Viewing github.com/django/django-stable-4.1.x/tests/delete

```
import datetime
```

from django.db import connection, models, transaction

from django.db.models import Exists, OuterRef

```
from django.test import (
```
```
    SimpleTestCase,
```
```
    TestCase,
```
```
    TransactionTestCase,
```
```
    skipUnlessDBFeature,
```
```
)
```
```
from .models import (
```
```
    Award,
```
```
    AwardNote,
```
```
    Book,
```
```
    Child,
```
```
    Contact,
```
```
    Eaten,
```
```
    Email,
```
```
    File,
```
```
    Food,
```
```
    FooFile,
```
```
    FooFileProxy,
```
```
    FooImage,
```
```
    FooPhoto,
```
```
    House,
```
```
    Image,
```
```
    Item,
```
```
    Location,
```
```
    Login,
```
```
    OrderedPerson,
```
```
    OrgUnit,
```
```
    Person,
```
```
    Photo,
```
```
    PlayedWith,
```
```
    PlayedWithNote,
```
```
    Policy,
```
```
    Researcher,
```
```
    Toy,
```
```
    Version,
```
```
)
```

# Can't run this test under SQLite, because you can't

# get two connections to an in-memory database.

@skipUnlessDBFeature("test_db_allows_multiple_connections")

class DeleteLockingTest(TransactionTestCase):

    available_apps = ["delete_regress"]

```
    def setUp(self):
```

        # Create a second connection to the default database

```
        self.conn2 = connection.copy()
```

        self.conn2.set_autocommit(False)

```
    def tearDown(self):
```

        # Close down the second connection.

```
        self.conn2.rollback()
```
```
        self.conn2.close()
```
```
    def test_concurrent_delete(self):
```

        """Concurrent deletes don't collide and lock the database (#9479)."""

```
        with transaction.atomic():
```

            Book.objects.create(id=1, pagecount=100)

            Book.objects.create(id=2, pagecount=200)

            Book.objects.create(id=3, pagecount=300)

```
        with transaction.atomic():
```

            # Start a transaction on the main connection.

            self.assertEqual(3, Book.objects.count())

            # Delete something using another database connection.

            with self.conn2.cursor() as cursor2:

                cursor2.execute("DELETE from delete_regress_book WHERE id = 1")

```
            self.conn2.commit()
```

            # In the same transaction on the main connection, perform a

            # queryset delete that covers the object deleted with the other

            # connection. This causes an infinite loop under MySQL InnoDB

            # unless we keep track of already deleted objects.

            Book.objects.filter(pagecount__lt=250).delete()

        self.assertEqual(1, Book.objects.count())

```
class DeleteCascadeTests(TestCase):
```

    def test_generic_relation_cascade(self):

```
        """
```

        Django cascades deletes through generic-related objects to their

```
        reverse relations.
```
```
        """
```

        person = Person.objects.create(name="Nelson Mandela")

        award = Award.objects.create(name="Nobel", content_object=person)

        AwardNote.objects.create(note="a peace prize", award=award)

        self.assertEqual(AwardNote.objects.count(), 1)

```
        person.delete()
```

        self.assertEqual(Award.objects.count(), 0)

        # first two asserts are just sanity checks, this is the kicker:

        self.assertEqual(AwardNote.objects.count(), 0)

```
    def test_fk_to_m2m_through(self):
```
```
        """
```

        If an M2M relationship has an explicitly-specified through model, and

        some other model has an FK to that through model, deletion is cascaded

        from one of the participants in the M2M, to the through model, to its

```
        related model.
```
```
        """
```

        juan = Child.objects.create(name="Juan")

        paints = Toy.objects.create(name="Paints")

        played = PlayedWith.objects.create(

            child=juan, toy=paints, date=datetime.date.today()

```
        )
```

        PlayedWithNote.objects.create(played=played, note="the next Jackson Pollock")

        self.assertEqual(PlayedWithNote.objects.count(), 1)

```
        paints.delete()
```

        self.assertEqual(PlayedWith.objects.count(), 0)

        # first two asserts just sanity checks, this is the kicker:

        self.assertEqual(PlayedWithNote.objects.count(), 0)

```
    def test_15776(self):
```

        policy = Policy.objects.create(pk=1, policy_number="1234")

        version = Version.objects.create(policy=policy)

        location = Location.objects.create(version=version)

        Item.objects.create(version=version, location=location)

```
        policy.delete()
```

class DeleteCascadeTransactionTests(TransactionTestCase):

    available_apps = ["delete_regress"]

```
    def test_inheritance(self):
```
```
        """
```

        Auto-created many-to-many through tables referencing a parent model are

        correctly found by the delete cascade when a child of that parent is

```
        deleted.
```
```
        Refs #14896.
```
```
        """
```

        r = Researcher.objects.create()

```
        email = Email.objects.create(
```

            label="office-email", email_address="[email protected]"

```
        )
```
```
        r.contacts.add(email)
```
```
        email.delete()
```
```
    def test_to_field(self):
```
```
        """
```

