+    top_op = eoe_stack_.top();
+    eoe_stack_.pop();
+  }
+  return top_op;
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/opt/post/repeat_pass.h

@@ -0,0 +1,98 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef DATASET_ENGINE_OPT_PASS_POST_REPEAT_PASS_
+#define DATASET_ENGINE_OPT_PASS_POST_REPEAT_PASS_
+
+#include <memory>
+#include <stack>
+#include <utility>
+#include "dataset/engine/opt/pass.h"
+
+namespace mindspore {
+namespace dataset {
+
+/// \class RepeatPass repeat_pass.h
+/// \brief This is a NodePass who's job is to perform setup actions for RepeatOps. A RepeatOp needs to have references
+///     to the eoe-producing (typically leaf) nodes underneath it.
+class RepeatPass : public NodePass {
+ public:
+  /// \brief Constructor
+  RepeatPass();
+
+  /// \brief Identifies the subtree below this node as being in a repeated path of the tree.
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status PreRunOnNode(std::shared_ptr<RepeatOp> node, bool *modified) override;
+
+  /// \brief Identifies the subtree below this node as being in a cache merge path
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status PreRunOnNode(std::shared_ptr<CacheMergeOp> node, bool *modified) override;
+
+  /// \brief Hooks up any identified eoe nodes under this repeat.
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<RepeatOp> node, bool *modified) override;
+
+  /// \brief CacheOp removes previous leaf ops and replaces them with itself
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<CacheOp> node, bool *modified) override;
+
+  /// \brief Turns of the tracking for operations under merge op
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<CacheMergeOp> node, bool *modified) override;
+
+  /// \brief Saves the lookup up in case it needs to be referenced by a repeat
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<CacheLookupOp> node, bool *modified) override;
+
+  /// \brief All operators have a flag that might be set related to the repeat and any leaf nodes need to be set up
+  ///     for use with a controlling repeat above it.
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<DatasetOp> node, bool *modified) override;
+
+ private:
+  /// \brief Adds an operator to the eoe operator stack save area
+  /// \param op - The dataset op to work add to eoe stack
+  /// \return Status - The error code return
+  void AddToEOEOpStack(std::shared_ptr<DatasetOp> dataset_op);
+
+  /// \brief Pops an operator from the eoe operator stack save area
+  /// \return shared_ptr to the popped operator
+  std::shared_ptr<DatasetOp> PopFromEOEOpStack();
+
+  bool is_repeated_;                                  // T/F if we are processing under a repeat
+  bool is_merge_;                                     // T/F if we are processing under a cache merge op
+  int32_t nested_repeats_;                            // A counter for nested repeats
+  std::stack<std::shared_ptr<DatasetOp>> eoe_stack_;  // A save area for leaf/eoe ops
+  std::shared_ptr<DatasetOp> cache_lookup_;           // A save area for a cache lookup op
+};
+}  // namespace dataset
+}  // namespace mindspore
+
+#endif  // DATASET_ENGINE_OPT_PASS_POST_REPEAT_PASS_

mindspore/ccsrc/dataset/engine/opt/pre/cache_pass.cc

@@ -0,0 +1,181 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <memory>
+#include "dataset/engine/opt/pre/cache_pass.h"
+#include "dataset/engine/opt/pre/cache_transform_pass.h"
+#include "dataset/engine/datasetops/cache_op.h"
+#include "dataset/engine/datasetops/source/celeba_op.h"
+#include "dataset/engine/datasetops/source/generator_op.h"
+#include "dataset/engine/datasetops/source/manifest_op.h"
+#include "dataset/engine/datasetops/source/mnist_op.h"
+#include "dataset/engine/datasetops/source/voc_op.h"
+#include "dataset/engine/datasetops/source/cifar_op.h"
+#include "dataset/engine/datasetops/source/coco_op.h"
+#include "dataset/engine/datasetops/source/image_folder_op.h"
+#include "dataset/engine/datasetops/source/random_data_op.h"
+#include "dataset/engine/datasetops/source/tf_reader_op.h"
+#include "dataset/engine/datasetops/source/mindrecord_op.h"
+
+namespace mindspore {
+namespace dataset {
+
+// Constructor
+CachePass::CachePass(CacheTransformPass *transform_pass)
+    : transform_pass_(transform_pass), is_caching_(false), leaf_op_(nullptr) {}
+
+// Identifies the subtree below this node as a cached descendant tree.
+Status CachePass::PreRunOnNode(std::shared_ptr<CacheOp> node, bool *modified) {
+  *modified = false;
+  MS_LOG(INFO) << "Cache transform pass: CacheOp found, identified descendant tree.";
+  if (is_caching_) {
+    RETURN_STATUS_UNEXPECTED("Nested cache operations is not supported!");
+  }
+  is_caching_ = true;
+  return Status::OK();
+}
+
+// Resets the tracking of the cache within the tree and assigns the operators that will be involved in a cache
+// transformation
+Status CachePass::RunOnNode(std::shared_ptr<CacheOp> node, bool *modified) {
+  *modified = false;
+  is_caching_ = false;  // We a no longer in a cache subtree.  clear the flag.
+  if (leaf_op_) {
+    MS_LOG(INFO) << "Cache transform pass: Set up transformation nodes for mappable cache.";
+    // Assign the leaf op into the transform pass, using move to null our copy of it, and also assign the cache op,
+    // using base class pointers.
+    transform_pass_->AddMappableCacheOperators(std::move(leaf_op_), node);
+  } else {
+    // If there was no leaf_op set, then this is a non-mappable scenario.
+
+    if (sampler_) {
+      // Grab the sampler that was saved from the leaf and plug it into the cache op
+      node->SetSampler(std::move(sampler_));
+      MS_LOG(INFO) << "Cache transform pass: Set up cache sampler from non-mappable leaf.";
+    } else {
+      // We're a cache op but no sampler was saved from leaf, so create a default sampler
+      int64_t num_samples = 0;
+      int64_t start_index = 0;
+      sampler_ = std::make_shared<SequentialSampler>(num_samples, start_index);
+      node->SetSampler(std::move(sampler_));
+      MS_LOG(INFO) << "Cache transform pass: Creating default sequential sampler for cache op.";
+    }
+
+    // Get the computed check sum from all ops in our cache path below us and ask the cache op to create it's cache
+    uint32_t cache_crc = DatasetOp::GenerateCRC(node);
+    RETURN_IF_NOT_OK(node->CreateCache(cache_crc));
+  }
+
+  return Status::OK();
+}
+
+// Common code for mappable leaf setup.
+Status CachePass::MappableCacheLeafSetup(std::shared_ptr<DatasetOp> leaf_op) {
+  // If a leaf has already been assigned, then we have more than one leaf inside this cache descendant tree.
+  if (is_caching_ && leaf_op_) {
+    RETURN_STATUS_UNEXPECTED("There is currently no support for multiple leaf nodes under cache.");
+  }
+
+  // If we are a leaf in the caching path, then save this leaf.
+  if (is_caching_) {
+    MS_LOG(DEBUG) << "Cache transform pass: Mappable leaf in a cache descendant tree detected";
+    leaf_op_ = std::move(leaf_op);
+  }
+  return Status::OK();
+}
+
+// Common code for non mappable leaf setup.
+Status CachePass::NonMappableCacheLeafSetup(std::shared_ptr<DatasetOp> leaf_op) {
+  // If a leaf has already been assigned, then we have more than one leaf inside this cache descendant tree.
+  if (is_caching_ && leaf_op_) {
+    RETURN_STATUS_UNEXPECTED("There is currently no support for multiple leaf nodes under cache.");
+  }
+
+  // Sampler for non mapable dataset only works if there is a downstream cache. Remove it from the leaf
+  // as save it for use by cache op in ascendant tree.
+  if (is_caching_) {
+    RETURN_IF_NOT_OK(leaf_op->FetchRemoveSampler(&sampler_));
+    MS_LOG(DEBUG) << "Cache transform pass: Non mappable leaf in a cache descendant tree detected";
+  } else {
+    // If we are a non-mappable leaf and are not in a cache tree, then this sampler is not used so we can
+    // remove it here.  The leaf itself will provide it's own methods of fetching the data (not sampler-based)
+    std::shared_ptr<Sampler> sampler_from_leaf;
+    RETURN_IF_NOT_OK(leaf_op->FetchRemoveSampler(&sampler_from_leaf));
+  }
+  return Status::OK();
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<TFReaderOp> node, bool *modified) {
+  if (is_caching_) {
+    // If we are a TF Reader in a caching tree, then change our config so that it becomes a basic
+    // TF reader that parses all files.  Selection of data will come from the sampler on the cache instead.
+    node->MakeSimpleProducer();
+  }
+  return NonMappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<RandomDataOp> node, bool *modified) {
+  return NonMappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<ImageFolderOp> node, bool *modified) {
+  return MappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<MnistOp> node, bool *modified) {
+  return MappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<GeneratorOp> node, bool *modified) {
+  return MappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<ManifestOp> node, bool *modified) {
+  return MappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<CifarOp> node, bool *modified) {
+  return MappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<VOCOp> node, bool *modified) {
+  return MappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<CocoOp> node, bool *modified) {
+  return MappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<CelebAOp> node, bool *modified) {
+  return MappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+
+// Perform leaf node cache tranform identifications
+Status CachePass::RunOnNode(std::shared_ptr<MindRecordOp> node, bool *modified) {
+  return MappableCacheLeafSetup(std::static_pointer_cast<DatasetOp>(node));
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/opt/pre/cache_pass.h

@@ -0,0 +1,138 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef DATASET_ENGINE_OPT_PASS_PRE_CACHE_PASS_H_
+#define DATASET_ENGINE_OPT_PASS_PRE_CACHE_PASS_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+#include "dataset/engine/opt/pass.h"
+
+namespace mindspore {
+namespace dataset {
+
+class CacheTransformPass;
+
+/// \class CachePass cache_pass.h
+/// \brief This is a NodePass who's job is to identify and set up the nodes that will be involved in a cache
+///     transformation. It works in conjunction with the CacheTransformPass
+class CachePass : public NodePass {
+ public:
+  /// \brief Constructor
+  /// \param[in] transform_pass Raw pointer back to controlling tree pass
+  explicit CachePass(CacheTransformPass *transform_pass);
+
+  /// \brief Identifies the subtree below this node as a cached descendant tree.
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status PreRunOnNode(std::shared_ptr<CacheOp> node, bool *modified) override;
+
+  /// \brief Resets the tracking of the cache within the tree and assigns the operators that will be involved in a cache
+  ///     transformation
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<CacheOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<TFReaderOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<RandomDataOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<ImageFolderOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<MnistOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<GeneratorOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<ManifestOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<CifarOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<VOCOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<CocoOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<CelebAOp> node, bool *modified) override;
+
+  /// \brief Perform leaf node cache tranform identifications
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<MindRecordOp> node, bool *modified) override;
+
+ private:
+  /// \brief Common code for mappable leaf setup.
+  /// \param[in] node The leaf node performing setup work.
+  /// \return Status The error code return
+  Status MappableCacheLeafSetup(std::shared_ptr<DatasetOp> leaf_op);
+
+  /// \brief Common code for non-mappable leaf setup.
+  /// \param[in] node The leaf node performing setup work.
+  /// \return Status The error code return
+  Status NonMappableCacheLeafSetup(std::shared_ptr<DatasetOp> leaf_op);
+
+  bool is_caching_;
+  std::shared_ptr<DatasetOp> leaf_op_;
+  std::shared_ptr<Sampler> sampler_;
+  CacheTransformPass *transform_pass_;  // Back pointer to the owning transform pass
+};
+
+}  // namespace dataset
+}  // namespace mindspore
+
+#endif  // DATASET_ENGINE_OPT_PASS_PRE_CACHE_PASS_

