Add indexs of alarm.enabled and alarm.type

When evaluating alarms, the evaluation service need query alarms filtered
by enabled=True every evaluation cycle. For the event alarms, the
type='event' is also a required filter. So Add indexs of "enabled" and
"type" of Alarm model can make a bit of improvement.

Change-Id: I676763a58eae24dced80aeb92e0100d3aa71e85a

aodh/storage/sqlalchemy/alembic/versions/f8c31b1ffe11_add_index_for_enabled_and_type.py

@@ -0,0 +1,37 @@
+# Copyright 2016 OpenStack Foundation
+#
+#    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.
+#
+
+"""add index for enabled and type
+
+Revision ID: f8c31b1ffe11
+Revises: bb07adac380
+Create Date: 2016-06-02 19:39:42.495020
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = 'f8c31b1ffe11'
+down_revision = 'bb07adac380'
+branch_labels = None
+depends_on = None
+
+from alembic import op
+
+
+def upgrade():
+    op.create_index(
+        'ix_alarm_enabled', 'alarm', ['enabled'], unique=False)
+    op.create_index(
+        'ix_alarm_type', 'alarm', ['type'], unique=False)

aodh/storage/sqlalchemy/models.py

@@ -116,6 +116,8 @@ class Alarm(Base):
     __table_args__ = (
         Index('ix_alarm_user_id', 'user_id'),
         Index('ix_alarm_project_id', 'project_id'),
+        Index('ix_alarm_enabled', 'enabled'),
+        Index('ix_alarm_type', 'type'),
     )
     alarm_id = Column(String(128), primary_key=True)
     enabled = Column(Boolean)