text: #    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 sqlalchemy import Column
  from sqlalchemy import MetaData, String, Table
  
  
  def upgrade(migrate_engine):
      """Add provider_id column to volumes."""
      meta = MetaData()
      meta.bind = migrate_engine
  
      volumes = Table('volumes', meta, autoload=True)
      provider_id = Column('provider_id', String(255))
      volumes.create_column(provider_id)
      volumes.update().values(provider_id=None).execute()
  