mindspore/ccsrc/dataset/engine/opt/pre/cache_transform_pass.cc

@@ -0,0 +1,108 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <vector>
+#include "dataset/engine/opt/pre/cache_pass.h"
+#include "dataset/engine/opt/pre/cache_transform_pass.h"
+#include "dataset/engine/execution_tree.h"
+#include "dataset/engine/cache/cache_client.h"
+#include "dataset/engine/datasetops/cache_lookup_op.h"
+#include "dataset/engine/datasetops/cache_merge_op.h"
+#include "dataset/engine/datasetops/cache_op.h"
+
+namespace mindspore {
+namespace dataset {
+
+// constructor
+CacheTransformPass::CacheTransformPass() {}
+
+// Runs a cache_pass first to set up the transformation nodes, and then drives any of these transformations
+Status CacheTransformPass::RunOnTree(ExecutionTree *tree, bool *modified) {
+  MS_LOG(INFO) << "Pre pass: Cache transform pass started.";
+  // Create the cache pass and run it.  The cache pass identifies and creates the leaf/cache pairs that we will
+  // use to execute a transform.
+  std::unique_ptr<Pass> cache_pass = std::make_unique<CachePass>(this);
+  RETURN_IF_NOT_OK(cache_pass->Run(tree, modified));
+
+  // Then, execute the transform for each pair
+  for (auto cache_pair : cache_pairs_) {
+    MS_LOG(DEBUG) << "Cache transform pass: Executing a cache op mappable transform.";
+    ExecuteCacheTransform(tree, cache_pair.first, cache_pair.second, cache_pair.second->cache_client());
+  }
+  MS_LOG(INFO) << "Pre pass: Cache transform pass complete.";
+  return Status::OK();
+}
+
+// Helper function to execute the cache transformation.
+Status CacheTransformPass::ExecuteCacheTransform(ExecutionTree *tree, std::shared_ptr<DatasetOp> leaf_op,
+                                                 std::shared_ptr<DatasetOp> cache_op,
+                                                 std::shared_ptr<CacheClient> cache_client) {
+  // Get local pointers the child/parent of the cache op.  It's possible that the parent is null if the cache was
+  // the root node.  It is also possible that cache_child == leaf_op
+  std::shared_ptr<DatasetOp> cache_child = cache_op->child(0);
+  DatasetOp *cache_parent = nullptr;
+  cache_op->Parent(&cache_parent, 0);  // fetch the cache op's parent
+
+  // Extract the sampler from the leaf.  We will overwrite this sampler with the lookup op later.
+  std::shared_ptr<Sampler> leaf_sampler = leaf_op->sampler();
+
+  // Construct the merge op with defaults
+  std::shared_ptr<CacheMergeOp> merge_op;
+  CacheMergeOp::Builder merge_builder;
+  RETURN_IF_NOT_OK(merge_builder.SetClient(cache_client).Build(&merge_op));
+  RETURN_IF_NOT_OK(tree->AssociateNode(merge_op));
+
+  // Construct the cache lookup op with defaults
+  std::shared_ptr<CacheLookupOp> cache_lookup_op;
+  CacheLookupOp::Builder lookup_builder;
+  RETURN_IF_NOT_OK(lookup_builder.SetClient(cache_client).SetSampler(std::move(leaf_sampler)).Build(&cache_lookup_op));
+  RETURN_IF_NOT_OK(tree->AssociateNode(cache_lookup_op));
+
+  // Overwrite the old sampler in this leaf op to become the lookup op
+  leaf_op->SetSampler(cache_lookup_op);
+
+  // If the cache had a parent, then go into that parent to remove the cache from it's child list and then
+  // replace it with the merge op.
+  if (cache_parent != nullptr) {
+    RETURN_IF_NOT_OK(cache_parent->RemoveChild(cache_op));
+    RETURN_IF_NOT_OK(cache_parent->AddChild(merge_op));
+  } else {
+    // If we didn't have a parent, then the merge op is the root node
+    RETURN_IF_NOT_OK(tree->AssignRoot(merge_op));
+  }
+
+  // Set the cache op to no longer be a parent over it's child. This will fully disconnect the old cache op.
+  // We maintain a local pointer to the old child though.
+  RETURN_IF_NOT_OK(cache_op->RemoveChild(cache_child));
+
+  // Connect the merge op
+  RETURN_IF_NOT_OK(merge_op->AddChild(std::move(cache_lookup_op)));
+  RETURN_IF_NOT_OK(merge_op->AddChild(std::move(cache_child)));
+
+  // At this point, the cache op has already had it's children and parents taken away. Calling remove
+  // on it at this point will not do any node hookups, and instead set internal fields to invalid.
+  RETURN_IF_NOT_OK(cache_op->Remove());
+
+  return Status::OK();
+}
+
+// Assigns the leaf and cache operators that are involved in a cache transformation
+void CacheTransformPass::AddMappableCacheOperators(std::shared_ptr<DatasetOp> leaf_op,
+                                                   std::shared_ptr<CacheOp> cache_op) {
+  cache_pairs_.push_back(std::make_pair(leaf_op, cache_op));
+}
+}  // namespace dataset
+}  // namespace mindspore

mindspore/ccsrc/dataset/engine/opt/pre/cache_transform_pass.h

@@ -0,0 +1,79 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef DATASET_ENGINE_OPT_PASS_PRE_CACHE_TRANSFORM_PASS_H_
+#define DATASET_ENGINE_OPT_PASS_PRE_CACHE_TRANSFORM_PASS_H_
+
+#include <memory>
+#include <utility>
+#include <vector>
+#include "dataset/engine/opt/pass.h"
+
+namespace mindspore {
+namespace dataset {
+
+class DatasetOp;
+
+class CacheClient;
+
+/// \class CacheTransformPass cache_transform_pass.h
+/// \brief This is a tree pass that will invoke a tree transformation to inject the correct operators for caching
+///     operations
+class CacheTransformPass : public TreePass {
+ public:
+  /// \brief Constructor
+  CacheTransformPass();
+
+  /// \brief Runs a cache_pass first to set up the transformation nodes, and then drives any of these transformations
+  /// \param[inout] tree The tree to operate on.
+  /// \param[inout] Indicate of the tree was modified.
+  /// \return Status The error code return
+  Status RunOnTree(ExecutionTree *tree, bool *modified) override;
+
+  /// \brief Assigns the leaf and cache operators that are involved in a cache transformation
+  /// \param[in] leaf_op The leaf operator involved in the cache transform
+  /// \param[in] cache_op The cache operator involved in the cache transform
+  void AddMappableCacheOperators(std::shared_ptr<DatasetOp> leaf_op, std::shared_ptr<CacheOp> cache_op);
+
+ private:
+  /// \brief Helper function to execute the cache transformation.
+  ///
+  ///     Input:
+  ///       Sampler
+  ///         |
+  ///       LeafOp --> OtherOps --> CacheOp
+  ///
+  ///     Transformed:
+  ///       Sampler --> CacheLookupOp ---------------->
+  ///                           |                       |
+  ///                           |                       MergeOp
+  ///                           |                       |
+  ///                           LeafOp --> OtherOps -->
+  ///
+  /// \param[in] leaf_op The leaf node in the transform
+  /// \param[in] cache_op The cache op in the transform (will get removed)
+  /// \param[in] cache_client The cache client
+  /// \return Status The error code return
+  Status ExecuteCacheTransform(ExecutionTree *tree, std::shared_ptr<DatasetOp> leaf_op,
+                               std::shared_ptr<DatasetOp> cache_op, std::shared_ptr<CacheClient> cache_client);
+
+  // The two operators that work together to establish the cache transform
+  std::vector<std::pair<std::shared_ptr<DatasetOp>, std::shared_ptr<CacheOp>>> cache_pairs_;
+};
+}  // namespace dataset
+}  // namespace mindspore
+
+#endif  // DATASET_ENGINE_OPT_PASS_PRE_CACHE_TRANSFORM_PASS_H_

mindspore/ccsrc/dataset/engine/opt/pre/removal_nodes.cc

@@ -24,12 +24,28 @@ namespace dataset {
 
 RemovalNodes::RemovalNodes(RemovalPass *removal_pass) : removal_pass_(removal_pass), is_caching_(false) {}
 
+// Identifies the subtree below this node as a cached descendant tree.
+Status RemovalNodes::PreRunOnNode(std::shared_ptr<CacheOp> node, bool *modified) {
+  *modified = false;
+  MS_LOG(INFO) << "Removal pass: CacheOp found, identified descendant tree.";
+  is_caching_ = true;
+  return Status::OK();
+}
+
+// Resets the tracking of the cache within the tree
+Status RemovalNodes::RunOnNode(std::shared_ptr<CacheOp> node, bool *modified) {
+  *modified = false;
+  MS_LOG(INFO) << "Removal pass: cache descendant tree complete.";
+  is_caching_ = false;
+  return Status::OK();
+}
+
 // Perform ShuffleOp removal check.
 Status RemovalNodes::RunOnNode(std::shared_ptr<ShuffleOp> node, bool *modified) {
   *modified = false;
   // If we are in a cache descendant tree, then this shuffle op needs to be removed
   if (is_caching_) {
-    MS_LOG(DEBUG) << "ShuffleOp identified for removal (CacheOp is in ascendant tree)";
+    MS_LOG(INFO) << "ShuffleOp identified for removal (CacheOp is in ascendant tree)";
     if (removal_pass_) {
       removal_pass_->AddToRemovalList(std::static_pointer_cast<DatasetOp>(node));
     } else {

mindspore/ccsrc/dataset/engine/opt/pre/removal_nodes.h

@@ -34,6 +34,18 @@ class RemovalNodes : public NodePass {
   /// \param[in] removal_pass Raw pointer back to controlling tree pass
   explicit RemovalNodes(RemovalPass *removal_pass);
 
+  /// \brief Identifies the subtree below this node as a cached descendant tree.
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status PreRunOnNode(std::shared_ptr<CacheOp> node, bool *modified) override;
+
+  /// \brief Resets the tracking of the cache within the tree
+  /// \param[in] node The node being visited
+  /// \param[inout] modified Indicator if the node was changed at all
+  /// \return Status The error code return
+  Status RunOnNode(std::shared_ptr<CacheOp> node, bool *modified) override;
+
   /// \brief Perform ShuffleOp removal check
   /// \param[in] node The node being visited
   /// \param[inout] modified Indicator if the node was changed at all

mindspore/ccsrc/dataset/engine/opt/pre/removal_pass.cc

@@ -28,6 +28,7 @@ RemovalPass::RemovalPass() {}
 
 // Runs a removal_nodes pass first to find out which nodes to remove, then removes them.
 Status RemovalPass::RunOnTree(ExecutionTree *tree, bool *modified) {
+  MS_LOG(INFO) << "Pre pass: removal pass started.";
   // Create the removal node pass which can identify which nodes need to be removed.
   std::unique_ptr<Pass> removal_nodes = std::make_unique<RemovalNodes>(this);
   RETURN_IF_NOT_OK(removal_nodes->Run(tree, modified));
@@ -36,6 +37,7 @@ Status RemovalPass::RunOnTree(ExecutionTree *tree, bool *modified) {
   for (auto node : removal_nodes_) {
     node->Remove();
   }
+  MS_LOG(INFO) << "Pre pass: removal pass complete.";
   return Status::OK();
 }
 

mindspore/ccsrc/dataset/util/allocator.h

@@ -87,8 +87,9 @@ class Allocator {
   std::shared_ptr<MemoryPool> pool_;
 };
 /// \brief It is a wrapper of unique_ptr with a custom allocator and acts like std::lock_guard such that the memory will
-/// be released when the object goes out of scope \tparam T The type of object to be allocated \tparam C Allocator.
-/// Default to std::allocator
+/// be released when the object goes out of scope
+/// \tparam T The type of object to be allocated
+/// \tparam C Allocator. Default to std::allocator
 template <typename T, typename C = std::allocator<T>>
 class MemGuard {
  public:
@@ -168,7 +169,7 @@ class MemGuard {
 
  private:
   allocator alloc_;
-  std::unique_ptr<T[], std::function<void(T *)>> ptr_;
+  std::unique_ptr<T[]> ptr_;
   size_t n_;
 };
 }  // namespace dataset

mindspore/ccsrc/dataset/util/cache_pool.cc

@@ -98,11 +98,6 @@ Status CachePool::Insert(const std::vector<ReadableSlice> &buf, CachePool::key_t
   } catch (std::bad_alloc &e) {
     if (sm_ != nullptr) {
       RETURN_IF_NOT_OK(sm_->Write(&bl.storage_key, buf));
-      // We have an assumption 0 is not a valid key from the design of AutoIndexObj.
-      // Make sure it is not 0.
-      if (bl.storage_key == 0) {
-        RETURN_STATUS_UNEXPECTED("Key 0 is returned which is unexpected");
-      }
     } else {
       return Status(StatusCode::kOutOfMemory, __LINE__, __FILE__);
     }

mindspore/ccsrc/dataset/util/services.cc

@@ -22,11 +22,11 @@
 #include <stdlib.h>
 #endif
 #include <unistd.h>
+#include "dataset/engine/cache/cache_server.h"
 #include "dataset/util/circular_pool.h"
 #include "dataset/util/random.h"
 #include "dataset/util/task_manager.h"
 
