Adds instance_uuid index for instance_system_metadata

DB migrating script don't create index on
instance_system_metadata.instance_uuid for SQLite,
PostgreSQL and IBM DB, it cause the listing instances
have low performance. Adds instance_uuid index
for these DB.

Change-Id: I8a6425b00fe5f491b1bd98b7b335e7d8b13eaf33
Closes-Bug: #1480029

nova/db/sqlalchemy/migrate_repo/versions/302_pgsql_add_instance_system_metadata_index.py

@@ -0,0 +1,36 @@
+# Copyright 2015 Huawei.
+# 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 oslo_db.sqlalchemy import utils
+
+
+INDEX_COLUMNS = ['instance_uuid']
+# using the index name same with mysql
+INDEX_NAME = 'instance_uuid'
+SYS_META_TABLE_NAME = 'instance_system_metadata'
+
+
+def upgrade(migrate_engine):
+    """Add instance_system_metadata indexes missing on PostgreSQL and other DB.
+    """
+
+    # This index was already added by migration 216 for MySQL
+    if migrate_engine.name != 'mysql':
+        # Adds index for PostgreSQL and other DB
+        if not utils.index_exists(migrate_engine, SYS_META_TABLE_NAME,
+                                  INDEX_NAME):
+            utils.add_index(migrate_engine, SYS_META_TABLE_NAME, INDEX_NAME,
+                            INDEX_COLUMNS)

nova/db/sqlalchemy/models.py

@@ -987,7 +987,9 @@ class InstanceMetadata(BASE, NovaBase):
 class InstanceSystemMetadata(BASE, NovaBase):
     """Represents a system-owned metadata key/value pair for an instance."""
     __tablename__ = 'instance_system_metadata'
-    __table_args__ = ()
+    __table_args__ = (
+        Index('instance_uuid', 'instance_uuid'),
+    )
     id = Column(Integer, primary_key=True)
     key = Column(String(255), nullable=False)
     value = Column(String(255))

nova/tests/unit/db/test_migrations.py

@@ -800,6 +800,10 @@ class NovaMigrationsCheckers(test_migrations.ModelsMigrationsSync,
         self.assertColumnExists(engine, 'compute_nodes',
                                 'ram_allocation_ratio')
 
+    def _check_302(self, engine, data):
+        self.assertIndexMembers(engine, 'instance_system_metadata',
+                                'instance_uuid', ['instance_uuid'])
+
 
 class TestNovaMigrationsSQLite(NovaMigrationsCheckers,
                                test_base.DbTestCase,