使用通用关系进行高效查询

发布于 2024-09-02 14:03:51 字数 764 浏览 5 评论 0原文

这些是我的模型：

class Comment(models.Model):

    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField(_('object ID'))
    content_object = generic.GenericForeignKey()
    user = models.ForeignKey(User)
    comment = models.TextField(_('comment'))


class Post(models.Model):

    title = models.CharField(_('name'), max_length=80)         
    creator = models.ForeignKey(User, related_name="created_posts")
    created = models.DateTimeField(_('created'), default=datetime.now)
    body = models.TextField(_('body'), null=True, blank=True)

现在在我的views.py中，我收到了一篇带有以下说明的帖子：

    post = get_object_or_404(Post, id=id)

此时在我的views.py中，获取该帖子的所有评论的最有效的查询（使用ORM）是什么？

原文

These are my models:

class Comment(models.Model):

    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField(_('object ID'))
    content_object = generic.GenericForeignKey()
    user = models.ForeignKey(User)
    comment = models.TextField(_('comment'))


class Post(models.Model):

    title = models.CharField(_('name'), max_length=80)         
    creator = models.ForeignKey(User, related_name="created_posts")
    created = models.DateTimeField(_('created'), default=datetime.now)
    body = models.TextField(_('body'), null=True, blank=True)

Now in my views.py I get a post with this istruction:

    post = get_object_or_404(Post, id=id)

At this point in my views.py, what is the most efficient query ( with ORM ) to get all comments of that post ?

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债姬 2024-09-09 14:03:51

您应该在帖子上定义comments = generic.GenericRelation(Comment)，以便您可以轻松地从帖子访问到评论。一旦完成，这就是一个简单的向后关系：

comments = post.comments.all()

请注意，这并不是真正的效率问题。通过向后通用关系获取所有相关项目始终最多会产生两个查询 - 一个查询获取相关的 ContentType（在第一次查找时自动缓存），另一个查询获取实际项目。

如果您询问如何尽可能有效地获取多个帖子的所有评论，我会指出您我的博客有一个很好的技术，但既然你没有，我不会，因为那只是博客嫖娼。

You should define comments = generic.GenericRelation(Comment) on the Post, to give you easy access from Post to Comment. Once you've done that, it's a simple backwards relationship:

comments = post.comments.all()

Note that this isn't really a question of efficiency. Getting all the related items via a backwards generic relationship will always incur at most two queries - one to get the relevant ContentType, which is automatically cached on first look-up, and once to get the actual items.

If you had asked how to get all the comments for multiple posts as efficiently as possible, I'd point you to my blog for a good technique, but since you haven't I won't because that would just be blog-whoring.

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