-#define SLOT_TASK_MGR 0
 namespace mindspore {
 namespace dataset {
 std::unique_ptr<Services> Services::instance_ = nullptr;
@@ -61,15 +61,25 @@ std::string Services::GetUniqueID() {
 
 TaskManager &Services::getTaskMgrInstance() {
   Services &sm = GetInstance();
-  return *(static_cast<TaskManager *>(sm.sa_[SLOT_TASK_MGR]));
+  return *(static_cast<TaskManager *>(sm.sa_[kSlotTaskMgr_]));
+}
+
+CacheServer &Services::getCacheServer() {
+  Services &sm = GetInstance();
+  return *(static_cast<CacheServer *>(sm.sa_[kSlotCacheMgr_]));
 }
 
 Status Services::CreateAllInstances() {
   // In order, TaskMgr, BufferMgr
   Status rc;
-  sa_[SLOT_TASK_MGR] = new (&rc, pool_) TaskManager();
+  sa_[kSlotTaskMgr_] = new (&rc, pool_) TaskManager();
   RETURN_IF_NOT_OK(rc);
-  rc = sa_[SLOT_TASK_MGR]->ServiceStart();
+  rc = sa_[kSlotTaskMgr_]->ServiceStart();
+  RETURN_IF_NOT_OK(rc);
+  // TODO(jesse) : Get the parameters from config file. Right now spill to /tmp and spawn 3 workers
+  sa_[kSlotCacheMgr_] = new (&rc, pool_) CacheServer("/tmp", 3);
+  RETURN_IF_NOT_OK(rc);
+  rc = sa_[kSlotCacheMgr_]->ServiceStart();
   return rc;
 }
 
@@ -83,8 +93,14 @@ Services::Services() : pool_(nullptr), sa_{nullptr} {
 Services::~Services() noexcept {
   try {
     // In reverse order
-    TaskManager *tm = static_cast<TaskManager *>(sa_[SLOT_TASK_MGR]);
-    if (tm) {
+    CacheServer *cs = static_cast<CacheServer *>(sa_[kSlotCacheMgr_]);
+    if (cs != nullptr) {
+      (void)cs->ServiceStop();
+      cs->~CacheServer();
+      pool_->Deallocate(cs);
+    }
+    TaskManager *tm = static_cast<TaskManager *>(sa_[kSlotTaskMgr_]);
+    if (tm != nullptr) {
       (void)tm->ServiceStop();
       tm->~TaskManager();
       pool_->Deallocate(tm);

mindspore/ccsrc/dataset/util/services.h

@@ -27,7 +27,7 @@
 namespace mindspore {
 namespace dataset {
 class TaskManager;
-
+class CacheServer;
 class Services {
  public:
   static Status CreateInstance() {
@@ -61,6 +61,8 @@ class Services {
 
   static TaskManager &getTaskMgrInstance();
 
+  static CacheServer &getCacheServer();
+
   std::shared_ptr<MemoryPool> GetServiceMemPool() { return pool_; }
 
 #if !defined(_WIN32) && !defined(_WIN64)
@@ -87,7 +89,9 @@ class Services {
   // We use pointers here instead of unique_ptr because we
   // want to have ultimate control on the order of
   // construction and destruction.
-  static constexpr int kNumServices_ = 1;
+  static constexpr int kSlotTaskMgr_ = 0;
+  static constexpr int kSlotCacheMgr_ = 1;
+  static constexpr int kNumServices_ = 2;
   Service *sa_[kNumServices_];
 
   Services();

mindspore/dataset/__init__.py

@@ -24,6 +24,7 @@ from .engine.datasets import TFRecordDataset, ImageFolderDatasetV2, MnistDataset
     TextFileDataset, CLUEDataset, Schema, Shuffle, zip, RandomDataset
 from .engine.samplers import DistributedSampler, PKSampler, RandomSampler, SequentialSampler, SubsetRandomSampler, \
     WeightedRandomSampler, Sampler
+from .engine.cache_client import DatasetCache
 from .engine.serializer_deserializer import serialize, deserialize, show
 from .engine.graphdata import GraphData
 

mindspore/dataset/engine/cache_client.py

@@ -0,0 +1,49 @@
+# Copyright 2019 Huawei Technologies Co., Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Cache client
+"""
+
+import copy
+from mindspore._c_dataengine import CacheClient
+
+class DatasetCache:
+    """
+    A client to interface with tensor caching service
+    """
+
+    def __init__(self, session_id=None, size=None, spilling=False):
+        if session_id is None:
+            raise RuntimeError("Session generation is not implemented yet. session id required")
+        self.size = size if size is not None else 0
+        if size < 0:
+            raise ValueError("cache size should be 0 or positive integer value but got: size={}".format(size))
+        if not isinstance(spilling, bool):
+            raise ValueError(
+                "spilling argument for cache should be a boolean value but got: spilling={}".format(spilling))
+        self.session_id = session_id
+        self.spilling = spilling
+        self.cache_client = CacheClient(session_id, size, spilling)
+
+    def __deepcopy__(self, memodict):
+        if id(self) in memodict:
+            return memodict[id(self)]
+        cls = self.__class__
+        new_cache = cls.__new__(cls)
+        memodict[id(self)] = new_cache
+        new_cache.session_id = copy.deepcopy(self.session_id, memodict)
+        new_cache.spilling = copy.deepcopy(self.spilling, memodict)
+        new_cache.size = copy.deepcopy(self.size, memodict)
+        new_cache.cache_client = self.cache_client
+        return new_cache

mindspore/dataset/engine/datasets.py

@@ -44,7 +44,7 @@ from .validators import check_batch, check_shuffle, check_map, check_filter, che
     check_take, check_project, check_imagefolderdatasetv2, check_mnist_cifar_dataset, check_manifestdataset, \
     check_tfrecorddataset, check_vocdataset, check_cocodataset, check_celebadataset, check_minddataset, \
     check_generatordataset, check_sync_wait, check_zip_dataset, check_add_column, check_textfiledataset, check_concat, \
-    check_split, check_bucket_batch_by_length, check_cluedataset, check_positive_int32
+    check_random_dataset, check_split, check_bucket_batch_by_length, check_cluedataset, check_positive_int32
 from ..core.datatypes import mstype_to_detype, mstypelist_to_detypelist
 
 try:
@@ -386,7 +386,7 @@ class Dataset:
 
     @check_map
     def map(self, input_columns=None, operations=None, output_columns=None, columns_order=None,
-            num_parallel_workers=None, python_multiprocessing=False):
+            num_parallel_workers=None, python_multiprocessing=False, cache=None):
         """
         Apply each operation in operations to this dataset.
 
@@ -427,6 +427,7 @@ class Dataset:
                 parallel (default=None, the value from the config will be used).
             python_multiprocessing (bool, optional): Parallelize python operations with multiple worker process. This
                 option could be beneficial if the python operation is computational heavy (default=False).
+            cache (DatasetCache, optional): Tensor cache to use. (default=None which means no cache is used)
 
         Returns:
             MapDataset, dataset after mapping operation.
@@ -541,7 +542,7 @@ class Dataset:
             >>> ds_mapped = ds_pyfunc.map(input_columns, operations, output_columns, columns_order)
         """
         return MapDataset(self, input_columns, operations, output_columns, columns_order, num_parallel_workers,
-                          python_multiprocessing)
+                          python_multiprocessing, cache)
 
     @check_filter
     def filter(self, predicate, input_columns=None, num_parallel_workers=1):
@@ -1868,13 +1869,14 @@ class MapDataset(DatasetOp):
             in parallel (default=None).
         python_multiprocessing (bool, optional): Parallelize python operations with multiple worker process. This
             option could be beneficial if the python operation is computational heavy (default=False).
+        cache (DatasetCache, optional): Tensor cache to use. (default=None which means no cache is used)
 
         Raises:
             ValueError: If len(input_columns) != len(output_columns) and columns_order is not specified.
     """
 
     def __init__(self, input_dataset, input_columns=None, operations=None, output_columns=None, columns_order=None,
-                 num_parallel_workers=None, python_multiprocessing=False):
+                 num_parallel_workers=None, python_multiprocessing=False, cache=None):
         super().__init__(num_parallel_workers)
         self.children.append(input_dataset)
         if input_columns is not None and not isinstance(input_columns, list):
@@ -1886,6 +1888,7 @@ class MapDataset(DatasetOp):
         if output_columns is not None and not isinstance(output_columns, list):
             output_columns = [output_columns]
         self.output_columns = output_columns
+        self.cache = cache
         self.columns_order = columns_order
 
         if self.input_columns and self.output_columns \
@@ -1904,6 +1907,7 @@ class MapDataset(DatasetOp):
         args["operations"] = self.operations
         args["output_columns"] = self.output_columns
         args["columns_order"] = self.columns_order
+        args["cache"] = self.cache.cache_client if self.cache is not None else None
         return args
 
     def get_dataset_size(self):
@@ -1929,6 +1933,7 @@ class MapDataset(DatasetOp):
         new_op.parent = copy.deepcopy(self.parent, memodict)
         new_op.input_indexs = copy.deepcopy(self._input_indexs, memodict)
         new_op.python_multiprocessing = copy.deepcopy(self.python_multiprocessing, memodict)
+        new_op.cache = copy.deepcopy(self.cache, memodict)
         new_op.operations = self.operations
         return new_op
 
@@ -2346,7 +2351,7 @@ class RangeDataset(MappableDataset):
         return False
 
 
-def _select_sampler(num_samples, input_sampler, shuffle, num_shards, shard_id):
+def _select_sampler(num_samples, input_sampler, shuffle, num_shards, shard_id, non_mappable=False):
     """
     Create sampler based on user input.
 