        Cascade deletion works with ForeignKey.to_field set to non-PK.

```
        """
```

        apple = Food.objects.create(name="apple")

        Eaten.objects.create(food=apple, meal="lunch")

```
        apple.delete()
```

        self.assertFalse(Food.objects.exists())

        self.assertFalse(Eaten.objects.exists())

```
class LargeDeleteTests(TestCase):
```
```
    def test_large_deletes(self):
```
```
        """
```

        If the number of objects > chunk size, deletion still occurs.

```
        """
```
```
        for x in range(300):
```

            Book.objects.create(pagecount=x + 100)

        # attach a signal to make sure we will not fast-delete

```
        def noop(*args, **kwargs):
```
```
            pass
```

        models.signals.post_delete.connect(noop, sender=Book)

```
        Book.objects.all().delete()
```

        models.signals.post_delete.disconnect(noop, sender=Book)

        self.assertEqual(Book.objects.count(), 0)

```
class ProxyDeleteTest(TestCase):
```
```
    """
```

    Tests on_delete behavior for proxy models.

```
    See #16128.
```
```
    """
```
```
    def create_image(self):
```

        """Return an Image referenced by both a FooImage and a FooFile."""

```
        # Create an Image
```
```
        test_image = Image()
```
```
        test_image.save()
```

        foo_image = FooImage(my_image=test_image)

```
        foo_image.save()
```

        # Get the Image instance as a File

        test_file = File.objects.get(pk=test_image.pk)

        foo_file = FooFile(my_file=test_file)

```
        foo_file.save()
```
```
        return test_image
```
```
    def test_delete_proxy(self):
```
```
        """
```

        Deleting the *proxy* instance bubbles through to its non-proxy and

        *all* referring objects are deleted.

```
        """
```
```
        self.create_image()
```
```
        Image.objects.all().delete()
```

        # An Image deletion == File deletion

        self.assertEqual(len(Image.objects.all()), 0)

        self.assertEqual(len(File.objects.all()), 0)

        # The Image deletion cascaded and *all* references to it are deleted.

        self.assertEqual(len(FooImage.objects.all()), 0)

        self.assertEqual(len(FooFile.objects.all()), 0)

    def test_delete_proxy_of_proxy(self):

```
        """
```

        Deleting a proxy-of-proxy instance should bubble through to its proxy

        and non-proxy parents, deleting *all* referring objects.

```
        """
```

        test_image = self.create_image()

```
        # Get the Image as a Photo
```

        test_photo = Photo.objects.get(pk=test_image.pk)

        foo_photo = FooPhoto(my_photo=test_photo)

```
        foo_photo.save()
```
```
        Photo.objects.all().delete()
```

        # A Photo deletion == Image deletion == File deletion

        self.assertEqual(len(Photo.objects.all()), 0)

        self.assertEqual(len(Image.objects.all()), 0)

        self.assertEqual(len(File.objects.all()), 0)

        # The Photo deletion should have cascaded and deleted *all*

```
        # references to it.
```

        self.assertEqual(len(FooPhoto.objects.all()), 0)

        self.assertEqual(len(FooFile.objects.all()), 0)

        self.assertEqual(len(FooImage.objects.all()), 0)

    def test_delete_concrete_parent(self):

```
        """
```

        Deleting an instance of a concrete model should also delete objects

        referencing its proxy subclass.

```
        """
```
```
        self.create_image()
```
```
        File.objects.all().delete()
```

        # A File deletion == Image deletion

        self.assertEqual(len(File.objects.all()), 0)

        self.assertEqual(len(Image.objects.all()), 0)

        # The File deletion should have cascaded and deleted *all* references

```
        # to it.
```

        self.assertEqual(len(FooFile.objects.all()), 0)

        self.assertEqual(len(FooImage.objects.all()), 0)

```
    def test_delete_proxy_pair(self):
```
```
        """
```

        If a pair of proxy models are linked by an FK from one concrete parent

        to the other, deleting one proxy model cascade-deletes the other, and

        the deletion happens in the right order (not triggering an

        IntegrityError on databases unable to defer integrity checks).

```
        Refs #17918.
```
```
        """
```

        # Create an Image (proxy of File) and FooFileProxy (proxy of FooFile,

```
        # which has an FK to File)
```
```
        image = Image.objects.create()
```

        as_file = File.objects.get(pk=image.pk)

        FooFileProxy.objects.create(my_file=as_file)

```
        Image.objects.all().delete()
```

        self.assertEqual(len(FooFileProxy.objects.all()), 0)

```
    def test_19187_values(self):
```

        msg = "Cannot call delete() after .values() or .values_list()"

        with self.assertRaisesMessage(TypeError, msg):

            Image.objects.values().delete()

        with self.assertRaisesMessage(TypeError, msg):

            Image.objects.values_list().delete()

```
class Ticket19102Tests(TestCase):
```
```
    """
```

    Test different queries which alter the SELECT clause of the query. We

    also must be using a subquery for the deletion (that is, the original

    query has a join in it). The deletion should be done as "fast-path"

    deletion (that is, just one query for the .delete() call).

