drop table if exists t1;
CREATE TABLE t1
(a int auto_increment primary key, 
b char(20)
);
'#--------------------FN_DYNVARS_084_01-------------------------#'
SELECT @@global.max_seeks_for_key = 10;
@@global.max_seeks_for_key = 10
0
SELECT @@session.max_seeks_for_key = 10;
@@session.max_seeks_for_key = 10
0
SET @@global.max_seeks_for_key = 20;
SELECT @@global.max_seeks_for_key;
@@global.max_seeks_for_key
20
INSERT into t1(b) values("AREc");
explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	system	NULL	NULL	NULL	NULL	1	
1	SIMPLE	t2	system	NULL	NULL	NULL	NULL	1	
SET @@session.max_seeks_for_key = 2;
SELECT @@session.max_seeks_for_key;
@@session.max_seeks_for_key
2
INSERT into t1(b) values("BREc");
INSERT into t1(b) values("CRec");
explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	3	Using where; Using join buffer
'#--------------------FN_DYNVARS_084_02-------------------------#'
SELECT @@global.max_seeks_for_key = 10;
@@global.max_seeks_for_key = 10
0
SELECT @@session.max_seeks_for_key = 10;
@@session.max_seeks_for_key = 10
0
SET @@global.max_seeks_for_key = 20;
SELECT @@global.max_seeks_for_key;
@@global.max_seeks_for_key
20
INSERT into t1(b) values("AREc");
explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	4	Using where; Using join buffer
SET @@session.max_seeks_for_key = 2;
SELECT @@session.max_seeks_for_key;
@@session.max_seeks_for_key
2
INSERT into t1(b) values("BREc");
INSERT into t1(b) values("CRec");
explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	6	
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
INSERT INTO t1 values(null,"test");
INSERT INTO t1 VALUES (null,"a"),(null,"a"),(null,"a"),
(null,"a"),(null,"a"),(null,"a"),(null,"a"),
(null,"a"),(null,"a"),(null,"a");
explain SELECT STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	17	
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	17	Using where; Using join buffer
analyze table t1;
Table	Op	Msg_type	Msg_text
test.t1	analyze	status	OK
SET MAX_SEEKS_FOR_KEY=1;
explain select STRAIGHT_JOIN * from t1,t1 as t2 where t1.b=t2.b;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	17	
1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	17	Using where; Using join buffer
SET MAX_SEEKS_FOR_KEY=DEFAULT;
drop table t1;