google-app-engine - 只有一个实体的跨组交易错误

Question

我正在尝试执行下面的代码。有时它工作正常。但有时它不起作用。

@db.transactional
def _add_data_to_site(self, key):
    site = models.Site.get_by_key_name('s:%s' % self.site_id)
    if not site:
        site = models.Site()

    if key not in site.data:
        site.data.append(key)
        site.put()
        memcache.delete_multi(['', ':0', ':1'], key_prefix='s%s' %                                                                       
            self.site_id)

我收到错误:

File "/base/data/home/apps/xxxxxxx/1-7-1.366398694339889874xxxxxxx.py", line 91, in _add_data_to_site
  site.put()
File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py", line 1070, in put
  return datastore.Put(self._entity, **kwargs)
File "/base/python_runtime/python_lib/versions/1/google/appengine/api/datastore.py", line 579, in Put
  return PutAsync(entities, **kwargs).get_result()
File "/base/python_runtime/python_lib/versions/1/google/appengine/api/apiproxy_stub_map.py", line 604, in get_result
  return self.__get_result_hook(self)
File "/base/python_runtime/python_lib/versions/1/google/appengine/datastore/datastore_rpc.py", line 1569, in __put_hook
  self.check_rpc_success(rpc)
File "/base/python_runtime/python_lib/versions/1/google/appengine/datastore/datastore_rpc.py", line 1224, in check_rpc_success
  raise _ToDatastoreError(err)
BadRequestError: cross-group transaction need to be explicitly specified, see TransactionOptions.Builder.withXG

那么，我的问题是:

如果我只更改一个实体 (models.Site)，为什么会出现跨组事务错误？

Answer 1

如日志中所述:“需要明确指定跨组事务”。尝试使用

指定它

@db.transactional(xg=True)

代替:

@db.transactional