from unittest import mock from django.contrib.contenttypes.models import ContentType from django.core.exceptions import ObjectDoesNotExist from django.db import NotSupportedError, connection from django.db.models import Prefetch, QuerySet, prefetch_related_objects from django.db.models.query import get_prefetcher from django.db.models.sql import Query from django.test import ( TestCase, override_settings, skipIfDBFeature, skipUnlessDBFeature, ) from django.test.utils import CaptureQueriesContext from .models import ( Article, Author, Author2, AuthorAddress, AuthorWithAge, Bio, Book, Bookmark, BookReview, BookWithYear, Comment, Department, Employee, FavoriteAuthors, House, LessonEntry, ModelIterableSubclass, Person, Qualification, Reader, Room, TaggedItem, Teacher, WordEntry, ) class TestDataMixin: @classmethod def setUpTestData(cls): cls.book1 = Book.objects.create(title="Poems") cls.book2 = Book.objects.create(title="Jane Eyre") cls.book3 = Book.objects.create(title="Wuthering Heights") cls.book4 = Book.objects.create(title="Sense and Sensibility") cls.author1 = Author.objects.create(name="Charlotte", first_book=cls.book1) cls.author2 = Author.objects.create(name="Anne", first_book=cls.book1) cls.author3 = Author.objects.create(name="Emily", first_book=cls.book1) cls.author4 = Author.objects.create(name="Jane", first_book=cls.book4) cls.book1.authors.add(cls.author1, cls.author2, cls.author3) cls.book2.authors.add(cls.author1) cls.book3.authors.add(cls.author3) cls.book4.authors.add(cls.author4) cls.reader1 = Reader.objects.create(name="Amy") cls.reader2 = Reader.objects.create(name="Belinda") cls.reader1.books_read.add(cls.book1, cls.book4) cls.reader2.books_read.add(cls.book2, cls.book4) class PrefetchRelatedTests(TestDataMixin, TestCase): def assertWhereContains(self, sql, needle): where_idx = sql.index("WHERE") self.assertEqual( sql.count(str(needle), where_idx), 1, msg="WHERE clause doesn't contain %s, actual SQL: %s" % (needle, sql[where_idx:]), ) def test_m2m_forward(self): with self.assertNumQueries(2): lists = [ list(b.authors.all()) for b in Book.objects.prefetch_related("authors") ] normal_lists = [list(b.authors.all()) for b in Book.objects.all()] self.assertEqual(lists, normal_lists) def test_m2m_reverse(self): with self.assertNumQueries(2): lists = [ list(a.books.all()) for a in Author.objects.prefetch_related("books") ] normal_lists = [list(a.books.all()) for a in Author.objects.all()] self.assertEqual(lists, normal_lists) def test_foreignkey_forward(self): with self.assertNumQueries(2): books = [ a.first_book for a in Author.objects.prefetch_related("first_book") ] normal_books = [a.first_book for a in Author.objects.all()] self.assertEqual(books, normal_books) def test_foreignkey_reverse(self): with self.assertNumQueries(2): [ list(b.first_time_authors.all()) for b in Book.objects.prefetch_related("first_time_authors") ] self.assertSequenceEqual(self.book2.authors.all(), [self.author1]) def test_onetoone_reverse_no_match(self): # Regression for #17439 with self.assertNumQueries(2): book = Book.objects.prefetch_related("bookwithyear").all()[0] with self.assertNumQueries(0): with self.assertRaises(BookWithYear.DoesNotExist): book.bookwithyear def test_onetoone_reverse_with_to_field_pk(self): """ A model (Bio) with a OneToOneField primary key (author) that references a non-pk field (name) on the related model (Author) is prefetchable. """ Bio.objects.bulk_create( [ Bio(author=self.author1), Bio(author=self.author2), Bio(author=self.author3), ] ) authors = Author.objects.filter( name__in=[self.author1, self.author2, self.author3], ).prefetch_related("bio") with self.assertNumQueries(2): for author in authors: self.assertEqual(author.name, author.bio.author.name) def test_survives_clone(self): with self.assertNumQueries(2): [ list(b.first_time_authors.all()) for b in Book.objects.prefetch_related("first_time_authors").exclude( id=1000 ) ] def test_len(self): with self.assertNumQueries(2): qs = Book.objects.prefetch_related("first_time_authors") len(qs) [list(b.first_time_authors.all()) for b in qs] def test_bool(self): with self.assertNumQueries(2): qs = Book.objects.prefetch_related("first_time_authors") bool(qs) [list(b.first_time_authors.all()) for b in qs] def test_count(self): with self.assertNumQueries(2): qs = Book.objects.prefetch_related("first_time_authors") [b.first_time_authors.count() for b in qs] def test_exists(self): with self.assertNumQueries(2): qs = Book.objects.prefetch_related("first_time_authors") [b.first_time_authors.exists() for b in qs] def test_in_and_prefetch_related(self): """ Regression test for #20242 - QuerySet "in" didn't work the first time when using prefetch_related. This was fixed by the removal of chunked reads from QuerySet iteration in 70679243d1786e03557c28929f9762a119e3ac14. """ qs = Book.objects.prefetch_related("first_time_authors") self.assertIn(qs[0], qs) def test_clear(self): with self.assertNumQueries(5): with_prefetch = Author.objects.prefetch_related("books") without_prefetch = with_prefetch.prefetch_related(None) [list(a.books.all()) for a in without_prefetch] def test_m2m_then_m2m(self): """A m2m can be followed through another m2m.""" with self.assertNumQueries(3): qs = Author.objects.prefetch_related("books__read_by") lists = [ [[str(r) for r in b.read_by.all()] for b in a.books.all()] for a in qs ] self.assertEqual( lists, [ [["Amy"], ["Belinda"]], # Charlotte - Poems, Jane Eyre [["Amy"]], # Anne - Poems [["Amy"], []], # Emily - Poems, Wuthering Heights [["Amy", "Belinda"]], # Jane - Sense and Sense ], ) def test_overriding_prefetch(self): with self.assertNumQueries(3): qs = Author.objects.prefetch_related("books", "books__read_by") lists = [ [[str(r) for r in b.read_by.all()] for b in a.books.all()] for a in qs ] self.assertEqual( lists, [ [["Amy"], ["Belinda"]], # Charlotte - Poems, Jane Eyre [["Amy"]], # Anne - Poems [["Amy"], []], # Emily - Poems, Wuthering Heights [["Amy", "Belinda"]], # Jane - Sense and Sense ], ) with self.assertNumQueries(3): qs = Author.objects.prefetch_related("books__read_by", "books") lists = [ [[str(r) for r in b.read_by.all()] for b in a.books.all()] for a in qs ] self.assertEqual( lists, [ [["Amy"], ["Belinda"]], # Charlotte - Poems, Jane Eyre [["Amy"]], # Anne - Poems [["Amy"], []], # Emily - Poems, Wuthering Heights [["Amy", "Belinda"]], # Jane - Sense and Sense ], ) def test_get(self): """ Objects retrieved with .get() get the prefetch behavior. """ # Need a double with self.assertNumQueries(3): author = Author.objects.prefetch_related("books__read_by").get( name="Charlotte" ) lists = [[str(r) for r in b.read_by.all()] for b in author.books.all()] self.assertEqual(lists, [["Amy"], ["Belinda"]]) # Poems, Jane Eyre def test_foreign_key_then_m2m(self): """ A m2m relation can be followed after a relation like ForeignKey that doesn't have many objects. """ with self.assertNumQueries(2): qs = Author.objects.select_related("first_book").prefetch_related( "first_book__read_by" ) lists = [[str(r) for r in a.first_book.read_by.all()] for a in qs] self.assertEqual(lists, [["Amy"], ["Amy"], ["Amy"], ["Amy", "Belinda"]]) def test_reverse_one_to_one_then_m2m(self): """ A m2m relation can be followed after going through the select_related reverse of an o2o. """ qs = Author.objects.prefetch_related("bio__books").select_related("bio") with