#26797: Reverse `related_name` of a proxy not accessible to inherited proxies in
queryset
-------------------------------------+-------------------------------------
Reporter: mlorant | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.9
(models, ORM) |
Severity: Normal | Resolution:
Keywords: related_name | Triage Stage:
reverse relation | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by mlorant):
* needs_docs: => 0
* needs_better_patch: => 0
* needs_tests: => 0
Old description:
> Taken the following example (not real world use case, but it is somewhat
> equivalent of something I encountered):
>
> {{{
> from django.db import models
>
> class Animal(models.Model):
> name = models.CharField("animal name", max_length=255, blank=True,
> null=False)
>
> class Mammal(Animal):
> class Meta:
> proxy = True
>
> class Cat(Mammal):
> class Meta:
> proxy = True
>
> class Dog(Mammal):
> class Meta:
> proxy = True
>
> class TrueFriendship(models.Model):
> mammal = models.ForeignKey(Mammal, related_name="dog_friends")
> dog = models.ForeignKey(Dog, related_name="mammal_friends")
> }}}
>
> I want to get the number of friends of a queryset of cats. However, doing
> this in a shell results in an exception:
>
> {{{
> >>> from nature.models import *
> >>> cat = Cat.objects.create(name="cat1")
> >>> dog = Dog.objects.create(name="dog1")
> >>> TrueFriendship.objects.create(cat=cat, dog=dog)
> >>> Cat.objects.annotate(nb_dog_friends=models.Count('dog_friends'))
> Traceback (most recent call last):
> File "/data/.virtualenvs/bugproxy/local/lib/python2.7/site-
> packages/django/db/models/manager.py", line 122, in manager_method
> return getattr(self.get_queryset(), name)(*args, **kwargs)
> [...]
> File "/data/.virtualenvs/bugproxy/local/lib/python2.7/site-
> packages/django/db/models/sql/query.py", line 1330, in names_to_path
> "Choices are: %s" % (name, ", ".join(available)))
> FieldError: Cannot resolve keyword 'dog_friends' into field. Choices are:
> id, name
> }}}
>
> (Full traceback attached in a file) However, the same query using the
> `Mammal` proxy works and the reverse relation is available on single
> object:
>
> {{{
> >>>
> Mammal.objects.annotate(nb_dog_friends=models.Count('dog_friends')).first().nb_dog_friends
> 1
> >>> Cat.objects.first().dog_friends.all()
> [<TrueFriendship: TrueFriendship object>]
> }}}
>
> Something is inconsistent here: I would expect to have access to
> `dog_friends` in both cases (on a model instance and a queryset)
New description:
Taken the following example (not real world use case, but it is somewhat
equivalent of something I encountered):
{{{
from django.db import models
class Animal(models.Model):
name = models.CharField("animal name", max_length=255, blank=True,
null=False)
class Mammal(Animal):
class Meta:
proxy = True
class Cat(Mammal):
class Meta:
proxy = True
class Dog(Mammal):
class Meta:
proxy = True
class TrueFriendship(models.Model):
mammal = models.ForeignKey(Mammal, related_name="dog_friends")
dog = models.ForeignKey(Dog, related_name="mammal_friends")
}}}
I want to get the number of friends of a queryset of cats. However, doing
this in a shell results in an exception:
{{{
>>> from nature.models import *
>>> cat = Cat.objects.create(name="cat1")
>>> dog = Dog.objects.create(name="dog1")
>>> TrueFriendship.objects.create(cat=cat, dog=dog)
>>> Cat.objects.annotate(nb_dog_friends=models.Count('dog_friends'))
Traceback (most recent call last):
File "/data/.virtualenvs/bugproxy/local/lib/python2.7/site-
packages/django/db/models/manager.py", line 122, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
[...]
File "/data/.virtualenvs/bugproxy/local/lib/python2.7/site-
packages/django/db/models/sql/query.py", line 1330, in names_to_path
"Choices are: %s" % (name, ", ".join(available)))
FieldError: Cannot resolve keyword 'dog_friends' into field. Choices are:
id, name
}}}
(Full traceback attached in a file) The same goes for "simple" query such
as `Cat.objects.filter(dog_friends__isnull=False)`. However, using the
`Mammal` proxy, both queries work and the reverse relation is available on
single `Cat` object:
{{{
>>>
Mammal.objects.annotate(nb_dog_friends=models.Count('dog_friends')).first().nb_dog_friends
1
>>> Cat.objects.first().dog_friends.all()
[<TrueFriendship: TrueFriendship object>]
}}}
Something is inconsistent here: I would expect to have access to
`dog_friends` in both cases (on a model instance and a queryset)
--
--
Ticket URL: <https://code.djangoproject.com/ticket/26797#comment:1>
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