[Django]-Django: Retrieve active threads by the time the last Post was created

by

2👍

Just add field ‘last_post_datetime’ in Thread and update this field in Post.save:

class Thread(models.Model)
    ...
    last_post_datetime = models.DateTimeField(blank=True,null=True) 

class Post(Meta):
    ...
    def save(self):
        super(Post, self).save()
        self.thread.last_post_datetime = max(self.thread.last_post_datetime, self.createtime)
        self.thread.save()

and use simple query

Thread.objects.order_by('-createtime')[:10]

And of course I recommend you to add index on this field:

ALTER TABLE <post> ADD INDEX createtime (createtime);
👤Mikhail Polykovskii

1👍

There is probably an easier way 🙂 Add a DateTimeField to the Post object with a “date_posted” field or something like that. Then do this:

Thread.objects.order_by('-post_set__date_posted')[:10]

This is basically a variant on the answer of Glader, but I like this better because it doesn’t require a custom save() method if you set the auto_now_add to True on the DateTimeField. I prefer to keep the logic of a model as much inside the model itself as possible.

👤Xudonax

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