django - Filter over queryset with a loop -

i have inital queryset , loop on this

stats = {} queryset = item.objects.all() sub in subject.objects.all():         stats[str(sub.id)] = queryset.filter(subjects=sub.id).count() 

how can without hit db often?

look django aggregation:

from django.db.models import count  stats = subject.objects.annotate(count=count('item')) 

now each stats object have count field:

stats[0].count