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set optimizer_switch='mrr=on,mrr_cost_based=off'; set @read_rnd_buffer_size_save= @@read_rnd_buffer_size; set read_rnd_buffer_size=79; select @@read_rnd_buffer_size; @@read_rnd_buffer_size 79 create table t1(a int); show create table t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) DEFAULT NULL ) ENGINE=MyISAM DEFAULT CHARSET=latin1 insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); create table t2(a int); insert into t2 select A.a + 10*(B.a + 10*C.a) from t1 A, t1 B, t1 C; create table t3 ( a char(8) not null, b char(8) not null, filler char(200), key(a) ); insert into t3 select @a:=concat('c-', 1000+ A.a, '=w'), @a, 'filler' from t2 A; insert into t3 select concat('c-', 1000+A.a, '=w'), concat('c-', 2000+A.a, '=w'), 'filler-1' from t2 A; insert into t3 select concat('c-', 1000+A.a, '=w'), concat('c-', 3000+A.a, '=w'), 'filler-2' from t2 A; select a,filler from t3 where a >= 'c-9011=w'; a filler select a,filler from t3 where a >= 'c-1011=w' and a <= 'c-1015=w'; a filler c-1011=w filler c-1011=w filler-1 c-1011=w filler-2 c-1012=w filler c-1012=w filler-1 c-1012=w filler-2 c-1013=w filler c-1013=w filler-1 c-1013=w filler-2 c-1014=w filler c-1014=w filler-1 c-1014=w filler-2 c-1015=w filler c-1015=w filler-1 c-1015=w filler-2 select a,filler from t3 where (a>='c-1011=w' and a <= 'c-1013=w') or (a>='c-1014=w' and a <= 'c-1015=w'); a filler c-1011=w filler c-1011=w filler-1 c-1011=w filler-2 c-1012=w filler c-1012=w filler-1 c-1012=w filler-2 c-1013=w filler c-1013=w filler-1 c-1013=w filler-2 c-1014=w filler c-1014=w filler-1 c-1014=w filler-2 c-1015=w filler c-1015=w filler-1 c-1015=w filler-2 insert into t3 values ('c-1013=z', 'c-1013=z', 'err'); insert into t3 values ('a-1014=w', 'a-1014=w', 'err'); select a,filler from t3 where (a>='c-1011=w' and a <= 'c-1013=w') or (a>='c-1014=w' and a <= 'c-1015=w'); a filler c-1011=w filler c-1011=w filler-1 c-1011=w filler-2 c-1012=w filler c-1012=w filler-1 c-1012=w filler-2 c-1013=w filler c-1013=w filler-1 c-1013=w filler-2 c-1014=w filler c-1014=w filler-1 c-1014=w filler-2 c-1015=w filler c-1015=w filler-1 c-1015=w filler-2 delete from t3 where b in ('c-1013=z', 'a-1014=w'); select a,filler from t3 where a='c-1011=w' or a='c-1012=w' or a='c-1013=w' or a='c-1014=w' or a='c-1015=w'; a filler c-1011=w filler c-1011=w filler-1 c-1011=w filler-2 c-1012=w filler c-1012=w filler-1 c-1012=w filler-2 c-1013=w filler c-1013=w filler-1 c-1013=w filler-2 c-1014=w filler c-1014=w filler-1 c-1014=w filler-2 c-1015=w filler c-1015=w filler-1 c-1015=w filler-2 insert into t3 values ('c-1013=w', 'del-me', 'inserted'); select a,filler from t3 where a='c-1011=w' or a='c-1012=w' or a='c-1013=w' or a='c-1014=w' or a='c-1015=w'; a filler c-1011=w filler c-1011=w filler-1 c-1011=w filler-2 c-1012=w filler c-1012=w filler-1 c-1012=w filler-2 c-1013=w filler c-1013=w filler-1 c-1013=w filler-2 c-1013=w inserted c-1014=w filler c-1014=w filler-1 c-1014=w filler-2 c-1015=w filler c-1015=w filler-1 c-1015=w filler-2 delete from t3 where b='del-me'; alter table t3 add primary key(b); select