Python google.appengine.ext.db 模块，non_transactional() 实例源码

def find_all_by_mapreduce_state(cls, mapreduce_state):
    """Find all shard states for given mapreduce.

    Args:
      mapreduce_state: MapreduceState instance

    Yields:
      shard states sorted by shard id.
    """
    keys = cls.calculate_keys_by_mapreduce_state(mapreduce_state)
    i = 0
    while i < len(keys):
      @db.non_transactional
      def no_tx_get(i):
        return db.get(keys[i:i+cls._MAX_STATES_IN_MEMORY])


      states = no_tx_get(i)
      for s in states:
        i += 1
        if s is not None:
          yield s