形成一对多关系的Django queryset

Question

I have a Django model defining a photo:

class Pic(models.Model):
    image = models.ImageField(upload_to=upload_pic_to_location, storage=OverwriteStorage())
    owner = models.ForeignKey(User)
    upload_time = models.DateTimeField(db_index=True, auto_now_add=True)

And another defining a message the above photo can be sent as:

class PicMessage(models.Model):
    which_pic = models.ForeignKey(Pic)
    sending_time = models.DateTimeField(auto_now_add=True)

Ie same pic can be sent as a different message multiple times. What's the most efficient way to find the most recent PicMessage sent by a given user ?

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I'm trying this: PicMessage.objects.filter(which_pic__in=Pic.objects.filter(owner=self.request.user)).latest('sending_time')

Answer 1

PicMessage.objects.filter(which_pic__owner=user).order_by('-sending_time').first()