from math import ceil from django.db import connection, models from django.db.models import ProtectedError, RestrictedError from django.db.models.deletion import Collector from django.db.models.sql.constants import GET_ITERATOR_CHUNK_SIZE from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature from .models import ( B1, B2, B3, MR, A, Avatar, B, Base, Child, DeleteBottom, DeleteTop, GenericB1, GenericB2, GenericDeleteBottom, HiddenUser, HiddenUserProfile, M, M2MFrom, M2MTo, MRNull, Origin, P, Parent, R, RChild, RChildChild, Referrer, S, T, User, create_a, get_default_r, ) class OnDeleteTests(TestCase): def setUp(self): self.DEFAULT = get_default_r() def test_auto(self): a = create_a('auto') a.auto.delete() self.assertFalse(A.objects.filter(name='auto').exists()) def test_non_callable(self): msg = 'on_delete must be callable.' with self.assertRaisesMessage(TypeError, msg): models.ForeignKey('self', on_delete=None) with self.assertRaisesMessage(TypeError, msg): models.OneToOneField('self', on_delete=None) def test_auto_nullable(self): a = create_a('auto_nullable') a.auto_nullable.delete() self.assertFalse(A.objects.filter(name='auto_nullable').exists()) def test_setvalue(self): a = create_a('setvalue') a.setvalue.delete() a = A.objects.get(pk=a.pk) self.assertEqual(self.DEFAULT, a.setvalue.pk) def test_setnull(self): a = create_a('setnull') a.setnull.delete() a = A.objects.get(pk=a.pk) self.assertIsNone(a.setnull) def test_setdefault(self): a = create_a('setdefault') a.setdefault.delete() a = A.objects.get(pk=a.pk) self.assertEqual(self.DEFAULT, a.setdefault.pk) def test_setdefault_none(self): a = create_a('setdefault_none') a.setdefault_none.delete() a = A.objects.get(pk=a.pk) self.assertIsNone(a.setdefault_none) def test_cascade(self): a = create_a('cascade') a.cascade.delete() self.assertFalse(A.objects.filter(name='cascade').exists()) def test_cascade_nullable(self): a = create_a('cascade_nullable') a.cascade_nullable.delete() self.assertFalse(A.objects.filter(name='cascade_nullable').exists()) def test_protect(self): a = create_a('protect') msg = ( "Cannot delete some instances of model 'R' because they are " "referenced through protected foreign keys: 'A.protect'." ) with self.assertRaisesMessage(ProtectedError, msg) as cm: a.protect.delete() self.assertEqual(cm.exception.protected_objects, {a}) def test_protect_multiple(self): a = create_a('protect') b = B.objects.create(protect=a.protect) msg = ( "Cannot delete some instances of model 'R' because they are " "referenced through protected foreign keys: 'A.protect', " "'B.protect'." ) with self.assertRaisesMessage(ProtectedError, msg) as cm: a.protect.delete() self.assertEqual(cm.exception.protected_objects, {a, b}) def test_protect_path(self): a = create_a('protect') a.protect.p = P.objects.create() a.protect.save() msg = ( "Cannot delete some instances of model 'P' because they are " "referenced through protected foreign keys: 'R.p'." ) with self.assertRaisesMessage(ProtectedError, msg) as cm: a.protect.p.delete() self.assertEqual(cm.exception.protected_objects, {a}) def test_do_nothing(self): # Testing DO_NOTHING is a bit harder: It would raise IntegrityError for a normal model, # so we connect to pre_delete and set the fk to a known value. replacement_r = R.objects.create() def check_do_nothing(sender, **kwargs): obj = kwargs['instance'] obj.donothing_set.update(donothing=replacement_r) models.signals.pre_delete.connect(check_do_nothing) a = create_a('do_nothing') a.donothing.delete() a = A.objects.get(pk=a.pk) self.assertEqual(replacement_r, a.donothing) models.signals.pre_delete.disconnect(check_do_nothing) def test_do_nothing_qscount(self): """ A models.DO_NOTHING relation doesn't trigger a query. """ b = Base.objects.create() with self.assertNumQueries(1): # RelToBase should not be queried. b.delete() self.assertEqual(Base.objects.count(), 0) def test_inheritance_cascade_up(self): child = RChild.objects.create() child.delete() self.assertFalse(R.objects.filter(pk=child.pk).exists()) def test_inheritance_cascade_down(self): child = RChild.objects.create() parent = child.r_ptr parent.delete() self.assertFalse(RChild.objects.filter(pk=child.pk).exists()) def test_cascade_from_child(self): a = create_a('child') a.child.delete() self.assertFalse(A.objects.filter(name='child').exists()) self.assertFalse(R.objects.filter(pk=a.child_id).exists()) def test_cascade_from_parent(self): a = create_a('child') R.objects.get(pk=a.child_id).delete() self.assertFalse(A.objects.filter(name='child').exists()) self.assertFalse(RChild.objects.filter(pk=a.child_id).exists()) def test_setnull_from_child(self): a = create_a('child_setnull') a.child_setnull.delete() self.assertFalse(R.objects.filter(pk=a.child_setnull_id).exists()) a = A.objects.get(pk=a.pk) self.assertIsNone(a.child_setnull) def test_setnull_from_parent(self): a = create_a('child_setnull') R.objects.get(pk=a.child_setnull_id).delete() self.assertFalse(RChild.objects.filter(pk=a.child_setnull_id).exists()) a = A.objects.get(pk=a.pk) self.assertIsNone(a.child_setnull) def test_o2o_setnull(self): a = create_a('o2o_setnull') a.o2o_setnull.delete() a = A.objects.get(pk=a.pk) self.assertIsNone(a.o2o_setnull) def test_restrict(self): a = create_a('restrict') msg = ( "Cannot delete some instances of model 'R' because they are " "referenced through restricted foreign keys: 'A.restrict'." ) with self.assertRaisesMessage(RestrictedError, msg) as cm: a.restrict.delete() self.assertEqual(cm.exception.restricted_objects, {a}) def test_restrict_multiple(self): a = create_a('restrict') b3 = B3.objects.create(restrict=a.restrict) msg = ( "Cannot delete some instances of model 'R' because they are " "referenced through restricted foreign keys: 'A.restrict', " "'B3.restrict'." ) with self.assertRaisesMessage(RestrictedError, msg) as cm: a.restrict.delete() self.assertEqual(cm.exception.restricted_objects, {a, b3}) def test_restrict_path_cascade_indirect(self): a = create_a('restrict') a.restrict.p = P.objects.create() a.restrict.save() msg = ( "Cannot delete some instances of model 'P' because they are " "referenced through restricted foreign keys: 'A.restrict'." ) with self.assertRaisesMessage(RestrictedError, msg) as cm: a.restrict.p.delete() self.assertEqual(cm.exception.restricted_objects, {a}) # Object referenced also with CASCADE relationship can be deleted. a.cascade.p = a.restrict.p a.cascade.save() a.restrict.p.delete() self.assertFalse(A.objects.filter(name='restrict').exists()) self.assertFalse(R.objects.filter(pk=a.restrict_id).exists()) def test_restrict_path_cascade_direct(self): a = create_a('restrict') a.restrict.p = P.objects.create() a.restrict.save() a.cascade_p = a.restrict.p a.save() a.restrict.p.delete() self.assertFalse(A.objects.filter(name='restrict').exists()) self.assertFalse(R.objects.filter(pk=a.restrict_id).exists()) def test_restrict_path_cascade_indirect_diamond(self): delete_top = DeleteTop.objects.create() b1 = B1.objects.create(delete_top=delete_top) b2 = B2.objects.create(delete_top=delete_top) delete_bottom = DeleteBottom.objects.create(b1=b1, b2=b2) msg = ( "Cannot delete some instances of model 'B1' because they are " "referenced through restricted foreign keys: 'DeleteBottom.b1'." ) with self.assertRaisesMessage(RestrictedError, msg) as cm: b1.delete() self.assertEqual(cm.exception.restricted_objects, {delete_bottom}) self.assertTrue(DeleteTop.objects.exists()) self.assertTrue(B1.objects.exists()) self.assertTrue(B2.objects.exists()) self.assertTrue(DeleteBottom.objects.exists()) # Object referenced also with CASCADE relationship can be deleted. delete_top.delete() self.assertFalse(DeleteTop.objects.exists()) self.assertFalse(B1.objects.exists()) self.assertFalse(B2.objects.exists()) self.assertFalse(DeleteBottom.objects.exists()) def test_restrict_gfk_no_fast_delete(self): delete_top = DeleteTop.objects.create() generic_b1 = GenericB1.objects.create(generic_delete_top=delete_top) generic_b2 = GenericB2.objects.create(generic_delete_top=delete_top) generic_delete_bottom = GenericDeleteBottom.objects.create( generic_b1=generic_b1, generic_b2=generic_b2, ) msg = ( "Cannot delete some instances of model 'GenericB1' because they " "are referenced through restricted foreign keys: " "'GenericDeleteBottom.generic_b1'." ) with self.assertRaisesMessage(RestrictedError, msg) as cm: generic_b1.delete() self.assertEqual(cm.exception.restricted_objects, {generic_delete_bottom}) self.assertTrue(DeleteTop.objects.exists()) self.assertTrue(GenericB1.objects.exists()) self.assertTrue(GenericB2.objects.exists()) self.assertTrue(GenericDeleteBottom.objects.exists()) # Object referenced also with CASCADE relationship can be deleted. delete_top.delete() self.assertFalse(DeleteTop.objects.exists()) self.assertFalse(GenericB1.objects.exists()) self.assertFalse(GenericB2.objects.exists()) self.assertFalse(GenericDeleteBottom.objects.exists()) class DeletionTests(TestCase): def test_sliced_queryset(self): msg = "Cannot use 'limit' or 'offset' with delete()." with self.assertRaisesMessage(TypeError, msg): M.objects.all()[0:5].delete() def test_pk_none(self): m = M() msg = "M object can't be deleted because its id attribute is set to None." with self.assertRaisesMessage(ValueError, msg): m.delete() def test_m2m(self): m = M.objects.create() r = R.objects.create() MR.objects.create(m=m, r=r) r.delete() self.assertFalse(MR.objects.exists()) r = R.objects.create() MR.objects.create(m=m, r=r) m.delete() self.assertFalse(MR.objects.exists()) m = M.objects.create() r = R.objects.create() m.m2m.add(r) r.delete() through = M._meta.get_field('m2m').remote_field.through self.assertFalse(through.objects.exists()) r = R.objects.create() m.m2m.add(r) m.delete() self.assertFalse(through.objects.exists()) m = M.objects.create() r = R.objects.create() MRNull.objects.create(m=m, r=r) r.delete() self.assertFalse(not MRNull.objects.exists()) self.assertFalse(m.m2m_through_null.exists()) def test_bulk(self): s = S.objects.create(r=R.objects.create()) for i in range(2 * GET_ITERATOR_CHUNK_SIZE): T.objects.create(s=s) # 1 (select related `T` instances) # + 1 (select related `U` instances) # + 2 (delete `T` instances in batches) # + 1 (delete `s`) self.assertNumQueries(5, s.delete) self.assertFalse(S.objects.exists()) def test_instance_update(self): deleted = [] related_setnull_sets = [] def pre_delete(sender, **kwargs): obj = kwargs['instance'] deleted.append(obj) if isinstance(obj, R): related_setnull_sets.append([a.pk for a in obj.setnull_set.all()]) models.signals.pre_delete.connect(pre_delete) a = create_a('update_setnull') a.setnull.delete() a = create_a('update_cascade') a.cascade.delete() for obj in deleted: self.assertIsNone(obj.pk) for pk_list in related_setnull_sets: for a in A.objects.filter(id__in=pk_list): self.assertIsNone(a.setnull) models.signals.pre_delete.disconnect(pre_delete) def test_deletion_order(self): pre_delete_order = [] post_delete_order = [] def log_post_delete(sender, **kwargs): pre_delete_order.append((sender, kwargs['instance'].pk)) def log_pre_delete(sender, **kwargs): post_delete_order.append((sender, kwargs['instance'].pk)) models.signals.post_delete.connect(log_post_delete) models.signals.pre_delete.connect(log_pre_delete) r = R.objects.create(pk=1) s1 = S.objects.create(pk=1, r=r) s2 = S.objects.create(pk=2, r=r) T.objects.create(pk=1, s=s1) T.objects.create(pk=2, s=s2) RChild.objects.create(r_ptr=r) r.delete() self.assertEqual( pre_delete_order, [(T, 2), (T, 1), (RChild, 1), (S, 2), (S, 1), (R, 1)] ) self.assertEqual( post_delete_order, [(T, 1), (T, 2), (RChild, 1), (S, 1), (S, 2), (R, 1)] ) models.signals.post_delete.disconnect(log_post_delete) models.signals.pre_delete.disconnect(log_pre_delete) def test_relational_post_delete_signals_happen_before_parent_object(self): deletions = [] def