Automerge from mysql-5.1-bugteam to mysql-trunk-merge.

1 files changed, 13 insertions, 1 deletions

diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 47426d28eb5..bdd32718a08 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -7231,7 +7231,19 @@ remove_const(JOIN *join,ORDER *first_order, COND *cond,
   for (order=first_order; order ; order=order->next)
   {
     table_map order_tables=order->item[0]->used_tables();
-    if (order->item[0]->with_sum_func)
+    if (order->item[0]->with_sum_func ||
+        /*
+          If the outer table of an outer join is const (either by itself or
+          after applying WHERE condition), grouping on a field from such a
+          table will be optimized away and filesort without temporary table
+          will be used unless we prevent that now. Filesort is not fit to
+          handle joins and the join condition is not applied. We can't detect
+          the case without an expensive test, however, so we force temporary
+          table for all queries containing more than one table, ROLLUP, and an
+          outer join.
+         */
+        (join->tables > 1 && join->rollup.state == ROLLUP::STATE_INITED &&
+        join->outer_join))
       *simple_order=0;				// Must do a temp table to sort
     else if (!(order_tables & not_const_tables))
     {