Fixed #15709 - Duplicated group_by condition

Thanks to ziangsong for report, and to mk for the patch

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16180 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/compiler.py

@@ -493,7 +493,11 @@ class SQLCompiler(object):
                 params.extend(extra_params)
             cols = (group_by + self.query.select +
                 self.query.related_select_cols + extra_selects)
+            seen = set()
             for col in cols:
+                if col in seen:
+                    continue
+                seen.add(col)
                 if isinstance(col, (list, tuple)):
                     result.append('%s.%s' % (qn(col[0]), qn(col[1])))
                 elif hasattr(col, 'as_sql'):

tests/regressiontests/aggregation_regress/tests.py

@@ -462,6 +462,12 @@ class AggregationTests(TestCase):
             lambda b: b.name
         )
 
+        # Regression for #15709 - Ensure each group_by field only exists once
+        # per query
+        qs = Book.objects.values('publisher').annotate(max_pages=Max('pages')).order_by()
+        grouping, gb_params = qs.query.get_compiler(qs.db).get_grouping()
+        self.assertEqual(len(grouping), 1)
+
     def test_duplicate_alias(self):
         # Regression for #11256 - duplicating a default alias raises ValueError.
         self.assertRaises(ValueError, Book.objects.all().annotate, Avg('authors__age'), authors__age__avg=Avg('authors__age'))