@@ -2356,7 +2361,11 @@ def _select_sampler(num_samples, input_sampler, shuffle, num_shards, shard_id):
         shuffle (bool): Shuffle.
         num_shards (int): Number of shard for sharding.
         shard_id (int): Shard ID.
+        non_mappable (bool, optional): Indicate if caller is non-mappable dataset for special handling (default=False).
     """
+    if non_mappable is True and all(arg is None for arg in [num_samples, shuffle, num_shards, shard_id, input_sampler]):
+        return None
+
     if input_sampler is not None:
         # If the user provided a sampler, then it doesn't matter what the other args are because
         # we are being asked specifically to use the given sampler.
@@ -2369,7 +2378,7 @@ def _select_sampler(num_samples, input_sampler, shuffle, num_shards, shard_id):
         if (isinstance(input_sampler, (samplers.SequentialSampler, samplers.DistributedSampler,
                                        samplers.RandomSampler, samplers.SubsetRandomSampler,
                                        samplers.WeightedRandomSampler, samplers.Sampler)) and
-                (num_shards is not None or shard_id is not None or shuffle is not None or num_samples is not None)):
+                (any(arg is not None for arg in [num_shards, shard_id, shuffle, num_samples]))):
             raise ValueError(
                 'Conflicting arguments during sampler assignments. num_samples: {}, num_shards: {},'
                 ' shard_id: {}, shuffle: {})'.format(num_samples, num_shards, shard_id, shuffle))
@@ -2458,6 +2467,7 @@ class ImageFolderDatasetV2(MappableDataset):
             into (default=None).
         shard_id (int, optional): The shard ID within num_shards (default=None). This
             argument should be specified only when num_shards is also specified.
+        cache (DatasetCache, optional): Tensor cache to use. (default=None which means no cache is used)
 
     Raises:
         RuntimeError: If sampler and shuffle are specified at the same time.
@@ -2482,7 +2492,7 @@ class ImageFolderDatasetV2(MappableDataset):
     @check_imagefolderdatasetv2
     def __init__(self, dataset_dir, num_samples=None, num_parallel_workers=None,
                  shuffle=None, sampler=None, extensions=None, class_indexing=None,
-                 decode=False, num_shards=None, shard_id=None):
+                 decode=False, num_shards=None, shard_id=None, cache=None):
         super().__init__(num_parallel_workers)
 
         self.dataset_dir = dataset_dir
@@ -2494,6 +2504,7 @@ class ImageFolderDatasetV2(MappableDataset):
         self.decode = decode
         self.num_shards = num_shards
         self.shard_id = shard_id
+        self.cache = cache
 
     def get_args(self):
         args = super().get_args()
@@ -2506,6 +2517,7 @@ class ImageFolderDatasetV2(MappableDataset):
         args["decode"] = self.decode
         args["num_shards"] = self.num_shards
         args["shard_id"] = self.shard_id
+        args["cache"] = self.cache.cache_client if self.cache is not None else None
         return args
 
     def get_dataset_size(self):
@@ -3251,6 +3263,7 @@ class TFRecordDataset(SourceDataset):
             argument should be specified only when num_shards is also specified.
         shard_equal_rows (bool): Get equal rows for all shards(default=False). If shard_equal_rows is false, number
             of rows of each shard may be not equal.
+        cache (DatasetCache, optional): Tensor cache to use. (default=None which means no cache is used)
     Examples:
         >>> import mindspore.dataset as ds
         >>> import mindspore.common.dtype as mstype
@@ -3268,7 +3281,7 @@ class TFRecordDataset(SourceDataset):
 
     @check_tfrecorddataset
     def __init__(self, dataset_files, schema=None, columns_list=None, num_samples=None, num_parallel_workers=None,
-                 shuffle=Shuffle.GLOBAL, num_shards=None, shard_id=None, shard_equal_rows=False):
+                 shuffle=Shuffle.GLOBAL, num_shards=None, shard_id=None, shard_equal_rows=False, cache=None):
         super().__init__(num_parallel_workers)
         self.dataset_files = self._find_files(dataset_files)
         self.dataset_files.sort()
@@ -3280,6 +3293,7 @@ class TFRecordDataset(SourceDataset):
         self.schema = schema
         self.columns_list = columns_list
         self.num_samples = num_samples
+        self.cache = cache
         if schema_obj is not None and num_samples is None:
             self.num_samples = schema_obj.num_rows
 
@@ -3295,6 +3309,14 @@ class TFRecordDataset(SourceDataset):
         else:
             self.shuffle_level = shuffle
             self.shuffle_files = True
+
+        # The TF record dataset does not directly support a sampler.  It has provided sampling arguments
+        # (shuffle, num_samples, num_shards, shard_id) and it DOES support sampling if somewhere above it in
+        # the pipeline contains a cache.  If there is no cache above it, then this sampler is not used.
+        sampler_shuffle = self.shuffle_files
+        sampler = None
+        self.sampler = _select_sampler(self.num_samples, sampler, sampler_shuffle, num_shards, shard_id,
+                                       non_mappable=True)
         self.shard_equal_rows = shard_equal_rows
 
     def get_args(self):
@@ -3318,6 +3340,8 @@ class TFRecordDataset(SourceDataset):
         args["num_shards"] = self.num_shards
         args["shard_id"] = self.shard_id
         args["shard_equal_rows"] = self.shard_equal_rows
+        args["cache"] = self.cache.cache_client if self.cache is not None else None
+        args["sampler"] = self.sampler
         return args
 
     def get_dataset_size(self, estimate=False):
@@ -3803,43 +3827,61 @@ class RandomDataset(SourceDataset):
     A source dataset that generates random data.
 
     Args:
-        num_samples (int): number of samples to generate.
+        total_rows (int): number of rows for the dataset to generate (default=None, number of rows is random)
         schema (str or Schema, optional): Path to the json schema file or schema object (default=None).
             If the schema is not provided, the random dataset generates a random schema.
         columns_list (list[str], optional): List of columns to be read (default=None, read all columns)
+        num_samples (int): number of samples to draw from the total. (default=None, which means all rows)
         num_parallel_workers (int, optional): number of workers to read the data
             (default=None, number set in the config).
+        cache (DatasetCache, optional): Tensor cache to use. (default=None which means no cache is used)
+        shuffle (bool, optional): Whether or not to perform shuffle on the dataset
+            (default=None, expected order behavior shown in the table).
+        num_shards (int, optional): Number of shards that the dataset should be divided
+            into (default=None).
+        shard_id (int, optional): The shard ID within num_shards (default=None). This
+            argument should be specified only when num_shards is also specified.
     """
 
-    def __init__(self, schema=None, columns_list=None, num_samples=None, num_parallel_workers=None):
+    @check_random_dataset
+    def __init__(self, total_rows=None, schema=None, columns_list=None, num_samples=None, num_parallel_workers=None,
+                 cache=None, shuffle=None, num_shards=None, shard_id=None):
         super().__init__(num_parallel_workers)
         schema_obj = None
         if (schema is not None) and (not isinstance(schema, Schema)):
             schema_obj = Schema(schema)  # read the schema file and convert to schema object to validate it
         self.schema = schema
         self.columns_list = columns_list
-        if schema_obj is not None and num_samples is None:
-            self.num_samples = schema_obj.num_rows
-        elif num_samples is None:
-            self.num_samples = 0
+        sampler = None
+        self.sampler = _select_sampler(num_samples, sampler, shuffle, num_shards, shard_id, non_mappable=True)
+        self.num_samples = num_samples
+        self.cache = cache
+        if schema_obj is not None and total_rows is None:
+            self.total_rows = schema_obj.num_rows
+        elif total_rows is None:
+            self.total_rows = 0
         else:
-            self.num_samples = num_samples
+            self.total_rows = total_rows
+        self.num_shards = num_shards
+        self.shard_id = shard_id
+        self.shuffle_level = shuffle
 
     def get_args(self):
         args = super().get_args()
         if self.schema is not None:
             if isinstance(self.schema, Schema):
                 self.schema.datasetType = 'Random'
-                if self.num_samples is not None:
-                    self.schema.num_rows = self.num_samples
+                if self.total_rows is not None:
+                    self.schema.num_rows = self.total_rows
                 args["schema_json_string"] = self.schema.to_json()
             else:
                 args["schema_file_path"] = self.schema
         args["schema"] = self.schema
-        if self.columns_list is not None:
-            args["columns_list"] = self.columns_list
-        if self.num_samples is not None:
-            args["num_samples"] = self.num_samples
+        args["columns_list"] = self.columns_list
+        args["num_samples"] = self.num_samples
+        args["total_rows"] = self.total_rows
+        args["cache"] = self.cache.cache_client if self.cache is not None else None
+        args["sampler"] = self.sampler
         return args
 
     def get_dataset_size(self):
@@ -3849,18 +3891,29 @@ class RandomDataset(SourceDataset):
         Return:
             Number, number of batches.
         """
+
+        num_rows = CifarOp.get_num_rows(self.dataset_dir, True)
+
+        rows_per_shard = get_num_rows(num_rows, self.num_shards)
         rows_from_sampler = self._get_sampler_dataset_size()
 
         if rows_from_sampler is None:
-            return self.num_samples
+            return rows_per_shard
 
-        return min(rows_from_sampler, self.num_samples)
+        return min(rows_from_sampler, rows_per_shard)
 
     def is_shuffled(self):
-        return True
+        if self.shuffle_level is None:
+            return True
+
+        return self.shuffle_level or self.sampler.is_shuffled()
 
     def is_sharded(self):
-        return False
+        if self.num_shards is not None:
+            return self.num_shards > 1
+
+        return self.sampler.is_sharded()
+
 
 
 class Schema:

mindspore/dataset/engine/serializer_deserializer.py

@@ -173,7 +173,9 @@ def traverse(node):
     #    num_samples, shard_id, num_shards, shuffle
     # These arguments get moved into the sampler itself, so they are no longer needed to
     # be set at the dataset level.
-    if 'sampler' in node_args.keys():
+    # TF Record is a special case because it uses both the dataset and sampler arguments
+    # which is not decided until later during tree preparation phase.
+    if node_repr['op_type'] != 'TFRecordDataset' and 'sampler' in node_args.keys():
         if 'num_samples' in node_repr.keys():
             node_repr['num_samples'] = None
         if 'shuffle' in node_repr.keys():

mindspore/dataset/engine/validators.py

@@ -29,10 +29,11 @@ from ..core.validator_helpers import parse_user_args, type_check, type_check_lis
 
 from . import datasets
 from . import samplers
+from . import cache_client
 
 
 def check_imagefolderdatasetv2(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(ImageFolderDatasetV2)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(ImageFolderDatasetV2)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -58,7 +59,7 @@ def check_imagefolderdatasetv2(method):
 
 
 def check_mnist_cifar_dataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(ManifestDataset, Cifar10/100Dataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(ManifestDataset, Cifar10/100Dataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -81,7 +82,7 @@ def check_mnist_cifar_dataset(method):
 
 
 def check_manifestdataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(ManifestDataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(ManifestDataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -108,7 +109,7 @@ def check_manifestdataset(method):
 
 
 def check_tfrecorddataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(TFRecordDataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(TFRecordDataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -134,7 +135,7 @@ def check_tfrecorddataset(method):
 
 
 def check_vocdataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(VOCDataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(VOCDataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -175,7 +176,7 @@ def check_vocdataset(method):
 
 
 def check_cocodataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(CocoDataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(CocoDataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -211,7 +212,7 @@ def check_cocodataset(method):
 
 
 def check_celebadataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(CelebADataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(CelebADataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -247,7 +248,7 @@ def check_celebadataset(method):
 
 
 def check_minddataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(MindDataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(MindDataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -279,7 +280,7 @@ def check_minddataset(method):
 
 
 def check_generatordataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(GeneratorDataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(GeneratorDataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -344,6 +345,27 @@ def check_generatordataset(method):
 
     return new_method
 
+def check_random_dataset(method):
+    """A wrapper that wraps a parameter checker to the original Dataset(RandomDataset)."""
+
+    @wraps(method)
+    def new_method(self, *args, **kwargs):
+        _, param_dict = parse_user_args(method, *args, **kwargs)
+
+        nreq_param_int = ['num_samples', 'num_parallel_workers', 'num_shards', 'shard_id', 'total_rows']
+        nreq_param_bool = ['shuffle']
+        nreq_param_list = ['columns_list']
+
+        validate_dataset_param_value(nreq_param_int, param_dict, int)
+        validate_dataset_param_value(nreq_param_bool, param_dict, bool)
+        validate_dataset_param_value(nreq_param_list, param_dict, list)
+
+        check_sampler_shuffle_shard_options(param_dict)
+
+        return method(self, *args, **kwargs)
+
+    return new_method
+
 
 def check_pad_info(key, val):
     """check the key and value pair of pad_info in batch"""
@@ -506,7 +528,7 @@ def check_map(method):
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
-        [input_columns, _, output_columns, columns_order, num_parallel_workers, python_multiprocessing], _ = \
+        [input_columns, _, output_columns, columns_order, num_parallel_workers, python_multiprocessing, cache], _ = \
             parse_user_args(method, *args, **kwargs)
 
         nreq_param_columns = ['input_columns', 'output_columns']
@@ -516,6 +538,8 @@ def check_map(method):
         if num_parallel_workers is not None:
             check_num_parallel_workers(num_parallel_workers)
         type_check(python_multiprocessing, (bool,), "python_multiprocessing")
+        if cache is not None:
+            type_check(cache, (cache_client.DatasetCache,), "cache")
 
         for param_name, param in zip(nreq_param_columns, [input_columns, output_columns]):
             if param is not None:
@@ -720,7 +744,7 @@ def check_add_column(method):
 
