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118 lines
4.6 KiB
Python
118 lines
4.6 KiB
Python
from django.db.models import Prefetch, prefetch_related_objects
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from django.test import TestCase
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from .models import Author, Book, Reader
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class PrefetchRelatedObjectsTests(TestCase):
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"""
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Since prefetch_related_objects() is just the inner part of
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prefetch_related(), only do basic tests to ensure its API hasn't changed.
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"""
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@classmethod
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def setUpTestData(cls):
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cls.book1 = Book.objects.create(title='Poems')
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cls.book2 = Book.objects.create(title='Jane Eyre')
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cls.book3 = Book.objects.create(title='Wuthering Heights')
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cls.book4 = Book.objects.create(title='Sense and Sensibility')
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cls.author1 = Author.objects.create(name='Charlotte', first_book=cls.book1)
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cls.author2 = Author.objects.create(name='Anne', first_book=cls.book1)
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cls.author3 = Author.objects.create(name='Emily', first_book=cls.book1)
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cls.author4 = Author.objects.create(name='Jane', first_book=cls.book4)
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cls.book1.authors.add(cls.author1, cls.author2, cls.author3)
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cls.book2.authors.add(cls.author1)
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cls.book3.authors.add(cls.author3)
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cls.book4.authors.add(cls.author4)
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cls.reader1 = Reader.objects.create(name='Amy')
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cls.reader2 = Reader.objects.create(name='Belinda')
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cls.reader1.books_read.add(cls.book1, cls.book4)
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cls.reader2.books_read.add(cls.book2, cls.book4)
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def test_unknown(self):
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book1 = Book.objects.get(id=self.book1.id)
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with self.assertRaises(AttributeError):
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prefetch_related_objects([book1], 'unknown_attribute')
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def test_m2m_forward(self):
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book1 = Book.objects.get(id=self.book1.id)
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with self.assertNumQueries(1):
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prefetch_related_objects([book1], 'authors')
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with self.assertNumQueries(0):
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self.assertCountEqual(book1.authors.all(), [self.author1, self.author2, self.author3])
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def test_m2m_reverse(self):
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author1 = Author.objects.get(id=self.author1.id)
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with self.assertNumQueries(1):
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prefetch_related_objects([author1], 'books')
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with self.assertNumQueries(0):
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self.assertCountEqual(author1.books.all(), [self.book1, self.book2])
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def test_foreignkey_forward(self):
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authors = list(Author.objects.all())
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with self.assertNumQueries(1):
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prefetch_related_objects(authors, 'first_book')
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with self.assertNumQueries(0):
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[author.first_book for author in authors]
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def test_foreignkey_reverse(self):
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books = list(Book.objects.all())
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with self.assertNumQueries(1):
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prefetch_related_objects(books, 'first_time_authors')
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with self.assertNumQueries(0):
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[list(book.first_time_authors.all()) for book in books]
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def test_m2m_then_m2m(self):
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"""A m2m can be followed through another m2m."""
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authors = list(Author.objects.all())
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with self.assertNumQueries(2):
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prefetch_related_objects(authors, 'books__read_by')
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with self.assertNumQueries(0):
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self.assertEqual(
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[
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[[str(r) for r in b.read_by.all()] for b in a.books.all()]
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for a in authors
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],
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[
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[['Amy'], ['Belinda']], # Charlotte - Poems, Jane Eyre
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[['Amy']], # Anne - Poems
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[['Amy'], []], # Emily - Poems, Wuthering Heights
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[['Amy', 'Belinda']], # Jane - Sense and Sense
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]
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)
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def test_prefetch_object(self):
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book1 = Book.objects.get(id=self.book1.id)
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with self.assertNumQueries(1):
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prefetch_related_objects([book1], Prefetch('authors'))
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with self.assertNumQueries(0):
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self.assertCountEqual(book1.authors.all(), [self.author1, self.author2, self.author3])
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def test_prefetch_object_to_attr(self):
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book1 = Book.objects.get(id=self.book1.id)
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with self.assertNumQueries(1):
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prefetch_related_objects([book1], Prefetch('authors', to_attr='the_authors'))
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with self.assertNumQueries(0):
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self.assertCountEqual(book1.the_authors, [self.author1, self.author2, self.author3])
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def test_prefetch_queryset(self):
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book1 = Book.objects.get(id=self.book1.id)
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with self.assertNumQueries(1):
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prefetch_related_objects(
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[book1],
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Prefetch('authors', queryset=Author.objects.filter(id__in=[self.author1.id, self.author2.id]))
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)
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with self.assertNumQueries(0):
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self.assertCountEqual(book1.authors.all(), [self.author1, self.author2])
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