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Code Issues 32 Releases Wiki Activity

Fixed #17003 - prefetch_related should support foreign keys/one-to-one

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Support for `GenericForeignKey` is also included.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16939 bcc190cf-cafb-0310-a4f2-bffc1f526a37
This commit is contained in:
Luke Plant
2011-10-07 16:05:53 +00:00
parent 672f2db24a
commit 052a011ee6
8 changed files with 366 additions and 119 deletions
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6
tests/modeltests/prefetch_related/models.py
View File

@@ -104,13 +104,17 @@ class Department(models.Model):
ordering = ['id']
## Generic relation tests
## GenericRelation/GenericForeignKey tests
class TaggedItem(models.Model):
tag = models.SlugField()
content_type = models.ForeignKey(ContentType, related_name="taggeditem_set2")
object_id = models.PositiveIntegerField()
content_object = generic.GenericForeignKey('content_type', 'object_id')
created_by_ct = models.ForeignKey(ContentType, null=True,
related_name='taggeditem_set3')
created_by_fkey = models.PositiveIntegerField(null=True)
created_by = generic.GenericForeignKey('created_by_ct', 'created_by_fkey',)
def __unicode__(self):
return self.tag

104
tests/modeltests/prefetch_related/tests.py
View File

@@ -54,6 +54,13 @@ class PrefetchRelatedTests(TestCase):
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):
lists = [list(b.first_time_authors.all())
@@ -175,12 +182,12 @@ class PrefetchRelatedTests(TestCase):
self.assertTrue('prefetch_related' in str(cm.exception))
def test_invalid_final_lookup(self):
qs = Book.objects.prefetch_related('authors__first_book')
qs = Book.objects.prefetch_related('authors__name')
with self.assertRaises(ValueError) as cm:
list(qs)
self.assertTrue('prefetch_related' in str(cm.exception))
self.assertTrue("first_book" in str(cm.exception))
self.assertTrue("name" in str(cm.exception))
class DefaultManagerTests(TestCase):
@@ -222,39 +229,68 @@ class DefaultManagerTests(TestCase):
class GenericRelationTests(TestCase):
def test_traverse_GFK(self):
"""
Test that we can traverse a 'content_object' with prefetch_related()
"""
# In fact, there is no special support for this in prefetch_related code
# - we can traverse any object that will lead us to objects that have
# related managers.
def setUp(self):
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)
book1.read_by.add(reader1, reader2)
book2.read_by.add(reader2)
book3.read_by.add(reader3)
TaggedItem.objects.create(tag="awesome", content_object=book1)
TaggedItem.objects.create(tag="awesome", content_object=book2)
self.book1, self.book2, self.book3 = book1, book2, book3
self.reader1, self.reader2, self.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="stupid", 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_traverse_GFK(self):
"""
Test that we can traverse a 'content_object' 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 4 queries - 1 for main query, 2 for each access to
# 'content_object' because these can't be handled by select_related, and
# 1 for the 'read_by' relation.
with self.assertNumQueries(4):
# 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.select_related('content_type').prefetch_related('content_object__read_by').filter(tag='awesome').filter(content_type=ct, tag='awesome')
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"])
qs = TaggedItem.objects.filter(content_type=ct, tag='awesome').prefetch_related('content_object__read_by')
readers_of_awesome_books = set([r.name for tag in qs
for r in tag.content_object.read_by.all()])
self.assertEqual(readers_of_awesome_books, set(["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):
b = Bookmark.objects.create(url='http://www.djangoproject.com/')
@@ -311,9 +347,14 @@ class MultiTableInheritanceTest(TestCase):
self.assertEquals(lst, lst2)
def test_parent_link_prefetch(self):
with self.assertRaises(ValueError) as cm:
qs = list(AuthorWithAge.objects.prefetch_related('author'))
self.assertTrue('prefetch_related' in str(cm.exception))
with self.assertNumQueries(2):
[a.author for a in AuthorWithAge.objects.prefetch_related('author')]
def test_child_link_prefetch(self):
with self.assertNumQueries(2):
l = [a.authorwithage for a in Author.objects.prefetch_related('authorwithage')]
self.assertEqual(l, [a.authorwithage for a in Author.objects.all()])
class ForeignKeyToFieldTest(TestCase):
@@ -406,6 +447,8 @@ class NullableTest(TestCase):
worker2 = 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 []
@@ -416,3 +459,16 @@ class NullableTest(TestCase):
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)