 
 def check_cluedataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(CLUEDataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(CLUEDataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -750,7 +774,7 @@ def check_cluedataset(method):
 
 
 def check_textfiledataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(TextFileDataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(TextFileDataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -823,7 +847,7 @@ def check_gnn_graphdata(method):
 
 
 def check_gnn_get_all_nodes(method):
-    """A wrapper that wrap a parameter checker to the GNN `get_all_nodes` function."""
+    """A wrapper that wraps a parameter checker to the GNN `get_all_nodes` function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -836,7 +860,7 @@ def check_gnn_get_all_nodes(method):
 
 
 def check_gnn_get_all_edges(method):
-    """A wrapper that wrap a parameter checker to the GNN `get_all_edges` function."""
+    """A wrapper that wraps a parameter checker to the GNN `get_all_edges` function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -849,7 +873,7 @@ def check_gnn_get_all_edges(method):
 
 
 def check_gnn_get_nodes_from_edges(method):
-    """A wrapper that wrap a parameter checker to the GNN `get_nodes_from_edges` function."""
+    """A wrapper that wraps a parameter checker to the GNN `get_nodes_from_edges` function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -862,7 +886,7 @@ def check_gnn_get_nodes_from_edges(method):
 
 
 def check_gnn_get_all_neighbors(method):
-    """A wrapper that wrap a parameter checker to the GNN `get_all_neighbors` function."""
+    """A wrapper that wraps a parameter checker to the GNN `get_all_neighbors` function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -877,7 +901,7 @@ def check_gnn_get_all_neighbors(method):
 
 
 def check_gnn_get_sampled_neighbors(method):
-    """A wrapper that wrap a parameter checker to the GNN `get_sampled_neighbors` function."""
+    """A wrapper that wraps a parameter checker to the GNN `get_sampled_neighbors` function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -905,7 +929,7 @@ def check_gnn_get_sampled_neighbors(method):
 
 
 def check_gnn_get_neg_sampled_neighbors(method):
-    """A wrapper that wrap a parameter checker to the GNN `get_neg_sampled_neighbors` function."""
+    """A wrapper that wraps a parameter checker to the GNN `get_neg_sampled_neighbors` function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -921,7 +945,7 @@ def check_gnn_get_neg_sampled_neighbors(method):
 
 
 def check_gnn_random_walk(method):
-    """A wrapper that wrap a parameter checker to the GNN `random_walk` function."""
+    """A wrapper that wraps a parameter checker to the GNN `random_walk` function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -968,7 +992,7 @@ def check_aligned_list(param, param_name, member_type):
 
 
 def check_gnn_get_node_feature(method):
-    """A wrapper that wrap a parameter checker to the GNN `get_node_feature` function."""
+    """A wrapper that wraps a parameter checker to the GNN `get_node_feature` function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -1012,7 +1036,7 @@ def check_gnn_get_edge_feature(method):
 
 
 def check_numpyslicesdataset(method):
-    """A wrapper that wrap a parameter checker to the original Dataset(NumpySlicesDataset)."""
+    """A wrapper that wraps a parameter checker to the original Dataset(NumpySlicesDataset)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):

mindspore/dataset/text/validators.py

@@ -39,7 +39,7 @@ def check_unique_list_of_words(words, arg_name):
 
 
 def check_lookup(method):
-    """A wrapper that wrap a parameter checker to the original function."""
+    """A wrapper that wraps a parameter checker to the original function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -56,7 +56,7 @@ def check_lookup(method):
 
 
 def check_from_file(method):
-    """A wrapper that wrap a parameter checker to the original function."""
+    """A wrapper that wraps a parameter checker to the original function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -74,7 +74,7 @@ def check_from_file(method):
 
 
 def check_from_list(method):
-    """A wrapper that wrap a parameter checker to the original function."""
+    """A wrapper that wraps a parameter checker to the original function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -97,7 +97,7 @@ def check_from_list(method):
 
 
 def check_from_dict(method):
-    """A wrapper that wrap a parameter checker to the original function."""
+    """A wrapper that wraps a parameter checker to the original function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -285,7 +285,7 @@ def check_bert_tokenizer(method):
 
 
 def check_from_dataset(method):
-    """A wrapper that wrap a parameter checker to the original function."""
+    """A wrapper that wraps a parameter checker to the original function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -328,7 +328,7 @@ def check_from_dataset(method):
 
 
 def check_ngram(method):
-    """A wrapper that wrap a parameter checker to the original function."""
+    """A wrapper that wraps a parameter checker to the original function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):

mindspore/dataset/transforms/vision/validators.py

@@ -114,7 +114,7 @@ def check_erasing_value(value):
 
 
 def check_crop(method):
-    """A wrapper that wrap a parameter checker to the original function(crop operation)."""
+    """A wrapper that wraps a parameter checker to the original function(crop operation)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -127,7 +127,7 @@ def check_crop(method):
 
 
 def check_resize_interpolation(method):
-    """A wrapper that wrap a parameter checker to the original function(resize interpolation operation)."""
+    """A wrapper that wraps a parameter checker to the original function(resize interpolation operation)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -142,7 +142,7 @@ def check_resize_interpolation(method):
 
 
 def check_resize(method):
-    """A wrapper that wrap a parameter checker to the original function(resize operation)."""
+    """A wrapper that wraps a parameter checker to the original function(resize operation)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -155,7 +155,7 @@ def check_resize(method):
 
 
 def check_random_resize_crop(method):
-    """A wrapper that wrap a parameter checker to the original function(random resize crop operation)."""
+    """A wrapper that wraps a parameter checker to the original function(random resize crop operation)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -178,7 +178,7 @@ def check_random_resize_crop(method):
 
 
 def check_prob(method):
-    """A wrapper that wrap a parameter checker(check the probability) to the original function."""
+    """A wrapper that wraps a parameter checker(check the probability) to the original function."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -192,7 +192,7 @@ def check_prob(method):
 
 
 def check_normalize_c(method):
-    """A wrapper that wrap a parameter checker to the original function(normalize operation written in C++)."""
+    """A wrapper that wraps a parameter checker to the original function(normalize operation written in C++)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):
@@ -205,7 +205,7 @@ def check_normalize_c(method):
 
 
 def check_normalize_py(method):
-    """A wrapper that wrap a parameter checker to the original function(normalize operation written in Python)."""
+    """A wrapper that wraps a parameter checker to the original function(normalize operation written in Python)."""
 
     @wraps(method)
     def new_method(self, *args, **kwargs):

tests/ut/cpp/dataset/c_api_test.cc

@@ -738,7 +738,7 @@ TEST_F(MindDataTestPipeline, TestProjectMap) {
   EXPECT_TRUE(ds != nullptr);
 
   // Create a Project operation on ds
-  std::vector<std::string> column_project = {"label"};
+  std::vector<std::string> column_project = {"image"};
   ds = ds->Project(column_project);
   EXPECT_TRUE(ds != nullptr);
 

