From f7f38f3a0b44d8c6d14344dae66b6ce52cd77b55 Mon Sep 17 00:00:00 2001
From: Simon Charette <charette.s@gmail.com>
Date: Wed, 2 Apr 2025 13:32:38 -0400
Subject: [PATCH] Fixed #36290 -- Made TupleIn() lookup discard tuples
 containing None.

Just like the In() lookup discards of None members TupleIn() should
discard tuples containing any None as NULL != NULL in SQL and the
framework expects such queries to be elided under some circumstances.

Refs #31667, #36116.

Thanks Basptise Mispelon for bisecting the regression to 626d77e.
---
 django/db/models/fields/tuple_lookups.py | 13 +++++++++++++
 docs/releases/5.2.1.txt                  |  3 +++
 tests/composite_pk/test_filter.py        |  7 +++++++
 tests/foreign_object/models/person.py    |  2 +-
 tests/foreign_object/tests.py            | 13 +++++++++++++
 5 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/django/db/models/fields/tuple_lookups.py b/django/db/models/fields/tuple_lookups.py
index e3cb696249..6a4e322589 100644
--- a/django/db/models/fields/tuple_lookups.py
+++ b/django/db/models/fields/tuple_lookups.py
@@ -329,6 +329,10 @@ class TupleIn(TupleLookupMixin, In):
         lhs = self.lhs
 
         for vals in rhs:
+            # Remove any tuple containing None from the list as NULL is never
+            # equal to anything.
+            if any(val is None for val in vals):
+                continue
             result.append(
                 Tuple(
                     *[
@@ -338,6 +342,9 @@ class TupleIn(TupleLookupMixin, In):
                 )
             )
 
+        if not result:
+            raise EmptyResultSet
+
         return compiler.compile(Tuple(*result))
 
     def get_fallback_sql(self, compiler, connection):
@@ -353,9 +360,15 @@ class TupleIn(TupleLookupMixin, In):
         lhs = self.lhs
 
         for vals in rhs:
+            # Remove any tuple containing None from the list as NULL is never
+            # equal to anything.
+            if any(val is None for val in vals):
+                continue
             lookups = [Exact(col, val) for col, val in zip(lhs, vals)]
             root.children.append(WhereNode(lookups, connector=AND))
 
+        if not root.children:
+            raise EmptyResultSet
         return root.as_sql(compiler, connection)
 
 
diff --git a/docs/releases/5.2.1.txt b/docs/releases/5.2.1.txt
index a4e73841bd..b17e63ebd1 100644
--- a/docs/releases/5.2.1.txt
+++ b/docs/releases/5.2.1.txt
@@ -12,3 +12,6 @@ Bugfixes
 * Fixed a regression in Django 5.2 that caused a crash when annotating
   aggregate expressions over query that uses explicit grouping by transforms
   followed by field references (:ticket:`36292`).
+
+* Fixed a regression in Django 5.2 that caused unnecessary queries when
+  prefetching nullable foreign key relationships (:ticket:`36290`).
diff --git a/tests/composite_pk/test_filter.py b/tests/composite_pk/test_filter.py
index c633348cc1..39f19daecc 100644
--- a/tests/composite_pk/test_filter.py
+++ b/tests/composite_pk/test_filter.py
@@ -206,6 +206,13 @@ class CompositePKFilterTests(TestCase):
             [self.comment_1],
         )
 
+    def test_filter_by_pk_in_none(self):
+        with self.assertNumQueries(0):
+            self.assertSequenceEqual(
+                Comment.objects.filter(pk__in=[(None, 1), (1, None)]),
+                [],
+            )
+
     def test_filter_comments_by_user_and_order_by_pk_asc(self):
         self.assertSequenceEqual(
             Comment.objects.filter(user=self.user_1).order_by("pk"),
diff --git a/tests/foreign_object/models/person.py b/tests/foreign_object/models/person.py
index d536ab63d7..4290ad6d3b 100644
--- a/tests/foreign_object/models/person.py
+++ b/tests/foreign_object/models/person.py
@@ -84,7 +84,7 @@ class Friendship(models.Model):
     )
     from_friend_id = models.IntegerField()
     to_friend_country_id = models.IntegerField()
-    to_friend_id = models.IntegerField()
+    to_friend_id = models.IntegerField(null=True)
 
     # Relation Fields
     from_friend = models.ForeignObject(
diff --git a/tests/foreign_object/tests.py b/tests/foreign_object/tests.py
index de80c705ab..00b6a8350e 100644
--- a/tests/foreign_object/tests.py
+++ b/tests/foreign_object/tests.py
@@ -296,6 +296,19 @@ class MultiColumnFKTests(TestCase):
             self.assertEqual(friendships[0].to_friend, self.george)
             self.assertEqual(friendships[1].to_friend, self.sam)
 
+    def test_prefetch_foreignobject_null_hidden_forward_skipped(self):
+        fiendship = Friendship.objects.create(
+            from_friend_country=self.usa,
+            from_friend_id=self.bob.id,
+            to_friend_country_id=self.usa.id,
+            to_friend_id=None,
+        )
+        with self.assertNumQueries(1):
+            self.assertEqual(
+                Friendship.objects.prefetch_related("to_friend").get(),
+                fiendship,
+            )
+
     def test_prefetch_foreignobject_reverse(self):
         Membership.objects.create(
             membership_country=self.usa, person=self.bob, group=self.cia