old_contents: # 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_config import cfg
  from oslo_db import api as db_api
  from oslo_log import log
  
  from freezer_api.db import base as db_base
  from freezer_api.db.sqlalchemy import api as db_session
  from freezer_api.db.sqlalchemy import models
  
  
  CONF = cfg.CONF
  LOG = log.getLogger(__name__)
  
  _BACKEND_MAPPING = {'sqlalchemy': 'freezer_api.db.sqlalchemy.api'}
  
  
  class SQLDriver(db_base.DBDriver):
  
      def __init__(self, backend):
          super(SQLDriver, self).__init__(backend)
          self.IMPL = db_api.DBAPI.from_config(CONF, _BACKEND_MAPPING)
          self._engine = None
  
      def get_engine(self):
          if not self._engine:
              self._engine = db_session.get_engine()
          return self._engine
  
      def get_api(self):
          return self.get_engine()
  
      def db_sync(self):
          if not self._engine:
              self._engine = self.get_engine()
          models.register_models(self._engine)
  
      def db_show(self):
          if not self._engine:
              self._engine = self.get_engine()
          return models.get_tables(self._engine)
  
      def db_remove(self):
          if not self._engine:
              self._engine = self.get_engine()
          models.unregister_models(self._engine)
  
      def name(self):
          return "sqlalchemy"
  
new_contents: # 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.
  
  import os
  import threading
  
  from stevedore import driver
  
  from oslo_config import cfg
  from oslo_db import api as db_api
  from oslo_db.sqlalchemy import migration
  from oslo_log import log
  
  from freezer_api.db import base as db_base
  from freezer_api.db.sqlalchemy import api as db_session
  from freezer_api.db.sqlalchemy import models
  
  
  INIT_VERSION = 0
  
  _IMPL = None
  _LOCK = threading.Lock()
  
  CONF = cfg.CONF
  LOG = log.getLogger(__name__)
  
  
  MIGRATE_REPO_PATH = os.path.join(
      os.path.abspath(os.path.dirname(__file__)),
      'migrate_repo',
  )
  
  _BACKEND_MAPPING = {'sqlalchemy': 'freezer_api.db.sqlalchemy.api'}
  
  
  class SQLDriver(db_base.DBDriver):
  
      def __init__(self, backend):
          super(SQLDriver, self).__init__(backend)
          self.IMPL = db_api.DBAPI.from_config(CONF, _BACKEND_MAPPING)
          self._engine = None
  
      def get_engine(self):
          if not self._engine:
              self._engine = db_session.get_engine()
          return self._engine
  
      def get_api(self):
          self.get_engine()
          return self.IMPL
  
      def get_backend(self):
          global _IMPL
          if _IMPL is None:
              with _LOCK:
                  if _IMPL is None:
                      _IMPL = driver.DriverManager(
                          "freezer.database.migration_backend",
                          cfg.CONF.database.backend).driver
          return _IMPL
  
      def db_sync(self, version=None, init_version=INIT_VERSION, engine=None):
          """Migrate the database to `version` or the most recent version."""
  
          if not self._engine:
              self._engine = self.get_engine()
          return migration.db_sync(engine=self._engine,
                                   abs_path=MIGRATE_REPO_PATH,
                                   version=version,
                                   init_version=init_version)
  
      def db_show(self):
          if not self._engine:
              self._engine = self.get_engine()
          return models.get_tables(self._engine)
  
      def db_remove(self):
          if not self._engine:
              self._engine = self.get_engine()
          models.unregister_models(self._engine)
  
      def name(self):
          return "sqlalchemy"
  
subject: Modify driver for bp add-mysql-support-for-freezer