tests/ut/cpp/dataset/cache_op_test.cc

@@ -0,0 +1,579 @@
+/**
+ * Copyright 2020 Huawei Technologies Co., Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <string>
+#include "dataset/core/client.h"
+#include "dataset/engine/cache/cache_client.h"
+#include "dataset/engine/execution_tree.h"
+#include "dataset/engine/datasetops/cache_op.h"
+#include "dataset/engine/datasetops/cache_lookup_op.h"
+#include "dataset/engine/datasetops/cache_merge_op.h"
+#include "dataset/engine/datasetops/source/image_folder_op.h"
+#include "common/common.h"
+#include "gtest/gtest.h"
+#include "utils/log_adapter.h"
+#include "dataset/util/storage_container.h"  // lint !e322
+#include "dataset/engine/datasetops/source/random_data_op.h"
+#include "dataset/engine/data_schema.h"
+
+using namespace mindspore::dataset;
+using mindspore::LogStream;
+using mindspore::dataset::CacheClient;
+using mindspore::dataset::TaskGroup;
+using mindspore::ExceptionType::NoExceptionType;
+using mindspore::MsLogLevel::INFO;
+
+class MindDataTestCacheOp : public UT::DatasetOpTesting {
+ public:
+  void SetUp() override {
+    DatasetOpTesting::SetUp();
+    GlobalInit();
+  }
+};
+
+TEST_F(MindDataTestCacheOp, TestCacheServer) {
+  Status rc;
+  CacheClient myClient(1, 0, true);  // use arbitrary session of 1, size of 0, spilling is true
+  // cksum value of 1 for CreateCache here...normally you do not directly create a cache and the cksum arg is generated.
+  rc = myClient.CreateCache(1, true);
+  EXPECT_TRUE(rc.IsOk());
+  std::cout << myClient << std::endl;
+
+  // Create a schema using the C api's
+  int32_t rank = 0;  // not used
+  std::unique_ptr<DataSchema> testSchema = std::make_unique<DataSchema>();
+  // 2 columns. First column is an "image" 640,480,3
+  TensorShape c1Shape({640, 480, 3});
+  ColDescriptor c1("image", DataType(DataType::DE_INT8), TensorImpl::kFlexible,
+                   rank,  // not used
+                   &c1Shape);
+  // Column 2 will just be a scalar label number
+  TensorShape c2Shape({});  // empty shape is a 1-value scalar Tensor
+  ColDescriptor c2("label", DataType(DataType::DE_UINT32), TensorImpl::kFlexible, rank, &c2Shape);
+
+  testSchema->AddColumn(c1);
+  testSchema->AddColumn(c2);
+
+  std::unordered_map<std::string, int32_t> map;
+  rc = testSchema->GetColumnNameMap(&map);
+  EXPECT_TRUE(rc.IsOk());
+
+  // Test the CacheSchema api
+  rc = myClient.CacheSchema(map);
+  EXPECT_TRUE(rc.IsOk());
+
+  // Create a tensor, take a snapshot and restore it back, and compare.
+  std::shared_ptr<Tensor> t = std::make_shared<Tensor>(TensorShape({2, 3}), DataType(DataType::DE_UINT64));
+  t->SetItemAt<uint64_t>({0, 0}, 1);
+  t->SetItemAt<uint64_t>({0, 1}, 2);
+  t->SetItemAt<uint64_t>({0, 2}, 3);
+  t->SetItemAt<uint64_t>({1, 0}, 4);
+  t->SetItemAt<uint64_t>({1, 1}, 5);
+  t->SetItemAt<uint64_t>({1, 2}, 6);
+  std::cout << *t << std::endl;
+  TensorTable tbl;
+  TensorRow row;
+  row.push_back(t);
+  int64_t row_id;
+  rc = myClient.WriteRow(row, &row_id);
+  EXPECT_TRUE(rc.IsOk());
+
+  // Switch off build phase.
+  rc = myClient.BuildPhaseDone();
+  EXPECT_TRUE(rc.IsOk());
+
+  // Now restore from cache.
+  row.clear();
+  rc = myClient.GetRows({row_id}, &tbl);
+  row = tbl.front();
+  EXPECT_TRUE(rc.IsOk());
+  auto r = row.front();
+  std::cout << *r << std::endl;
+  // Compare
+  bool cmp = (*t == *r);
+  EXPECT_TRUE(cmp);
+
+  // Get back the schema and verify
+  std::unordered_map<std::string, int32_t> map_out;
+  rc = myClient.FetchSchema(&map_out);
+  EXPECT_TRUE(rc.IsOk());
+  cmp = (map_out == map);
+  EXPECT_TRUE(cmp);
+
+  // Test Purge and Destroy
+  rc = myClient.PurgeCache();
+  EXPECT_TRUE(rc.IsOk());
+  rc = myClient.DestroyCache();
+  EXPECT_TRUE(rc.IsOk());
+}
+
+TEST_F(MindDataTestCacheOp, TestConcurrencyRequest) {
+  // Clear the rc of the master thread if any
+  (void)TaskManager::GetMasterThreadRc();
+  TaskGroup vg;
+  Status rc;
+  CacheClient myClient(1, 1, true);  // use arbitrary session of 1, size 1, spilling is true
+  // cksum value of 1 for CreateCache here...normally you do not directly create a cache and the cksum arg is generated.
+  rc = myClient.CreateCache(1, true);
+  EXPECT_TRUE(rc.IsOk());
+  std::cout << myClient << std::endl;
+  std::shared_ptr<Tensor> t = std::make_shared<Tensor>(TensorShape({2, 3}), DataType(DataType::DE_UINT64));
+  t->SetItemAt<uint64_t>({0, 0}, 1);
+  t->SetItemAt<uint64_t>({0, 1}, 2);
+  t->SetItemAt<uint64_t>({0, 2}, 3);
+  t->SetItemAt<uint64_t>({1, 0}, 4);
+  t->SetItemAt<uint64_t>({1, 1}, 5);
+  t->SetItemAt<uint64_t>({1, 2}, 6);
+  TensorTable tbl;
+  TensorRow row;
+  row.push_back(t);
+  // Cache tensor row t 5000 times using 10 threads.
+  for (auto k = 0; k < 10; ++k) {
+    Status vg_rc = vg.CreateAsyncTask("Test agent", [&myClient, &row]() -> Status {
+      TaskManager::FindMe()->Post();
+      for (auto i = 0; i < 500; i++) {
+        RETURN_IF_NOT_OK(myClient.WriteRow(row));
+      }
+      return Status::OK();
+    });
+    EXPECT_TRUE(vg_rc.IsOk());
+  }
+  ASSERT_TRUE(vg.join_all().IsOk());
+  ASSERT_TRUE(vg.GetTaskErrorIfAny().IsOk());
+  rc = myClient.BuildPhaseDone();
+  ASSERT_TRUE(rc.IsOk());
+  // Get statistics from the server.
+  CacheClient::ServiceStat stat{};
+  rc = myClient.GetStat(&stat);
+  ASSERT_TRUE(rc.IsOk());
+  std::cout << stat.min_row_id << ":" << stat.max_row_id << ":" << stat.num_mem_cached << ":" << stat.num_disk_cached
+            << "\n";
+  // Expect there are 5000 rows there.
+  EXPECT_EQ(5000, stat.max_row_id - stat.min_row_id + 1);
+  // Get them all back using row id and compare with tensor t.
+  for (auto i = stat.min_row_id; i <= stat.max_row_id; ++i) {
+    tbl.clear();
+    row.clear();
+    rc = myClient.GetRows({i}, &tbl);
+    EXPECT_TRUE(rc.IsOk());
+    row = tbl.front();
+    auto r = row.front();
+    bool cmp = (*t == *r);
+    EXPECT_TRUE(cmp);
+  }
+  rc = myClient.DestroyCache();
+  EXPECT_TRUE(rc.IsOk());
+}
+
+// Simple test with a repeated cache op over random data producer
+//
+//     RepeatOp
+//        |
+//     CacheOp
+//        |
+//   RandomDataOp
+//
+TEST_F(MindDataTestCacheOp, TestRandomDataCache1) {
+  Status rc;
+  int32_t rank = 0;  // not used
+  MS_LOG(INFO) << "UT test TestRandomDataCache1";
+  // Start with an empty execution tree
+  auto myTree = std::make_shared<ExecutionTree>();
+
+  // Create a schema using the C api's
+  std::unique_ptr<DataSchema> testSchema = std::make_unique<DataSchema>();
+
+  // 2 columns. First column is an "image" 640,480,3
+  TensorShape c1Shape({640, 480, 3});
+  ColDescriptor c1("image", DataType(DataType::DE_INT8), TensorImpl::kFlexible,
+                   rank,  // not used
+                   &c1Shape);
+
+  // Column 2 will just be a scalar label number
+  TensorShape c2Shape({});  // empty shape is a 1-value scalar Tensor
+  ColDescriptor c2("label", DataType(DataType::DE_UINT32), TensorImpl::kFlexible, rank, &c2Shape);
+
+  testSchema->AddColumn(c1);
+  testSchema->AddColumn(c2);
+
+  // RandomDataOp
+  std::shared_ptr<RandomDataOp> myRandomDataOp;
+  rc = RandomDataOp::Builder()
+         .SetRowsPerBuffer(4)
+         .SetNumWorkers(4)
+         .SetDataSchema(std::move(testSchema))
+         .SetTotalRows(50)  // 50 samples for now
+         .Build(&myRandomDataOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myRandomDataOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  // CacheOp
+  // size of 0, spilling is true
+  std::shared_ptr<CacheClient> myClient = std::make_shared<CacheClient>(1, 0, true);
+  std::shared_ptr<CacheOp> myCacheOp;
+
+  int64_t num_samples = 0;
+  int64_t start_index = 0;
+  auto seq_sampler = std::make_shared<SequentialSampler>(num_samples, start_index);
+  rc = CacheOp::Builder()
+         .SetNumWorkers(5)
+         .SetClient(myClient)
+         .SetRowsPerBuffer(4)
+         .SetSampler(std::move(seq_sampler))
+         .Build(&myCacheOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myCacheOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  // RepeatOp
+  uint32_t numRepeats = 4;
+  std::shared_ptr<RepeatOp> myRepeatOp;
+  rc = RepeatOp::Builder(numRepeats).Build(&myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  // Assign tree relations and root
+  rc = myRepeatOp->AddChild(myCacheOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myCacheOp->AddChild(myRandomDataOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssignRoot(myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  MS_LOG(INFO) << "Launching tree and begin iteration";
+  rc = myTree->Prepare();
+  EXPECT_TRUE(rc.IsOk());
+
+  // quick check to see what tree looks like
+  std::ostringstream ss;
+  ss << *myTree;  // some funny const error if I try to write directly to ms log stream
+  MS_LOG(INFO) << "Here's the tree:\n" << ss.str();
+
+  std::cout << *myClient << std::endl;
+
+  rc = myTree->Launch();
+  EXPECT_TRUE(rc.IsOk());
+
+  // Start the loop of reading tensors from our pipeline
+  DatasetIterator dI(myTree);
+  TensorRow tensorList;
+  rc = dI.FetchNextTensorRow(&tensorList);
+  EXPECT_TRUE(rc.IsOk());
+  int rowCount = 0;
+  while (!tensorList.empty()) {
+    // Don't display these rows, just count them
+    MS_LOG(INFO) << "Row fetched #: " << rowCount;
+    rc = dI.FetchNextTensorRow(&tensorList);
+    EXPECT_TRUE(rc.IsOk());
+    rowCount++;
+  }
+  ASSERT_EQ(rowCount, 200);
+  rc = myClient->DestroyCache();
+  EXPECT_TRUE(rc.IsOk());
+}
+
+//// Simple test with a repeated cache op over random data producer.
+//// This one will exceed memory and require a spill.
+////
+////     RepeatOp
+////        |
+////     CacheOp
+////        |
+////   RandomDataOp
+////
+TEST_F(MindDataTestCacheOp, TestRandomDataCacheSpill) {
+  Status rc;
+  int32_t rank = 0;  // not used
+  MS_LOG(INFO) << "UT test TestRandomDataCacheSpill";
+  // Start with an empty execution tree
+  auto myTree = std::make_shared<ExecutionTree>();
+
+  // Create a schema using the C api's
+  std::unique_ptr<DataSchema> testSchema = std::make_unique<DataSchema>();
+
+  // 2 columns. First column is an "image" 640,480,3
+  TensorShape c1Shape({640, 480, 3});
+  ColDescriptor c1("image", DataType(DataType::DE_INT8), TensorImpl::kFlexible,
+                   rank,  // not used
+                   &c1Shape);
+
+  // Column 2 will just be a scalar label number
+  TensorShape c2Shape({});  // empty shape is a 1-value scalar Tensor
+  ColDescriptor c2("label", DataType(DataType::DE_UINT32), TensorImpl::kFlexible, rank, &c2Shape);
+
+  testSchema->AddColumn(c1);
+  testSchema->AddColumn(c2);
+
+  // RandomDataOp
+  std::shared_ptr<RandomDataOp> myRandomDataOp;
+  rc = RandomDataOp::Builder()
+         .SetRowsPerBuffer(2)
+         .SetNumWorkers(4)
+         .SetDataSchema(std::move(testSchema))
+         .SetTotalRows(10)
+         .Build(&myRandomDataOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myRandomDataOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  // CacheOp
+  int64_t num_samples = 0;
+  int64_t start_index = 0;
+  auto seq_sampler = std::make_shared<SequentialSampler>(num_samples, start_index);
+  std::shared_ptr<CacheClient> myClient = std::make_shared<CacheClient>(1, 4, true);
+  std::shared_ptr<CacheOp> myCacheOp;
+  rc = CacheOp::Builder()
+         .SetNumWorkers(4)
+         .SetClient(myClient)
+         .SetRowsPerBuffer(3)
+         .SetSampler(std::move(seq_sampler))
+         .Build(&myCacheOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myCacheOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  // RepeatOp
+  uint32_t numRepeats = 4;
+  std::shared_ptr<RepeatOp> myRepeatOp;
+  rc = RepeatOp::Builder(numRepeats).Build(&myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  // Assign tree relations and root
+  rc = myRepeatOp->AddChild(myCacheOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myCacheOp->AddChild(myRandomDataOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssignRoot(myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  MS_LOG(INFO) << "Launching tree and begin iteration";
+  rc = myTree->Prepare();
+  EXPECT_TRUE(rc.IsOk());
+
+  std::cout << *myClient << std::endl;
+
+  rc = myTree->Launch();
+  EXPECT_TRUE(rc.IsOk());
+
+  // Start the loop of reading tensors from our pipeline
+  DatasetIterator dI(myTree);
+  TensorRow tensorList;
+  rc = dI.FetchNextTensorRow(&tensorList);
+  EXPECT_TRUE(rc.IsOk());
+  int rowCount = 0;
+  while (!tensorList.empty()) {
+    // Don't display these rows, just count them
+    MS_LOG(INFO) << "Row fetched #: " << rowCount;
+    rc = dI.FetchNextTensorRow(&tensorList);
+    EXPECT_TRUE(rc.IsOk());
+    rowCount++;
+  }
+  ASSERT_EQ(rowCount, 40);
+  rc = myClient->DestroyCache();
+  EXPECT_TRUE(rc.IsOk());
+}
+
+TEST_F(MindDataTestCacheOp, TestImageFolderCacheMerge) {
+  Status rc;
+  int64_t num_samples = 0;
+  int64_t start_index = 0;
+  auto seq_sampler = std::make_shared<SequentialSampler>(num_samples, start_index);
+
+  std::shared_ptr<CacheClient> myClient = std::make_shared<CacheClient>(1, 0, true);
+
+  std::shared_ptr<CacheMergeOp> myMergeOp;
+  rc = CacheMergeOp::Builder().SetNumWorkers(3).SetOpConnectorSize(3).SetNumCleaner(2).SetClient(myClient).Build(
+    &myMergeOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  std::shared_ptr<CacheLookupOp> myLookupOp;
+  rc = CacheLookupOp::Builder()
+         .SetNumWorkers(3)
+         .SetOpConnectorSize(3)
+         .SetClient(myClient)
+         .SetSampler(seq_sampler)
+         .Build(&myLookupOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  std::shared_ptr<ImageFolderOp> so;
+  ImageFolderOp::Builder builder;
+  builder.SetSampler(myLookupOp)
+    .SetOpConnectorSize(3)
+    .SetNumWorkers(3)
+    .SetRowsPerBuffer(2)
+    .SetExtensions({".jpg", ".JPEG"})
+    .SetRecursive(true)
+    .SetImageFolderDir(datasets_root_path_ + "/testPK/data");
+  rc = builder.Build(&so);
+  EXPECT_TRUE(rc.IsOk());
+
+  // RepeatOp
+  uint32_t numRepeats = 4;
+  std::shared_ptr<RepeatOp> myRepeatOp;
+  rc = RepeatOp::Builder(numRepeats).Build(&myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  auto myTree = std::make_shared<ExecutionTree>();
+  rc = myTree->AssociateNode(so);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myLookupOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myMergeOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssignRoot(myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  rc = myRepeatOp->AddChild(myMergeOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myMergeOp->AddChild(myLookupOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myMergeOp->AddChild(so);
+  EXPECT_TRUE(rc.IsOk());
+
+  rc = myTree->Prepare();
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->Launch();
+  EXPECT_TRUE(rc.IsOk());
+  // Start the loop of reading tensors from our pipeline
+  DatasetIterator dI(myTree);
+  TensorRow tensorList;
+  rc = dI.FetchNextTensorRow(&tensorList);
+  EXPECT_TRUE(rc.IsOk());
+  int rowCount = 0;
+  while (!tensorList.empty()) {
+    rc = dI.FetchNextTensorRow(&tensorList);
+    EXPECT_TRUE(rc.IsOk());
+    if (rc.IsError()) {
+      std::cout << rc << std::endl;
+      break;
+    }
+    rowCount++;
+  }
+  ASSERT_EQ(rowCount, 176);
+  std::cout << "Row count : " << rowCount << std::endl;
+  rc = myClient->DestroyCache();
+  EXPECT_TRUE(rc.IsOk());
+}
+
+//// Simple test with a repeated cache op over random data producer.
+//// The difference in this one is that you do not add the sampler to the cache op directly.
+//// Instead, the sampler is added as part of the leaf op construction.  Then, the prepare
+//// phase will pull this up from the leaf and into the cache.
+//// It removes the sampler from the leaf op, which doesn't make sense there anyway for
+//// the RandomDataOp which doesn't support sampling without a cache.
+////
+////     RepeatOp
+////        |
+////     CacheOp
+////        |
+////   RandomDataOp
+////
+TEST_F(MindDataTestCacheOp, TestCacheInheritSampler) {
+  Status rc;
+  int32_t rank = 0;  // not used
+  MS_LOG(INFO) << "UT test TestCacheInheritSampler";
+
+  int64_t num_samples = 0;
+  int64_t start_index = 0;
+  auto seq_sampler = std::make_shared<SequentialSampler>(num_samples, start_index);
+
+  // Start with an empty execution tree
+  auto myTree = std::make_shared<ExecutionTree>();
+
+  // Create a schema using the C api's
+  std::unique_ptr<DataSchema> testSchema = std::make_unique<DataSchema>();
+
+  // 2 columns. First column is an "image" 640,480,3
+  TensorShape c1Shape({640, 480, 3});
+  ColDescriptor c1("image", DataType(DataType::DE_INT8), TensorImpl::kFlexible,
+                   rank,  // not used
+                   &c1Shape);
+
+  // Column 2 will just be a scalar label number
+  TensorShape c2Shape({});  // empty shape is a 1-value scalar Tensor
+  ColDescriptor c2("label", DataType(DataType::DE_UINT32), TensorImpl::kFlexible, rank, &c2Shape);
+
+  testSchema->AddColumn(c1);
+  testSchema->AddColumn(c2);
+
+  // RandomDataOp
+  std::shared_ptr<RandomDataOp> myRandomDataOp;
+  rc = RandomDataOp::Builder()
+         .SetRowsPerBuffer(2)
+         .SetNumWorkers(4)
+         .SetDataSchema(std::move(testSchema))
+         .SetTotalRows(10)
+         .SetSampler(std::move(seq_sampler))
+         .Build(&myRandomDataOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myRandomDataOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  // CacheOp
+  std::shared_ptr<CacheClient> myClient = std::make_shared<CacheClient>(1, 4, true);
+  std::shared_ptr<CacheOp> myCacheOp;
+  rc = CacheOp::Builder().SetNumWorkers(4).SetClient(myClient).SetRowsPerBuffer(3).Build(&myCacheOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myCacheOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  // RepeatOp
+  uint32_t numRepeats = 4;
+  std::shared_ptr<RepeatOp> myRepeatOp;
+  rc = RepeatOp::Builder(numRepeats).Build(&myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssociateNode(myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  // Assign tree relations and root
+  rc = myRepeatOp->AddChild(myCacheOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myCacheOp->AddChild(myRandomDataOp);
+  EXPECT_TRUE(rc.IsOk());
+  rc = myTree->AssignRoot(myRepeatOp);
+  EXPECT_TRUE(rc.IsOk());
+
+  MS_LOG(INFO) << "Launching tree and begin iteration";
+  rc = myTree->Prepare();
+  EXPECT_TRUE(rc.IsOk());
+
+  std::cout << *myClient << std::endl;
+
+  rc = myTree->Launch();
+  EXPECT_TRUE(rc.IsOk());
+
+  // Start the loop of reading tensors from our pipeline
+  DatasetIterator dI(myTree);
+  TensorRow tensorList;
+  rc = dI.FetchNextTensorRow(&tensorList);
+  EXPECT_TRUE(rc.IsOk());
+  int rowCount = 0;
+  while (!tensorList.empty()) {
+    // Don't display these rows, just count them
+    MS_LOG(INFO) << "Row fetched #: " << rowCount;
+    rc = dI.FetchNextTensorRow(&tensorList);
+    EXPECT_TRUE(rc.IsOk());
+    rowCount++;
+  }
+  ASSERT_EQ(rowCount, 40);
+  rc = myClient->DestroyCache();
+  EXPECT_TRUE(rc.IsOk());
+}

