#30368: prefetch_related does not work for GenericForeignKey field when its
primary
key is also a foreign key
-------------------------------------+-------------------------------------
Reporter: Vinny Do | Owner: nobody
Type: Bug | Status: new
Component: Database | Version: master
layer (models, ORM) | Keywords: prefetch_related
Severity: Normal | genericforeignkey
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
**Steps to reproduce**
Create `Base` model with an `AutoField` primary key
{{{#!python
class Base(models.Model):
title = models.TextField()
}}}
Create a model where the primary key is also a foreign key
{{{#!python
class Extended(models.Model):
base = models.OneToOneField(Base, on_delete=models.CASCADE,
primary_key=True)
}}}
Create model with `GenericForeignKey`
{{{#!python
class Comment(models.Model):
content_type = models.ForeignKey(ContentType,
on_delete=models.CASCADE)
object_pk = models.TextField()
content_object = GenericForeignKey(ct_field="content_type",
fk_field="object_pk")
}}}
Prefetch the GenericForeignKey field `content_object` expecting it to have
a value but get `None` instead.
{{{#!python
# Setup
base = Base.objects.create(title="foo")
extended = Extended.objects.create(base=base)
Comment.objects.create(content_object=extended)
# Exercise
comment = Comment.objects.prefetch_related("content_object").get()
print(comment.content_object)
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/30368>
Django <https://code.djangoproject.com/>
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