bug #27531: 5.1 part of the fix:

 - added join cache indication in EXPLAIN (Extra column).
 - prefer filesort over full scan over 
   index for ORDER BY (because it's faster).
 - when switching from REF to RANGE because
   RANGE uses longer key turn off sort on
   the head table only as the resulting 
   RANGE access is a candidate for join cache
   and we don't want to disable it by sorting
   on the first table only. 


mysql-test/r/archive_gis.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/compress.result:
  bug #27531:
   - join cache in EXPLAIN. 
   - prefer filesort over full scan over index for ORDER BY.
mysql-test/r/ctype_utf8.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/derived.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/distinct.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/func_group.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/func_group_innodb.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/gis.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/greedy_optimizer.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/group_by.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/group_min_max.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/index_merge_myisam.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/information_schema.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/innodb_gis.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/innodb_mysql.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/join.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/join_nested.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/key_diff.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/myisam.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/ndb_condition_pushdown.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/ndb_gis.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/range.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/row.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/select.result:
  bug #27531:
   - join cache in EXPLAIN.
   - prefer filesort over full scan over index for ORDER BY.
mysql-test/r/ssl.result:
  bug #27531:
   - join cache in EXPLAIN.
   - prefer filesort over full scan over index for ORDER BY.
mysql-test/r/ssl_compress.result:
  bug #27531:
   - join cache in EXPLAIN.
   - prefer filesort over full scan over index for ORDER BY.
mysql-test/r/subselect.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/subselect3.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/union.result:
  bug #27531: join cache in EXPLAIN
mysql-test/r/view.result:
  bug #27531: join cache in EXPLAIN
sql/sql_select.cc:
  bug #27531:
   - join cache in EXPLAIN.
   - prefer filesort over full scan over
     index for ORDER BY.
   - disable sorting on the first table only
     when switching from REF to RANGE.

1 files changed, 8 insertions, 8 deletions

diff --git a/mysql-test/r/range.result b/mysql-test/r/range.result
index d9efe21c5d0..c2cb7426a74 100644
--- a/mysql-test/r/range.result
+++ b/mysql-test/r/range.result
@@ -220,27 +220,27 @@ insert into t1 (x) values (1),(2),(3),(4),(5),(6),(7),(8),(9);
 update t1 set y=x;
 explain select * from t1, t1 t2 where t1.y = 8 and t2.x between 7 and t1.y+0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	y	y	5	const	1	Using where
+1	SIMPLE	t1	ref	y	y	5	const	1	Using where; Using join cache
 1	SIMPLE	t2	range	x	x	5	NULL	2	Using where
 explain select * from t1, t1 t2 where t1.y = 8 and t2.x >= 7 and t2.x <= t1.y+0;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	y	y	5	const	1	Using where
+1	SIMPLE	t1	ref	y	y	5	const	1	Using where; Using join cache
 1	SIMPLE	t2	range	x	x	5	NULL	2	Using where
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x between t1.y-1 and t1.y+1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	y	y	5	const	1	Using where
+1	SIMPLE	t1	ref	y	y	5	const	1	Using where; Using join cache
 1	SIMPLE	t2	range	x	x	5	NULL	3	Using where
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x >= t1.y-1 and t2.x <= t1.y+1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	y	y	5	const	1	Using where
+1	SIMPLE	t1	ref	y	y	5	const	1	Using where; Using join cache
 1	SIMPLE	t2	range	x	x	5	NULL	3	Using where
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x between 0 and t1.y;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	y	y	5	const	1	Using where
+1	SIMPLE	t1	ref	y	y	5	const	1	Using where; Using join cache
 1	SIMPLE	t2	range	x	x	5	NULL	2	Using where
 explain select * from t1, t1 t2 where t1.y = 2 and t2.x >= 0 and t2.x <= t1.y;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ref	y	y	5	const	1	Using where
+1	SIMPLE	t1	ref	y	y	5	const	1	Using where; Using join cache
 1	SIMPLE	t2	range	x	x	5	NULL	2	Using where
 explain select count(*) from t1 where x in (1);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
@@ -255,12 +255,12 @@ CREATE TABLE t2 (keya int(11) NOT NULL default '0', KEY j1 (keya));
 INSERT INTO t2 VALUES (0),(0),(1),(1),(2),(2);
 explain select * from t1, t2 where (t1.key1 <t2.keya + 1) and t2.keya=3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ref	j1	j1	4	const	1	Using index
+1	SIMPLE	t2	ref	j1	j1	4	const	1	Using index; Using join cache
 1	SIMPLE	t1	index	i1	i1	4	NULL	7	Using where; Using index
 explain select * from t1 force index(i1), t2 force index(j1) where 
 (t1.key1 <t2.keya + 1) and t2.keya=3;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ref	j1	j1	4	const	1	Using index
+1	SIMPLE	t2	ref	j1	j1	4	const	1	Using index; Using join cache
 1	SIMPLE	t1	index	i1	i1	4	NULL	7	Using where; Using index
 DROP TABLE t1,t2;
 CREATE TABLE t1 (