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, 6 insertions, 6 deletions

diff --git a/mysql-test/r/distinct.result b/mysql-test/r/distinct.result
index 8bf8c95c6fb..3419ce150eb 100644
--- a/mysql-test/r/distinct.result
+++ b/mysql-test/r/distinct.result
@@ -174,7 +174,7 @@ INSERT INTO t3 VALUES (1,'1'),(2,'2'),(1,'1'),(2,'2');
 explain SELECT distinct t3.a FROM t3,t2,t1 WHERE t3.a=t1.b AND t1.a=t2.a;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	4	Using temporary
-1	SIMPLE	t3	ref	a	a	5	test.t1.b	2	Using where; Using index
+1	SIMPLE	t3	ref	a	a	5	test.t1.b	2	Using where; Using index; Using join cache
 1	SIMPLE	t2	index	a	a	4	NULL	5	Using where; Using index; Distinct
 SELECT distinct t3.a FROM t3,t2,t1 WHERE t3.a=t1.b AND t1.a=t2.a;
 a
@@ -299,11 +299,11 @@ WHERE
 ((t1.id=j_lj_t2.id AND t2_lj.id IS NULL) OR (t1.id=t2.id AND t2.idx=2))
 AND ((t1.id=j_lj_t3.id AND t3_lj.id IS NULL) OR (t1.id=t3.id AND t3.idx=2));
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	index	id	id	4	NULL	2	Using index; Using temporary
-1	SIMPLE	t2	index	id	id	8	NULL	1	Using index; Distinct
-1	SIMPLE	t3	index	id	id	8	NULL	1	Using index; Distinct
+1	SIMPLE	t1	index	id	id	4	NULL	2	Using index; Using temporary; Using join cache
+1	SIMPLE	t2	index	id	id	8	NULL	1	Using index; Distinct; Using join cache
+1	SIMPLE	t3	index	id	id	8	NULL	1	Using index; Distinct; Using join cache
 1	SIMPLE	j_lj_t2	index	id	id	4	NULL	2	Using where; Using index; Distinct
-1	SIMPLE	t2_lj	ref	id	id	4	test.j_lj_t2.id	1	Using where; Using index; Distinct
+1	SIMPLE	t2_lj	ref	id	id	4	test.j_lj_t2.id	1	Using where; Using index; Distinct; Using join cache
 1	SIMPLE	j_lj_t3	index	id	id	4	NULL	2	Using where; Using index; Distinct
 1	SIMPLE	t3_lj	ref	id	id	4	test.j_lj_t3.id	1	Using where; Using index; Distinct
 SELECT DISTINCT
@@ -514,7 +514,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	
 EXPLAIN SELECT DISTINCT t1_1.a, t1_1.b FROM t1 t1_1, t1 t1_2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1_1	ALL	NULL	NULL	NULL	NULL	3	Using temporary
+1	SIMPLE	t1_1	ALL	NULL	NULL	NULL	NULL	3	Using temporary; Using join cache
 1	SIMPLE	t1_2	index	NULL	PRIMARY	4	NULL	3	Using index; Distinct
 EXPLAIN SELECT DISTINCT t1_1.a, t1_1.b FROM t1 t1_1, t1 t1_2
 WHERE t1_1.a = t1_2.a;