python - django GAE 中的数据库错误“MultiQuery 不支持 keys_only”

Question

我正在将 djangoappengine 与 django non-rel 一起使用。

class Subject(TimeStampedModel):

    class_room = models.ForeignKey( ClassRoom, related_name='class_subject')
    subject = models.CharField( max_length=255)
    tutor = models.ForeignKey( UserProfile, related_name='tutor')

    def __unicode__(self):
        return self.subject





def quick_delete_subject(request, classroom_id, subject_id):

    if request.method == 'GET':
        classroom = ClassRoom.objects.get(pk=classroom_id)
        school = classroom.school
        school_id = school.pk

    try:
        old_subject = Subject.objects.get(pk=subject_id)
        old_subject.delete()
    except:
        raise

    return HttpResponse('Deleted')

但是，当我尝试在视图中删除主题对象时，会出现此错误。奇怪的是有时对象被删除而没有任何错误。

Django Version:     1.5.5
Exception Type:     DatabaseError
Exception Value:    MultiQuery does not support keys_only.