self.assertNumQueries(1): list(qs.all()) Bio.objects.create(author=self.author1) with self.assertNumQueries(2): list(qs.all()) def test_attribute_error(self): qs = Reader.objects.prefetch_related("books_read__xyz") msg = ( "Cannot find 'xyz' on Book object, 'books_read__xyz' " "is an invalid parameter to prefetch_related()" ) with self.assertRaisesMessage(AttributeError, msg) as cm: list(qs) self.assertIn("prefetch_related", str(cm.exception)) def test_invalid_final_lookup(self): qs = Book.objects.prefetch_related("authors__name") msg = ( "'authors__name' does not resolve to an item that supports " "prefetching - this is an invalid parameter to prefetch_related()." ) with self.assertRaisesMessage(ValueError, msg) as cm: list(qs) self.assertIn("prefetch_related", str(cm.exception)) self.assertIn("name", str(cm.exception)) def test_prefetch_eq(self): prefetch_1 = Prefetch("authors", queryset=Author.objects.all()) prefetch_2 = Prefetch("books", queryset=Book.objects.all()) self.assertEqual(prefetch_1, prefetch_1) self.assertEqual(prefetch_1, mock.ANY) self.assertNotEqual(prefetch_1, prefetch_2) def test_forward_m2m_to_attr_conflict(self): msg = "to_attr=authors conflicts with a field on the Book model." authors = Author.objects.all() with self.assertRaisesMessage(ValueError, msg): list( Book.objects.prefetch_related( Prefetch("authors", queryset=authors, to_attr="authors"), ) ) # Without the ValueError, an author was deleted due to the implicit # save of the relation assignment. self.assertEqual(self.book1.authors.count(), 3) def test_reverse_m2m_to_attr_conflict(self): msg = "to_attr=books conflicts with a field on the Author model." poems = Book.objects.filter(title="Poems") with self.assertRaisesMessage(ValueError, msg): list( Author.objects.prefetch_related( Prefetch("books", queryset=poems, to_attr="books"), ) ) # Without the ValueError, a book was deleted due to the implicit # save of reverse relation assignment. self.assertEqual(self.author1.books.count(), 2) def test_m2m_then_reverse_fk_object_ids(self): with CaptureQueriesContext(connection) as queries: list(Book.objects.prefetch_related("authors__addresses")) sql = queries[-1]["sql"] self.assertWhereContains(sql, self.author1.name) def test_m2m_then_m2m_object_ids(self): with CaptureQueriesContext(connection) as queries: list(Book.objects.prefetch_related("authors__favorite_authors")) sql = queries[-1]["sql"] self.assertWhereContains(sql, self.author1.name) def test_m2m_then_reverse_one_to_one_object_ids(self): with CaptureQueriesContext(connection) as queries: list(Book.objects.prefetch_related("authors__authorwithage")) sql = queries[-1]["sql"] self.assertWhereContains(sql, self.author1.id) def test_filter_deferred(self): """ Related filtering of prefetched querysets is deferred on m2m and reverse m2o relations until necessary. """ add_q = Query.add_q for relation in ["authors", "first_time_authors"]: with self.subTest(relation=relation): with mock.patch.object( Query, "add_q", autospec=True, side_effect=lambda self, q: add_q(self, q), ) as add_q_mock: list(Book.objects.prefetch_related(relation)) self.assertEqual(add_q_mock.call_count, 1) def test_named_values_list(self): qs = Author.objects.prefetch_related("books") self.assertCountEqual( [value.name for value in qs.values_list("name", named=True)], ["Anne", "Charlotte", "Emily", "Jane"], ) def test_m2m_prefetching_iterator_with_chunks(self): with self.assertNumQueries(3): authors = [ b.authors.first() for b in Book.objects.prefetch_related("authors").iterator(chunk_size=2) ] self.assertEqual( authors, [self.author1, self.author1, self.author3, self.author4], ) def test_m2m_prefetching_iterator_without_chunks_error(self): msg = ( "chunk_size must be provided when using QuerySet.iterator() after " "prefetch_related()." ) with self.assertRaisesMessage(ValueError, msg): Book.objects.prefetch_related("authors").iterator() class RawQuerySetTests(TestDataMixin, TestCase): def test_basic(self): with self.assertNumQueries(2): books = Book.objects.raw( "SELECT * FROM prefetch_related_book WHERE id = %s", (self.book1.id,) ).prefetch_related("authors") book1 = list(books)[0] with self.assertNumQueries(0): self.assertCountEqual( book1.authors.all(), [self.author1, self.author2, self.author3] ) def test_prefetch_before_raw(self): with self.assertNumQueries(2): books = Book.objects.prefetch_related("authors").raw( "SELECT * FROM prefetch_related_book WHERE id = %s", (self.book1.id,) ) book1 = list(books)[0] with self.assertNumQueries(0): self.assertCountEqual( book1.authors.all(), [self.author1, self.author2, self.author3] ) def test_clear(self): with self.assertNumQueries(5): with_prefetch = Author.objects.raw( "SELECT * FROM prefetch_related_author" ).prefetch_related("books") without_prefetch = with_prefetch.prefetch_related(None) [list(a.books.all()) for a in without_prefetch] class CustomPrefetchTests(TestCase): @classmethod def traverse_qs(cls, obj_iter, path): """ Helper method that returns a list containing a list of the objects in the obj_iter. Then for each object in the obj_iter, the path will be recursively travelled and the found objects are added to the return value. """ ret_val = [] if hasattr(obj_iter, "all"): obj_iter = obj_iter.all() try: iter(obj_iter) except TypeError: obj_iter = [obj_iter] for obj in obj_iter: rel_objs = [] for part in path: if not part: continue try: related = getattr(obj, part[0]) except ObjectDoesNotExist: continue if related is not None: rel_objs.extend(cls.traverse_qs(related, [part[1:]])) ret_val.append((obj, rel_objs)) return ret_val @classmethod def setUpTestData(cls): cls.person1 = Person.objects.create(name="Joe") cls.person2 = Person.objects.create(name="Mary") # Set main_room for each house before creating the next one for # databases where supports_nullable_unique_constraints is False. cls.house1 = House.objects.create( name="House 1", address="123 Main St", owner=cls.person1 ) cls.room1_1 = Room.objects.create(name="Dining room", house=cls.house1) cls.room1_2 = Room.objects.create(name="Lounge", house=cls.house1) cls.room1_3 = Room.objects.create(name="Kitchen", house=cls.house1) cls.house1.main_room = cls.room1_1 cls.house1.save() cls.person1.houses.add(cls.house1) cls.house2 = House.objects.create( name="House 2", address="45 Side St", owner=cls.person1 ) cls.room2_1 = Room.objects.create(name="Dining room", house=cls.house2) cls.room2_2 = Room.objects.create(name="Lounge", house=cls.house2) cls.room2_3 = Room.objects.create(name="Kitchen", house=cls.house2) cls.house2.main_room = cls.room2_1 cls.house2.save() cls.person1.houses.add(cls.house2) cls.house3 = House.objects.create( name="House 3", address="6 Downing St", owner=cls.person2 ) cls.room3_1 = Room.objects.create(name="Dining room", house=cls.house3) cls.room3_2 = Room.objects.create(name="Lounge", house=cls.house3) cls.room3_3 = Room.objects.create(name="Kitchen", house=cls.house3) cls.house3.main_room = cls.room3_1 cls.house3.save() cls.person2.houses.add(cls.house3) cls.house4 = House.objects.create( name="house 4", address="7 Regents St", owner=cls.person2 ) cls.room4_1 = Room.objects.create(name="Dining room", house=cls.house4) cls.room4_2 = Room.objects.create(name="Lounge", house=cls.house4) cls.room4_3 = Room.objects.create(name="Kitchen", house=cls.house4) cls.house4.main_room = cls.room4_1 