Django-MPTT - ordering root nodes by count of immediate descendants

Question

I'm using Django-MPTT to do a display a simple 2 level hierarchy (root => child(ren)). I'm looking for a way to structure my queryset so that nodes get returned with the root node having the most children first and the node with the least children (if any) last.

Answer 1

Take a look at your parent field and make note of the related_name. Suppose it is children. Then do the following:

from django.db.models import Count

MyMPTTModel.objects.root_nodes().annotate(
    Count('children')).order_by('-children__count')

If you need access to the child instances themselves, you may also want to look at doing a qs.prefetch_related('children') as well.