**** CubicPower OpenStack Study ****
def upgrade(migrate_engine):
"""Add source volume id column to volumes."""
meta = MetaData()
meta.bind = migrate_engine
volumes = Table('volumes', meta, autoload=True)
source_volid = Column('source_volid', String(36))
volumes.create_column(source_volid)
volumes.update().values(source_volid=None).execute()
**** CubicPower OpenStack Study ****
def downgrade(migrate_engine):
"""Remove source volume id column to volumes."""
meta = MetaData()
meta.bind = migrate_engine
volumes = Table('volumes', meta, autoload=True)
source_volid = Column('source_volid', String(36))
volumes.drop_column(source_volid)