Using Django ORM query How to annotate if multiple levels of foreign key hierarchy exists

Question

My Django models looks like

class Parent(models.Model):
    name = models.CharField(('name'), max_length=30)

class Child(models.Model):
    parent = models.ForeignKey(Parent)
    name = models.CharField(('name'), max_length=30)

class GrandChild(models.Model):
    child = models.ForeignKey(Child)
    name = models.CharField(('name'), max_length=30)

-> To Get Number of Childs for parent following query does               
    Parent.objects.annotate(childs=Count('Child')).values('childs')

-> To Get Number of Grand Childs for parent following query does               
    Parent.objects.annotate(childs=Count('child')).annotate(grandchilds=Count('child__grandchild'))

But how can I get the count of number of childs and number of grand childs for each parent

These kinds of things are solved with recursion, for example you make a get_children method that iterates over each child and calls their get_children until there are no more to call. — Lauri Elias, Jul 08 '16 at 14:48

score 1 · Accepted Answer · answered Jul 08 '16 at 14:49

1

Try to use distinct:

Count('child', distinct=True)

Using Django ORM query How to annotate if multiple levels of foreign key hierarchy exists

1 Answers1