from django.test import TestCase

from regressiontests.null_fk_ordering.models import *

class NullFkOrderingTests(TestCase):

    def test_ordering_across_null_fk(self):

        """

        Regression test for #7512

        ordering across nullable Foreign Keys shouldn't exclude results

        """

        author_1 = Author.objects.create(name='Tom Jones')

        author_2 = Author.objects.create(name='Bob Smith')

        article_1 = Article.objects.create(title='No author on this article')

        article_2 = Article.objects.create(author=author_1, title='This article written by Tom Jones')

        article_3 = Article.objects.create(author=author_2, title='This article written by Bob Smith')

        # We can't compare results directly (since different databases sort NULLs to

        # different ends of the ordering), but we can check that all results are

        # returned.

        self.assertTrue(len(list(Article.objects.all())) == 3)

        s = SystemInfo.objects.create(system_name='System Info')

        f = Forum.objects.create(system_info=s, forum_name='First forum')

        p = Post.objects.create(forum=f, title='First Post')

        c1 = Comment.objects.create(post=p, comment_text='My first comment')

        c2 = Comment.objects.create(comment_text='My second comment')

        s2 = SystemInfo.objects.create(system_name='More System Info')

        f2 = Forum.objects.create(system_info=s2, forum_name='Second forum')

        p2 = Post.objects.create(forum=f2, title='Second Post')

        c3 = Comment.objects.create(comment_text='Another first comment')

        c4 = Comment.objects.create(post=p2, comment_text='Another second comment')

        # We have to test this carefully. Some databases sort NULL values before

        # everything else, some sort them afterwards. So we extract the ordered list

        # and check the length. Before the fix, this list was too short (some values

        # were omitted).

        self.assertTrue(len(list(Comment.objects.all())) == 4)