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|
drop table if exists t1,t2,t3,t4;
set @subselect_extra_tmp=@@optimizer_switch;
set optimizer_switch='semijoin=on,firstmatch=on,loosescan=on';
# From explain.test:
#
# Bug#37870: Usage of uninitialized value caused failed assertion.
#
create table t1 (dt datetime not null, t time not null);
create table t2 (dt datetime not null);
insert into t1 values ('2001-01-01 1:1:1', '1:1:1'),
('2001-01-01 1:1:1', '1:1:1');
insert into t2 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');
flush tables;
EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY OUTR ALL NULL NULL NULL NULL 2 Using where; Start temporary
1 PRIMARY INNR ALL NULL NULL NULL NULL 2 Using where; End temporary; Using join buffer (flat, BNL join)
flush tables;
SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
dt
flush tables;
EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN ( SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.t < '2005-11-13 7:41:31' );
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY OUTR ALL NULL NULL NULL NULL 2 Using where; Start temporary
1 PRIMARY INNR ALL NULL NULL NULL NULL 2 Using where; End temporary; Using join buffer (flat, BNL join)
flush tables;
SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN ( SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.t < '2005-11-13 7:41:31' );
dt
2001-01-01 01:01:01
2001-01-01 01:01:01
drop tables t1, t2;
# From type_datetime.test:
#
# Bug #32694: NOT NULL table field in a subquery produces invalid results
#
create table t1 (id int(10) not null, cur_date datetime not null);
create table t2 (id int(10) not null, cur_date date not null);
insert into t1 (id, cur_date) values (1, '2007-04-25 18:30:22');
insert into t2 (id, cur_date) values (1, '2007-04-25');
explain extended
select * from t1
where id in (select id from t1 as x1 where (t1.cur_date is null));
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1276 Field or reference 'test.t1.cur_date' of SELECT #2 was resolved in SELECT #1
Note 1003 select 1 AS `id`,'2007-04-25 18:30:22' AS `cur_date` from (dual) where (('2007-04-25 18:30:22' = 0))
select * from t1
where id in (select id from t1 as x1 where (t1.cur_date is null));
id cur_date
explain extended
select * from t2
where id in (select id from t2 as x1 where (t2.cur_date is null));
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY NULL NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables
Warnings:
Note 1276 Field or reference 'test.t2.cur_date' of SELECT #2 was resolved in SELECT #1
Note 1003 select 1 AS `id`,'2007-04-25' AS `cur_date` from (dual) where (('2007-04-25' = 0))
select * from t2
where id in (select id from t2 as x1 where (t2.cur_date is null));
id cur_date
insert into t1 (id, cur_date) values (2, '2007-04-26 18:30:22');
insert into t2 (id, cur_date) values (2, '2007-04-26');
explain extended
select * from t1
where id in (select id from t1 as x1 where (t1.cur_date is null));
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 100.00 Using where; Start temporary
1 PRIMARY x1 ALL NULL NULL NULL NULL 2 100.00 Using where; End temporary; Using join buffer (flat, BNL join)
Warnings:
Note 1276 Field or reference 'test.t1.cur_date' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`t1`.`id` AS `id`,`test`.`t1`.`cur_date` AS `cur_date` from `test`.`t1` semi join (`test`.`t1` `x1`) where ((`test`.`x1`.`id` = `test`.`t1`.`id`) and (`test`.`t1`.`cur_date` = 0))
select * from t1
where id in (select id from t1 as x1 where (t1.cur_date is null));
id cur_date
explain extended
select * from t2
where id in (select id from t2 as x1 where (t2.cur_date is null));
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 100.00 Using where; Start temporary
1 PRIMARY x1 ALL NULL NULL NULL NULL 2 100.00 Using where; End temporary; Using join buffer (flat, BNL join)
Warnings:
Note 1276 Field or reference 'test.t2.cur_date' of SELECT #2 was resolved in SELECT #1
Note 1003 select `test`.`t2`.`id` AS `id`,`test`.`t2`.`cur_date` AS `cur_date` from `test`.`t2` semi join (`test`.`t2` `x1`) where ((`test`.`x1`.`id` = `test`.`t2`.`id`) and (`test`.`t2`.`cur_date` = 0))
select * from t2
