Fixed #32511 -- Corrected handling prefetched nested reverse relationships.

When prefetching a set of child objects related to a set of parent
objects, we usually want to populate the relationship back from the
child to the parent to avoid a query when accessing that relationship
attribute. However, there's an edge case where the child queryset
itself specifies a prefetch back to the parent. In that case, we want
to use the prefetched relationship rather than populating the reverse
relationship from the parent.

1 files changed, 3 insertions, 2 deletions

diff --git a/django/db/models/fields/related_descriptors.py b/django/db/models/fields/related_descriptors.py
index d5aa968400..9c50ef16ce 100644
--- a/django/db/models/fields/related_descriptors.py
+++ b/django/db/models/fields/related_descriptors.py
@@ -646,8 +646,9 @@ def create_reverse_many_to_one_manager(superclass, rel):
             # Since we just bypassed this class' get_queryset(), we must manage
             # the reverse relation manually.
             for rel_obj in queryset:
-                instance = instances_dict[rel_obj_attr(rel_obj)]
-                setattr(rel_obj, self.field.name, instance)
+                if not self.field.is_cached(rel_obj):
+                    instance = instances_dict[rel_obj_attr(rel_obj)]
+                    setattr(rel_obj, self.field.name, instance)
             cache_name = self.field.remote_field.get_cache_name()
             return queryset, rel_obj_attr, instance_attr, False, cache_name, False