python - Custom aggregate annotation in Django -

python - Custom aggregate annotation in Django -

i have many groups each has revision , each revision has months.

i want output grouping objects annotation.

for each grouping should select latest revision , sum months.

i'm not sure if can done in django. tried like

group.objects.annotate( month_sum=revision.objects.filter(date__lte=my_date).latest('date').aggregate(sum('months__amount')) )

and hoped queryset groups each has sum month_sum.

can seek one:

qs = group.objects.filter(revision__date__lte=my_date).annotate(month_sum=sum('months__amount'))

you can debug , seek undestand how create right query printing generated db query in shell:

print str(qs.query)

edit:

to show groups old revision think django-aggregate-if may help you

run pip install django-aggregate-if

from django.db.models import q aggregate_if import sum revision = revision.objects.filter(revision__date__lte=my_date).latest() qs = group.objects.all().annotate(month_sum=sum('months__amount', only=q(revision=revision)))

python django django-models django-views django-queryset