Remove duplicated index on table 'records' of pDNS backend

Remove duplicated index `rec_name_index` on table 'records' of pDNS backend.

Change-Id: I9e8723b464522a588f0e0ef6ff261b71609b0726
Closes-Bug: 1446980

designate/backend/impl_powerdns/migrate_repo/versions/012_records_drop_duped_index.py

@@ -0,0 +1,41 @@
+# Copyright 2015 NetEase, Inc.
+#
+# Author: Zhang Gengyuan <stanzgy@gmail.com>
+#
+# 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.
+from sqlalchemy import MetaData, Index, Table
+
+meta = MetaData()
+
+
+# Backport of 017_records_drop_duped_index.py to Kilo
+
+
+def upgrade(migrate_engine):
+    meta.bind = migrate_engine
+
+    records_table = Table('records', meta, autoload=True)
+
+    name_idx = Index('rec_name_index',
+                     records_table.c.name)
+    name_idx.drop()
+
+
+def downgrade(migrate_engine):
+    meta.bind = migrate_engine
+
+    records_table = Table('records', meta, autoload=True)
+
+    name_idx = Index('rec_name_index',
+                     records_table.c.name)
+    name_idx.create()