def db_sync(engine, abs_path, version=None, init_version=0):
    if version is not None:
        try:
            version = int(version)
        except ValueError:
            raise exception.DbMigrationError(
                message=_("version should be an integer"))

    current_version = db_version(engine, abs_path, init_version)
    repository = _find_migrate_repo(abs_path)
    _db_schema_sanity_check(engine)
    if version is None or version > current_version:
        return versioning_api.upgrade(engine, repository, version)
    else:
        return versioning_api.downgrade(engine, repository,
                                        version)
Upgrade or downgrade a database.
dataset/ETHPy150Open openstack/rack/rack/openstack/common/db/sqlalchemy/migration.py/db_sync