!1704 fix num rows bug in sampler

Merge pull request !1704 from Peilin/fix-random-sampler-bug

mindspore/ccsrc/dataset/engine/datasetops/source/sampler/random_sampler.cc

@@ -76,6 +76,7 @@ Status RandomSampler::InitSampler() {
 
   if (replacement_ == false) {
     num_samples_ = std::min(num_samples_, num_rows_);
+    num_samples_ = std::min(num_samples_, user_num_samples_);
 
     shuffled_ids_.reserve(num_rows_);
     for (int64_t i = 0; i < num_rows_; i++) {

tests/ut/python/dataset/test_datasets_imagefolder.py

@@ -57,6 +57,24 @@ def test_imagefolder_numsamples():
     logger.info("Number of data in data1: {}".format(num_iter))
     assert num_iter == 10
 
+    random_sampler = ds.RandomSampler(num_samples=3, replacement=True)
+    data1 = ds.ImageFolderDatasetV2(DATA_DIR, num_samples=10, num_parallel_workers=2, sampler=random_sampler)
+
+    num_iter = 0
+    for item in data1.create_dict_iterator():
+        num_iter += 1
+
+    assert num_iter == 3
+
+    random_sampler = ds.RandomSampler(num_samples=3, replacement=False)
+    data1 = ds.ImageFolderDatasetV2(DATA_DIR, num_samples=10, num_parallel_workers=2, sampler=random_sampler)
+
+    num_iter = 0
+    for item in data1.create_dict_iterator():
+        num_iter += 1
+
+    assert num_iter == 3
+
 
 def test_imagefolder_numshards():
     logger.info("Test Case numShards")