Question

How can I query for count of related models satisfying a predicate? Let’s say I have a model

class Comment(Model):
    text = CharField(max_length=100)
    parent = ForeignKey('Comment')
    created_at = DateTimeField()

and I want to select all comments with count of child comments created after certain date. Something equivalent to SQL

select c1.*, count(c2.*) from comments c1 
left join comments c2 on c1.id = c2.parent_id and c2.created_at > the_date
group by c1.*

Is there a way to do it using QuerySet?

Answer 1

Comment.objects.filter(comment__created_at__gte=the_date).annotate(Count('comment'))