log_post_delete(instance, **kwargs): self.assertTrue(R.objects.filter(pk=instance.r_id)) self.assertIs(type(instance), S) deletions.append(instance.id) r = R.objects.create(pk=1) S.objects.create(pk=1, r=r) models.signals.post_delete.connect(log_post_delete, sender=S) try: r.delete() finally: models.signals.post_delete.disconnect(log_post_delete) self.assertEqual(len(deletions), 1) self.assertEqual(deletions[0], 1) @skipUnlessDBFeature("can_defer_constraint_checks") def test_can_defer_constraint_checks(self): u = User.objects.create( avatar=Avatar.objects.create() ) a = Avatar.objects.get(pk=u.avatar_id) # 1 query to find the users for the avatar. # 1 query to delete the user # 1 query to delete the avatar # The important thing is that when we can defer constraint checks there # is no need to do an UPDATE on User.avatar to null it out. # Attach a signal to make sure we will not do fast_deletes. calls = [] def noop(*args, **kwargs): calls.append('') models.signals.post_delete.connect(noop, sender=User) self.assertNumQueries(3, a.delete) self.assertFalse(User.objects.exists()) self.assertFalse(Avatar.objects.exists()) self.assertEqual(len(calls), 1) models.signals.post_delete.disconnect(noop, sender=User) @skipIfDBFeature("can_defer_constraint_checks") def test_cannot_defer_constraint_checks(self): u = User.objects.create( avatar=Avatar.objects.create() ) # Attach a signal to make sure we will not do fast_deletes. calls = [] def noop(*args, **kwargs): calls.append('') models.signals.post_delete.connect(noop, sender=User) a = Avatar.objects.get(pk=u.avatar_id) # The below doesn't make sense... Why do we need to null out # user.avatar if we are going to delete the user immediately after it, # and there are no more cascades. # 1 query to find the users for the avatar. # 1 query to delete the user # 1 query to null out user.avatar, because we can't defer the constraint # 1 query to delete the avatar self.assertNumQueries(4, a.delete) self.assertFalse(User.objects.exists()) self.assertFalse(Avatar.objects.exists()) self.assertEqual(len(calls), 1) models.signals.post_delete.disconnect(noop, sender=User) def test_hidden_related(self): r = R.objects.create() h = HiddenUser.objects.create(r=r) HiddenUserProfile.objects.create(user=h) r.delete() self.assertEqual(HiddenUserProfile.objects.count(), 0) def test_large_delete(self): TEST_SIZE = 2000 objs = [Avatar() for i in range(0, TEST_SIZE)] Avatar.objects.bulk_create(objs) # Calculate the number of queries needed. batch_size = connection.ops.bulk_batch_size(['pk'], objs) # The related fetches are done in batches. batches = ceil(len(objs) / batch_size) # One query for Avatar.objects.all() and then one related fast delete for # each batch. fetches_to_mem = 1 + batches # The Avatar objects are going to be deleted in batches of GET_ITERATOR_CHUNK_SIZE queries = fetches_to_mem + TEST_SIZE // GET_ITERATOR_CHUNK_SIZE self.assertNumQueries(queries, Avatar.objects.all().delete) self.assertFalse(Avatar.objects.exists()) def test_large_delete_related(self): TEST_SIZE = 2000 s = S.objects.create(r=R.objects.create()) for i in range(TEST_SIZE): T.objects.create(s=s) batch_size = max(connection.ops.bulk_batch_size(['pk'], range(TEST_SIZE)), 1) # TEST_SIZE / batch_size (select related `T` instances) # + 1 (select related `U` instances) # + TEST_SIZE / GET_ITERATOR_CHUNK_SIZE (delete `T` instances in batches) # + 1 (delete `s`) expected_num_queries = ceil(TEST_SIZE / batch_size) expected_num_queries += ceil(TEST_SIZE / GET_ITERATOR_CHUNK_SIZE) + 2 self.assertNumQueries(expected_num_queries, s.delete) self.assertFalse(S.objects.exists()) self.assertFalse(T.objects.exists()) def test_delete_with_keeping_parents(self): child = RChild.objects.create() parent_id = child.r_ptr_id child.delete(keep_parents=True) self.assertFalse(RChild.objects.filter(id=child.id).exists()) self.assertTrue(R.objects.filter(id=parent_id).exists()) def test_delete_with_keeping_parents_relationships(self): child = RChild.objects.create() parent_id = child.r_ptr_id parent_referent_id = S.objects.create(r=child.r_ptr).pk child.delete(keep_parents=True) self.assertFalse(RChild.objects.filter(id=child.id).exists()) self.assertTrue(R.objects.filter(id=parent_id).exists()) self.assertTrue(S.objects.filter(pk=parent_referent_id).exists()) childchild = RChildChild.objects.create() parent_id = childchild.rchild_ptr.r_ptr_id child_id = childchild.rchild_ptr_id parent_referent_id = S.objects.create(r=childchild.rchild_ptr.r_ptr).pk childchild.delete(keep_parents=True) self.assertFalse(RChildChild.objects.filter(id=childchild.id).exists()) self.assertTrue(RChild.objects.filter(id=child_id).exists()) self.assertTrue(R.objects.filter(id=parent_id).exists()) self.assertTrue(S.objects.filter(pk=parent_referent_id).exists()) def test_queryset_delete_returns_num_rows(self): """ QuerySet.delete() should return the number of deleted rows and a dictionary with the number of deletions for each object type. """ Avatar.objects.bulk_create([Avatar(desc='a'), Avatar(desc='b'), Avatar(desc='c')]) avatars_count = Avatar.objects.count() deleted, rows_count = Avatar.objects.all().delete() self.assertEqual(deleted, avatars_count) # more complex example with multiple object types r = R.objects.create() h1 = HiddenUser.objects.create(r=r) HiddenUser.objects.create(r=r) HiddenUserProfile.objects.create(user=h1) existed_objs = { R._meta.label: R.objects.count(), HiddenUser._meta.label: HiddenUser.objects.count(), HiddenUserProfile._meta.label: HiddenUserProfile.objects.count(), } deleted, deleted_objs = R.objects.all().delete() self.assertCountEqual(deleted_objs.keys(), existed_objs.keys()) for k, v in existed_objs.items(): self.assertEqual(deleted_objs[k], v) def test_model_delete_returns_num_rows(self): """ Model.delete() should return the number of deleted rows and a dictionary with the number of deletions for each object type. """ r = R.objects.create() h1 = HiddenUser.objects.create(r=r) h2 = HiddenUser.objects.create(r=r) HiddenUser.objects.create(r=r) HiddenUserProfile.objects.create(user=h1) HiddenUserProfile.objects.create(user=h2) m1 = M.objects.create() m2 = M.objects.create() MR.objects.create(r=r, m=m1) r.m_set.add(m1) r.m_set.add(m2) r.save() existed_objs = { R._meta.label: R.objects.count(), HiddenUser._meta.label: HiddenUser.objects.count(), MR._meta.label: MR.objects.count(), HiddenUserProfile._meta.label: HiddenUserProfile.objects.count(), M.m2m.through._meta.label: M.m2m.through.objects.count(), } deleted, deleted_objs = r.delete() self.assertEqual(deleted, sum(existed_objs.values())) self.assertCountEqual(deleted_objs.keys(), existed_objs.keys()) for k, v in existed_objs.items(): self.assertEqual(deleted_objs[k], v) def test_proxied_model_duplicate_queries(self): """ #25685 - Deleting instances of a model with existing proxy classes should not issue multiple queries during cascade deletion of referring models. """ avatar = Avatar.objects.create() # One query for the Avatar table and a second for the User one. with self.assertNumQueries(2): avatar.delete() def test_only_referenced_fields_selected(self): """ Only referenced fields are selected during cascade deletion SELECT unless deletion signals are connected. """ origin = Origin.objects.create() expected_sql = str( Referrer.objects.only( # Both fields are referenced by SecondReferrer. 'id', 'unique_field', ).filter(origin__in=[origin]).query ) with self.assertNumQueries(2) as ctx: origin.delete() self.assertEqual(ctx.captured_queries[0]['sql'], expected_sql) def receiver(instance, **kwargs): pass # All fields are selected if deletion signals are connected. for signal_name in ('pre_delete', 'post_delete'): with self.subTest(signal=signal_name): origin = Origin.objects.create() signal = getattr(models.signals, signal_name) signal.connect(receiver, sender=Referrer) with self.assertNumQueries(2) as ctx: origin.delete() self.assertIn( connection.ops.quote_name('large_field'), ctx.captured_queries[0]['sql'], ) signal.disconnect(receiver, sender=Referrer) class