Add index on instances table across project_id and updated_at

We should have an index on the instances.updated_at table because
that's what's used to filter instances when using the --changes-since
filter parameter with nova list.

Closes-Bug: #1642729

Change-Id: I4c723839f36efddd95cd24d745fb71c96c75d2c1

nova/db/sqlalchemy/migrate_repo/versions/347_add_updated_at_index.py

@@ -0,0 +1,58 @@
+#    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 oslo_log import log as logging
+from sqlalchemy import MetaData, Table, Index
+from sqlalchemy.engine import reflection
+
+from nova.i18n import _LI
+
+LOG = logging.getLogger(__name__)
+
+INDEX_COLUMNS_1 = ['project_id']
+INDEX_NAME_1 = 'instances_project_id_idx'
+
+INDEX_COLUMNS_2 = ['updated_at', 'project_id']
+INDEX_NAME_2 = 'instances_updated_at_project_id_idx'
+
+TABLE_NAME = 'instances'
+
+
+def _get_table_index(migrate_engine, table_name, index_columns):
+    inspector = reflection.Inspector.from_engine(migrate_engine)
+    for idx in inspector.get_indexes(table_name):
+        if idx['column_names'] == index_columns:
+            break
+    else:
+        idx = None
+    return idx
+
+
+def upgrade(migrate_engine):
+    meta = MetaData()
+    meta.bind = migrate_engine
+    table = Table(TABLE_NAME, meta, autoload=True)
+    if _get_table_index(migrate_engine, TABLE_NAME, INDEX_COLUMNS_1):
+        LOG.info(_LI('Skipped adding %s because an equivalent index'
+                     ' already exists.'), INDEX_NAME_1)
+    else:
+        columns = [getattr(table.c, col_name) for col_name in INDEX_COLUMNS_1]
+        index = Index(INDEX_NAME_1, *columns)
+        index.create(migrate_engine)
+
+    if _get_table_index(migrate_engine, TABLE_NAME, INDEX_COLUMNS_2):
+        LOG.info(_LI('Skipped adding %s because an equivalent index'
+                     ' already exists.'), INDEX_NAME_2)
+    else:
+        columns = [getattr(table.c, col_name) for col_name in INDEX_COLUMNS_2]
+        index = Index(INDEX_NAME_2, *columns)
+        index.create(migrate_engine)

nova/db/sqlalchemy/models.py

@@ -198,6 +198,7 @@ class Instance(BASE, NovaBase, models.SoftDeleteMixin):
     __tablename__ = 'instances'
     __table_args__ = (
         Index('uuid', 'uuid', unique=True),
+        Index('instances_project_id_idx', 'project_id'),
         Index('instances_project_id_deleted_idx',
               'project_id', 'deleted'),
         Index('instances_reservation_id_idx',
@@ -214,6 +215,8 @@ class Instance(BASE, NovaBase, models.SoftDeleteMixin):
               'host', 'deleted', 'cleaned'),
         Index('instances_deleted_created_at_idx',
               'deleted', 'created_at'),
+        Index('instances_updated_at_project_id_idx',
+              'updated_at', 'project_id'),
         schema.UniqueConstraint('uuid', name='uniq_instances0uuid'),
     )
     injected_files = []

nova/tests/unit/db/test_migrations.py

@@ -933,6 +933,14 @@ class NovaMigrationsCheckers(test_migrations.ModelsMigrationsSync,
         self.assertColumnNotExists(engine, 'instances', 'scheduled_at')
         self.assertColumnNotExists(engine, 'shadow_instances', 'scheduled_at')
 
+    def _check_347(self, engine, data):
+        self.assertIndexMembers(engine, 'instances',
+                                'instances_project_id_idx',
+                                ['project_id'])
+        self.assertIndexMembers(engine, 'instances',
+                                'instances_updated_at_project_id_idx',
+                                ['updated_at', 'project_id'])
+
 
 class TestNovaMigrationsSQLite(NovaMigrationsCheckers,
                                test_base.DbTestCase,