where id in (select id from t2 as x1 where (t2.cur_date is null));
id cur_date
drop table t1,t2;
#
# From group_min_max.test
#
create table t1 (
a1 char(64), a2 char(64), b char(16), c char(16) not null, d char(16), dummy char(64) default ' '
);
insert into t1 (a1, a2, b, c, d) values
('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4'),
('d','a','a','a411','xy1'),('d','a','a','b411','xy2'),('d','a','a','c411','xy3'),('d','a','a','d411','xy4'),
('d','a','b','e412','xy1'),('d','a','b','f412','xy2'),('d','a','b','g412','xy3'),('d','a','b','h412','xy4'),
('d','b','a','i421','xy1'),('d','b','a','j421','xy2'),('d','b','a','k421','xy3'),('d','b','a','l421','xy4'),
('d','b','b','m422','xy1'),('d','b','b','n422','xy2'),('d','b','b','o422','xy3'),('d','b','b','p422','xy4'),
('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4'),
('d','a','a','a411','xy1'),('d','a','a','b411','xy2'),('d','a','a','c411','xy3'),('d','a','a','d411','xy4'),
('d','a','b','e412','xy1'),('d','a','b','f412','xy2'),('d','a','b','g412','xy3'),('d','a','b','h412','xy4'),
('d','b','a','i421','xy1'),('d','b','a','j421','xy2'),('d','b','a','k421','xy3'),('d','b','a','l421','xy4'),
('d','b','b','m422','xy1'),('d','b','b','n422','xy2'),('d','b','b','o422','xy3'),('d','b','b','p422','xy4');
create index idx_t1_0 on t1 (a1);
create index idx_t1_1 on t1 (a1,a2,b,c);
create index idx_t1_2 on t1 (a1,a2,b);
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status Table is already up to date
create table t2 (
a1 char(64), a2 char(64) not null, b char(16), c char(16), d char(16), dummy char(64) default ' '
);
insert into t2 select * from t1;
insert into t2 (a1, a2, b, c, d) values
('a','a',NULL,'a777','xyz'),('a','a',NULL,'a888','xyz'),('a','a',NULL,'a999','xyz'),
('a','a','a',NULL,'xyz'),
('a','a','b',NULL,'xyz'),
('a','b','a',NULL,'xyz'),
('c','a',NULL,'c777','xyz'),('c','a',NULL,'c888','xyz'),('c','a',NULL,'c999','xyz'),
('d','b','b',NULL,'xyz'),
('e','a','a',NULL,'xyz'),('e','a','a',NULL,'xyz'),('e','a','a',NULL,'xyz'),('e','a','a',NULL,'xyz'),
('e','a','b',NULL,'xyz'),('e','a','b',NULL,'xyz'),('e','a','b',NULL,'xyz'),('e','a','b',NULL,'xyz'),
('a','a',NULL,'a777','xyz'),('a','a',NULL,'a888','xyz'),('a','a',NULL,'a999','xyz'),
('a','a','a',NULL,'xyz'),
('a','a','b',NULL,'xyz'),
('a','b','a',NULL,'xyz'),
('c','a',NULL,'c777','xyz'),('c','a',NULL,'c888','xyz'),('c','a',NULL,'c999','xyz'),
('d','b','b',NULL,'xyz'),
('e','a','a',NULL,'xyz'),('e','a','a',NULL,'xyz'),('e','a','a',NULL,'xyz'),('e','a','a',NULL,'xyz'),
('e','a','b',NULL,'xyz'),('e','a','b',NULL,'xyz'),('e','a','b',NULL,'xyz'),('e','a','b',NULL,'xyz');
create index idx_t2_0 on t2 (a1);
create index idx_t2_1 on t2 (a1,a2,b,c);
create index idx_t2_2 on t2 (a1,a2,b);
analyze table t2;
Table Op Msg_type Msg_text
test.t2 analyze status Table is already up to date
create table t3 (
a1 char(1), a2 char(1), b char(1), c char(4) not null, d char(3), dummy char(1) default ' '
);
insert into t3 (a1, a2, b, c, d) values
('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4');
insert into t3 (a1, a2, b, c, d) values
('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4');
insert into t3 (a1, a2, b, c, d) values
('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4');
insert into t3 (a1, a2, b, c, d) values
('a','a','a','a111','xy1'),('a','a','a','b111','xy2'),('a','a','a','c111','xy3'),('a','a','a','d111','xy4'),
('a','a','b','e112','xy1'),('a','a','b','f112','xy2'),('a','a','b','g112','xy3'),('a','a','b','h112','xy4'),
('a','b','a','i121','xy1'),('a','b','a','j121','xy2'),('a','b','a','k121','xy3'),('a','b','a','l121','xy4'),
('a','b','b','m122','xy1'),('a','b','b','n122','xy2'),('a','b','b','o122','xy3'),('a','b','b','p122','xy4'),
('b','a','a','a211','xy1'),('b','a','a','b211','xy2'),('b','a','a','c211','xy3'),('b','a','a','d211','xy4'),
('b','a','b','e212','xy1'),('b','a','b','f212','xy2'),('b','a','b','g212','xy3'),('b','a','b','h212','xy4'),
('b','b','a','i221','xy1'),('b','b','a','j221','xy2'),('b','b','a','k221','xy3'),('b','b','a','l221','xy4'),
('b','b','b','m222','xy1'),('b','b','b','n222','xy2'),('b','b','b','o222','xy3'),('b','b','b','p222','xy4'),
