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
33838	Querying issue with ForeignKeys where db_constraint=False	Alex Bailey	nobody	"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, expected to return all 3. 
>>> 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. The 3rd query should be a simple union of the first 2 queries. 

All 3 books fit into the expected query of `books WHERE foo__name = 'Alex' OR  bar__name = 'Alex'` but the Django behavior does not reflect this.
"	Bug	new	Database layer (models, ORM)	4.0	Normal				Unreviewed	0	0	0	0	0	0