DB downgrade from 7.0 to 6.1 fixed

Tests for downgrading added.
Alembic migration file for 7.0 fixed.

Change-Id: I333e832b0eaef9e6214d86949c9035206c409770
Closes-Bug: #1471792

nailgun/nailgun/db/migration/alembic_migrations/versions/fuel_7_0.py

@@ -67,14 +67,16 @@ task_names_new = consts.TASK_NAMES
 
 def upgrade():
     op.create_foreign_key(
-        None, 'network_groups', 'nodegroups', ['group_id'], ['id'])
+        'network_groups_nodegroups_fk', 'network_groups', 'nodegroups',
+        ['group_id'], ['id'])
     op.create_foreign_key(
-        None, 'nodes', 'nodegroups', ['group_id'], ['id'])
+        'nodes_nodegroups_fk', 'nodes', 'nodegroups', ['group_id'], ['id'])
     op.alter_column(
         'oswl_stats', 'resource_checksum', existing_type=sa.TEXT(),
         nullable=False)
     op.create_unique_constraint(
-        None, 'oswl_stats', ['cluster_id', 'created_date', 'resource_type'])
+        'oswl_stats_cluster_id_created_date_resource_type_unique_key',
+        'oswl_stats', ['cluster_id', 'created_date', 'resource_type'])
 
     extend_ip_addrs_model_upgrade()
     extend_node_model_upgrade()
@@ -101,12 +103,15 @@ def downgrade():
     downgrade_task_names()
     vms_conf_downgrade()
 
-    op.drop_constraint(None, 'oswl_stats', type_='unique')
+    op.drop_constraint(
+        'oswl_stats_cluster_id_created_date_resource_type_unique_key',
+        'oswl_stats', type_='unique')
     op.alter_column(
         'oswl_stats', 'resource_checksum', existing_type=sa.TEXT(),
         nullable=True)
-    op.drop_constraint(None, 'nodes', type_='foreignkey')
-    op.drop_constraint(None, 'network_groups', type_='foreignkey')
+    op.drop_constraint('nodes_nodegroups_fk', 'nodes', type_='foreignkey')
+    op.drop_constraint('network_groups_nodegroups_fk', 'network_groups',
+                       type_='foreignkey')
 
 
 def extend_node_model_upgrade():
@@ -225,7 +230,9 @@ def extend_ip_addrs_model_downgrade():
     vrouter_enum = sa.Enum('haproxy', 'vrouter',
                            name='network_vip_types')
     vrouter_enum.create(op.get_bind(), checkfirst=False)
-    op.alter_column('ip_addrs', 'vip_type', type_=vrouter_enum)
+    op.execute('ALTER TABLE ip_addrs ALTER COLUMN vip_type '
+               'TYPE network_vip_types '
+               'USING vip_type::text::network_vip_types')
 
 
 def extend_releases_model_upgrade():

nailgun/nailgun/test/unit/test_db_migrations.py

@@ -0,0 +1,30 @@
+#    Copyright 2015 Mirantis, Inc.
+#
+#    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.
+
+
+import alembic
+
+from nailgun.db import dropdb
+from nailgun.db.migration import ALEMBIC_CONFIG
+from nailgun.test import base
+
+
+class TestDbMigrations(base.BaseTestCase):
+
+    def test_clean_downgrade(self):
+        # We don't have data migration for clusters with vip_type 'ovs'
+        # so checking migration only for clean DB
+        dropdb()
+        alembic.command.upgrade(ALEMBIC_CONFIG, 'head')
+        alembic.command.downgrade(ALEMBIC_CONFIG, 'base')