Clarify that custom managers don't apply to intermediate joins

[Andrew Badr]

I have a custom Manager to filter out model instances with where the field deleted is True. I'm using an ORM query that looks like user1.page_set.filter(membership__user=user2).

My expectation is that Membership objects with the deleted flag set are not included in the query. Instead, they are being included.

[Matt Austin]

Attempted to reproduce this, but require more info on model relationships.

[jedediah]

class BagelManager(Manager):
    use_for_related_fields = True

    def get_query_set(self):
        return super(BagelManager, self).get_query_set().filter(deleted=False)

class Bagel(Model):
    deleted = BooleanField()

    objects = BagelManager()
    all_bagels = Manager()

    def __str__(self):
        return "deleted" if self.deleted else "active"

class Customer(Model):
    bagels = ManyToManyField(Bagel)

>>> Bagel.objects.create(deleted=False)
<Bagel: active>
>>> Bagel.objects.create(deleted=True)
<Bagel: deleted>
>>> Bagel.all_bagels.all()
[<Bagel: active>, <Bagel: deleted>]
>>> Bagel.objects.all()
[<Bagel: active>]
>>> Bagel.objects.filter(deleted=True)
[]

Correct so far... deleted bagel is invisible through default manager

>>> c = Customer.objects.create()
>>> c.bagels.add(*Bagel.all_bagels.all())
>>> c.bagels.all()
[<Bagel: active>]
>>> c.bagels.filter(deleted=True)
[]

Still good... deleted bagel is invisible to related fields

>>> Customer.objects.filter(bagels__deleted=True)
[<Customer: Customer object>]

Here's the problem. The query join sees the deleted bagel. I would expect queries through relations to see the same data as the relations themselves.

This should either be fixed or documented as a known limitation.

[Tim Graham]

I don't think this a behavior that's going to change, so documentation seems like the way to go. If you'd like to write a patch, I'll be happy to review it.

[Tim Graham]

​PR with comments for improvement.

[Tim Graham]

yanikkoval, not sure why you assigned yourself to the ticket. In case you didn't see it, we have a patch awaiting review linked in comment:8.

[Yanik Koval]

Sorry, didn't notice.

[Tim Graham]

I felt the existing proposal is more verbose than needed, so I created an alternate ​PR.

[GitHub <noreply@…>]

In 8fb53c50:

Fixed #19222 -- Documented that default managers aren't used for related queries.

[Tim Graham <timograham@…>]

In 8df2da3:

[1.10.x] Fixed #19222 -- Documented that default managers aren't used for related queries.

Backport of 8fb53c50ce1c759c740960c9e1cef3cef39cabc5 from master