cls.house4.save() cls.person2.houses.add(cls.house4) def test_traverse_qs(self): qs = Person.objects.prefetch_related("houses") related_objs_normal = ([list(p.houses.all()) for p in qs],) related_objs_from_traverse = [ [inner[0] for inner in o[1]] for o in self.traverse_qs(qs, [["houses"]]) ] self.assertEqual(related_objs_normal, (related_objs_from_traverse,)) def test_ambiguous(self): # Ambiguous: Lookup was already seen with a different queryset. msg = ( "'houses' lookup was already seen with a different queryset. You " "may need to adjust the ordering of your lookups." ) # lookup.queryset shouldn't be evaluated. with self.assertNumQueries(3): with self.assertRaisesMessage(ValueError, msg): self.traverse_qs( Person.objects.prefetch_related( "houses__rooms", Prefetch("houses", queryset=House.objects.all()), ), [["houses", "rooms"]], ) # Ambiguous: Lookup houses_lst doesn't yet exist when performing # houses_lst__rooms. msg = ( "Cannot find 'houses_lst' on Person object, 'houses_lst__rooms' is " "an invalid parameter to prefetch_related()" ) with self.assertRaisesMessage(AttributeError, msg): self.traverse_qs( Person.objects.prefetch_related( "houses_lst__rooms", Prefetch( "houses", queryset=House.objects.all(), to_attr="houses_lst" ), ), [["houses", "rooms"]], ) # Not ambiguous. self.traverse_qs( Person.objects.prefetch_related("houses__rooms", "houses"), [["houses", "rooms"]], ) self.traverse_qs( Person.objects.prefetch_related( "houses__rooms", Prefetch("houses", queryset=House.objects.all(), to_attr="houses_lst"), ), [["houses", "rooms"]], ) def test_m2m(self): # Control lookups. with self.assertNumQueries(2): lst1 = self.traverse_qs( Person.objects.prefetch_related("houses"), [["houses"]] ) # Test lookups. with self.assertNumQueries(2): lst2 = self.traverse_qs( Person.objects.prefetch_related(Prefetch("houses")), [["houses"]] ) self.assertEqual(lst1, lst2) with self.assertNumQueries(2): lst2 = self.traverse_qs( Person.objects.prefetch_related( Prefetch("houses", to_attr="houses_lst") ), [["houses_lst"]], ) self.assertEqual(lst1, lst2) def test_reverse_m2m(self): # Control lookups. with self.assertNumQueries(2): lst1 = self.traverse_qs( House.objects.prefetch_related("occupants"), [["occupants"]] ) # Test lookups. with self.assertNumQueries(2): lst2 = self.traverse_qs( House.objects.prefetch_related(Prefetch("occupants")), [["occupants"]] ) self.assertEqual(lst1, lst2) with self.assertNumQueries(2): lst2 = self.traverse_qs( House.objects.prefetch_related( Prefetch("occupants", to_attr="occupants_lst") ), [["occupants_lst"]], ) self.assertEqual(lst1, lst2) def test_m2m_through_fk(self): # Control lookups. with self.assertNumQueries(3): lst1 = self.traverse_qs( Room.objects.prefetch_related("house__occupants"), [["house", "occupants"]], ) # Test lookups. with self.assertNumQueries(3): lst2 = self.traverse_qs( Room.objects.prefetch_related(Prefetch("house__occupants")), [["house", "occupants"]], ) self.assertEqual(lst1, lst2) with self.assertNumQueries(3): lst2 = self.traverse_qs( Room.objects.prefetch_related( Prefetch("house__occupants", to_attr="occupants_lst") ), [["house", "occupants_lst"]], ) self.assertEqual(lst1, lst2) def test_m2m_through_gfk(self): TaggedItem.objects.create(tag="houses", content_object=self.house1) TaggedItem.objects.create(tag="houses", content_object=self.house2) # Control lookups. with self.assertNumQueries(3): lst1 = self.traverse_qs( TaggedItem.objects.filter(tag="houses").prefetch_related( "content_object__rooms" ), [["content_object", "rooms"]], ) # Test lookups. with self.assertNumQueries(3): lst2 = self.traverse_qs( TaggedItem.objects.prefetch_related( Prefetch("content_object"), Prefetch("content_object__rooms", to_attr="rooms_lst"), ), [["content_object", "rooms_lst"]], ) self.assertEqual(lst1, lst2) def test_o2m_through_m2m(self): # Control lookups. with self.assertNumQueries(3): lst1 = self.traverse_qs( Person.objects.prefetch_related("houses", "houses__rooms"), [["houses", "rooms"]], ) # Test lookups. with self.assertNumQueries(3): lst2 = self.traverse_qs( Person.objects.prefetch_related(Prefetch("houses"), "houses__rooms"), [["houses", "rooms"]], ) self.assertEqual(lst1, lst2) with self.assertNumQueries(3): lst2 = self.traverse_qs( Person.objects.prefetch_related( Prefetch("houses"), Prefetch("houses__rooms") ), [["houses", "rooms"]], ) self.assertEqual(lst1, lst2) with self.assertNumQueries(3): lst2 = self.traverse_qs( Person.objects.prefetch_related( Prefetch("houses", to_attr="houses_lst"), "houses_lst__rooms" ), [["houses_lst", "rooms"]], ) self.assertEqual(lst1, lst2) with self.assertNumQueries(3): lst2 = self.traverse_qs( Person.objects.prefetch_related( Prefetch("houses", to_attr="houses_lst"), Prefetch("houses_lst__rooms", to_attr="rooms_lst"), ), [["houses_lst", "rooms_lst"]], ) self.assertEqual(lst1, lst2) def test_generic_rel(self): bookmark = Bookmark.objects.create(url="http://www.djangoproject.com/") TaggedItem.objects.create(content_object=bookmark, tag="django") TaggedItem.objects.create( content_object=bookmark, favorite=bookmark, tag="python" ) # Control lookups. with self.assertNumQueries(4): lst1 = self.traverse_qs( Bookmark.objects.prefetch_related( "tags", "tags__content_object", "favorite_tags" ), [["tags", "content_object"], ["favorite_tags"]], ) # Test lookups. with self.assertNumQueries(4): lst2 = self.traverse_qs( Bookmark.objects.prefetch_related( Prefetch("tags", to_attr="tags_lst"), Prefetch("tags_lst__content_object"), Prefetch("favorite_tags"), ), [["tags_lst", "content_object"], ["favorite_tags"]], ) self.assertEqual(lst1, lst2) def test_traverse_single_item_property(self): # Control lookups. with self.assertNumQueries(5): lst1 = self.traverse_qs( Person.objects.prefetch_related( "houses__rooms", "primary_house__occupants__houses", ), [["primary_house", "occupants", "houses"]], ) # Test lookups. with self.assertNumQueries(5): lst2 = self.traverse_qs( Person.objects.prefetch_related( "houses__rooms", Prefetch("primary_house__occupants", to_attr="occupants_lst"), "primary_house__occupants_lst__houses", ), [["primary_house", "occupants_lst", "houses"]], ) self.assertEqual(lst1, lst2) def test_traverse_multiple_items_property(self): # Control lookups. with self.assertNumQueries(4): lst1 = self.traverse_qs( Person.objects.prefetch_related( "houses", "all_houses__occupants__houses", ), [["all_houses", "occupants", "houses"]], ) # Test lookups. with self.assertNumQueries(4): lst2 = self.traverse_qs( Person.objects.prefetch_related( "houses", Prefetch("all_houses__occupants", to_attr="occupants_lst"), "all_houses__occupants_lst__houses", ), [["all_houses", "occupants_lst", "houses"]], ) self.assertEqual(lst1, lst2) def test_custom_qs(self): # Test basic. with self.assertNumQueries(2): lst1 = list(Person.objects.prefetch_related("houses")) with self.assertNumQueries(2): lst2 = list( Person.objects.prefetch_related( Prefetch( "houses", queryset=House.objects.all(), to_attr="houses_lst" ) ) ) self.assertEqual( self.traverse_qs(lst1, [["houses"]]), self.traverse_qs(lst2, [["houses_lst"]]), ) # Test queryset filtering. with self.assertNumQueries(2): lst2 = list( Person.objects.prefetch_related( Prefetch( "houses", queryset=House.objects.filter( pk__in=[self.house1.pk, self.house3.pk] ), to_attr="houses_lst", ) ) ) self.assertEqual(len(lst2[0].houses_lst), 