old_contents: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  # Copyright 2011 MORITA Kazutaka.
  # 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 sqlalchemy import Column, Table, MetaData, Boolean, String
  
  meta = MetaData()
  
  fixed_ips_host = Column('host', String(255))
  
  networks_multi_host = Column('multi_host', Boolean, default=False)
  
  
  def upgrade(migrate_engine):
      # Upgrade operations go here. Don't create your own engine;
      # bind migrate_engine to your metadata
      meta.bind = migrate_engine
  
      # Add columns to existing tables
      fixed_ips = Table('fixed_ips', meta, autoload=True)
      fixed_ips.create_column(fixed_ips_host)
  
      networks = Table('networks', meta, autoload=True)
      networks.create_column(networks_multi_host)
  
new_contents: # vim: tabstop=4 shiftwidth=4 softtabstop=4
  
  # Copyright (c) 2011 OpenStack, LLC.
  # 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 sqlalchemy import Column, Table, MetaData, Boolean, String
  
  meta = MetaData()
  
  fixed_ips_host = Column('host', String(255))
  
  networks_multi_host = Column('multi_host', Boolean, default=False)
  
  
  def upgrade(migrate_engine):
      meta.bind = migrate_engine
  
      fixed_ips = Table('fixed_ips', meta, autoload=True)
      fixed_ips.create_column(fixed_ips_host)
  
      networks = Table('networks', meta, autoload=True)
      networks.create_column(networks_multi_host)
  
  
  def downgrade(migrate_engine):
      meta.bind = migrate_engine
  
      fixed_ips = Table('fixed_ips', meta, autoload=True)
      fixed_ips.drop_column(fixed_ips_host)
  
      networks = Table('networks', meta, autoload=True)
      networks.drop_column(networks_multi_host)
  
subject: add downgrade