def upgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine
    instances = Table('instances', meta, autoload=True)
    instances.create_column(
        Column(COLUMN_NAME, String(36), ForeignKey('instances.id')),
        nullable=True)

def downgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine
    modules = Table('modules', meta, autoload=True)
    modules.drop_column(COLUMN_NAME_1)
    modules.drop_column(COLUMN_NAME_2)
    modules.drop_column(COLUMN_NAME_3)

def upgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine

    # add column:
    backups = Table('backups', meta, autoload=True)
    backups.create_column(Column('parent_id', String(36), nullable=True))

def upgrade(migrate_engine):
    meta = MetaData(bind=migrate_engine)
    configurations = Table('configurations', meta, autoload=True)
    created = Column('created', DateTime())
    updated = Column('updated', DateTime())
    configurations.create_column(created)
    configurations.create_column(updated)

def downgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine

    # drop column:
    backups = Table('backups', meta, autoload=True)
    backups.drop_column('parent_id')

def upgrade(migrate_engine):
    meta.bind = migrate_engine
    create_tables([configurations])
    create_tables([configuration_parameters])
    instances = Table('instances', meta, autoload=True)
    instances.create_column(Column('configuration_id', String(36),
                                   ForeignKey("configurations.id")))

def upgrade(migrate_engine):
    meta.bind = migrate_engine
    # Load 'configurations' table to MetaData.
    Table('configurations', meta, autoload=True, autoload_with=migrate_engine)
    instances = Table('clusters', meta, autoload=True)
    instances.create_column(Column('configuration_id', String(36),
                                   ForeignKey("configurations.id")))

def upgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine
    instances = Table('instances', meta, autoload=True)
    service_type = Column('service_type', String(36))
    instances.create_column(service_type)
    instances.update().values({'service_type': 'mysql'}).execute()

def upgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine

    # add column:
    instances = Table('instances', meta, autoload=True)
    instances.create_column(Column('tenant_id', String(36), nullable=True))
    instances.create_column(Column('server_status', String(64)))

def upgrade(migrate_engine):
    meta.bind = migrate_engine
    create_tables([datastores, datastore_versions])
    instances = Table('instances', meta, autoload=True)
    datastore_version_id = Column('datastore_version_id', String(36),
                                  ForeignKey('datastore_versions.id'))
    instances.create_column(datastore_version_id)
    instances.drop_column('service_type')

def downgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine

    # drop column:
    instances = Table('instances', meta, autoload=True)
    instances.drop_column('deleted')
    instances.drop_column('deleted_at')

def upgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine

    # add column:
    instances = Table('instances', meta, autoload=True)
    instances.create_column(Column('deleted', Boolean()))
    instances.create_column(Column('deleted_at', DateTime()))

def upgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine
    backups = Table('backups', meta, autoload=True)
    Table('datastore_versions', meta, autoload=True)
    datastore_version_id = Column('datastore_version_id', String(36),
                                  ForeignKey('datastore_versions.id'))
    backups.create_column(datastore_version_id)

def downgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine

    # drop column:
    backups = Table('backups', meta, autoload=True)
    migrate_engine.execute('DROP INDEX backups_parent_id_idx ON backups')
    migrate_engine.execute('DROP INDEX backups_deleted_idx ON backups')
    backups.drop_column('parent_id')

def upgrade(migrate_engine):
    meta.bind = migrate_engine
    instance_vip = Table('instance_vip', meta, autoload=True)
    instance_vip.create_column(Column('virtual_instance_id', String(36)))
    
    def update_instance_vips():
        update(table = instance_vip, whereclause="deleted = 0", 
               values=dict(virtual_instance_id = instance_vip.c.instance_id)).execute()
    
    update_instance_vips()

def downgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine
    instances = Table("instances", meta, autoload=True)
    constraint_names = db_utils.get_foreign_key_constraint_names(
        engine=migrate_engine, table="instances", columns=[COLUMN_NAME], ref_table="instances", ref_columns=["id"]
    )
    db_utils.drop_foreign_key_constraints(
        constraint_names=constraint_names, columns=[instances.c.slave_of_id], ref_columns=[instances.c.id]
    )
    instances.drop_column(COLUMN_NAME)

def upgrade(migrate_engine):
    meta = MetaData()
    meta.bind = migrate_engine

    # add column:
    instances = Table('instances', meta, autoload=True)
    volume_size = Column('volume_size', Integer())
    flavor_id = Column('flavor_id', String(36))

    instances.create_column(flavor_id)
    instances.create_column(volume_size)

def upgrade(migrate_engine):
    meta.bind = migrate_engine
    create_tables([datastores, datastore_versions])
    
#     ----------------------------------------------------
#     Fore. 2014/06/19 Not modify old schemas on Instance.
#     ----------------------------------------------------
    instances = Table('instances', meta, autoload=True)
#     datastore_version_id = Column('datastore_version_id', String(36),
#                                   ForeignKey('datastore_versions.id'))
    datastore_version_id = Column('datastore_version_id', String(36), nullable = True)
    instances.create_column(datastore_version_id)

def downgrade(migrate_engine):
    meta.bind = migrate_engine
    instances = Table('instances', meta, autoload=True)
    constraint_names = db_utils.get_foreign_key_constraint_names(
        engine=migrate_engine,
        table='instances',
        columns=['configuration_id'],
        ref_table='configurations',
        ref_columns=['id'])
    db_utils.drop_foreign_key_constraints(
        constraint_names=constraint_names,
        columns=[instances.c.configuration_id],
        ref_columns=[configurations.c.id])
    instances.drop_column('configuration_id')
    drop_tables([configuration_parameters, configurations])

def upgrade(migrate_engine):
    meta.bind = migrate_engine

    # since the downgrade is a no-op, an upgrade after a downgrade will
    # cause an exception because the tables already exist
    # we will catch that case and log an info message
    try:
        create_tables([configurations])
        create_tables([configuration_parameters])

        instances = Table('instances', meta, autoload=True)
        instances.create_column(Column('configuration_id', String(36),
                                       ForeignKey("configurations.id")))
    except OperationalError as e:
        logger.info(e)