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Fixed #26916 -- Fixed prefetch_related when using a cached_property as to_attr.
Thanks Trac alias karyon for the report and Tim for the review.
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@ -25,7 +25,7 @@ from django.db.models.query_utils import (
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from django.db.models.sql.constants import CURSOR
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from django.utils import six, timezone
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from django.utils.deprecation import RemovedInDjango20Warning
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from django.utils.functional import partition
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from django.utils.functional import cached_property, partition
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from django.utils.version import get_version
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# The maximum number of items to display in a QuerySet.__repr__
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@ -1545,7 +1545,12 @@ def get_prefetcher(instance, through_attr, to_attr):
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if hasattr(rel_obj, 'get_prefetch_queryset'):
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prefetcher = rel_obj
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if through_attr != to_attr:
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is_fetched = hasattr(instance, to_attr)
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# Special case cached_property instances because hasattr
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# triggers attribute computation and assignment.
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if isinstance(getattr(instance.__class__, to_attr, None), cached_property):
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is_fetched = to_attr in instance.__dict__
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else:
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is_fetched = hasattr(instance, to_attr)
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else:
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is_fetched = through_attr in instance._prefetched_objects_cache
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return prefetcher, rel_obj_descriptor, attr_found, is_fetched
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@ -6,6 +6,7 @@ from django.contrib.contenttypes.fields import (
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from django.contrib.contenttypes.models import ContentType
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from django.db import models
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from django.utils.encoding import python_2_unicode_compatible
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from django.utils.functional import cached_property
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# Basic tests
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@ -219,6 +220,10 @@ class Person(models.Model):
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def all_houses(self):
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return list(self.houses.all())
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@cached_property
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def cached_all_houses(self):
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return self.all_houses
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class Meta:
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ordering = ['id']
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@ -743,6 +743,17 @@ class CustomPrefetchTests(TestCase):
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).get(pk=self.house3.pk)
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self.assertIsInstance(house.rooms.all(), QuerySet)
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def test_to_attr_cached_property(self):
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persons = Person.objects.prefetch_related(
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Prefetch('houses', House.objects.all(), to_attr='cached_all_houses'),
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)
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for person in persons:
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# To bypass caching at the related descriptor level, don't use
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# person.houses.all() here.
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all_houses = list(House.objects.filter(occupants=person))
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with self.assertNumQueries(0):
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self.assertEqual(person.cached_all_houses, all_houses)
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class DefaultManagerTests(TestCase):
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