tests/ut/python/dataset/test_cache_map.py

@@ -0,0 +1,157 @@
+# Copyright 2020 Huawei Technologies Co., Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""
+Testing cache operator with mappable datasets
+"""
+import mindspore.dataset as ds
+import mindspore.dataset.transforms.vision.c_transforms as c_vision
+from mindspore import log as logger
+from util import save_and_check_md5
+
+DATA_DIR = "../data/dataset/testImageNetData/train/"
+
+GENERATE_GOLDEN = False
+
+def test_cache_map_basic1():
+    """
+    Test mappable leaf with cache op right over the leaf
+
+       Repeat
+         |
+     Map(decode)
+         |
+       Cache
+         |
+     ImageFolder
+    """
+
+    logger.info("Test cache map basic 1")
+
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+
+    # This DATA_DIR only has 2 images in it
+    ds1 = ds.ImageFolderDatasetV2(dataset_dir=DATA_DIR, cache=some_cache)
+    decode_op = c_vision.Decode()
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op)
+    ds1 = ds1.repeat(4)
+
+    filename = "cache_map_01_result.npz"
+    save_and_check_md5(ds1, filename, generate_golden=GENERATE_GOLDEN)
+
+    logger.info("test_cache_map_basic1 Ended.\n")
+
+
+def test_cache_map_basic2():
+    """
+    Test mappable leaf with the cache op later in the tree above the map(decode)
+
+       Repeat
+         |
+       Cache
+         |
+     Map(decode)
+         |
+     ImageFolder
+    """
+
+    logger.info("Test cache map basic 2")
+
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+
+    # This DATA_DIR only has 2 images in it
+    ds1 = ds.ImageFolderDatasetV2(dataset_dir=DATA_DIR)
+    decode_op = c_vision.Decode()
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op, cache=some_cache)
+    ds1 = ds1.repeat(4)
+
+    filename = "cache_map_02_result.npz"
+    save_and_check_md5(ds1, filename, generate_golden=GENERATE_GOLDEN)
+
+    logger.info("test_cache_map_basic2 Ended.\n")
+
+
+def test_cache_map_basic3():
+    """
+    Test a repeat under mappable cache
+
+        Cache
+          |
+      Map(decode)
+          |
+        Repeat
+          |
+      ImageFolder
+    """
+
+    logger.info("Test cache basic 3")
+
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+
+    # This DATA_DIR only has 2 images in it
+    ds1 = ds.ImageFolderDatasetV2(dataset_dir=DATA_DIR)
+    decode_op = c_vision.Decode()
+    ds1 = ds1.repeat(4)
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op, cache=some_cache)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 8
+    logger.info('test_cache_basic3 Ended.\n')
+
+
+def test_cache_map_failure1():
+    """
+    Test nested cache (failure)
+
+        Repeat
+          |
+        Cache
+          |
+      Map(decode)
+          |
+        Cache
+          |
+      ImageFolder
+
+    """
+    logger.info("Test cache failure 1")
+
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+
+    # This DATA_DIR only has 2 images in it
+    ds1 = ds.ImageFolderDatasetV2(dataset_dir=DATA_DIR, cache=some_cache)
+    decode_op = c_vision.Decode()
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op, cache=some_cache)
+    ds1 = ds1.repeat(4)
+
+    try:
+        num_iter = 0
+        for _ in ds1.create_dict_iterator():
+            num_iter += 1
+    except RuntimeError as e:
+        logger.info("Got an exception in DE: {}".format(str(e)))
+        assert "Nested cache operations is not supported!" in str(e)
+
+    assert num_iter == 0
+    logger.info('test_cache_failure1 Ended.\n')
+
+if __name__ == '__main__':
+    test_cache_map_basic1()
+    test_cache_map_basic2()
+    test_cache_map_basic3()
+    test_cache_map_failure1()

