Fixed #12328 -- Corrected the handling of subqueries with ordering and slicing, especially when used in delete subqueries. Thanks to Walter Doekes for the report.

This fixes a feature that isn't available under MySQL and Oracle (Refs #10099).

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12912 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/queries/tests.py

@@ -1,27 +1,65 @@
 import unittest
-from models import Tag, Annotation
+
+from django.db import DatabaseError, connections, DEFAULT_DB_ALIAS
 from django.db.models import Count
+from django.test import TestCase
+
+from models import Tag, Annotation, DumbCategory
 
 class QuerysetOrderedTests(unittest.TestCase):
     """
     Tests for the Queryset.ordered attribute.
     """
-    
+
     def test_no_default_or_explicit_ordering(self):
         self.assertEqual(Annotation.objects.all().ordered, False)
 
     def test_cleared_default_ordering(self):
         self.assertEqual(Tag.objects.all().ordered, True)
         self.assertEqual(Tag.objects.all().order_by().ordered, False)
-        
+
     def test_explicit_ordering(self):
         self.assertEqual(Annotation.objects.all().order_by('id').ordered, True)
-        
+
     def test_order_by_extra(self):
         self.assertEqual(Annotation.objects.all().extra(order_by=['id']).ordered, True)
-        
+
     def test_annotated_ordering(self):
         qs = Annotation.objects.annotate(num_notes=Count('notes'))
         self.assertEqual(qs.ordered, False)
         self.assertEqual(qs.order_by('num_notes').ordered, True)
-        
+
+
+class SubqueryTests(TestCase):
+    def setUp(self):
+        DumbCategory.objects.create(id=1)
+        DumbCategory.objects.create(id=2)
+        DumbCategory.objects.create(id=3)
+
+    def test_ordered_subselect(self):
+        "Subselects honor any manual ordering"
+        try:
+            query = DumbCategory.objects.filter(id__in=DumbCategory.objects.order_by('-id')[0:2])
+            self.assertEquals(set(query.values_list('id', flat=True)), set([2,3]))
+
+            query = DumbCategory.objects.filter(id__in=DumbCategory.objects.order_by('-id')[:2])
+            self.assertEquals(set(query.values_list('id', flat=True)), set([2,3]))
+
+            query = DumbCategory.objects.filter(id__in=DumbCategory.objects.order_by('-id')[2:])
+            self.assertEquals(set(query.values_list('id', flat=True)), set([1]))
+        except DatabaseError:
+            # Oracle and MySQL both have problems with sliced subselects.
+            # This prevents us from even evaluating this test case at all.
+            # Refs #10099
+            self.assertFalse(connections[DEFAULT_DB_ALIAS].features.allow_sliced_subqueries)
+
+    def test_sliced_delete(self):
+        "Delete queries can safely contain sliced subqueries"
+        try:
+            DumbCategory.objects.filter(id__in=DumbCategory.objects.order_by('-id')[0:1]).delete()
+            self.assertEquals(set(DumbCategory.objects.values_list('id', flat=True)), set([1,2]))
+        except DatabaseError:
+            # Oracle and MySQL both have problems with sliced subselects.
+            # This prevents us from even evaluating this test case at all.
+            # Refs #10099
+            self.assertFalse(connections[DEFAULT_DB_ALIAS].features.allow_sliced_subqueries)