OpenStack Study: 023_drop_credential_constraints.py

**** CubicPower OpenStack Study ****

def list_constraints(migrate_engine):

    meta = sqlalchemy.MetaData()

    meta.bind = migrate_engine

    user_table = sqlalchemy.Table('user', meta, autoload=True)

    proj_table = sqlalchemy.Table('project', meta, autoload=True)

    cred_table = sqlalchemy.Table('credential', meta, autoload=True)

    constraints = [{'table': cred_table,

                    'fk_column': 'user_id',

                    'ref_column': user_table.c.id},

                   {'table': cred_table,

                    'fk_column': 'project_id',

                    'ref_column': proj_table.c.id}]

    return constraints

**** CubicPower OpenStack Study ****

def upgrade(migrate_engine):

    # SQLite does not support constraints, and querying the constraints

    # raises an exception

    if migrate_engine.name == 'sqlite':

        return

    migration_helpers.remove_constraints(list_constraints(migrate_engine))

**** CubicPower OpenStack Study ****

def downgrade(migrate_engine):

    if migrate_engine.name == 'sqlite':

        return

    migration_helpers.add_constraints(list_constraints(migrate_engine))