Re: [Django] #34633: Add prefetch_related() cache invalidation for create() in reverse many-to-one managers. (was: RelatedManager._remove_prefetched_objects() not called in RelatedManager.create())

[Django]

#34633: Add prefetch_related() cache invalidation for create() in reverse many-to-
one managers.
-------------------------------------+-------------------------------------
Reporter: Rob Percival | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 4.2
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Mariusz Felisiak):

* stage: Unreviewed => Accepted

Comment:

Thanks for the report, it seems that it's only missing for `create()` in
reverse many-to-one managers. It works for many-to-many managers (we could
add an extra test method for this) and `GenericRelation` (see #29612). See
a regression test:
{{{#!diff
diff --git a/tests/many_to_one/tests.py b/tests/many_to_one/tests.py
index 7a6d112a09..d360cd9164 100644
--- a/tests/many_to_one/tests.py
+++ b/tests/many_to_one/tests.py
@@ -799,6 +799,14 @@ class ManyToOneTests(TestCase):
# refs #21563
self.assertFalse(hasattr(Article(), "reporter"))

+ def test_create_after_prefetch(self):
+ c = City.objects.create(name="Musical City")
+ d1 = District.objects.create(name="Ladida", city=c)
+ city = City.objects.prefetch_related("districts").get(id=c.id)
+ self.assertSequenceEqual(city.districts.all(), [d1])
+ d2 = city.districts.create(name="Goa")
+ self.assertSequenceEqual(city.districts.all(), [d1, d2])
+
def test_clear_after_prefetch(self):
c = City.objects.create(name="Musical City")
d = District.objects.create(name="Ladida", city=c)

}}}

Rob, would you like to prepare a patch?

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Ticket URL: <https://code.djangoproject.com/ticket/34633#comment:2>
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