1) self.assertEqual(lst2[0].houses_lst[0], self.house1) self.assertEqual(len(lst2[1].houses_lst), 1) self.assertEqual(lst2[1].houses_lst[0], self.house3) # Test flattened. with self.assertNumQueries(3): lst1 = list(Person.objects.prefetch_related("houses__rooms")) with self.assertNumQueries(3): lst2 = list( Person.objects.prefetch_related( Prefetch( "houses__rooms", queryset=Room.objects.all(), to_attr="rooms_lst", ) ) ) self.assertEqual( self.traverse_qs(lst1, [["houses", "rooms"]]), self.traverse_qs(lst2, [["houses", "rooms_lst"]]), ) # Test inner select_related. with self.assertNumQueries(3): lst1 = list(Person.objects.prefetch_related("houses__owner")) with self.assertNumQueries(2): lst2 = list( Person.objects.prefetch_related( Prefetch("houses", queryset=House.objects.select_related("owner")) ) ) self.assertEqual( self.traverse_qs(lst1, [["houses", "owner"]]), self.traverse_qs(lst2, [["houses", "owner"]]), ) # Test inner prefetch. inner_rooms_qs = Room.objects.filter(pk__in=[self.room1_1.pk, self.room1_2.pk]) houses_qs_prf = House.objects.prefetch_related( Prefetch("rooms", queryset=inner_rooms_qs, to_attr="rooms_lst") ) with self.assertNumQueries(4): lst2 = list( Person.objects.prefetch_related( Prefetch( "houses", queryset=houses_qs_prf.filter(pk=self.house1.pk), to_attr="houses_lst", ), Prefetch("houses_lst__rooms_lst__main_room_of"), ) ) self.assertEqual(len(lst2[0].houses_lst[0].rooms_lst), 2) self.assertEqual(lst2[0].houses_lst[0].rooms_lst[0], self.room1_1) self.assertEqual(lst2[0].houses_lst[0].rooms_lst[1], self.room1_2) self.assertEqual(lst2[0].houses_lst[0].rooms_lst[0].main_room_of, self.house1) self.assertEqual(len(lst2[1].houses_lst), 0) # Test ForwardManyToOneDescriptor. houses = House.objects.select_related("owner") with self.assertNumQueries(6): rooms = Room.objects.prefetch_related("house") lst1 = self.traverse_qs(rooms, [["house", "owner"]]) with self.assertNumQueries(2): rooms = Room.objects.prefetch_related(Prefetch("house", queryset=houses)) lst2 = self.traverse_qs(rooms, [["house", "owner"]]) self.assertEqual(lst1, lst2) with self.assertNumQueries(2): houses = House.objects.select_related("owner") rooms = Room.objects.prefetch_related( Prefetch("house", queryset=houses, to_attr="house_attr") ) lst2 = self.traverse_qs(rooms, [["house_attr", "owner"]]) self.assertEqual(lst1, lst2) room = Room.objects.prefetch_related( Prefetch("house", queryset=houses.filter(address="DoesNotExist")) ).first() with self.assertRaises(ObjectDoesNotExist): getattr(room, "house") room = Room.objects.prefetch_related( Prefetch( "house", queryset=houses.filter(address="DoesNotExist"), to_attr="house_attr", ) ).first() self.assertIsNone(room.house_attr) rooms = Room.objects.prefetch_related( Prefetch("house", queryset=House.objects.only("name")) ) with self.assertNumQueries(2): getattr(rooms.first().house, "name") with self.assertNumQueries(3): getattr(rooms.first().house, "address") # Test ReverseOneToOneDescriptor. houses = House.objects.select_related("owner") with self.assertNumQueries(6): rooms = Room.objects.prefetch_related("main_room_of") lst1 = self.traverse_qs(rooms, [["main_room_of", "owner"]]) with self.assertNumQueries(2): rooms = Room.objects.prefetch_related( Prefetch("main_room_of", queryset=houses) ) lst2 = self.traverse_qs(rooms, [["main_room_of", "owner"]]) self.assertEqual(lst1, lst2) with self.assertNumQueries(2): rooms = list( Room.objects.prefetch_related( Prefetch( "main_room_of", queryset=houses, to_attr="main_room_of_attr", ) ) ) lst2 = self.traverse_qs(rooms, [["main_room_of_attr", "owner"]]) self.assertEqual(lst1, lst2) room = ( Room.objects.filter(main_room_of__isnull=False) .prefetch_related( Prefetch("main_room_of", queryset=houses.filter(address="DoesNotExist")) ) .first() ) with self.assertRaises(ObjectDoesNotExist): getattr(room, "main_room_of") room = ( Room.objects.filter(main_room_of__isnull=False) .prefetch_related( Prefetch( "main_room_of", queryset=houses.filter(address="DoesNotExist"), to_attr="main_room_of_attr", ) ) .first() ) self.assertIsNone(room.main_room_of_attr) # The custom queryset filters should be applied to the queryset # instance returned by the manager. person = Person.objects.prefetch_related( Prefetch("houses", queryset=House.objects.filter(name="House 1")), ).get(pk=self.person1.pk) self.assertEqual( list(person.houses.all()), list(person.houses.all().all()), ) def test_nested_prefetch_related_are_not_overwritten(self): # Regression test for #24873 houses_2 = House.objects.prefetch_related(Prefetch("rooms")) persons = Person.objects.prefetch_related(Prefetch("houses", queryset=houses_2)) houses = House.objects.prefetch_related(Prefetch("occupants", queryset=persons)) list(houses) # queryset must be evaluated once to reproduce the bug. self.assertEqual( houses.all()[0].occupants.all()[0].houses.all()[1].rooms.all()[0], self.room2_1, ) def test_nested_prefetch_related_with_duplicate_prefetcher(self): """ Nested prefetches whose name clashes with descriptor names (Person.houses here) are allowed. """ occupants = Person.objects.prefetch_related( Prefetch("houses", to_attr="some_attr_name"), Prefetch("houses", queryset=House.objects.prefetch_related("main_room")), ) houses = House.objects.prefetch_related( Prefetch("occupants", queryset=occupants) ) with self.assertNumQueries(5): self.traverse_qs(list(houses), [["occupants", "houses", "main_room"]]) def test_values_queryset(self): msg = "Prefetch querysets cannot use raw(), values(), and values_list()." with self.assertRaisesMessage(ValueError, msg): Prefetch("houses", House.objects.values("pk")) with self.assertRaisesMessage(ValueError, msg): Prefetch("houses", House.objects.values_list("pk")) # That error doesn't affect managers with custom ModelIterable subclasses self.assertIs( Teacher.objects_custom.all()._iterable_class, ModelIterableSubclass ) Prefetch("teachers", Teacher.objects_custom.all()) def test_raw_queryset(self): msg = "Prefetch querysets cannot use raw(), values(), and values_list()." with self.assertRaisesMessage(ValueError, msg): Prefetch("houses", House.objects.raw("select pk from house")) def test_to_attr_doesnt_cache_through_attr_as_list(self): house = House.objects.prefetch_related( Prefetch("rooms", queryset=Room.objects.all(), to_attr="to_rooms"), ).get(pk=self.house3.pk) self.assertIsInstance(house.rooms.all(), QuerySet) def test_to_attr_cached_property(self): persons = Person.objects.prefetch_related( Prefetch("houses", House.objects.all(), to_attr="cached_all_houses"), ) for person in persons: # To bypass caching at the related descriptor level, don't use # person.houses.all() here. all_houses = list(House.objects.filter(occupants=person)) with self.assertNumQueries(0): self.assertEqual(person.cached_all_houses, all_houses) def test_filter_deferred(self): """ Related filtering of prefetched querysets is deferred until necessary. """ add_q = Query.add_q with mock.patch.object( Query, "add_q", autospec=True, side_effect=lambda self, q: add_q(self, q), ) as add_q_mock: list( House.objects.prefetch_related( Prefetch("occupants", queryset=Person.objects.all()) ) ) self.assertEqual(add_q_mock.call_count, 1) class DefaultManagerTests(TestCase): @classmethod def setUpTestData(cls): cls.qual1 = Qualification.objects.create(name="BA") cls.qual2 = Qualification.objects.create(name="BSci") cls.qual3 = Qualification.objects.create(name="MA") cls.qual4 = Qualification.objects.create(name="PhD") cls.teacher1 = Teacher.objects.create(name="Mr Cleese") cls.teacher2 = Teacher.objects.create(name="Mr Idle") cls.teacher3 = Teacher.objects.create(name="Mr Chapman") cls.teacher1.qualifications.add(cls.qual1, cls.qual2, cls.qual3, cls.qual4) cls.teacher2.qualifications.add(cls.qual1) cls.teacher3.qualifications.add(cls.qual2) cls.dept1 = Department.objects.create(name="English") cls.dept2 = Department.objects.create(name="Physics") cls.dept1.teachers.add(cls.teacher1, cls.teacher2) cls.dept2.teachers.add(cls.teacher1, cls.teacher3) def test_m2m_then_m2m(self): with self.assertNumQueries(3): # When we prefetch the teachers, and force the query, we don't want # the default manager on teachers to immediately get all the related # qualifications, since this will do one query per teacher. qs = Department.objects.prefetch_related("teachers") depts = "".join( "%s department: %s\n" % (dept.name, ", ".join(str(t) for t in dept.teachers.all())) for dept in qs ) self.assertEqual( depts, "English department: Mr Cleese (BA, BSci, MA, PhD), Mr Idle (BA)\n" "Physics department: Mr Cleese (BA, BSci, MA, PhD), Mr Chapman " "(BSci)\n", ) class GenericRelationTests(TestCase): @classmethod def setUpTestData(cls): book1 = Book.objects.create(title="Winnie the Pooh") book2 = Book.objects.create(title="Do you like green eggs and spam?") book3 = Book.objects.create(title="Three Men In A Boat") reader1 = Reader.objects.create(name="me") reader2 = Reader.objects.create(name="you") reader3 = Reader.objects.create(name="someone") book1.read_by.add(reader1, reader2) book2.read_by.add(reader2) book3.read_by.add(reader3) cls.book1, cls.book2, cls.book3 = book1, book2, book3 cls.reader1, cls.reader2, cls.reader3 = reader1, reader2, reader3 def test_prefetch_GFK(self): TaggedItem.objects.create(tag="awesome", content_object=self.book1) TaggedItem.objects.create(tag="great", content_object=self.reader1) TaggedItem.objects.create(tag="outstanding", content_object=self.book2) TaggedItem.objects.create(tag="amazing", content_object=self.reader3) # 1 for TaggedItem table, 1 for Book table, 1 for Reader table with self.assertNumQueries(3): qs = TaggedItem.objects.prefetch_related("content_object") list(qs) def test_prefetch_GFK_nonint_pk(self): Comment.objects.create(comment="awesome", content_object=self.book1) # 1 for Comment table, 1 for Book table with self.assertNumQueries(2): qs = Comment.objects.prefetch_related("content_object") [c.content_object for c in qs] def test_prefetch_GFK_uuid_pk(self): article = Article.objects.create(name="Django") Comment.objects.create(comment="awesome", content_object_uuid=article) qs = Comment.objects.prefetch_related("content_object_uuid") self.assertEqual([c.content_object_uuid for c in qs], [article]) def test_prefetch_GFK_fk_pk(self): book = Book.objects.create(title="Poems") book_with_year = BookWithYear.objects.create(book=book, published_year=2019) Comment.objects.create(comment="awesome", content_object=book_with_year) qs = Comment.objects.prefetch_related("content_object") self.assertEqual([c.content_object for c in qs], [book_with_year]) def test_traverse_GFK(self): """ A 'content_object' can be traversed with prefetch_related() and get to related objects on the other side (assuming it is suitably filtered) """ TaggedItem.objects.create(tag="awesome", content_object=self.book1) TaggedItem.objects.create(tag="awesome", content_object=self.book2) TaggedItem.objects.create(tag="awesome", content_object=self.book3) TaggedItem.objects.create(tag="awesome", content_object=self.reader1) TaggedItem.objects.create(tag="awesome", content_object=self.reader2) ct = ContentType.objects.get_for_model(Book) # We get 3 queries - 1 for main query, 1 for content_objects since they # all use the same table, and 1 for the 'read_by' relation. with self.assertNumQueries(3): # If we limit to books, we know that they will have 'read_by' # attributes, so the following makes sense: qs = TaggedItem.objects.filter( content_type=ct, tag="awesome" ).prefetch_related("content_object__read_by") readers_of_awesome_books = { r.name for tag in qs for r in tag.content_object.read_by.all() } self.assertEqual(readers_of_awesome_books, {"me", "you", "someone"}) def test_nullable_GFK(self): TaggedItem.objects.create( tag="awesome", content_object=self.book1, created_by=self.reader1 ) TaggedItem.objects.create(tag="great", content_object=self.book2) TaggedItem.objects.create(tag="rubbish", content_object=self.book3) with self.assertNumQueries(2): result = [ t.created_by for t in TaggedItem.objects.prefetch_related("created_by") ] self.assertEqual(result, [t.created_by for t in TaggedItem.objects.all()]) def test_generic_relation(self): bookmark = Bookmark.objects.create(url="http://www.djangoproject.com/") TaggedItem.objects.create(content_object=bookmark, tag="django") TaggedItem.objects.create(content_object=bookmark, tag="python") with self.assertNumQueries(2): tags = [ t.tag for b in Bookmark.objects.prefetch_related("tags") for t in b.tags.all() ] self.assertEqual(sorted(tags), ["django", "python"]) def test_charfield_GFK(self): b = Bookmark.objects.create(url="http://www.djangoproject.com/") TaggedItem.objects.create(content_object=b, tag="django") TaggedItem.objects.create(content_object=b, favorite=b, tag="python") with self.assertNumQueries(3): bookmark = Bookmark.objects.filter(pk=b.pk).prefetch_related( "tags", "favorite_tags" )[0] self.assertEqual( sorted(i.tag for i in bookmark.tags.all()), ["django", "python"] ) self.assertEqual([i.tag for i in bookmark.favorite_tags.all()], ["python"]) def test_custom_queryset(self): bookmark = Bookmark.objects.create(url="http://www.djangoproject.com/") django_tag = TaggedItem.objects.create(content_object=bookmark, tag="django") TaggedItem.objects.create(content_object=bookmark, tag="python") with self.assertNumQueries(2): bookmark = Bookmark.objects.prefetch_related( Prefetch("tags", TaggedItem.objects.filter(tag="django")), ).get() with self.assertNumQueries(0): self.assertEqual(list(bookmark.tags.all()), [django_tag]) # The custom queryset filters should be applied to the queryset # instance returned by the manager. self.assertEqual(list(bookmark.tags.all()), list(bookmark.tags.all().all())) def test_deleted_GFK(self): TaggedItem.objects.create(tag="awesome", content_object=self.book1) TaggedItem.objects.create(tag="awesome", content_object=self.book2) ct = ContentType.objects.get_for_model(Book) book1_pk = self.book1.pk self.book1.delete() with self.assertNumQueries(2): qs = TaggedItem.objects.filter(tag="awesome").prefetch_related( "content_object" ) result = [ (tag.object_id, tag.content_type_id, tag.content_object) for tag in qs ] self.assertEqual( result, [ (book1_pk, ct.pk, None), (self.book2.pk, ct.pk, self.book2), ], ) class MultiTableInheritanceTest(TestCase): @classmethod def setUpTestData(cls): cls.book1 = BookWithYear.objects.create(title="Poems", published_year=2010) cls.book2 = BookWithYear.objects.create(title="More poems", published_year=2011) cls.author1 = AuthorWithAge.objects.create( name="Jane", first_book=cls.book1, age=50 ) cls.author2 = AuthorWithAge.objects.create( name="Tom", first_book=cls.book1, age=49 ) cls.author3 = AuthorWithAge.objects.create( name="Robert", first_book=cls.book2, age=48 ) cls.author_address = AuthorAddress.objects.create( author=cls.author1, address="SomeStreet 1" ) cls.book2.aged_authors.add(cls.author2, cls.author3) cls.br1 = BookReview.objects.create(book=cls.book1, notes="review book1") cls.br2 = BookReview.objects.create(book=cls.book2, notes="review book2") def test_foreignkey(self): with self.assertNumQueries(2): qs = AuthorWithAge.objects.prefetch_related("addresses") addresses = [ [str(address) for address in obj.addresses.all()] for obj in qs ] self.assertEqual(addresses, [[str(self.author_address)], [], []]) def test_foreignkey_to_inherited(self): with self.assertNumQueries(2): qs = BookReview.objects.prefetch_related("book") titles = [obj.book.title for obj in qs] self.assertCountEqual(titles, ["Poems", "More poems"]) def test_m2m_to_inheriting_model(self): qs = AuthorWithAge.objects.prefetch_related("books_with_year") with self.assertNumQueries(2): lst = [ [str(book) for book in author.books_with_year.all()] for author in qs ] qs = AuthorWithAge.objects.all() lst2 = [[str(book) for book in author.books_with_year.all()] for author in qs] self.assertEqual(lst, lst2) qs = BookWithYear.objects.prefetch_related("aged_authors") with self.assertNumQueries(2): lst = [[str(author) for author in book.aged_authors.all()] for book in qs] qs = BookWithYear.objects.all() lst2 = [[str(author) for author in book.aged_authors.all()] for book in qs] self.assertEqual(lst, lst2) def test_parent_link_prefetch(self): with self.assertNumQueries(2): [a.author for a in AuthorWithAge.objects.prefetch_related("author")] @override_settings(DEBUG=True) def test_child_link_prefetch(self): with self.assertNumQueries(2): authors = [ a.authorwithage for a in Author.objects.prefetch_related("authorwithage") ] # Regression for #18090: the prefetching query must include an IN clause. # Note that on Oracle the table name is upper case in the generated SQL, # thus the .lower() call. self.assertIn("authorwithage", connection.queries[-1]["sql"].lower()) self.assertIn(" IN ", connection.queries[-1]["sql"]) self.assertEqual(authors, [a.authorwithage for a in Author.objects.all()]) class ForeignKeyToFieldTest(TestCase): @classmethod def setUpTestData(cls): cls.book = Book.objects.create(title="Poems") cls.author1 = Author.objects.create(name="Jane", first_book=cls.book) cls.author2 = Author.objects.create(name="Tom", first_book=cls.book) cls.author3 = Author.objects.create(name="Robert", first_book=cls.book) cls.author_address = AuthorAddress.objects.create( author=cls.author1, address="SomeStreet 1" ) FavoriteAuthors.objects.create(author=cls.author1, likes_author=cls.author2) FavoriteAuthors.objects.create(author=cls.author2, likes_author=cls.author3) FavoriteAuthors.objects.create(author=cls.author3, likes_author=cls.author1) def test_foreignkey(self): with self.assertNumQueries(2): qs = Author.objects.prefetch_related("addresses") addresses = [ [str(address) for address in obj.addresses.all()] for obj in qs ] self.assertEqual(addresses, [[str(self.author_address)], [], []]) def test_m2m(self): with self.assertNumQueries(3): qs = Author.objects.prefetch_related("favorite_authors", "favors_me") favorites = [ ( [str(i_like) for i_like in author.favorite_authors.all()], [str(likes_me) for likes_me in author.favors_me.all()], ) for author in qs ] self.assertEqual( favorites, [ ([str(self.author2)], [str(self.author3)]), ([str(self.author3)], [str(self.author1)]), ([str(self.author1)], [str(self.author2)]), ], ) class LookupOrderingTest(TestCase): """ Test cases that demonstrate that ordering of lookups is important, and ensure it is preserved. """ @classmethod def setUpTestData(cls): person1 = Person.objects.create(name="Joe") person2 = Person.objects.create(name="Mary") # Set main_room for each house before creating the next one for # databases where supports_nullable_unique_constraints is False. house1 = House.objects.create(address="123 Main St") room1_1 = Room.objects.create(name="Dining room", house=house1) Room.objects.create(name="Lounge", house=house1) Room.objects.create(name="Kitchen", house=house1) house1.main_room = room1_1 house1.save() person1.houses.add(house1) house2 = House.objects.create(address="45 Side St") room2_1 = Room.objects.create(name="Dining room", house=house2) Room.objects.create(name="Lounge", house=house2) house2.main_room = room2_1 house2.save() person1.houses.add(house2) house3 = House.objects.create(address="6 Downing St") room3_1 = Room.objects.create(name="Dining room", house=house3) Room.objects.create(name="Lounge", house=house3) Room.objects.create(name="Kitchen", house=house3) house3.main_room = room3_1 house3.save() person2.houses.add(house3) house4 = House.objects.create(address="7 Regents St") room4_1 = Room.objects.create(name="Dining room", house=house4) Room.objects.create(name="Lounge", house=house4) house4.main_room = room4_1 house4.save() person2.houses.add(house4) def test_order(self): with self.assertNumQueries(4): # The following two queries must be done in the same order as written, # otherwise 'primary_house' will cause non-prefetched lookups qs = Person.objects.prefetch_related( "houses__rooms", "primary_house__occupants" ) [list(p.primary_house.occupants.all()) for p in qs] class NullableTest(TestCase): @classmethod def setUpTestData(cls): boss = Employee.objects.create(name="Peter") Employee.objects.create(name="Joe", boss=boss) Employee.objects.create(name="Angela", boss=boss) def test_traverse_nullable(self): # Because we use select_related() for 'boss', it doesn't need to be # prefetched, but we can still traverse it although it contains some nulls with self.assertNumQueries(2): qs = Employee.objects.select_related("boss").prefetch_related("boss__serfs") co_serfs = [ list(e.boss.serfs.all()) if e.boss is not None else [] for e in qs ] qs2 = Employee.objects.select_related("boss") co_serfs2 = [ list(e.boss.serfs.all()) if e.boss is not None else [] for e in qs2 ] self.assertEqual(co_serfs, co_serfs2) def test_prefetch_nullable(self): # One for main employee, one for boss, one for serfs with self.assertNumQueries(3): qs = Employee.objects.prefetch_related("boss__serfs") co_serfs = [ list(e.boss.serfs.all()) if e.boss is not None else [] for e in qs ] qs2 = Employee.objects.all() co_serfs2 = [ list(e.boss.serfs.all()) if e.boss is not None else [] for e in qs2 ] self.assertEqual(co_serfs, co_serfs2) def test_in_bulk(self): """ In-bulk does correctly prefetch objects by not using .iterator() directly. """ boss1 = Employee.objects.create(name="Peter") boss2 = Employee.objects.create(name="Jack") with self.assertNumQueries(2): # Prefetch is done and it does not cause any errors. bulk = Employee.objects.prefetch_related("serfs").in_bulk( [boss1.pk, boss2.pk] ) for b in bulk.values(): list(b.serfs.all()) class MultiDbTests(TestCase): databases = {"default", "other"} def test_using_is_honored_m2m(self): B = Book.objects.using("other") A = Author.objects.using("other") book1 = B.create(title="Poems") book2 = B.create(title="Jane Eyre") book3 = B.create(title="Wuthering Heights") book4 = B.create(title="Sense and Sensibility") author1 = A.create(name="Charlotte", first_book=book1) author2 = A.create(name="Anne", first_book=book1) author3 = A.create(name="Emily", first_book=book1) author4 = A.create(name="Jane", first_book=book4) book1.authors.add(author1, author2, author3) book2.authors.add(author1) book3.authors.add(author3) book4.authors.add(author4) # Forward qs1 = B.prefetch_related("authors") with self.assertNumQueries(2, using="other"): books = "".join( "%s (%s)\n" % (book.title, ", ".join(a.name for a in book.authors.all())) for book in qs1 ) self.assertEqual( books, "Poems (Charlotte, Anne, Emily)\n" "Jane Eyre (Charlotte)\n" "Wuthering Heights (Emily)\n" "Sense and Sensibility (Jane)\n", ) # Reverse qs2 = A.prefetch_related("books") with self.assertNumQueries(2, using="other"): authors = "".join( "%s: %s\n" % (author.name, ", ".join(b.title for b in author.books.all())) for author in qs2 ) self.assertEqual( authors, "Charlotte: Poems, Jane Eyre\n" "Anne: Poems\n" "Emily: Poems, Wuthering Heights\n" "Jane: Sense and Sensibility\n", ) def test_using_is_honored_fkey(self): B = Book.objects.using("other") A = Author.objects.using("other") book1 = B.create(title="Poems") book2 = B.create(title="Sense and Sensibility") A.create(name="Charlotte Bronte", first_book=book1) A.create(name="Jane Austen", first_book=book2) # Forward with self.assertNumQueries(2, using="other"): books = ", ".join( a.first_book.title for a in A.prefetch_related("first_book") ) self.assertEqual("Poems, Sense and Sensibility", books) # Reverse with self.assertNumQueries(2, using="other"): books = "".join( "%s (%s)\n" % (b.title, ", ".join(a.name for a in b.first_time_authors.all())) for b in B.prefetch_related("first_time_authors") ) self.assertEqual( books, "Poems (Charlotte Bronte)\nSense and Sensibility (Jane Austen)\n", ) def test_using_is_honored_inheritance(self): B = BookWithYear.objects.using("other") A = AuthorWithAge.objects.using("other") book1 = B.create(title="Poems", published_year=2010) B.create(title="More poems", published_year=2011) A.create(name="Jane", first_book=book1, age=50) A.create(name="Tom", first_book=book1, age=49) # parent link with self.assertNumQueries(2, using="other"): authors = ", ".join(a.author.name for a in A.prefetch_related("author")) self.assertEqual(authors, "Jane, Tom") # child link with self.assertNumQueries(2, using="other"): ages = ", ".join( str(a.authorwithage.age) for a in A.prefetch_related("authorwithage") ) self.assertEqual(ages, "50, 49") def test_using_is_honored_custom_qs(self): B = Book.objects.using("other") A = Author.objects.using("other") book1 = B.create(title="Poems") book2 = B.create(title="Sense and Sensibility") A.create(name="Charlotte Bronte", first_book=book1) A.create(name="Jane Austen", first_book=book2) # Implicit hinting with self.assertNumQueries(2, using="other"): prefetch = Prefetch("first_time_authors", queryset=Author.objects.all()) books = "".join( "%s (%s)\n" % (b.title, ", ".join(a.name for a in b.first_time_authors.all())) for b in B.prefetch_related(prefetch) ) self.assertEqual( books, "Poems (Charlotte Bronte)\nSense and Sensibility (Jane Austen)\n", ) # Explicit using on the same db. with self.assertNumQueries(2, using="other"): prefetch = Prefetch( "first_time_authors", queryset=Author.objects.using("other") ) books = "".join( "%s (%s)\n" % (b.title, ", ".join(a.name for a in b.first_time_authors.all())) for b in B.prefetch_related(prefetch) ) self.assertEqual( books, "Poems (Charlotte Bronte)\nSense and Sensibility (Jane Austen)\n", ) # Explicit using on a different db. with self.assertNumQueries(1, using="default"), self.assertNumQueries( 1, using="other" ): prefetch = Prefetch( "first_time_authors", queryset=Author.objects.using("default") ) books = "".join( "%s (%s)\n" % (b.title, ", ".join(a.name for a in b.first_time_authors.all())) for b in B.prefetch_related(prefetch) ) self.assertEqual(books, "Poems ()\n" "Sense and Sensibility ()\n") class Ticket19607Tests(TestCase): @classmethod def setUpTestData(cls): LessonEntry.objects.bulk_create( LessonEntry(id=id_, name1=name1, name2=name2) for id_, name1, name2 in [ (1, "einfach", "simple"), (2, "schwierig", "difficult"), ] ) WordEntry.objects.bulk_create( WordEntry(id=id_, lesson_entry_id=lesson_entry_id, name=name) for id_, lesson_entry_id, name in [ (1, 1, "einfach"), (2, 1, "simple"), (3, 2, "schwierig"), (4, 2, "difficult"), ] ) def test_bug(self): list( WordEntry.objects.prefetch_related( "lesson_entry", "lesson_entry__wordentry_set" ) ) class Ticket21410Tests(TestCase): @classmethod def setUpTestData(cls): book1 = Book.objects.create(title="Poems") book2 = Book.objects.create(title="Jane Eyre") book3 = Book.objects.create(title="Wuthering Heights") book4 = Book.objects.create(title="Sense and Sensibility") author1 = Author2.objects.create(name="Charlotte", first_book=book1) author2 = Author2.objects.create(name="Anne", first_book=book1) author3 = Author2.objects.create(name="Emily", first_book=book1) author4 = Author2.objects.create(name="Jane", first_book=book4) author1.favorite_books.add(book1, book2, book3) author2.favorite_books.add(book1) author3.favorite_books.add(book2) author4.favorite_books.add(book3) def test_bug(self): list(Author2.objects.prefetch_related("first_book", "favorite_books")) class Ticket21760Tests(TestCase): @classmethod def setUpTestData(cls): cls.rooms = [] for _ in range(3): house = House.objects.create() for _ in range(3): cls.rooms.append(Room.objects.create(house=house)) # Set main_room for each house before creating the next one for # databases where supports_nullable_unique_constraints is False. house.main_room = cls.rooms[-3] house.save() def test_bug(self): prefetcher = get_prefetcher(self.rooms[0], "house", "house")[0] queryset = prefetcher.get_prefetch_queryset(list(Room.objects.all()))[0] self.assertNotIn(" JOIN ", str(queryset.query)) class DirectPrefetchedObjectCacheReuseTests(TestCase): """ prefetch_related() reuses objects fetched in _prefetched_objects_cache. When objects are prefetched and not stored as an instance attribute (often intermediary relationships), they are saved to the _prefetched_objects_cache attribute. prefetch_related() takes _prefetched_objects_cache into account when determining whether an object has been fetched[1] and retrieves results from it when it is populated [2]. [1]: #25546 (duplicate queries on nested Prefetch) [2]: #27554 (queryset evaluation fails with a mix of nested and flattened prefetches) """ @classmethod def setUpTestData(cls): cls.book1, cls.book2 = [ Book.objects.create(title="book1"), Book.objects.create(title="book2"), ] cls.author11, cls.author12, cls.author21 = [ Author.objects.create(first_book=cls.book1, name="Author11"), Author.objects.create(first_book=cls.book1, name="Author12"), Author.objects.create(first_book=cls.book2, name="Author21"), ] cls.author1_address1, cls.author1_address2, cls.author2_address1 = [ AuthorAddress.objects.create(author=cls.author11, address="Happy place"), AuthorAddress.objects.create(author=cls.author12, address="Haunted house"), AuthorAddress.objects.create(author=cls.author21, address="Happy place"), ] cls.bookwithyear1 = BookWithYear.objects.create( title="Poems", published_year=2010 ) cls.bookreview1 = BookReview.objects.create(book=cls.bookwithyear1) def test_detect_is_fetched(self): """ Nested prefetch_related() shouldn't trigger duplicate queries for the same lookup. """ with self.assertNumQueries(3): books = Book.objects.filter(title__in=["book1", "book2"]).prefetch_related( Prefetch( "first_time_authors", Author.objects.prefetch_related( Prefetch( "addresses", AuthorAddress.objects.filter(address="Happy