[AIRFLOW-3001] Add index 'ti_dag_date' to taskinstance (apache#3885)

To optimize query performance

Author: ubermen

airflow/migrations/versions/bf00311e1990_add_index_to_taskinstance.py

@@ -0,0 +1,46 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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 to taskinstance
+
+Revision ID: bf00311e1990
+Revises: dd25f486b8ea
+Create Date: 2018-09-12 09:53:52.007433
+
+"""
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision = 'bf00311e1990'
+down_revision = 'dd25f486b8ea'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    op.create_index(
+        'ti_dag_date',
+        'task_instance',
+        ['dag_id', 'execution_date'],
+        unique=False
+    )
+
+
+def downgrade():
+    op.drop_index('ti_dag_date', table_name='task_instance')

airflow/models.py

@@ -887,6 +887,7 @@ class TaskInstance(Base, LoggingMixin):
 
     __table_args__ = (
         Index('ti_dag_state', dag_id, state),
+        Index('ti_dag_date', dag_id, execution_date),
         Index('ti_state', state),
         Index('ti_state_lkp', dag_id, task_id, execution_date, state),
         Index('ti_pool', pool, state, priority_weight),