Fixed #22650 -- Fixed regression on prefetch_related.
Regression from f51c1f59
when using select_related then prefetch_related
on the reverse side of an O2O:
Author.objects.select_related('bio').prefetch_related('bio__books')
Thanks Aymeric Augustin for the report and tests. Refs #17001.
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@ -1790,15 +1790,6 @@ def prefetch_related_objects(result_cache, related_lookups):
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done_queries[prefetch_to] = obj_list
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auto_lookups.extend(normalize_prefetch_lookups(additional_lookups, prefetch_to))
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followed_descriptors.add(descriptor)
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elif isinstance(getattr(first_obj, through_attr), list):
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# The current part of the lookup relates to a custom Prefetch.
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# This means that obj.attr is a list of related objects, and
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# thus we must turn the obj.attr lists into a single related
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# object list.
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new_list = []
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for obj in obj_list:
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new_list.extend(getattr(obj, through_attr))
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obj_list = new_list
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else:
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# Either a singly related object that has already been fetched
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# (e.g. via select_related), or hopefully some other property
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@ -1815,7 +1806,13 @@ def prefetch_related_objects(result_cache, related_lookups):
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continue
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if new_obj is None:
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continue
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new_obj_list.append(new_obj)
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# We special-case `list` rather than something more generic
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# like `Iterable` because we don't want to accidentally match
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# user models that define __iter__.
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if isinstance(new_obj, list):
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new_obj_list.extend(new_obj)
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else:
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new_obj_list.append(new_obj)
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obj_list = new_obj_list
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@ -66,6 +66,11 @@ class BookWithYear(Book):
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AuthorWithAge, related_name='books_with_year')
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class Bio(models.Model):
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author = models.OneToOneField(Author)
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books = models.ManyToManyField(Book, blank=True)
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@python_2_unicode_compatible
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class Reader(models.Model):
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name = models.CharField(max_length=50)
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@ -196,6 +201,10 @@ class Person(models.Model):
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# Assume business logic forces every person to have at least one house.
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return sorted(self.houses.all(), key=lambda house: -house.rooms.count())[0]
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@property
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def all_houses(self):
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return list(self.houses.all())
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class Meta:
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ordering = ['id']
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@ -9,7 +9,7 @@ from django.test import TestCase, override_settings
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from django.utils import six
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from django.utils.encoding import force_text
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from .models import (Author, Book, Reader, Qualification, Teacher, Department,
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from .models import (Author, Bio, Book, Reader, Qualification, Teacher, Department,
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TaggedItem, Bookmark, AuthorAddress, FavoriteAuthors, AuthorWithAge,
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BookWithYear, BookReview, Person, House, Room, Employee, Comment,
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LessonEntry, WordEntry, Author2)
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@ -192,6 +192,20 @@ class PrefetchRelatedTests(TestCase):
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["Amy"],
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["Amy", "Belinda"]])
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def test_reverse_one_to_one_then_m2m(self):
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"""
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Test that we can follow a m2m relation after going through
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the select_related reverse of a o2o.
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"""
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qs = Author.objects.prefetch_related('bio__books').select_related('bio')
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with self.assertNumQueries(1):
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list(qs.all())
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Bio.objects.create(author=self.author1)
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with self.assertNumQueries(2):
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list(qs.all())
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def test_attribute_error(self):
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qs = Reader.objects.all().prefetch_related('books_read__xyz')
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with self.assertRaises(AttributeError) as cm:
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@ -452,6 +466,52 @@ class CustomPrefetchTests(TestCase):
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)
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self.assertEqual(lst1, lst2)
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def test_traverse_single_item_property(self):
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# Control lookups.
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with self.assertNumQueries(5):
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lst1 = self.traverse_qs(
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Person.objects.prefetch_related(
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'houses__rooms',
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'primary_house__occupants__houses',
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),
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[['primary_house', 'occupants', 'houses']]
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)
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# Test lookups.
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with self.assertNumQueries(5):
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lst2 = self.traverse_qs(
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Person.objects.prefetch_related(
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'houses__rooms',
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Prefetch('primary_house__occupants', to_attr='occupants_lst'),
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'primary_house__occupants_lst__houses',
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),
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[['primary_house', 'occupants_lst', 'houses']]
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)
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self.assertEqual(lst1, lst2)
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def test_traverse_multiple_items_property(self):
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# Control lookups.
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with self.assertNumQueries(4):
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lst1 = self.traverse_qs(
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Person.objects.prefetch_related(
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'houses',
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'all_houses__occupants__houses',
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),
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[['all_houses', 'occupants', 'houses']]
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)
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# Test lookups.
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with self.assertNumQueries(4):
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lst2 = self.traverse_qs(
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Person.objects.prefetch_related(
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'houses',
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Prefetch('all_houses__occupants', to_attr='occupants_lst'),
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'all_houses__occupants_lst__houses',
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),
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[['all_houses', 'occupants_lst', 'houses']]
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)
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self.assertEqual(lst1, lst2)
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def test_custom_qs(self):
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# Test basic.
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with self.assertNumQueries(2):
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