b,filler from t3 where (b>='c-1011=w' and b<= 'c-1018=w') or b IN ('c-1019=w', 'c-1020=w', 'c-1021=w', 'c-1022=w', 'c-1023=w', 'c-1024=w'); b filler c-1011=w filler c-1012=w filler c-1013=w filler c-1014=w filler c-1015=w filler c-1016=w filler c-1017=w filler c-1018=w filler c-1019=w filler c-1020=w filler c-1021=w filler c-1022=w filler c-1023=w filler c-1024=w filler select b,filler from t3 where (b>='c-1011=w' and b<= 'c-1020=w') or b IN ('c-1021=w', 'c-1022=w', 'c-1023=w'); b filler c-1011=w filler c-1012=w filler c-1013=w filler c-1014=w filler c-1015=w filler c-1016=w filler c-1017=w filler c-1018=w filler c-1019=w filler c-1020=w filler c-1021=w filler c-1022=w filler c-1023=w filler select b,filler from t3 where (b>='c-1011=w' and b<= 'c-1018=w') or b IN ('c-1019=w', 'c-1020=w') or (b>='c-1021=w' and b<= 'c-1023=w'); b filler c-1011=w filler c-1012=w filler c-1013=w filler c-1014=w filler c-1015=w filler c-1016=w filler c-1017=w filler c-1018=w filler c-1019=w filler c-1020=w filler c-1021=w filler c-1022=w filler c-1023=w filler create table t4 (a varchar(10), b int, c char(10), filler char(200), key idx1 (a, b, c)); insert into t4 (filler) select concat('NULL-', 15-a) from t2 order by a limit 15; insert into t4 (a,b,c,filler) select 'b-1',NULL,'c-1', concat('NULL-', 15-a) from t2 order by a limit 15; insert into t4 (a,b,c,filler) select 'b-1',NULL,'c-222', concat('NULL-', 15-a) from t2 order by a limit 15; insert into t4 (a,b,c,filler) select 'bb-1',NULL,'cc-2', concat('NULL-', 15-a) from t2 order by a limit 15; insert into t4 (a,b,c,filler) select 'zz-1',NULL,'cc-2', 'filler-data' from t2 order by a limit 500; explain select * from t4 where a IS NULL and b IS NULL and (c IS NULL or c='no-such-row1' or c='no-such-row2'); id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t4 range idx1 idx1 29 NULL 10 Using where; Using MRR select * from t4 where a IS NULL and b IS NULL and (c IS NULL or c='no-such-row1' or c='no-such-row2'); a b c filler NULL NULL NULL NULL-15 NULL NULL NULL NULL-14 NULL NULL NULL NULL-13 NULL NULL NULL NULL-12 NULL NULL NULL NULL-11 NULL NULL NULL NULL-10 NULL NULL NULL NULL-9 NULL NULL NULL NULL-8 NULL NULL NULL NULL-7 NULL NULL NULL NULL-6 NULL NULL NULL NULL-5 NULL NULL NULL NULL-4 NULL NULL NULL NULL-3 NULL NULL NULL NULL-2 NULL NULL NULL NULL-1 explain select * from t4 where (a ='b-1' or a='bb-1') and b IS NULL and (c='c-1' or c='cc-2'); id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t4 range idx1 idx1 29 NULL 21 Using where; Using MRR select * from t4 where (a ='b-1' or a='bb-1') and b IS NULL and (c='c-1' or c='cc-2'); a b c filler b-1 NULL c-1 NULL-15 b-1 NULL c-1 NULL-14 b-1 NULL c-1 NULL-13 b-1 NULL c-1 NULL-12 b-1 NULL c-1 NULL-11 b-1 NULL c-1 NULL-10 b-1 NULL c-1 NULL-9 b-1 NULL c-1 NULL-8 b-1 NULL c-1 NULL-7 b-1 NULL c-1 NULL-6 b-1 NULL c-1 NULL-5 b-1 NULL c-1 NULL-4 b-1 NULL c-1 NULL-3 b-1 NULL c-1 NULL-2 b-1 NULL c-1 NULL-1 bb-1 NULL cc-2 NULL-15 bb-1 NULL cc-2 NULL-14 bb-1 NULL cc-2 NULL-13 bb-1 NULL cc-2 NULL-12 bb-1 NULL cc-2 NULL-11 bb-1 NULL cc-2 NULL-10 bb-1 NULL cc-2 NULL-9 bb-1 NULL cc-2 NULL-8 bb-1 