@datastore_rpc.ConfigOption
  def prefetch_size(value):
    datastore_types.ValidateInteger(value,
                                    'prefetch_size',
                                    datastore_errors.BadArgumentError,
                                    zero_ok=True)
    return value
Number of results to attempt to return on the initial request.
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/datastore/datastore_query.py/QueryOptions.prefetch_size