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Fixed #33759 -- Avoided unnecessary subquery in QuerySet.delete() with self-referential subqueries if supported.
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@ -12,6 +12,9 @@ class BaseDatabaseFeatures:
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allows_group_by_select_index = True
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empty_fetchmany_value = []
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update_can_self_select = True
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# Does the backend support self-reference subqueries in the DELETE
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# statement?
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delete_can_self_reference_subquery = True
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# Does the backend distinguish between '' and None?
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interprets_empty_strings_as_nulls = False
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@ -24,6 +24,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
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supports_slicing_ordering_in_compound = True
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supports_index_on_text_field = False
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supports_update_conflicts = True
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delete_can_self_reference_subquery = False
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create_test_procedure_without_params_sql = """
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CREATE PROCEDURE test_procedure ()
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BEGIN
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@ -1890,7 +1890,10 @@ class SQLDeleteCompiler(SQLCompiler):
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Create the SQL for this query. Return the SQL string and list of
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parameters.
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"""
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if self.single_alias and not self.contains_self_reference_subquery:
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if self.single_alias and (
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self.connection.features.delete_can_self_reference_subquery
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or not self.contains_self_reference_subquery
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):
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return self._as_sql(self.query)
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innerq = self.query.clone()
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innerq.__class__ = Query
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@ -379,15 +379,20 @@ class DeleteTests(TestCase):
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child = Child.objects.create(name="Juan")
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Book.objects.create(pagecount=500, owner=child)
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PlayedWith.objects.create(child=child, toy=toy, date=datetime.date.today())
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Book.objects.filter(
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Exists(
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Book.objects.filter(
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pk=OuterRef("pk"),
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owner__toys=toy.pk,
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),
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)
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).delete()
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with self.assertNumQueries(1) as ctx:
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Book.objects.filter(
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Exists(
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Book.objects.filter(
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pk=OuterRef("pk"),
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owner__toys=toy.pk,
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),
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)
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).delete()
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self.assertIs(Book.objects.exists(), False)
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sql = ctx.captured_queries[0]["sql"].lower()
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if connection.features.delete_can_self_reference_subquery:
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self.assertEqual(sql.count("select"), 1)
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class DeleteDistinct(SimpleTestCase):
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