from unittest import mock
from django.contrib.contenttypes.models import ContentType
from django.core.exceptions import ObjectDoesNotExist
from django.db import 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
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.all().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'],
)
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.all().prefetch_related('house')
lst1 = self.traverse_qs(rooms, [['house', 'owner']])
with self.assertNumQueries(2):
rooms = Room.objects.all().prefetch_related(Prefetch('house', queryset=houses.all()))
lst2 = self.traverse_qs(rooms, [['house', 'owner']])
self.assertEqual(lst1, lst2)
with self.assertNumQueries(2):
houses = House.objects.select_related('owner')
rooms = Room.objects.all().prefetch_related(Prefetch('house', queryset=houses.all(), to_attr='house_attr'))
lst2 = self.traverse_qs(rooms, [['house_attr', 'owner']])
self.assertEqual(lst1, lst2)
room = Room.objects.all().prefetch_related(
Prefetch('house', queryset=houses.filter(address='DoesNotExist'))
).first()
with self.assertRaises(ObjectDoesNotExist):
getattr(room, 'house')
room = Room.objects.all().prefetch_related(
Prefetch('house', queryset=houses.filter(address='DoesNotExist'), to_attr='house_attr')
).first()
self.assertIsNone(room.house_attr)
rooms = Room.objects.all().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.all().prefetch_related('main_room_of')
lst1 = self.traverse_qs(rooms, [['main_room_of', 'owner']])
with self.assertNumQueries(2):
rooms = Room.objects.all().prefetch_related(Prefetch('main_room_of', queryset=houses.all()))
lst2 = self.traverse_qs(rooms, [['main_room_of', 'owner']])
self.assertEqual(lst1, lst2)
with self.assertNumQueries(2):
rooms = list(
Room.objects.all().prefetch_related(
Prefetch('main_room_of', queryset=houses.all(), 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()))
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.assertEqual(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.all().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)\n"
"Sense 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)\n"
"Sense 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)\n"
"Sense 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])