Merge pull request #3 from Learnware-LAMDA/use_default_dbname

[MNT] use default dbname when create database

learnware/market/database_ops.py

@@ -58,7 +58,7 @@ class DatabaseOperations(object):
             # it is postgresql
             dbname_start = url.rfind("/")
             dbname = url[dbname_start+1:]
-            url_no_dbname = url[:dbname_start]
+            url_no_dbname = url[:dbname_start] + "/postgres"
             engine = create_engine(url_no_dbname)
 
             with engine.connect() as conn: