Fix past migration scripts discrepancies

It is important that running all migration scripts from first to last
will give the expected model.

This fix is a first step. It fixes all discrepancies from previous
scripts.

There are still changes in the model that needs to have a migration
script written for them, but that is not handled now.

Change-Id: Ie4079eecef6766ed91c210ccefa058175e0f22d0

mistral/db/sqlalchemy/migration/alembic_migrations/versions/014_fix_past_scripts_discrepancies.py

@@ -0,0 +1,74 @@
+# 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.
+
+"""fix_past_scripts_discrepancies
+
+Revision ID: 014
+Revises: 013
+Create Date: 2016-08-07 13:12:34.958845
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '014'
+down_revision = '013'
+
+from alembic import op
+from sqlalchemy.dialects import mysql
+from sqlalchemy.engine import reflection
+
+
+def upgrade():
+
+    inspect = reflection.Inspector.from_engine(op.get_bind())
+    ct_unique_constraints = [
+        uc['name'] for uc in inspect.get_unique_constraints('cron_triggers_v2')
+    ]
+
+    # unique constraint was added in 001, 002 and 003 with slight variations
+    # without deleting the previous ones.
+    # here we try to delete all three in case they exist
+    if 'workflow_input_hash' in ct_unique_constraints:
+        op.drop_index('workflow_input_hash', table_name='cron_triggers_v2')
+    if 'workflow_input_hash_2' in ct_unique_constraints:
+        op.drop_index('workflow_input_hash_2', table_name='cron_triggers_v2')
+    if 'workflow_input_hash_3' in ct_unique_constraints:
+        op.drop_index('workflow_input_hash_3', table_name='cron_triggers_v2')
+
+    # create the correct latest unique constraint for table cron_triggers_v2
+    op.create_unique_constraint(
+        None,
+        'cron_triggers_v2', [
+            'workflow_input_hash', 'workflow_name', 'pattern',
+            'project_id', 'workflow_params_hash', 'remaining_executions',
+            'first_execution_time'
+        ]
+    )
+
+    # column was added in 012. nullable value does not match today's model.
+    op.alter_column(
+        'event_triggers_v2',
+        'workflow_id',
+        existing_type=mysql.VARCHAR(length=36),
+        nullable=True
+    )
+
+    # column was added in 010. nullable value does not match today's model
+    op.alter_column(
+        'resource_members_v2',
+        'project_id',
+        existing_type=mysql.VARCHAR(length=80),
+        nullable=True
+    )