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Fixed #18949 -- Improve performance of model_to_dict with many-to-many

When calling model_to_dict, improve performance of the generated SQL by
using values_list to determine primary keys of many to many objects. Add
a specific test for this function, test_model_to_dict_many_to_many

Thanks to brian for the original report and suggested fix.
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aisipos committed Nov 4, 2012
1 parent 8d3f932 commit e44ab5bb4fd3aa826ca4243a8ea9fd7125800da2
Showing with 37 additions and 1 deletion.
  1. +1 −1 django/forms/
  2. +36 −0 tests/modeltests/model_forms/
@@ -126,7 +126,7 @@ def model_to_dict(instance, fields=None, exclude=None):
data[] = []
# MultipleChoiceWidget needs a list of pks, not object instances.
data[] = [ for obj in f.value_from_object(instance)]
data[] = list(f.value_from_object(instance).values_list('pk', flat=True))
data[] = f.value_from_object(instance)
return data
@@ -561,6 +561,42 @@ def test_unique_for_date_with_nullable_date(self):
"slug": "Django 1.0"}, instance=p)
class ModelToDictTests(TestCase):
Tests for forms.models.model_to_dict
def test_model_to_dict_many_to_many(self):
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:
writer = Writer(name='Test writer')
art = Article(
headline='Test article',
slug='test-article',, 1, 4),
for c in categories:
with self.assertNumQueries(1):
d = model_to_dict(art)
#Ensure all many-to-many categories appear in model_to_dict
for c in categories:
self.assertIn(, 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)

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