id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
24762	Proxy models with children which inherit from the proxy cannot select_related said children	Keryn Knight	nobody	"This has only been briefly checked on `1.7`, `1.8` and `django-1.9.dev20150506223347` (`master`), and appears to silently pass on 1.6 (because `select_related` previously didn't raise errors)

Given the following models:
{{{
class InheritanceProxyConcrete(models.Model):
    pass

class InheritanceProxy(InheritanceProxyConcrete):
    class Meta:
        proxy = True

class InheritanceProxyChild(InheritanceProxy):
    pass
}}}
I would expect to be able to do the following:
{{{
>>> InheritanceProxy.objects.select_related('inheritanceproxychild')
[<InheritanceProxy: InheritanceProxy object>]
# equating to something like
SELECT ""tests_inheritanceproxyconcrete"".""id"", ""tests_inheritanceproxychild"".""inheritanceproxyconcrete_ptr_id"" FROM ""tests_inheritanceproxyconcrete"" LEFT OUTER JOIN ""tests_inheritanceproxychild"" ON ( ""tests_inheritanceproxyconcrete"".""id"" = ""tests_inheritanceproxychild"".""inheritanceproxyconcrete_ptr_id"" )
}}}
however, it transpires that it doesn't work:
{{{
>>> InheritanceProxyConcrete.objects.select_related('inheritanceproxychild')
[<InheritanceProxyConcrete: InheritanceProxyConcrete object>]
>>> InheritanceProxy.objects.select_related('inheritanceproxychild')
FieldError: Invalid field name(s) given in select_related: 'inheritanceproxychild'. Choices are: (none)
>>> InheritanceProxy.objects.select_related('inheritanceproxychild_ptr')
FieldError: Invalid field name(s) given in select_related: 'inheritanceproxychild_ptr'. Choices are: (none)
}}}

Furthering the quirkiness of the problem:
{{{
>>> dir(InheritanceProxy)
['DoesNotExist', 'MultipleObjectsReturned', '__class__', ... 'inheritanceproxychild', ...]
>>> InheritanceProxy.inheritanceproxychild
<django.db.models.fields.related.SingleRelatedObjectDescriptor object at 0xBLAHBlAH>
}}}
I've not worked with proxies much, and certainly not recently, so there's a good probability I'm making assumptions about what functionality should be provided based on an incomplete understanding of their use cases.

I've not tested explicit `OneToOnes`, `ForeignKeys`, `ManyToManys` or `prefetch_related`, so the possibility remains that it is only implicit parentage `OneToOnes` which are affected.

This stems from a ticket downstream in [https://github.com/carljm/django-model-utils/issues/168 django-model-utils] regarding using a Proxy model as the parent for auto-downcasting model instances (using it's `InheritanceManager`)"	Bug	closed	Database layer (models, ORM)	dev	Normal	duplicate		django@…	Accepted	0	0	0	0	0	0