#33838: Querying issue with ForeignKeys where db_constraint=False
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Reporter: | Owner: nobody
MrAlexBailey |
Type: Bug | Status: new
Component: Database | Version: 4.0
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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models.py
{{{
from django.db import models
class Person(models.Model):
name = models.CharField(max_length=25)
class Book(models.Model):
foo = models.ForeignKey(Person, db_constraint=False,
on_delete=models.DO_NOTHING, related_name='foo')
bar = models.ForeignKey(Person, db_constraint=False,
on_delete=models.DO_NOTHING, related_name='bar')
}}}
setup
{{{
from .models import Book, Person
alex = Person.objects.create(name='Alex')
Book.objects.create(foo=alex, bar=alex)
Book.objects.create(foo=alex, bar_id=999)
Book.objects.create(foo_id=999, bar=alex)
}}}
shell
{{{
>>> from django.db.models import Q
#Correct: Returns both books where foo__name == 'Alex'
>>> Book.objects.filter(foo__name='Alex')
<QuerySet [<Book: Book object (1)>, <Book: Book object (2)>]>
#Correct: Returns both books where bar__name == 'Alex'
>>> Book.objects.filter(bar__name='Alex')
<QuerySet [<Book: Book object (1)>, <Book: Book object (3)>]>
#Only returns one book where both foo__name and bar__name == 'Alex'
>>> Book.objects.filter(Q(foo__name='Alex') | Q(bar__name='Alex'))
<QuerySet [<Book: Book object (1)>]>
}}}
I am working with an existing DB where it is possible for a `Person` to no
longer exist, hence the lack of `db_constraint` in the `ForeignKey`.
`Books` can refer to non-existent `Persons` but it still seems like
expected behavior would be for the queryset OR to return all 3 books. I
believe this is coming from the Django ORM doing an INNER JOIN.
--
Ticket URL: <https://code.djangoproject.com/ticket/33838>
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