Adding constants to Annotations

Using Django Using the ORM
1

Board.objects.annotate(execs=Sum(top__active__value)) gives me a QuerySet with sums added as annotations (i.e execs). I am trying to figure out how to add a constant to the summation. That is, the sum of values in the specified columns added to, say, ‘3’ becomes the annotation. How do I do that?

2

Annotations and aggregations support the basic numeric operations in the annotation expression.
e.g: Board.objects.annotate(execs=Sum(top__active__value)+3)

See Query Expressions | Django documentation | Django

3

That is not working in my scenario:

Board.objects.get(pk=staff_id)
        .deptfk.members.filter(active__exact=True)
        .order_by("reference")
        .prefetch_related("memberpoints")
        .annotate(
            score=Sum(
                "memberpoints__taskfk__value",
                filter=Q(memberpoints__managerfk__id__exact=staff_id),
            ) + 3
        )

The above gives me:
TypeError: unsupported operand type(s) for +: 'Q' and 'int'

Without the filter, it works but I need the filter

4

I’m not at my computer, so I’m winging this. Two ideas come to mind -

  • wrap the Sum clause in a set of parens
    • e.g. .annotate(score=(Sum(…))+3)
  • calculate the sum in a subsequent annotate.
    • e.g. .annotate(score=…).annotate(score3=F(‘score’)+3)
1 Like
5

Thanks. It is working now. Much appreciated