Add index to reservations.uuid column

Committing or rolling back reservations gets slow once a large number of
reservations have built up in the db.  Since they're being queried by
uuid this adds an index to speed up that operation.

Note that this can be slow with a large number of rows.

bug 1203872

Change-Id: Ida503206194a567a5c6811a304154d067c5faa83

nova/db/sqlalchemy/migrate_repo/versions/204_add_indexes_to_reservations.py

@@ -0,0 +1,41 @@
+# All Rights Reserved.
+#
+#    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 Index, MetaData, Table
+from sqlalchemy.exc import IntegrityError
+
+
+def upgrade(migrate_engine):
+    meta = MetaData()
+    meta.bind = migrate_engine
+
+    reservations = Table('reservations', meta, autoload=True)
+
+    # Based on _quota_reservations_query
+    # from: nova/db/sqlalchemy/api.py
+    index = Index('reservations_uuid_idx', reservations.c.uuid)
+    try:
+        index.create(migrate_engine)
+    except IntegrityError:
+        pass
+
+
+def downgrade(migrate_engine):
+    meta = MetaData()
+    meta.bind = migrate_engine
+
+    reservations = Table('reservations', meta, autoload=True)
+
+    index = Index('reservations_uuid_idx', reservations.c.uuid)
+    index.drop(migrate_engine)

nova/db/sqlalchemy/models.py

@@ -470,6 +470,7 @@ class Reservation(BASE, NovaBase):
     __tablename__ = 'reservations'
     __table_args__ = (
         Index('ix_reservations_project_id', 'project_id'),
+        Index('reservations_uuid_idx', 'uuid'),
     )
     id = Column(Integer, primary_key=True, nullable=False)
     uuid = Column(String(36), nullable=False)

nova/tests/db/test_migrations.py

@@ -2410,6 +2410,29 @@ def _post_downgrade_203(self, engine):
         self.assertFalse('user_id' in reservation)
         self.assertFalse(table_exist)
 
+    def _check_204(self, engine, data):
+        if engine.name != 'sqlite':
+            return
+
+        meta = sqlalchemy.MetaData()
+        meta.bind = engine
+        reservations = sqlalchemy.Table('reservations', meta, autoload=True)
+
+        index_data = [(idx.name, idx.columns.keys())
+                      for idx in reservations.indexes]
+
+        if engine.name == "postgresql":
+            # we can not get correct order of columns in index
+            # definition to postgresql using sqlalchemy. So we sort
+            # columns list before compare
+            # bug http://www.sqlalchemy.org/trac/ticket/2767
+            self.assertIn(
+                ('reservations_uuid_idx', sorted(['uuid'])),
+                ([(idx[0], sorted(idx[1])) for idx in index_data])
+            )
+        else:
+            self.assertIn(('reservations_uuid_idx', ['uuid']), index_data)
+
 
 class TestBaremetalMigrations(BaseMigrationTestCase, CommonTestsMixIn):
     """Test sqlalchemy-migrate migrations."""