Fixed #12822: Don't copy the _aggregate_select_cache when cloning a query set,

as that can lead to incorrect SQL being generated for the query. Thanks to mat
for the report and test, tobias for the fix, and Alex for review.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@12830 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -240,10 +240,12 @@ class Query(object):
             obj.aggregate_select_mask = None
         else:
             obj.aggregate_select_mask = self.aggregate_select_mask.copy()
-        if self._aggregate_select_cache is None:
+        # _aggregate_select_cache cannot be copied, as doing so breaks the
+        # (necessary) state in which both aggregates and
+        # _aggregate_select_cache point to the same underlying objects.
+        # It will get re-populated in the cloned queryset the next time it's
+        # used.
         obj._aggregate_select_cache = None
-        else:
-            obj._aggregate_select_cache = self._aggregate_select_cache.copy()
         obj.max_depth = self.max_depth
         obj.extra = self.extra.copy()
         if self.extra_select_mask is None:

tests/regressiontests/aggregation_regress/tests.py

@@ -0,0 +1,48 @@
+from django.test import TestCase
+from django.db.models import Max
+
+from regressiontests.aggregation_regress.models import *
+
+
+class AggregationTests(TestCase):
+
+    def test_aggregates_in_where_clause(self):
+        """
+        Regression test for #12822: DatabaseError: aggregates not allowed in
+        WHERE clause
+
+        Tests that the subselect works and returns results equivalent to a
+        query with the IDs listed.
+        
+        Before the corresponding fix for this bug, this test passed in 1.1 and
+        failed in 1.2-beta (trunk).
+        """
+        qs = Book.objects.values('contact').annotate(Max('id'))
+        qs = qs.order_by('contact').values_list('id__max', flat=True)
+        # don't do anything with the queryset (qs) before including it as a
+        # subquery
+        books = Book.objects.order_by('id')
+        qs1 = books.filter(id__in=qs)
+        qs2 = books.filter(id__in=list(qs))
+        self.assertEqual(list(qs1), list(qs2))
+
+    def test_aggregates_in_where_clause_pre_eval(self):
+        """
+        Regression test for #12822: DatabaseError: aggregates not allowed in
+        WHERE clause
+
+        Same as the above test, but evaluates the queryset for the subquery
+        before it's used as a subquery.
+        
+        Before the corresponding fix for this bug, this test failed in both
+        1.1 and 1.2-beta (trunk).
+        """
+        qs = Book.objects.values('contact').annotate(Max('id'))
+        qs = qs.order_by('contact').values_list('id__max', flat=True)
+        # force the queryset (qs) for the subquery to be evaluated in its
+        # current state
+        list(qs)
+        books = Book.objects.order_by('id')
+        qs1 = books.filter(id__in=qs)
+        qs2 = books.filter(id__in=list(qs))
+        self.assertEqual(list(qs1), list(qs2))