Fixed #9406 -- Ensure that each database column is only represented once in the

"ORDER BY" clause of an SQL statement.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@9251 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -621,6 +621,12 @@ class Query(object):
             asc, desc = ORDER_DIR['ASC']
         else:
             asc, desc = ORDER_DIR['DESC']
+
+        # It's possible, due to model inheritance, that normal usage might try
+        # to include the same field more than once in the ordering. We track
+        # the table/column pairs we use and discard any after the first use.
+        processed_pairs = set()
+
         for field in ordering:
             if field == '?':
                 result.append(self.connection.ops.random_function_sql())
@@ -638,7 +644,9 @@ class Query(object):
                 # on verbatim.
                 col, order = get_order_dir(field, asc)
                 table, col = col.split('.', 1)
+                if (table, col) not in processed_pairs:
                     elt = '%s.%s' % (qn(table), col)
+                    processed_pairs.add((table, col))
                     if not distinct or elt in select_aliases:
                         result.append('%s %s' % (elt, order))
             elif get_order_dir(field)[0] not in self.extra_select:
@@ -646,7 +654,9 @@ class Query(object):
                 # '-field1__field2__field', etc.
                 for table, col, order in self.find_ordering_name(field,
                         self.model._meta, default_order=asc):
+                    if (table, col) not in processed_pairs:
                         elt = '%s.%s' % (qn(table), qn2(col))
+                        processed_pairs.add((table, col))
                         if distinct and elt not in select_aliases:
                             ordering_aliases.append(elt)
                         result.append('%s %s' % (elt, order))

tests/regressiontests/model_inheritance_regress/models.py

@@ -257,4 +257,14 @@ DoesNotExist: ArticleWithAuthor matching query does not exist.
 # without error.
 >>> _ = QualityControl.objects.create(headline="Problems in Django", pub_date=datetime.datetime.now(), quality=10, assignee="adrian")
 
+# Ordering should not include any database column more than once (this is most
+# likely to ocurr naturally with model inheritance, so we check it here).
+# Regression test for #9390. This necessarily pokes at the SQL string for the
+# query, since the duplicate problems are only apparent at that late stage.
+>>> sql = ArticleWithAuthor.objects.order_by('pub_date', 'pk').query.as_sql()[0]
+>>> fragment = sql[sql.find('ORDER BY'):]
+>>> pos = fragment.find('pub_date')
+>>> fragment.find('pub_date', pos + 1) == -1
+True
+
 """}