Bug #21302: Result not properly sorted when using an ORDER BY on a second

             table in a join
 The optimizer removes redundant columns in ORDER BY. It is considering 
redundant every reference to const table column, e.g b in :
create table t1 (a int, b int, primary key(a)); 
select 1 from t1 order by b where a = 1

But it must not remove references to const table columns if the 
const table is an outer table because there still can be 2 values :
the const value and NULL. e.g.:
create table t1 (a int, b int, primary key(a));
select t2.b c from t1 left join t1 t2 on (t1.a = t2.a and t2.a = 5) 
  order by c;

1 files changed, 1 insertions, 1 deletions

diff --git a/mysql-test/r/join_outer.result b/mysql-test/r/join_outer.result
index eae023813b5..7fc1f8b6489 100644
--- a/mysql-test/r/join_outer.result
+++ b/mysql-test/r/join_outer.result
@@ -735,7 +735,7 @@ explain select s.*, '*', m.*, (s.match_1_h - m.home) UUX from
 (t2 s left join t1 m on m.match_id = 1) 
 order by m.match_id desc;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	s	ALL	NULL	NULL	NULL	NULL	10	
+1	SIMPLE	s	ALL	NULL	NULL	NULL	NULL	10	Using temporary; Using filesort
 1	SIMPLE	m	const	match_id,match_id_2	match_id	1	const	1	
 explain select s.*, '*', m.*, (s.match_1_h - m.home) UUX from 
 (t2 s left join t1 m on m.match_id = 1)