place"), ) ), ), ) book1, book2 = list(books) with self.assertNumQueries(0): self.assertSequenceEqual( book1.first_time_authors.all(), [self.author11, self.author12] ) self.assertSequenceEqual(book2.first_time_authors.all(), [self.author21]) self.assertSequenceEqual( book1.first_time_authors.all()[0].addresses.all(), [self.author1_address1], ) self.assertSequenceEqual( book1.first_time_authors.all()[1].addresses.all(), [] ) self.assertSequenceEqual( book2.first_time_authors.all()[0].addresses.all(), [self.author2_address1], ) self.assertEqual( list(book1.first_time_authors.all()), list(book1.first_time_authors.all().all()), ) self.assertEqual( list(book2.first_time_authors.all()), list(book2.first_time_authors.all().all()), ) self.assertEqual( list(book1.first_time_authors.all()[0].addresses.all()), list(book1.first_time_authors.all()[0].addresses.all().all()), ) self.assertEqual( list(book1.first_time_authors.all()[1].addresses.all()), list(book1.first_time_authors.all()[1].addresses.all().all()), ) self.assertEqual( list(book2.first_time_authors.all()[0].addresses.all()), list(book2.first_time_authors.all()[0].addresses.all().all()), ) def test_detect_is_fetched_with_to_attr(self): with self.assertNumQueries(3): books = Book.objects.filter(title__in=["book1", "book2"]).prefetch_related( Prefetch( "first_time_authors", Author.objects.prefetch_related( Prefetch( "addresses", AuthorAddress.objects.filter(address="Happy place"), to_attr="happy_place", ) ), to_attr="first_authors", ), ) book1, book2 = list(books) with self.assertNumQueries(0): self.assertEqual(book1.first_authors, [self.author11, self.author12]) self.assertEqual(book2.first_authors, [self.author21]) self.assertEqual( book1.first_authors[0].happy_place, [self.author1_address1] ) self.assertEqual(book1.first_authors[1].happy_place, []) self.assertEqual( book2.first_authors[0].happy_place, [self.author2_address1] ) def test_prefetch_reverse_foreign_key(self): with self.assertNumQueries(2): (bookwithyear1,) = BookWithYear.objects.prefetch_related("bookreview_set") with self.assertNumQueries(0): self.assertCountEqual( bookwithyear1.bookreview_set.all(), [self.bookreview1] ) with self.assertNumQueries(0): prefetch_related_objects([bookwithyear1], "bookreview_set") def test_add_clears_prefetched_objects(self): bookwithyear = BookWithYear.objects.get(pk=self.bookwithyear1.pk) prefetch_related_objects([bookwithyear], "bookreview_set") self.assertCountEqual(bookwithyear.bookreview_set.all(), [self.bookreview1]) new_review = BookReview.objects.create() bookwithyear.bookreview_set.add(new_review) self.assertCountEqual( bookwithyear.bookreview_set.all(), [self.bookreview1, new_review] ) def test_remove_clears_prefetched_objects(self): bookwithyear = BookWithYear.objects.get(pk=self.bookwithyear1.pk) prefetch_related_objects([bookwithyear], "bookreview_set") self.assertCountEqual(bookwithyear.bookreview_set.all(), [self.bookreview1]) bookwithyear.bookreview_set.remove(self.bookreview1) self.assertCountEqual(bookwithyear.bookreview_set.all(), []) class ReadPrefetchedObjectsCacheTests(TestCase): @classmethod def setUpTestData(cls): cls.book1 = Book.objects.create(title="Les confessions Volume I") cls.book2 = Book.objects.create(title="Candide") cls.author1 = AuthorWithAge.objects.create( name="Rousseau", first_book=cls.book1, age=70 ) cls.author2 = AuthorWithAge.objects.create( name="Voltaire", first_book=cls.book2, age=65 ) cls.book1.authors.add(cls.author1) cls.book2.authors.add(cls.author2) FavoriteAuthors.objects.create(author=cls.author1, likes_author=cls.author2) def test_retrieves_results_from_prefetched_objects_cache(self): """ When intermediary results are prefetched without a destination attribute, they are saved in the RelatedManager's cache (_prefetched_objects_cache). prefetch_related() uses this cache (#27554). """ authors = AuthorWithAge.objects.prefetch_related( Prefetch( "author", queryset=Author.objects.prefetch_related( # Results are saved in the RelatedManager's cache # (_prefetched_objects_cache) and do not replace the # RelatedManager on Author instances (favorite_authors) Prefetch("favorite_authors__first_book"), ), ), ) with self.assertNumQueries(4): # AuthorWithAge -> Author -> FavoriteAuthors, Book self.assertSequenceEqual(authors, [self.author1, self.author2]) class NestedPrefetchTests(TestCase): @classmethod def setUpTestData(cls): house = House.objects.create(name="Big house", address="123 Main St") cls.room = Room.objects.create(name="Kitchen", house=house) def test_nested_prefetch_is_not_overwritten_by_related_object(self): """ The prefetched relationship is used rather than populating the reverse relationship from the parent, when prefetching a set of child objects related to a set of parent objects and the child queryset itself specifies a prefetch back to the parent. """ queryset = House.objects.only("name").prefetch_related( Prefetch( "rooms", queryset=Room.objects.prefetch_related( Prefetch("house", queryset=House.objects.only("address")), ), ), ) with self.assertNumQueries(3): house = queryset.first() self.assertIs(Room.house.is_cached(self.room), True) with self.assertNumQueries(0): house.rooms.first().house.address class PrefetchLimitTests(TestDataMixin, TestCase): @skipUnlessDBFeature("supports_over_clause") def test_m2m_forward(self): authors = Author.objects.all() # Meta.ordering with self.assertNumQueries(3): books = list( Book.objects.prefetch_related( Prefetch("authors", authors), Prefetch("authors", authors[1:], to_attr="authors_sliced"), ) ) for book in books: with self.subTest(book=book): self.assertEqual(book.authors_sliced, list(book.authors.all())[1:]) @skipUnlessDBFeature("supports_over_clause") def test_m2m_reverse(self): books = Book.objects.order_by("title") with self.assertNumQueries(3): authors = list( Author.objects.prefetch_related( Prefetch("books", books), Prefetch("books", books[1:2], to_attr="books_sliced"), ) ) for author in authors: with self.subTest(author=author): self.assertEqual(author.books_sliced, list(author.books.all())[1:2]) @skipUnlessDBFeature("supports_over_clause") def test_foreignkey_reverse(self): authors = Author.objects.order_by("-name") with self.assertNumQueries(3): books = list( Book.objects.prefetch_related( Prefetch( "first_time_authors", authors, ), Prefetch( "first_time_authors", authors[1:], to_attr="first_time_authors_sliced", ), ) ) for book in books: with self.subTest(book=book): self.assertEqual( book.first_time_authors_sliced, list(book.first_time_authors.all())[1:], ) @skipUnlessDBFeature("supports_over_clause") def test_reverse_ordering(self): authors = Author.objects.reverse() # Reverse Meta.ordering with self.assertNumQueries(3): books = list( Book.objects.prefetch_related( Prefetch("authors", authors), Prefetch("authors", authors[1:], to_attr="authors_sliced"), ) ) for book in books: with self.subTest(book=book): self.assertEqual(book.authors_sliced, list(book.authors.all())[1:]) @skipIfDBFeature("supports_over_clause") def test_window_not_supported(self): authors = Author.objects.all() msg = ( "Prefetching from a limited queryset is only supported on backends that " "support window functions." ) with self.assertRaisesMessage(NotSupportedError, msg): list(Book.objects.prefetch_related(Prefetch("authors", authors[1:])))