Sum of Subquery fields django

Question

I have the following subquery:

Subquery(
         ContestTaskRelationship.objects.filter(
             contest=contest,
             solved=OuterRef('id')
         ).values('cost').all()
)

I need then to annotate my QuerySet with sum of cost values returned by each Subquery. How to do that? Wrapping the subquery in Sum returns only the first element of each subquery.

Look at this answer: https://stackoverflow.com/a/42648980/641249 — neverwalkaloner, Jun 29 '18 at 10:15
@neverwalkaloner, that does not work for me, as I have to sum all results of subquery, not annotate each with something — pomo_mondreganto, Jun 29 '18 at 10:23

score 0 · Accepted Answer · answered Oct 23 '18 at 20:25

I found a way without Subquery:

cost_sum=Sum(
            Case(
                When(
                    contest_task_relationship__contest=contest,
                    then='contest_task_relationship__cost'
                ),
                default=V(0),
                output_field=IntegerField()
            )
        )

Not an elegant way, but it works.

Sum of Subquery fields django

1 Answers1