model - Django: Using F arguments in datetime.timedelta inside a query

Question

Using Django model syntax, if I do this:

ThatModel.objects.filter(
    last_datetime__lte=now + datetime.timedelta(seconds=F("interval")))

I get:

TypeError: unsupported type for timedelta days component: ExpressionNode

Is there a way to make this work with pure Django syntax (and not parsing all the results with Python)?

Answer 1

Just avoid timedelta's F-ignorance

filter knows about F, but timedelta does not. The trick is to keep the F out of the timedelta argument list:

ThatModel.objects.filter(
    last_datetime__lte=now + datetime.timedelta(seconds=1)*F("interval"))

This will work with PostgreSQL, but, alas, not with SQlite.