('c','a','a','a311','xy1'),('c','a','a','b311','xy2'),('c','a','a','c311','xy3'),('c','a','a','d311','xy4'),
('c','a','b','e312','xy1'),('c','a','b','f312','xy2'),('c','a','b','g312','xy3'),('c','a','b','h312','xy4'),
('c','b','a','i321','xy1'),('c','b','a','j321','xy2'),('c','b','a','k321','xy3'),('c','b','a','l321','xy4'),
('c','b','b','m322','xy1'),('c','b','b','n322','xy2'),('c','b','b','o322','xy3'),('c','b','b','p322','xy4');
create index idx_t3_0 on t3 (a1);
create index idx_t3_1 on t3 (a1,a2,b,c);
create index idx_t3_2 on t3 (a1,a2,b);
analyze table t3;
Table Op Msg_type Msg_text
test.t3 analyze status Table is already up to date
explain select a1,a2,b,c,min(c), max(c) from t1
where exists ( select * from t2
where t2.c in (select c from t3 where t3.c > t1.b) and
t2.c > 'b1' )
group by a1,a2,b;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 range NULL idx_t1_1 147 NULL 17 Using where; Using index for group-by
2 DEPENDENT SUBQUERY t2 index NULL idx_t2_1 163 NULL 164 Using where; Using index
2 DEPENDENT SUBQUERY t3 index NULL idx_t3_1 10 NULL 192 Using where; Using index; FirstMatch(t2)
select a1,a2,b,c,min(c), max(c) from t1
where exists ( select * from t2
where t2.c in (select c from t3 where t3.c > t1.b) and
t2.c > 'b1' )
group by a1,a2,b;
a1 a2 b c min(c) max(c)
a a a d111 a111 d111
a a b h112 e112 h112
a b a l121 i121 l121
a b b p122 m122 p122
b a a d211 a211 d211
b a b h212 e212 h212
b b a l221 i221 l221
b b b p222 m222 p222
c a a d311 a311 d311
c a b h312 e312 h312
c b a l321 i321 l321
c b b p322 m322 p322
d a a d411 a411 d411
d a b h412 e412 h412
d b a l421 i421 l421
d b b p422 m422 p422
explain select a1,a2,b,c,min(c), max(c) from t1
where exists ( select * from t2
where t2.c in (select c from t3 where t3.c > t1.c) and
t2.c > 'b1' )
group by a1,a2,b;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 index NULL idx_t1_1 163 NULL 128 Using where; Using index
2 DEPENDENT SUBQUERY t2 index NULL idx_t2_1 163 NULL 164 Using where; Using index
2 DEPENDENT SUBQUERY t3 index NULL idx_t3_1 10 NULL 192 Using where; Using index; FirstMatch(t2)
select a1,a2,b,c,min(c), max(c) from t1
where exists ( select * from t2
where t2.c in (select c from t3 where t3.c > t1.c) and
t2.c > 'b1' )
group by a1,a2,b;
a1 a2 b c min(c) max(c)
a a a a111 a111 d111
a a b e112 e112 h112
a b a i121 i121 l121
a b b m122 m122 p122
b a a a211 a211 d211
b a b e212 e212 h212
b b a i221 i221 l221
b b b m222 m222 p222
c a a a311 a311 d311
c a b e312 e312 h312
c b a i321 i321 l321
c b b m322 m322 o322
d a a a411 a411 d411
d a b e412 e412 h412
d b a i421 i421 l421
d b b m422 m422 o422
drop table t1, t2, t3;
#
# From group_by.test
#
# Bug #21174: Index degrades sort performance and
# optimizer does not honor IGNORE INDEX.
# a.k.a WL3527.
#
CREATE TABLE t1 (a INT, b INT,
PRIMARY KEY (a),
KEY i2(a,b));
INSERT INTO t1 VALUES (1,1),(2,2),(3,3),(4,4),(5,5),(6,6),(7,7),(8,8);
INSERT INTO t1 SELECT a + 8,b FROM t1;
INSERT INTO t1 SELECT a + 16,b FROM t1;
INSERT INTO t1 SELECT a + 32,b FROM t1;
INSERT INTO t1 SELECT a + 64,b FROM t1;
INSERT INTO t1 SELECT a + 128,b FROM t1 limit 16;
ANALYZE TABLE t1;
Table Op Msg_type Msg_text
test.t1 analyze status OK
EXPLAIN SELECT 1 FROM t1 WHERE a IN
(SELECT a FROM t1 USE INDEX (i2) IGNORE INDEX (i2));
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 index PRIMARY,i2 PRIMARY 4 NULL 144 Using index
1 PRIMARY t1 ALL NULL NULL NULL NULL 144 Using where; FirstMatch(t1)
CREATE TABLE t2 (a INT, b INT, KEY(a));
INSERT INTO t2 VALUES (1, 1), (2, 2), (3,3), (4,4);
EXPLAIN SELECT a, SUM(b) FROM t2 GROUP BY a LIMIT 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index NULL a 5 NULL 2
EXPLAIN SELECT a, SUM(b) FROM t2 IGNORE INDEX (a) GROUP BY a LIMIT 2;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 ALL NULL NULL NULL NULL 4 Using temporary; Using filesort
EXPLAIN SELECT 1 FROM t2 WHERE a IN
(SELECT a FROM t1 USE INDEX (i2) IGNORE INDEX (i2));
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t2 index a a 5 NULL 4 Using index
1 PRIMARY t1 ALL NULL NULL NULL NULL 144 Using where; FirstMatch(t2)
DROP TABLE t1, t2;
set optimizer_switch= @subselect_extra_tmp;
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