django一对一左连接是空的？

I've got models like those in django:

我有像django那样的模型:

class User(models.Model):
  name = models.CharField(max_length = 128)

class Message(models.Model):
  sender = models.ForeignKey(User, related_name = 'messages_sent')
  recipient = models.ForeignKey(User, related_name = 'messages_recieved')
  subject = models.CharField(max_length = 128)
  body = models.CharField(max_length = 3500)

class Response(models.Model):
  message = models.OneToOneField(Message, primary_key = True)
  reply = models.TextField()

and I'm trying to get all the messages for the user that have no response, something I would write in SQL as:

我正在尝试为没有响应的用户获取所有消息,我将在SQL中编写:

select * from user u
         join message m on (u.id = m.recipient_id)
         left join response r on (m.id = r.message_id)
where r.message_id = null

I'd think the natural way to do this would be:

我认为这样做的自然方式是:

u.messages_recieved.filter(response = None)

u.messages_recieved.filter(response__message_id__isnull = True)

but the SQL generated always ends up being:

但生成的SQL总是最终成为:

WHERE ("project_message"."recipient_id" = 1  AND "project_message"."id" IS NULL)

Am I doing something stupid, or is this a bug in Django?

我做了一些愚蠢的事,或者这是Django中的一个错误?

2 个解决方案

#1

Try:

user.messages_recieved.filter(response__isnull=True)

the resulting query is:

生成的查询是:

SELECT "messaging_message"."id", "messaging_message"."sender_id", "messaging_message"."recipient_id", "messaging_message"."subject", "messaging_message"."body" FROM "messaging_message" LEFT OUTER JOIN "messaging_response" ON ("messaging_message"."id" = "messaging_response"."message_id") WHERE ("messaging_message"."recipient_id" = 1  AND "messaging_response"."message_id" IS NULL)

which I think is proper. It is indeed doing the left outer join and then checking for rows with null response message id.

我认为这是正确的。它确实在执行左外连接,然后检查具有空响应消息ID的行。

u.messages_recieved.filter(response=None)

works fine too.

工作得很好。

I'm using django 1.1 RC but this should work in 1.0+.

我正在使用django 1.1 RC,但这应该适用于1.0+。

#2

Something that I've done when trying to achieve a similar result is:

我在尝试获得类似结果时所做的一切是:

u.messages_received.filter(~Q(response__id__gt=0))

#1