If an SQL query doesn't specify any ordering, avoid the implicit sort

that happens with MySQL when a "GROUP BY" clause is included. This is a
backend-specific operation, so any other databases requiring similar
encouragement can have a function added to their own backend code.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@9637 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -288,6 +288,8 @@ class BaseQuery(object):
         if self.group_by:
             grouping = self.get_grouping()
             result.append('GROUP BY %s' % ', '.join(grouping))
+            if not ordering:
+                ordering = self.connection.ops.force_no_ordering()
 
         if self.having:
             having, h_params = self.get_having()