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DROP TABLE IF EXISTS t1;
CREATE TABLE t1
(a INT AUTO_INCREMENT PRIMARY KEY,
b CHAR(20)
);
SET @start_value= @@global.max_seeks_for_key;
'#--------------------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 partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 NULL ALL NULL NULL NULL NULL # # NULL
1 SIMPLE t2 NULL ALL NULL NULL NULL NULL # # Using where; Using join buffer (Block Nested Loop)
Warnings:
Note 1003 /* select#1 */ select straight_join `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` join `test`.`t1` `t2` where (`test`.`t2`.`b` = `test`.`t1`.`b`)
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 partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 NULL ALL NULL NULL NULL NULL # # NULL
1 SIMPLE t2 NULL ALL NULL NULL NULL NULL # # Using where; Using join buffer (Block Nested Loop)
Warnings:
Note 1003 /* select#1 */ select straight_join `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` join `test`.`t1` `t2` where (`test`.`t2`.`b` = `test`.`t1`.`b`)
'#--------------------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 partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 NULL ALL NULL NULL NULL NULL # # NULL
1 SIMPLE t2 NULL ALL NULL NULL NULL NULL # # Using where; Using join buffer (Block Nested Loop)
Warnings:
Note 1003 /* select#1 */ select straight_join `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` join `test`.`t1` `t2` where (`test`.`t2`.`b` = `test`.`t1`.`b`)
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 partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 NULL ALL NULL NULL NULL NULL # # NULL
1 SIMPLE t2 NULL ALL NULL NULL NULL NULL # # Using where; Using join buffer (Block Nested Loop)
Warnings:
Note 1003 /* select#1 */ select straight_join `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` join `test`.`t1` `t2` where (`test`.`t2`.`b` = `test`.`t1`.`b`)
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 partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 NULL ALL NULL NULL NULL NULL # # NULL
1 SIMPLE t2 NULL ALL NULL NULL NULL NULL # # Using where; Using join buffer (Block Nested Loop)
Warnings:
Note 1003 /* select#1 */ select straight_join `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` join `test`.`t1` `t2` where (`test`.`t2`.`b` = `test`.`t1`.`b`)
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 partitions type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1 NULL ALL NULL NULL NULL NULL # # NULL
1 SIMPLE t2 NULL ALL NULL NULL NULL NULL # # Using where; Using join buffer (Block Nested Loop)
Warnings:
Note 1003 /* select#1 */ select straight_join `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` join `test`.`t1` `t2` where (`test`.`t2`.`b` = `test`.`t1`.`b`)
SET MAX_SEEKS_FOR_KEY=DEFAULT;
DROP TABLE t1;
SET @@global.max_seeks_for_key= @start_value;