**** CubicPower OpenStack Study ****
def upgrade(migrate_engine):
meta = MetaData()
meta.bind = migrate_engine
nodes = Table('bm_nodes', meta, autoload=True)
nodes.drop_column('prov_mac_address')
**** CubicPower OpenStack Study ****
def downgrade(migrate_engine):
meta = MetaData()
meta.bind = migrate_engine
nodes = Table('bm_nodes', meta, autoload=True)
nodes.create_column(Column('prov_mac_address', String(length=255)))
# NOTE(arata): The values held by prov_mac_address are lost in upgrade.
# So downgrade has no other choice but to set the column to NULL.