'Regression test for #10362
It is possible to call update() and only change a field in
an ancestor model.'

def test_queryset_update_on_parent_model(self):

    article = ArticleWithAuthor.objects.create(author='fred', headline='Hey    there!', pub_date=datetime.datetime(2009, 3, 1, 8, 0, 0))
    update = ArticleWithAuthor.objects.filter(author='fred').update(headline='Oh,    no!')
    self.assertEqual(update, 1)
    update = ArticleWithAuthor.objects.filter(pk=article.pk).update(headline='Oh,    no!')
    self.assertEqual(update, 1)
    derivedm1 = DerivedM.objects.create(customPK=44, base_name='b1', derived_name='d1')
    self.assertEqual(derivedm1.customPK, 44)
    self.assertEqual(derivedm1.base_name, 'b1')
    self.assertEqual(derivedm1.derived_name, 'd1')
    derivedms = list(DerivedM.objects.all())
    self.assertEqual(derivedms, [derivedm1])
