def downgrade_schema(config: metadata_store_pb2.ConnectionConfig,
downgrade_to_schema_version: int) -> None:
"""Downgrades the db specified in the connection config to a schema version.
If `downgrade_to_schema_version` is greater or equals to zero and less than
the current library's schema version, it runs a downgrade transaction to
revert the db schema and migrate the data. The update is transactional, and
any failure will cause a full rollback of the downgrade. Once the downgrade
is done, the user needs to use the older version of the library to connect to
the database.
Args:
config: a metadata_store_pb2.ConnectionConfig having the connection params
downgrade_to_schema_version: downgrades the given database to a specific
version. For v0.13.2 release, the schema_version is 0. For 0.14.0 and
0.15.0 release, the schema_version is 4. More details are described in
g3doc/get_start.md#upgrade-mlmd-library
Raises:
InvalidArgumentError: if the `downgrade_to_schema_version` is not given or
it is negative or greater than the library version.
RuntimeError: if the downgrade is not finished, return detailed error.
"""
if downgrade_to_schema_version < 0:
raise _make_exception('downgrade_to_schema_version not specified',
errors.INVALID_ARGUMENT)
try:
migration_options = metadata_store_pb2.MigrationOptions()
migration_options.disable_upgrade_migration = True
migration_options.downgrade_to_schema_version = downgrade_to_schema_version
metadata_store_serialized.CreateMetadataStore(
config.SerializeToString(), migration_options.SerializeToString())
except RuntimeError as e:
if str(e).startswith('MLMD cannot be downgraded to schema_version'):
raise _make_exception(str(e), errors.INVALID_ARGUMENT)
if not str(e).startswith('Downgrade migration was performed.'):
raise e
# downgrade is done.
logging.log(logging.INFO, str(e))
def __init__(self, config: metadata_store_pb2.ConnectionConfig):
self._metadata_store = metadata_store_serialized.CreateMetadataStore(
config.SerializeToString())
# If you remove this line, errors are not thrown correctly.
logging.log(logging.INFO, "MetadataStore initialized")