Django: Sum the count of a sub sub foreign object

问题

I have many hits by Twavail I have many Twavail for a Twaffic

I would like to sum the number of Hits for a Twaffic, and get an additionel field in Twaffic entries (hits_count), but I have some difficulties.

Here are my models:

class Twaffic(models.Model):
    user = models.ForeignKey(User,editable=False)
    enchere = models.PositiveIntegerField(default=1)

class Twavail(models.Model):

    user = models.ForeignKey(User,editable=False)
    twaffic = models.ForeignKey(Twaffic,editable=False,related_name='twavaux')
    tweet_id = models.CharField(max_length=20,default=0, editable=False)

class Hit(models.Model):
    twavail = models.ForeignKey(Twavail,editable=False,related_name='hits')
    date = models.DateTimeField(max_length=140,auto_now=True,default="")

I tried:

twaffics=Twaffic.objects.annotate(hits_count=Sum('twavaux__hits__count')).filter(user=request.user)

But I get the following error:

Cannot resolve keyword 'hits' into field. Choices are: twaffic, user

Is it really impossible to get this informations 2 levels ago? hits is the right related name.. Maybe I missed something?

Thx for your help.

回答1:

Try using this...

hit_count = Hit.objects.filter(twavail__id__in = Twavail.objects.filter(twaffic = twaffic_obj).values_list('id', flat=True)).count()

回答2:

I found the answer:

twaffics=Twaffic.objects.annotate(hits_count=Count('twavaux__hits')).filter(user=request.user)

After having added hits application to my settings.py it works, that was the big point.

来源：https://stackoverflow.com/questions/13013333/django-sum-the-count-of-a-sub-sub-foreign-object

标签

django

django-models