    Note that .values() is not tested here on purpose. .values().delete()

    doesn't work for non fast-path deletes at all.

```
    """
```
```
    @classmethod
```
```
    def setUpTestData(cls):
```

        cls.o1 = OrgUnit.objects.create(name="o1")

        cls.o2 = OrgUnit.objects.create(name="o2")

        cls.l1 = Login.objects.create(description="l1", orgunit=cls.o1)

        cls.l2 = Login.objects.create(description="l2", orgunit=cls.o2)

    @skipUnlessDBFeature("update_can_self_select")

    def test_ticket_19102_annotate(self):

```
        with self.assertNumQueries(1):
```

            Login.objects.order_by("description").filter(

                orgunit__name__isnull=False

            ).annotate(n=models.Count("description")).filter(

```
                n=1, pk=self.l1.pk
```
```
            ).delete()
```

        self.assertFalse(Login.objects.filter(pk=self.l1.pk).exists())

        self.assertTrue(Login.objects.filter(pk=self.l2.pk).exists())

    @skipUnlessDBFeature("update_can_self_select")

```
    def test_ticket_19102_extra(self):
```
```
        with self.assertNumQueries(1):
```

            Login.objects.order_by("description").filter(

                orgunit__name__isnull=False

            ).extra(select={"extraf": "1"}).filter(pk=self.l1.pk).delete()

        self.assertFalse(Login.objects.filter(pk=self.l1.pk).exists())

        self.assertTrue(Login.objects.filter(pk=self.l2.pk).exists())

    @skipUnlessDBFeature("update_can_self_select")

    def test_ticket_19102_select_related(self):

```
        with self.assertNumQueries(1):
```

            Login.objects.filter(pk=self.l1.pk).filter(

                orgunit__name__isnull=False

            ).order_by("description").select_related("orgunit").delete()

        self.assertFalse(Login.objects.filter(pk=self.l1.pk).exists())

        self.assertTrue(Login.objects.filter(pk=self.l2.pk).exists())

    @skipUnlessDBFeature("update_can_self_select")

```
    def test_ticket_19102_defer(self):
```
```
        with self.assertNumQueries(1):
```

            Login.objects.filter(pk=self.l1.pk).filter(

                orgunit__name__isnull=False

            ).order_by("description").only("id").delete()

        self.assertFalse(Login.objects.filter(pk=self.l1.pk).exists())

        self.assertTrue(Login.objects.filter(pk=self.l2.pk).exists())

```
class DeleteTests(TestCase):
```

    def test_meta_ordered_delete(self):

        # When a subquery is performed by deletion code, the subquery must be

        # cleared of all ordering. There was a but that caused _meta ordering

```
        # to be used. Refs #19720.
```

        h = House.objects.create(address="Foo")

        OrderedPerson.objects.create(name="Jack", lives_in=h)

        OrderedPerson.objects.create(name="Bob", lives_in=h)

        OrderedPerson.objects.filter(lives_in__address="Foo").delete()

        self.assertEqual(OrderedPerson.objects.count(), 0)

    def test_foreign_key_delete_nullifies_correct_columns(self):

```
        """
```

        With a model (Researcher) that has two foreign keys pointing to the

        same model (Contact), deleting an instance of the target model

        (contact1) nullifies the correct fields of Researcher.

```
        """
```

        contact1 = Contact.objects.create(label="Contact 1")

        contact2 = Contact.objects.create(label="Contact 2")

        researcher1 = Researcher.objects.create(

```
            primary_contact=contact1,
```

            secondary_contact=contact2,

```
        )
```

        researcher2 = Researcher.objects.create(

```
            primary_contact=contact2,
```

            secondary_contact=contact1,

```
        )
```
```
        contact1.delete()
```
```
        researcher1.refresh_from_db()
```
```
        researcher2.refresh_from_db()
```

        self.assertIsNone(researcher1.primary_contact)

        self.assertEqual(researcher1.secondary_contact, contact2)

        self.assertEqual(researcher2.primary_contact, contact2)

        self.assertIsNone(researcher2.secondary_contact)

    def test_self_reference_with_through_m2m_at_second_level(self):

        toy = Toy.objects.create(name="Paints")

        child = Child.objects.create(name="Juan")

        Book.objects.create(pagecount=500, owner=child)

        PlayedWith.objects.create(child=child, toy=toy, date=datetime.date.today())

```
        Book.objects.filter(
```
```
            Exists(
```
```
                Book.objects.filter(
```
```
                    pk=OuterRef("pk"),
```

                    owner__toys=toy.pk,

```
                ),
```
```
            )
```
```
        ).delete()
```

        self.assertIs(Book.objects.exists(), False)

```
class DeleteDistinct(SimpleTestCase):
```

    def test_disallowed_delete_distinct(self):

        msg = "Cannot call delete() after .distinct()."

        with self.assertRaisesMessage(TypeError, msg):

            Book.objects.distinct().delete()

        with self.assertRaisesMessage(TypeError, msg):

            Book.objects.distinct("id").delete()