FastDeleteTests(TestCase): def test_fast_delete_all(self): with self.assertNumQueries(1) as ctx: User.objects.all().delete() sql = ctx.captured_queries[0]['sql'] # No subqueries is used when performing a full delete. self.assertNotIn('SELECT', sql) def test_fast_delete_fk(self): u = User.objects.create( avatar=Avatar.objects.create() ) a = Avatar.objects.get(pk=u.avatar_id) # 1 query to fast-delete the user # 1 query to delete the avatar self.assertNumQueries(2, a.delete) self.assertFalse(User.objects.exists()) self.assertFalse(Avatar.objects.exists()) def test_fast_delete_m2m(self): t = M2MTo.objects.create() f = M2MFrom.objects.create() f.m2m.add(t) # 1 to delete f, 1 to fast-delete m2m for f self.assertNumQueries(2, f.delete) def test_fast_delete_revm2m(self): t = M2MTo.objects.create() f = M2MFrom.objects.create() f.m2m.add(t) # 1 to delete t, 1 to fast-delete t's m_set self.assertNumQueries(2, f.delete) def test_fast_delete_qs(self): u1 = User.objects.create() u2 = User.objects.create() self.assertNumQueries(1, User.objects.filter(pk=u1.pk).delete) self.assertEqual(User.objects.count(), 1) self.assertTrue(User.objects.filter(pk=u2.pk).exists()) def test_fast_delete_instance_set_pk_none(self): u = User.objects.create() # User can be fast-deleted. collector = Collector(using='default') self.assertTrue(collector.can_fast_delete(u)) u.delete() self.assertIsNone(u.pk) def test_fast_delete_joined_qs(self): a = Avatar.objects.create(desc='a') User.objects.create(avatar=a) u2 = User.objects.create() self.assertNumQueries(1, User.objects.filter(avatar__desc='a').delete) self.assertEqual(User.objects.count(), 1) self.assertTrue(User.objects.filter(pk=u2.pk).exists()) def test_fast_delete_inheritance(self): c = Child.objects.create() p = Parent.objects.create() # 1 for self, 1 for parent self.assertNumQueries(2, c.delete) self.assertFalse(Child.objects.exists()) self.assertEqual(Parent.objects.count(), 1) self.assertEqual(Parent.objects.filter(pk=p.pk).count(), 1) # 1 for self delete, 1 for fast delete of empty "child" qs. self.assertNumQueries(2, p.delete) self.assertFalse(Parent.objects.exists()) # 1 for self delete, 1 for fast delete of empty "child" qs. c = Child.objects.create() p = c.parent_ptr self.assertNumQueries(2, p.delete) self.assertFalse(Parent.objects.exists()) self.assertFalse(Child.objects.exists()) def test_fast_delete_large_batch(self): User.objects.bulk_create(User() for i in range(0, 2000)) # No problems here - we aren't going to cascade, so we will fast # delete the objects in a single query. self.assertNumQueries(1, User.objects.all().delete) a = Avatar.objects.create(desc='a') User.objects.bulk_create(User(avatar=a) for i in range(0, 2000)) # We don't hit parameter amount limits for a, so just one query for # that + fast delete of the related objs. self.assertNumQueries(2, a.delete) self.assertEqual(User.objects.count(), 0) def test_fast_delete_empty_no_update_can_self_select(self): """ Fast deleting when DatabaseFeatures.update_can_self_select = False works even if the specified filter doesn't match any row (#25932). """ with self.assertNumQueries(1): self.assertEqual( User.objects.filter(avatar__desc='missing').delete(), (0, {}), ) def test_fast_delete_combined_relationships(self): # The cascading fast-delete of SecondReferrer should be combined # in a single DELETE WHERE referrer_id OR unique_field. origin = Origin.objects.create() referer = Referrer.objects.create(origin=origin, unique_field=42) with self.assertNumQueries(2): referer.delete() def test_fast_delete_aggregation(self): # Fast-deleting when filtering against an aggregation result in # a single query containing a subquery. Base.objects.create() with self.assertNumQueries(1): self.assertEqual( Base.objects.annotate( rels_count=models.Count('rels'), ).filter(rels_count=0).delete(), (1, {'delete.Base': 1}), ) self.assertIs(Base.objects.exists(), False)