Django Count() in multiple annotations

Question

Say I have a simple forum model:

class User(models.Model):
    username = models.CharField(max_length=25)
    ...

class Topic(models.Model):
    user = models.F         


        

Answer 1

I think Count('topics', distinct=True) should do the right thing. That will use COUNT(DISTINCT topic.id) instead of COUNT(topic.id) to avoid duplicates.

User.objects.filter(
    username_startswith="ab").annotate(
    posts=Count('post', distinct=True)).annotate(
    topics=Count('topic', distinct=True)).values_list(
    "username","posts", "topics")

Answer 2

Try adding distinct to your last queryset:

User.objects.filter(
    username_startswith="ab").annotate(
    posts=Count('post')).annotate(
    topics=Count('topic')).values_list(
    "username","posts", "topics").distinct()

See https://docs.djangoproject.com/en/1.3/ref/models/querysets/#distinct for more details, but basically you're getting duplicate rows because the annotations span multiple tables.