キーでNDBクエリを注文する方法は？

Question

Google App Engineでタスクキューを使用しようとしています。 App Engineのドキュメント「Background work with the deferred library」に示されているMapperクラスを利用したいと思います。 は私がキー

def get_query(self): 
    ... 
    q = q.order("__key__") 
    ... 

例外でクエリ結果の順序に例外を取得：

File "C:... mapper.py", line 41, in get_query 
    q = q.order("__key__") 
    File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\ndb\query.py", line 1124, in order 
    'received %r' % arg) 
TypeError: order() expects a Property or query Order; received '__key__' 
INFO  2017-03-09 11:56:32,448 module.py:806] default: "POST /_ah/queue/deferred HTTP/1.1" 500 114 

記事は、2009年からなので、私は何かが変わったかもしれませんね。 私の環境：Windows 7、Python 2.7.9、Google App Engine SDK 1.9.50

NDBでの注文については、somewhat similar questionsがあります。 このコードは、2017年2月に（最近）更新され、評判によってSOユーザーの上位0.1％以内に投稿された恐らく、このコードは公式ドキュメントからのものです。

私は間違ったことをする必要があります。解決策は何ですか？

Answer 1

ビンゴ。 Avinash Rajが正しいです。それが答えだったら私はそれを受け入れるだろう。 はここで完全なクラスコード

#!/usr/bin/python2.7 
# -*- coding: utf-8 -*- 
from google.appengine.ext import deferred 
from google.appengine.ext import ndb 
from google.appengine.runtime import DeadlineExceededError 
import logging 

class Mapper(object): 
    """ 
    from https://cloud.google.com/appengine/docs/standard/python/ndb/queries 
    corrected with suggestions from Stack Overflow 
    http://stackoverflow.com/questions/42692319/how-to-order-ndb-query-by-the-key 
    """ 
    # Subclasses should replace this with a model class (eg, model.Person). 
    KIND = None 

    # Subclasses can replace this with a list of (property, value) tuples to filter by. 
    FILTERS = [] 

    def __init__(self): 
     logging.info("Mapper.__init__: {}") 
     self.to_put = [] 
     self.to_delete = [] 

    def map(self, entity): 
     """Updates a single entity. 
     Implementers should return a tuple containing two iterables (to_update, to_delete). 
     """ 
     return ([], []) 

    def finish(self): 
     """Called when the mapper has finished, to allow for any final work to be done.""" 
     pass 

    def get_query(self): 
     """Returns a query over the specified kind, with any appropriate filters applied.""" 
     q = self.KIND.query() 
     for prop, value in self.FILTERS: 
      q = q.filter(prop == value) 
     if __name__ == '__main__': 
      q = q.order(self.KIND.key) # the fixed version. The original q.order('__key__') failed 
      # see http://stackoverflow.com/questions/42692319/how-to-order-ndb-query-by-the-key 
     return q 

    def run(self, batch_size=100): 
     """Starts the mapper running.""" 
     logging.info("Mapper.run: batch_size: {}".format(batch_size)) 
     self._continue(None, batch_size) 

    def _batch_write(self): 
     """Writes updates and deletes entities in a batch.""" 
     if self.to_put: 
      ndb.put_multi(self.to_put) 
      self.to_put = [] 
     if self.to_delete: 
      ndb.delete_multi(self.to_delete) 
      self.to_delete = [] 

    def _continue(self, start_key, batch_size): 
     q = self.get_query() 
     # If we're resuming, pick up where we left off last time. 
     if start_key: 
      key_prop = getattr(self.KIND, '_key') 
      q = q.filter(key_prop > start_key) 
     # Keep updating records until we run out of time. 
     try: 
      # Steps over the results, returning each entity and its index. 
      for i, entity in enumerate(q): 
       map_updates, map_deletes = self.map(entity) 
       self.to_put.extend(map_updates) 
       self.to_delete.extend(map_deletes) 
       # Do updates and deletes in batches. 
       if (i + 1) % batch_size == 0: 
        self._batch_write() 
       # Record the last entity we processed. 
       start_key = entity.key 
      self._batch_write() 
     except DeadlineExceededError: 
      # Write any unfinished updates to the datastore. 
      self._batch_write() 
      # Queue a new task to pick up where we left off. 
      deferred.defer(self._continue, start_key, batch_size) 
      return 
     self.finish()