Django Q object is adding extra - IS NOT NULL - django

Question

for the below raw query, I want to build Django ORM query
Select * from employee
WHERE (address_id is not null OR address_id<>'*')
AND (xyz_id is null OR xyz_id='*')
AND (abc_id is null OR abc_id='*')
So I have build ORM query as below
data = Employee.objects.filter(~Q(address_id="23") | Q(address_id__isnull=False),
Q(xyz_id__isnull=False) | Q(xyz_id='*'),
Q(abc_id__isnull=True) | Q(abc_id=‘*’))
and when i print the query, it is showing as below
SELECT "employee"."id", "employee"."xyz_id", "employee"."abc_id" FROM
"employee" WHERE ((NOT ("employee"."address_id" = 23 AND
"employee"."address_id" IS NOT NULL) OR "employee"."address_id" IS
NOT NULL) AND ("employee"."xyz_id" IS NOT NULL OR "employee"."xyz_id"
= *) AND ("employee"."abc_id" IS NULL OR "employee"."abc_id" = *))
my question is why Q object in Django is adding bolded line in above generated query ? which is not solving for above raw sql criteria.
i am using Django 2.2 version
Kindly advise

Answer 1

If you write Q(foo=bar), then an implicit constraint is that foo is not NULL, if you negate that however, it will write NOT (foo = bar) but if foo is NULL, then NOT (foo = bar) is NOT (NULL = bar) which is NULL, so this will be filtered out of the queryset. which would thus result in FALSE whereas for NULL, one would expect that this is TRUE.
To thus ensure that ~Q(…) is the full opposite of Q(…), it thus should add foo IS NOT NULL to the condition.
In this specific case however the query optimizer could probably indeed figure out that it is not necessary due to the address_id IS NOT NULL later in the query, but here apparently the optimizer does not eliminate that clause.