If empty, the new update request is assigned an automatically-generated operation ID. Otherwise, operation_id is used to construct the name of the resulting Operation. Specifying an explicit operation ID simplifies determining whether the statements were executed in the event that the UpdateDatabaseDdl call is replayed, or the return value is otherwise lost: the database and operation_id fields can be combined to form the name of the resulting longrunning.Operation: /operations/. operation_id should be unique within the database, and must be a valid identifier: a-z*. Note that automatically-generated operation IDs always begin with an underscore. If the named operation already exists, UpdateDatabaseDdl returns ALREADY_EXISTS.

Optional. Proto descriptors used by CREATE/ALTER PROTO BUNDLE statements. Contains a protobuf-serialized google.protobuf.FileDescriptorSet. To generate it, install and run protoc with --include_imports and --descriptor_set_out. For example, to generate for moon/shot/app.proto, run $protoc --proto_path=/app_path --proto_path=/lib_path \ --include_imports \ --descriptor_set_out=descriptors.data \ moon/shot/app.proto For more details, see protobuffer self description.