tests/ut/python/dataset/test_cache_nomap.py

@@ -0,0 +1,429 @@
+# Copyright 2020 Huawei Technologies Co., Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""
+Testing cache operator with non-mappable datasets
+"""
+import mindspore.common.dtype as mstype
+import mindspore.dataset as ds
+import mindspore.dataset.transforms.vision.c_transforms as c_vision
+from mindspore import log as logger
+
+DATA_DIR = ["../data/dataset/test_tf_file_3_images/train-0000-of-0001.data"]
+SCHEMA_DIR = "../data/dataset/test_tf_file_3_images/datasetSchema.json"
+
+GENERATE_GOLDEN = False
+
+def test_cache_nomap_basic1():
+    """
+    A random dataset (a non mappable dataset) with a cache over it just after the leaf
+    """
+
+    logger.info("Test cache nomap basic 1")
+
+    schema = ds.Schema()
+    schema.add_column('image', de_type=mstype.uint8,
+                      shape=[640, 480, 3])  # 921600 bytes (a bit less than 1 MB per image)
+    schema.add_column('label', de_type=mstype.uint8, shape=[1])
+
+    # create a cache.  arbitrary session_id for now
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+
+    # User-created sampler here
+    ds1 = ds.RandomDataset(schema=schema, total_rows=10, num_parallel_workers=4, cache=some_cache)
+    ds1 = ds1.repeat(4)
+
+    num_iter = 0
+    for data in ds1.create_dict_iterator():
+        logger.info("printing the label: {}".format(data["label"]))
+        num_iter += 1
+
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 40
+    logger.info("test_cache_nomap_basic1 Ended.\n")
+
+
+def test_cache_nomap_basic2():
+    """
+    A random dataset (a non mappable dataset) with a cache over it just after the leaf
+    """
+
+    logger.info("Test cache nomap basic 2")
+
+    schema = ds.Schema()
+    schema.add_column('image', de_type=mstype.uint8,
+                      shape=[640, 480, 3])  # 921600 bytes (a bit less than 1 MB per image)
+    schema.add_column('label', de_type=mstype.uint8, shape=[1])
+
+    # create a cache.  arbitrary session_id for now
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+
+    # sampler arg not given directly, however any of these args will auto-generate an appropriate sampler:
+    # num_samples, shuffle, num_shards, shard_id
+    # In this case, the presence of num_samples chooses a sampler.
+    ds1 = ds.RandomDataset(schema=schema, total_rows=20, num_samples=20, num_parallel_workers=4, cache=some_cache)
+    ds1 = ds1.repeat(2)
+
+    num_iter = 0
+    for data in ds1.create_dict_iterator():
+        logger.info("printing the label: {}".format(data["label"]))
+        num_iter += 1
+
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 40
+    logger.info("test_cache_nomap_basic2 Ended.\n")
+
+
+def test_cache_nomap_basic3():
+    """
+    A TF reader dataset (a non mappable dataset) with a cache over it just after the leaf
+
+       Repeat
+         |
+     Map(decode)
+         |
+       Cache
+         |
+      TFReader
+    """
+
+    logger.info("Test cache nomap basic 3")
+
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+    ds1 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], shuffle=False, cache=some_cache)
+    decode_op = c_vision.Decode()
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op)
+    ds1 = ds1.repeat(4)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 12
+    logger.info("test_cache_nomap_basic3 Ended.\n")
+
+
+def test_cache_nomap_basic4():
+    """
+    A TF reader dataset (a non mappable dataset) with a map decode and cache after it
+    Since a global shuffle is used for the tf reader, it will inject a shuffle op over the tf.
+    But, if there's a cache later, that shuffle becomes invalid and should be removed.
+
+       Repeat
+         |
+       Cache
+         |
+     Map(decode)
+         |
+      TFReader
+    """
+
+    logger.info("Test cache nomap basic 4")
+
+    # This dataset has 3 records in it only
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+    # With shuffle not being set, TF defaults to a "global" shuffle when there is no cache
+    # in the picture.  This causes a shuffle-injection over the TF.  For clarify, this test will
+    # explicitly give the global option, even though it's the default in python.
+    # But, when caching is added in the ascendent tree above TF, we do global shuffling
+    # through the sampler over the cache, not by the shuffle op.  In that case, tree prepare
+    # will remove the shuffle op that got injected by the initial tree creation.
+    ds1 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], shuffle=ds.Shuffle.GLOBAL)
+    decode_op = c_vision.Decode()
+
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op, cache=some_cache)
+    ds1 = ds1.repeat(4)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 12
+    logger.info("test_cache_nomap_basic4 Ended.\n")
+
+
+def test_cache_nomap_basic5():
+    """
+    A TF reader dataset (a non mappable dataset) with a cache over it just after the leaf
+    Same as test 3, but this one does not have shuffle arg, causing tf to default to global
+    shuffle which attempts to inject a shuffle operator.  However, since there is a cache
+    we do not need global shuffle, so the shuffle will not be built.  It ends up being
+    identical to test basic 3, however we arrive at the same tree in different codepaths
+    (if there was no cache, then the shuffle IS built)
+
+       Repeat
+         |
+     Map(decode)
+         |
+       Cache
+         |
+      TFReader
+    """
+
+    logger.info("Test cache nomap basic 5")
+
+    # This dataset has 3 records in it only
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+    ds1 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], cache=some_cache)
+    decode_op = c_vision.Decode()
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op)
+    ds1 = ds1.repeat(4)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 12
+    logger.info("test_cache_nomap_basic5 Ended.\n")
+
+
+def test_cache_nomap_basic6():
+    """
+    A TF reader dataset (a non mappable dataset) with a cache over it just after the leaf
+    In this one, the tf dataset will be given sharding configuration, however since a cache is
+    used, the tree prepare should undo the sharding configuration and instead, a distributed
+    sampler will be chosen with the same shard config.
+
+       Repeat
+         |
+     Map(decode)
+         |
+       Cache
+         |
+      TFReader
+    """
+
+    logger.info("Test cache nomap basic 6")
+
+    # This dataset has 3 records in it only
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+
+    # With only 3 records shard into 3, we expect only 1 record returned for this shard
+    # However, the sharding will be done by the sampler, not by the tf record leaf node
+    # In this case, it is a row-based sharding, not the file-based sharding that would happen if
+    # there was not any cache.
+    ds1 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], num_shards=3, shard_id=1, cache=some_cache)
+    decode_op = c_vision.Decode()
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op)
+    ds1 = ds1.repeat(4)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 4
+    logger.info("test_cache_nomap_basic6 Ended.\n")
+
+
+def test_cache_nomap_basic7():
+    """
+    A TF reader dataset (a non mappable dataset) that uses global shuffle, and is cached followed by
+    map.
+    In this one, the tf dataset with global shuffle might want to inject a shuffle op over top of the
+    tf reader, but since a cache is given, it will choose not to.
+
+       Repeat
+         |
+     Map(decode)
+         |
+       cache
+         |
+      TFReader
+    """
+
+    logger.info("Test cache nomap basic 7")
+
+    # This dataset has 3 records in it only
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+
+    ds1 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], shuffle=ds.Shuffle.GLOBAL, cache=some_cache)
+    decode_op = c_vision.Decode()
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op)
+    ds1 = ds1.repeat(4)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 12
+    logger.info("test_cache_nomap_basic7 Ended.\n")
+
+
+def test_cache_nomap_allowed_share1():
+    """
+    It is allowed to share the cache between the following two trees:
+
+       Repeat     Shuffle
+         |           |
+       Cache       Cache
+         |           |
+      TFReader    TFReader
+    """
+
+    logger.info("Test cache nomap allowed share 1")
+
+    ds.config.set_seed(1)
+    # This dataset has 3 records in it only
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+    ds1 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], shuffle=False, cache=some_cache)
+    ds1 = ds1.repeat(4)
+
+    ds2 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], shuffle=False, cache=some_cache)
+    ds2 = ds2.shuffle(buffer_size=2)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+    assert num_iter == 12
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+
+    num_iter = 0
+    for _ in ds2.create_dict_iterator():
+        num_iter += 1
+    assert num_iter == 3
+    logger.info("test_cache_nomap_allowed_share1 Ended.\n")
+
+
+def test_cache_nomap_allowed_share2():
+    """
+    It is allowed to share the cache between the following two trees (with map decode):
+
+       Repeat     Shuffle
+         |           |
+       Cache       Cache
+         |           |
+     Map(decode) Map(decode)
+         |           |
+      TFReader    TFReader
+    """
+
+    logger.info("Test cache nomap allowed share 2")
+
+    ds.config.set_seed(1)
+    # This dataset has 3 records in it only
+    some_cache = ds.DatasetCache(session_id=2, size=0, spilling=True)
+    decode_op = c_vision.Decode()
+
+    ds1 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], shuffle=False)
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op, cache=some_cache)
+    ds1 = ds1.repeat(4)
+
+    ds2 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], shuffle=False)
+    ds2 = ds2.map(input_columns=["image"], operations=decode_op, cache=some_cache)
+    ds2 = ds2.shuffle(buffer_size=2)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 12
+
+    num_iter = 0
+    for _ in ds2.create_dict_iterator():
+        num_iter += 1
+    assert num_iter == 3
+    logger.info("test_cache_nomap_allowed_share2 Ended.\n")
+
+
+def test_cache_nomap_allowed_share3():
+    """
+    It is allowed to share the cache between the following two trees (different shard ids):
+
+       Repeat                     Repeat
+         |                          |
+       Cache                      Cache
+         |                          |
+      TFReader(shard_id = 0)     TFReader(shard_id = 1)
+    """
+
+    logger.info("Test cache nomap allowed share 3")
+
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+
+    tf_files = ["../data/dataset/tf_file_dataset/test1.data", "../data/dataset/tf_file_dataset/test2.data"]
+    ds1 = ds.TFRecordDataset(tf_files, num_shards=2, shard_id=0, num_samples=3, shuffle=False, cache=some_cache)
+    ds1 = ds1.repeat(4)
+
+    ds2 = ds.TFRecordDataset(tf_files, num_shards=2, shard_id=1, num_samples=3, shuffle=False, cache=some_cache)
+    ds2 = ds2.repeat(4)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 12
+
+    num_iter = 0
+    for _ in ds2.create_dict_iterator():
+        num_iter += 1
+    assert num_iter == 12
+    logger.info("test_cache_nomap_allowed_share3 Ended.\n")
+
+
+def test_cache_nomap_disallowed_share1():
+    """
+    It is not allowed to share the cache between the following two trees:
+
+       Cache       Cache
+         |           |
+     Map(decode) Map(rescale)
+         |           |
+      TFReader    TFReader
+    """
+
+    logger.info("Test cache nomap disallowed share1")
+
+    # This dataset has 3 records in it only
+    some_cache = ds.DatasetCache(session_id=1, size=0, spilling=True)
+    decode_op = c_vision.Decode()
+    rescale_op = c_vision.Rescale(1.0 / 255.0, -1.0)
+
+    ds1 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], shuffle=False)
+    ds1 = ds1.map(input_columns=["image"], operations=decode_op, cache=some_cache)
+
+    ds2 = ds.TFRecordDataset(DATA_DIR, SCHEMA_DIR, columns_list=["image"], shuffle=False)
+    ds2 = ds2.map(input_columns=["image"], operations=rescale_op, cache=some_cache)
+
+    num_iter = 0
+    for _ in ds1.create_dict_iterator():
+        num_iter += 1
+    logger.info("Number of data in ds1: {} ".format(num_iter))
+    assert num_iter == 3
+
+    try:
+        sum([1 for _ in ds2])
+    except RuntimeError as e:
+        logger.info("Got an exception in DE: {}".format(str(e)))
+        assert "Attempt to re-use a cache for a different tree!" in str(e)
+
+    logger.info("test_cache_nomap_disallowed_share1 Ended.\n")
+
+
+if __name__ == '__main__':
+    test_cache_nomap_basic1()
+    test_cache_nomap_basic2()
+    test_cache_nomap_basic3()
+    test_cache_nomap_basic4()
+    test_cache_nomap_basic5()
+    test_cache_nomap_basic6()
+    test_cache_nomap_basic7()
+    test_cache_nomap_allowed_share1()
+    test_cache_nomap_allowed_share2()
+    test_cache_nomap_allowed_share3()
+    test_cache_nomap_disallowed_share1()

tests/ut/python/dataset/test_random_dataset.py

@@ -16,17 +16,16 @@ import mindspore.common.dtype as mstype
 import mindspore.dataset as ds
 from mindspore import log as logger
 
-
 # just a basic test with parallel random data op
 def test_randomdataset_basic1():
-    logger.info("Test randomdataset basic")
+    logger.info("Test randomdataset basic 1")
 
     schema = ds.Schema()
     schema.add_column('image', de_type=mstype.uint8, shape=[2])
     schema.add_column('label', de_type=mstype.uint8, shape=[1])
 
     # apply dataset operations
-    ds1 = ds.RandomDataset(schema=schema, num_samples=50, num_parallel_workers=4)
+    ds1 = ds.RandomDataset(schema=schema, total_rows=50, num_parallel_workers=4)
     ds1 = ds1.repeat(4)
 
     num_iter = 0
@@ -36,8 +35,9 @@ def test_randomdataset_basic1():
         logger.info("{} label: {}".format(num_iter, data["label"]))
         num_iter += 1
 
-    logger.info("Number of data in ds1: ", num_iter)
+    logger.info("Number of data in ds1: {}".format(num_iter))
     assert num_iter == 200
+    logger.info("Test randomdataset basic 1 complete")
 
 
 # Another simple test
@@ -49,10 +49,8 @@ def test_randomdataset_basic2():
                       shape=[640, 480, 3])  # 921600 bytes (a bit less than 1 MB per image)
     schema.add_column('label', de_type=mstype.uint8, shape=[1])
 
-    # Make up about 10 samples
-    ds1 = ds.RandomDataset(schema=schema, num_samples=10, num_parallel_workers=1)
-
-    # cache size allows for about 4 images since each image just a bit less than 1MB, after that we will have to spill
+    # Make up 10 rows
+    ds1 = ds.RandomDataset(schema=schema, total_rows=10, num_parallel_workers=1)
     ds1 = ds1.repeat(4)
 
     num_iter = 0
@@ -62,11 +60,31 @@ def test_randomdataset_basic2():
         logger.info("printing the label: {}".format(data["label"]))
         num_iter += 1
 
-    logger.info("Number of data in ds1: ", num_iter)
+    logger.info("Number of data in ds1: {}".format(num_iter))
     assert num_iter == 40
+    logger.info("Test randomdataset basic 2 complete")
+
+
+# Another simple test
+def test_randomdataset_basic3():
+    logger.info("Test randomdataset basic 3")
+
+    # Make up 10 samples, but here even the schema is randomly created
+    # The columns are named like this "c0", "c1", "c2" etc
+    # But, we will use a tuple iterator instead of dict iterator so the column names
+    # are not needed to iterate
+    ds1 = ds.RandomDataset(total_rows=10, num_parallel_workers=1)
+    ds1 = ds1.repeat(2)
+
+    num_iter = 0
+    for _ in ds1.create_tuple_iterator():
+        num_iter += 1
 
+    logger.info("Number of data in ds1: {}".format(num_iter))
+    assert num_iter == 20
+    logger.info("Test randomdataset basic 3 Complete")
 
 if __name__ == '__main__':
     test_randomdataset_basic1()
     test_randomdataset_basic2()
-    logger.info('test_randomdataset_basic Ended.\n')
+    test_randomdataset_basic3()