From 539e3693d4712b249a95cfad8cfdeecdad1777a6 Mon Sep 17 00:00:00 2001 From: Jim Bailey Date: Fri, 1 Nov 2013 12:55:35 +0000 Subject: Fixed #20849 -- ModelForms do not work well with prefetch_related. model_to_dict() (used when rendering forms) queries the database to get the list of primary keys for ManyToMany fields. This is unnecessary if the field queryset has been prefetched, all the keys are already in memory and can be obtained with a simple iteration. --- tests/model_forms/tests.py | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) (limited to 'tests/model_forms') diff --git a/tests/model_forms/tests.py b/tests/model_forms/tests.py index ddc7a4ceef..4b6c3b36ad 100644 --- a/tests/model_forms/tests.py +++ b/tests/model_forms/tests.py @@ -824,6 +824,41 @@ class ModelToDictTests(TestCase): # Ensure many-to-many relation appears as a list self.assertIsInstance(d['categories'], list) + def test_reuse_prefetched(self): + # model_to_dict should not hit the database if it can reuse + # the data populated by prefetch_related. + categories = [ + Category(name='TestName1', slug='TestName1', url='url1'), + Category(name='TestName2', slug='TestName2', url='url2'), + Category(name='TestName3', slug='TestName3', url='url3') + ] + for c in categories: + c.save() + writer = Writer(name='Test writer') + writer.save() + + art = Article( + headline='Test article', + slug='test-article', + pub_date=datetime.date(1988, 1, 4), + writer=writer, + article='Hello.' + ) + art.save() + for c in categories: + art.categories.add(c) + + art = Article.objects.prefetch_related('categories').get(pk=art.pk) + + with self.assertNumQueries(0): + d = model_to_dict(art) + + #Ensure all many-to-many categories appear in model_to_dict + for c in categories: + self.assertIn(c.pk, d['categories']) + #Ensure many-to-many relation appears as a list + self.assertIsInstance(d['categories'], list) + class OldFormForXTests(TestCase): def test_base_form(self): self.assertEqual(Category.objects.count(), 0) -- cgit v1.3