3

我有一个db.SelfReferenceProperty用于创建树状结构的类。

尝试使用 填充数据库appcfg.py upload_data -- config_file=bulkloader.yaml --kind=Group --filename=group.csv (...) 时，我收到一个异常消息BadValueError: name must not be empty。（下面的完整堆栈）

我尝试对数据进行排序以确保具有指向它们的外键的组是第一个。那没有用。

通过从 bulkloader.yaml 中注释进行转换的行“import_transform：transform.create_foreign_key('Group')”，数据被上传，但它将该属性存储为字符串，破坏了我的应用程序逻辑。

- 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

有什么方法可以让批量加载器考虑到自引用，或者我应该对批量加载的数据进行转换服务器端还是实现我自己的批量加载算法？

----
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.

4

2 回答 2

4

使用对类似问题的答案作为基础，我可以通过创建一个小helpers.py文件作为包装器来成功解决这个问题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

一旦该文件与您的 yaml bolk 上传配置文件 ( bulkloader.yaml) 位于同一目录中，您将其添加到该文件中：

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

通过这些更改，批量上传现在可以正常工作。

在使用它之前，你绝对应该修改 catch all except，并用 may be 替换它except BadValueError。

于 2010-09-13T22:44:43.290 回答
2

transform.py（可能只是最近）包含解决此问题的装饰器：

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

所以使用下面的也能解决问题，不用引入自定义helpers.py文件：

transform.none_if_empty(transform.create_foreign_key('Group'))
于 2011-08-31T12:29:23.163 回答