How can I use bulkuploader to populate a class using db.SelfReferenceProperty?

Question

I have a class that uses db.SelfReferencePropertyto create a tree structure.

When I try to populate the database with appcfg.py upload_data -- config_file=bulkloader.yaml --kind=Group --filename=group.csv (...) , I get an exception saying BadValueError: name must not be empty. ^{(Full stack below)}

I tried organizing the data to make sure that the groups that had the foreign key pointing to them were the first. This did not work.

Commenting out a line from bulkloader.yaml that does the conversion "import_transform: transform.create_foreign_key ('Group')", the data is loaded, but it saves this property as a string, violating my application logic.

- kind: Group
  connector: csv
  connector_options:
  property_map:
    - property: __key__
      external_name: key
      export_transform: transform.key_id_or_name_as_string

    - property: name
      external_name: name
      # Type: String Stats: 9 properties of this type in this kind.

    - property: section
      external_name: section
      # Type: Key Stats: 6 properties of this type in this kind.
      import_transform: transform.create_foreign_key('Group')
      export_transform: transform.key_id_or_name_as_string

, ?

----
Traceback (most recent call last):
  File "/home/username/src/google_appengine/google/appengine/tools/adaptive_thread_pool.py", line 150, in WorkOnItems
    status, instruction = item.PerformWork(self.__thread_pool)
  File "/home/username/src/google_appengine/google/appengine/tools/bulkloader.py", line 691, in PerformWork
    transfer_time = self._TransferItem(thread_pool)
  File "/home/username/src/google_appengine/google/appengine/tools/bulkloader.py", line 846, in _TransferItem
    self.content = self.request_manager.EncodeContent(self.rows)
  File "/home/username/src/google_appengine/google/appengine/tools/bulkloader.py", line 1267, in EncodeContent
    entity = loader.create_entity(values, key_name=key, parent=parent)
  File "/home/username/src/google_appengine/google/appengine/ext/bulkload/bulkloader_config.py", line 382, in create_entity
    return self.dict_to_entity(input_dict, self.bulkload_state)
  File "/home/username/src/google_appengine/google/appengine/ext/bulkload/bulkloader_config.py", line 133, in dict_to_entity
    self.__run_import_transforms(input_dict, instance, bulkload_state_copy)
  File "/home/username/src/google_appengine/google/appengine/ext/bulkload/bulkloader_config.py", line 230, in __run_import_transforms
    value = self.__dict_to_prop(transform, input_dict, bulkload_state)
  File "/home/username/src/google_appengine/google/appengine/ext/bulkload/bulkloader_config.py", line 188, in __dict_to_prop
    value = transform.import_transform(value)
  File "/home/username/src/google_appengine/google/appengine/ext/bulkload/bulkloader_parser.py", line 93, in __call__
    return self.method(*args, **kwargs)
  File "/home/username/src/google_appengine/google/appengine/ext/bulkload/transform.py", line 114, in generate_foreign_key_lambda
        return datastore.Key.from_path(kind, value)
  File "/home/username/src/google_appengine/google/appengine/api/datastore_types.py", line 384, in from_path
    ValidateString(id_or_name, 'name')
  File "/home/username/src/google_appengine/google/appengine/api/datastore_types.py", line 109, in ValidateString
    raise exception('%s must not be empty.' % name)
BadValueError: name must not be empty.

Answer 1

, , , helpers.py, transform.create_foreign_key:

from google.appengine.api import datastore

def create_foreign_key(kind, key_is_id=False):
  def generate_foreign_key_lambda(value):
    if value is None:
      return None

    if key_is_id:
      value = int(value)
    try:
      return datastore.Key.from_path(kind, value)
    except:
      return None

  return generate_foreign_key_lambda

, yaml bolk (bulkloader.yaml), :

python_preamble:
- (...)
- import: helpers

transformers:

- kind: Group
  connector: csv
  connector_options:
  property_map:
    - property: __key__
      external_name: key
      export_transform: transform.key_id_or_name_as_string

    - property: name
      external_name: name

    - property: section
      external_name: section
      import_transform: helpers.create_foreign_key('Group')
                      # ^^^^^^^ we use the wrapper instead
      export_transform: transform.key_id_or_name_as_string

.

, catch except, except BadValueError.

Answer 2

transform.py (, ) , :

def none_if_empty(fn):
  """A decorator which returns None if its input is empty else fn(x).

  Useful on import.  Can be used in config files
  (e.g. "transform.none_if_empty(int)" or as a decorator.

  Args:
    fn: Single argument transform function.

  Returns:
    Wrapped function.
  """

  def wrapper(value):


    if value == '' or value is None or value == []:
      return None
    return fn(value)

  return wrapper

, helpers.py:

transform.none_if_empty(transform.create_foreign_key('Group'))