From 804607df0e174c524a3ea880b8ecbb555ecb4abb Mon Sep 17 00:00:00 2001
From: Keryn Knight <keryn@kerynknight.com>
Date: Sat, 10 Jan 2026 08:39:45 +0100
Subject: Refs #28455 -- Avoided QuerySet cloning in simple prefetch_related()
 usages.
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manager.get_queryset() always returns freshly instantiated per-instance
QuerySet which doesn't need subsequent cloning.

Based on work originally done by Anssi Kääriäinen and Tim Graham.
---
 django/contrib/contenttypes/fields.py          | 11 ++++++-----
 django/db/models/fields/related_descriptors.py | 26 ++++++++++++++------------
 django/db/models/query.py                      |  2 +-
 3 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/django/contrib/contenttypes/fields.py b/django/contrib/contenttypes/fields.py
index 300fec4289..0d7ef0f256 100644
--- a/django/contrib/contenttypes/fields.py
+++ b/django/contrib/contenttypes/fields.py
@@ -651,11 +651,12 @@ def create_generic_related_manager(superclass, rel):
             Filter the queryset for the instance this manager is bound to.
             """
             db = self._db or router.db_for_read(self.model, instance=self.instance)
-            return (
-                queryset.using(db)
-                .fetch_mode(self.instance._state.fetch_mode)
-                .filter(**self.core_filters)
-            )
+            with queryset._avoid_cloning():
+                return (
+                    queryset.using(db)
+                    .fetch_mode(self.instance._state.fetch_mode)
+                    .filter(**self.core_filters)
+                )
 
         def _remove_prefetched_objects(self):
             try:
diff --git a/django/db/models/fields/related_descriptors.py b/django/db/models/fields/related_descriptors.py
index 40ad8b260f..87b4921a6c 100644
--- a/django/db/models/fields/related_descriptors.py
+++ b/django/db/models/fields/related_descriptors.py
@@ -738,12 +738,13 @@ def create_reverse_many_to_one_manager(superclass, rel):
             empty_strings_as_null = connections[
                 db
             ].features.interprets_empty_strings_as_nulls
-            queryset._add_hints(instance=self.instance)
-            if self._db:
-                queryset = queryset.using(self._db)
-            queryset._fetch_mode = self.instance._state.fetch_mode
-            queryset._defer_next_filter = True
-            queryset = queryset.filter(**self.core_filters)
+            with queryset._avoid_cloning():
+                queryset._add_hints(instance=self.instance)
+                if self._db:
+                    queryset = queryset.using(self._db)
+                queryset._fetch_mode = self.instance._state.fetch_mode
+                queryset._defer_next_filter = True
+                queryset = queryset.filter(**self.core_filters)
             for field in self.field.foreign_related_fields:
                 val = getattr(self.instance, field.attname)
                 if val is None or (val == "" and empty_strings_as_null):
@@ -1140,12 +1141,13 @@ def create_forward_many_to_many_manager(superclass, rel, reverse):
             """
             Filter the queryset for the instance this manager is bound to.
             """
-            queryset._add_hints(instance=self.instance)
-            if self._db:
-                queryset = queryset.using(self._db)
-            queryset._fetch_mode = self.instance._state.fetch_mode
-            queryset._defer_next_filter = True
-            return queryset._next_is_sticky().filter(**self.core_filters)
+            with queryset._avoid_cloning():
+                queryset._add_hints(instance=self.instance)
+                if self._db:
+                    queryset = queryset.using(self._db)
+                queryset._fetch_mode = self.instance._state.fetch_mode
+                queryset._defer_next_filter = True
+                return queryset._next_is_sticky().filter(**self.core_filters)
 
         def get_prefetch_cache(self):
             # Walk up the ancestor-chain (if cached) to try and find a prefetch
diff --git a/django/db/models/query.py b/django/db/models/query.py
index d4775308b8..dca504e441 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -2906,7 +2906,7 @@ def prefetch_one_level(instances, prefetcher, lookup, level):
             else:
                 manager = getattr(obj, to_attr)
                 if leaf and lookup.queryset is not None:
-                    qs = manager._apply_rel_filters(lookup.queryset)
+                    qs = manager._apply_rel_filters(lookup.queryset._chain())
                 else:
                     qs = manager.get_queryset()
                 qs._result_cache = vals
-- 
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