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django/tests/prefetch_related/tests.py

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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, ignore_warnings
from django.utils.deprecation import RemovedInDjango50Warning
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],
)
@ignore_warnings(category=RemovedInDjango50Warning)
def test_m2m_prefetching_iterator_without_chunks(self):
# prefetch_related() is ignored.
with self.assertNumQueries(5):
authors = [
b.authors.first()
for b in Book.objects.prefetch_related("authors").iterator()
]
self.assertEqual(
authors,
[self.author1, self.author1, self.author3, self.author4],
)
def test_m2m_prefetching_iterator_without_chunks_warning(self):
msg = (
"Using QuerySet.iterator() after prefetch_related() without "
"specifying chunk_size is deprecated."
)
with self.assertWarnsMessage(RemovedInDjango50Warning, 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:])))
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