Commit 55da775c authored by Anssi Kääriäinen's avatar Anssi Kääriäinen
Browse files

Fixed #17541 -- Fixed non-saved/nullable fk querying

parent 34ee7d98

django/db/models/fields/related.py

+2 −0
Original line number Diff line number Diff line
@@ -496,6 +496,8 @@ class ForeignRelatedObjectsDescriptor(object): 
                except (AttributeError, KeyError):

                    db = self._db or router.db_for_read(self.model, instance=self.instance)

                    qs = super(RelatedManager, self).get_query_set().using(db).filter(**self.core_filters)

                    if getattr(self.instance, attname) is None:

                        return qs.none()

                    qs._known_related_objects = {rel_field: {self.instance.pk: self.instance}}

                    return qs

tests/regressiontests/many_to_one_regress/models.py

+6 −0
Original line number Diff line number Diff line
@@ -48,3 +48,9 @@ class Relation(models.Model): 


    def __str__(self):

        return "%s - %s" % (self.left.category.name, self.right.category.name)



class Car(models.Model):

    make = models.CharField(max_length=100, null=True, unique=True)



class Driver(models.Model):

    car = models.ForeignKey(Car, to_field='make', null=True, related_name='drivers')

tests/regressiontests/many_to_one_regress/tests.py

+24 −1
Original line number Diff line number Diff line
@@ -4,7 +4,8 @@ from django.db import models 
from django.test import TestCase

from django.utils import six



from .models import First, Third, Parent, Child, Category, Record, Relation

from .models import (

    First, Third, Parent, Child, Category, Record, Relation, Car, Driver)





class ManyToOneRegressionTests(TestCase):
@@ -111,3 +112,25 @@ class ManyToOneRegressionTests(TestCase): 
        # of a model, and interrogate its related field.

        cat = models.ForeignKey(Category)

        self.assertEqual('id', cat.rel.get_related_field().name)



    def test_relation_unsaved(self):

        # Test that the <field>_set manager does not join on Null value fields (#17541)

        Third.objects.create(name='Third 1')

        Third.objects.create(name='Third 2')

        th = Third(name="testing")

        # The object isn't saved an thus the relation field is null - we won't even

        # execute a query in this case.

        with self.assertNumQueries(0):

            self.assertEqual(th.child_set.count(), 0)

        th.save()

        # Now the model is saved, so we will need to execute an query.

        with self.assertNumQueries(1):

            self.assertEqual(th.child_set.count(), 0)

    

    def test_related_null_to_field(self):

        c1 = Car.objects.create()

        c2 = Car.objects.create()

        d1 = Driver.objects.create()

        self.assertIs(d1.car, None)

        with self.assertNumQueries(0):

            self.assertEqual(list(c1.drivers.all()), [])