#18012: Propagate reverse foreign keys from proxy models to base class
-------------------------------------+-------------------------------------
Reporter: akaariai | Owner: charettes
Type: | Status: assigned
Cleanup/optimization |
Component: Database layer | Version: 1.4
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by akaariai):
My example wasn't that great, sorry for that.
What I'm after is that if we add proxy relations to the parent models we
don't break anything (except for backwards incompatibility in the Meta
API). The same isn't true for MTI inheritance, where a lot would break if
we added child model relations to parent models.
We do support an inheritance chain of Concrete -> ProxyConcrete ->
ProxyConcreteChild. Interestingly this chain actually creates a foreign
key from ProxyConcreteChild directly to Concrete in the model definition.
This is inconsistent, the foreign key should be to ProxyConcrete. But we
can't do that, as then
Concrete.objects.select_related('proxyconcretechild') wouldn't work, as
Concrete doesn't have the reverse descriptor for the relation from
ProxyConcreteChild to ProxyConcrete.
Also, my reverse_queryset example is broken. This assumes you want to get
the *reverse* relation as proxy instances, whereas the foreign key to
proxy feature is about getting the *direct* relation as proxy instances.
While maybe an useful feature, it doesn't change anything for this ticket.
Instead we should have fk = models.ForeignKey(ConcreteModel,
fetch_as=ProxyModel) or something like that. This might actually make some
sense if done automatically. The user writes ForeignKey(ProxyModel),
internally Django interprets it as ForeignKey(ConcreteModel,
fetch_as=ProxyModel). But I guess we do have more important problems to
solve.
Even if I see a slight advantage in publishing reverse relations to
concrete parents, I guess I'm slightly in favor of closing this one and
moving on to something more productive.
--
Ticket URL: <https://code.djangoproject.com/ticket/18012#comment:16>
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