Refs #32682 -- Fixed QuerySet.delete() crash on querysets with self-referential subqueries on MySQL.

django/db/models/sql/compiler.py

@@ -1452,6 +1452,24 @@ class SQLDeleteCompiler(SQLCompiler):
         self.query.get_initial_alias()
         return sum(self.query.alias_refcount[t] > 0 for t in self.query.alias_map) == 1
 
+    @classmethod
+    def _expr_refs_base_model(cls, expr, base_model):
+        if isinstance(expr, Query):
+            return expr.model == base_model
+        if not hasattr(expr, 'get_source_expressions'):
+            return False
+        return any(
+            cls._expr_refs_base_model(source_expr, base_model)
+            for source_expr in expr.get_source_expressions()
+        )
+
+    @cached_property
+    def contains_self_reference_subquery(self):
+        return any(
+            self._expr_refs_base_model(expr, self.query.model)
+            for expr in chain(self.query.annotations.values(), self.query.where.children)
+        )
+
     def _as_sql(self, query):
         result = [
             'DELETE FROM %s' % self.quote_name_unless_alias(query.base_table)
@@ -1466,7 +1484,7 @@ class SQLDeleteCompiler(SQLCompiler):
         Create the SQL for this query. Return the SQL string and list of
         parameters.
         """
-        if self.single_alias:
+        if self.single_alias and not self.contains_self_reference_subquery:
             return self._as_sql(self.query)
         innerq = self.query.clone()
         innerq.__class__ = Query

tests/delete_regress/models.py

@@ -24,6 +24,7 @@ class Person(models.Model):
 
 class Book(models.Model):
     pagecount = models.IntegerField()
+    owner = models.ForeignKey('Child', models.CASCADE, null=True)
 
 
 class Toy(models.Model):

tests/delete_regress/tests.py

@@ -1,6 +1,7 @@
 import datetime
 
 from django.db import connection, models, transaction
+from django.db.models import Exists, OuterRef
 from django.test import (
     SimpleTestCase, TestCase, TransactionTestCase, skipUnlessDBFeature,
 )
@@ -355,6 +356,19 @@ class DeleteTests(TestCase):
         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):