SNOW-127998 SQLAlchemy empty comments

Author: sfc-gh-stakeda

snowdialect.py

@@ -461,7 +461,7 @@ def _get_table_columns(self, connection, table_name, schema=None, **kw):
                 'nullable': is_nullable == 'YES',
                 'default': column_default,
                 'autoincrement': is_identity == 'YES',
-                'comment': comment,
+                'comment': comment if comment != '' else None,
                 'primary_key': (column_name in schema_primary_keys[table_name][
                     'constrained_columns']) if current_table_pks else False,
             })
@@ -583,7 +583,7 @@ def get_table_comment(self, connection, table_name, schema=None, **kw):
                                     )
         cursor = connection.execute(sql_command)
         ans = cursor.fetchone()
-        return {'text': ans['comment']}
+        return {'text': ans['comment'] if ans['comment'] else None}
 
 
 @sa_vnt.listens_for(Table, 'before_create')

test/test_core.py

@@ -1206,3 +1206,17 @@ def mock_helper(command, *args, **kwargs):
     assert len(column_metadata) == 4
     # Clean up
     metadata.drop_all(engine_testaccount)
+
+
+def test_empty_comments(engine_testaccount):
+    """Test that no comment returns None"""
+    table_name = ''.join(random.choice(string.ascii_uppercase) for _ in range(5))
+    try:
+        engine_testaccount.execute("create table public.{} (\"col1\" text);".format(table_name))
+        engine_testaccount.execute("select comment from information_schema.columns where table_name='{}'".format(table_name)).fetchall()
+        inspector = inspect(engine_testaccount)
+        columns = inspector.get_columns(table_name, schema='PUBLIC')
+        assert inspector.get_table_comment(table_name, schema='PUBLIC') == {'text': None}
+        assert all([c['comment'] is None for c in columns])
+    finally:
+        engine_testaccount.execute("drop table public.{}".format(table_name))