Django orm subquery - in clause without substitution

Question

I need to build a query using Django ORM, that looks like this one in SQL:

select * from A where id not in (select a_id from B where ... )

I try to use such code:

ids = B.objects.filter(...)
a_objects = A.object.exclude(id__in=Subquery(ids.values('a__id'))).all()

The problem is that instead of nested select Django generates query that looks like

select * from A where id not in (1, 2, 3, 4, 5 ....)

where in clause explicitly lists all ids that should be excluded, making result sql unreadable when it is printed into logs. Is it possible to adjst this query, so nested select is used?

Answer 1

So I see that your goal is to get all the A's that have no foreign key relations from B's. If I'm right, then you can just use inverse lookup to do it.

So, when you define models like that:

class A:
    pass

class B:
    a = ForeignKey(to=a, related_name='bs')

You can filter it like this:

A.objects.filter(bs__isnull=True)

Also, if you don't define related_name, it will default to b_set, so you will be able to A.objects.filter(b_set__isnull=True)