NULL cc-2 NULL-7 bb-1 NULL cc-2 NULL-6 bb-1 NULL cc-2 NULL-5 bb-1 NULL cc-2 NULL-4 bb-1 NULL cc-2 NULL-3 bb-1 NULL cc-2 NULL-2 bb-1 NULL cc-2 NULL-1 select * from t4 ignore index(idx1) where (a ='b-1' or a='bb-1') and b IS NULL and (c='c-1' or c='cc-2'); a b c filler b-1 NULL c-1 NULL-15 b-1 NULL c-1 NULL-14 b-1 NULL c-1 NULL-13 b-1 NULL c-1 NULL-12 b-1 NULL c-1 NULL-11 b-1 NULL c-1 NULL-10 b-1 NULL c-1 NULL-9 b-1 NULL c-1 NULL-8 b-1 NULL c-1 NULL-7 b-1 NULL c-1 NULL-6 b-1 NULL c-1 NULL-5 b-1 NULL c-1 NULL-4 b-1 NULL c-1 NULL-3 b-1 NULL c-1 NULL-2 b-1 NULL c-1 NULL-1 bb-1 NULL cc-2 NULL-15 bb-1 NULL cc-2 NULL-14 bb-1 NULL cc-2 NULL-13 bb-1 NULL cc-2 NULL-12 bb-1 NULL cc-2 NULL-11 bb-1 NULL cc-2 NULL-10 bb-1 NULL cc-2 NULL-9 bb-1 NULL cc-2 NULL-8 bb-1 NULL cc-2 NULL-7 bb-1 NULL cc-2 NULL-6 bb-1 NULL cc-2 NULL-5 bb-1 NULL cc-2 NULL-4 bb-1 NULL cc-2 NULL-3 bb-1 NULL cc-2 NULL-2 bb-1 NULL cc-2 NULL-1 drop table t1, t2, t3, t4; create table t1 (a int, b int not null,unique key (a,b),index(b)); insert ignore into t1 values (1,1),(2,2),(3,3),(4,4),(5,5),(6,6),(null,7),(9,9),(8,8),(7,7),(null,9),(null,9),(6,6); create table t2 like t1; insert into t2 select * from t1; alter table t1 modify b blob not null, add c int not null, drop key a, add unique key (a,b(20),c), drop key b, add key (b(10)); select * from t1 where a is null; a b c NULL 7 0 NULL 9 0 NULL 9 0 select * from t1 where (a is null or a > 0 and a < 3) and b > 7 limit 3; a b c NULL 9 0 NULL 9 0 select * from t1 where a is null and b=9 or a is null and b=7 limit 3; a b c NULL 7 0 NULL 9 0 NULL 9 0 drop table t1, t2; CREATE TABLE t1 ( ID int(10) unsigned NOT NULL AUTO_INCREMENT, col1 int(10) unsigned DEFAULT NULL, key1 int(10) unsigned NOT NULL DEFAULT '0', key2 int(10) unsigned DEFAULT NULL, text1 text, text2 text, col2 smallint(6) DEFAULT '100', col3 enum('headers','bodyandsubject') NOT NULL DEFAULT 'bodyandsubject', col4 tinyint(3) unsigned NOT NULL DEFAULT '0', PRIMARY KEY (ID), KEY (key1), KEY (key2) ) AUTO_INCREMENT=6 DEFAULT CHARSET=utf8; INSERT INTO t1 VALUES (1,NULL,1130,NULL,'Hello',NULL,100,'bodyandsubject',0), (2,NULL,1130,NULL,'bye',NULL,100,'bodyandsubject',0), (3,NULL,1130,NULL,'red',NULL,100,'bodyandsubject',0), (4,NULL,1130,NULL,'yellow',NULL,100,'bodyandsubject',0), (5,NULL,1130,NULL,'blue',NULL,100,'bodyandsubject',0); select * FROM t1 WHERE key1=1130 AND col1 IS NULL ORDER BY text1; ID col1 key1 key2 text1 text2 col2 col3 col4 5 NULL 1130 NULL blue NULL 100 bodyandsubject 0 2 NULL 1130 NULL bye NULL 100 bodyandsubject 0 1 NULL 1130 NULL Hello NULL 100 bodyandsubject 0 3 NULL 1130 NULL red NULL 100 bodyandsubject 0 4 NULL 1130 NULL yellow NULL 100 bodyandsubject 0 drop table t1; BUG#37851: Crash in test_if_skip_sort_order tab->select is zero CREATE TABLE t1 ( pk int(11) NOT NULL AUTO_INCREMENT, PRIMARY KEY (pk) ); INSERT INTO t1 VALUES (1); CREATE TABLE t2 ( pk int(11) NOT NULL AUTO_INCREMENT, int_key int(11) DEFAULT NULL, PRIMARY KEY (pk), KEY int_key (int_key) ); INSERT INTO t2 VALUES (1,1),(2,6),(3,0); EXPLAIN EXTENDED SELECT MIN(t1.pk) FROM t1 WHERE EXISTS ( SELECT t2.pk FROM t2 WHERE t2.int_key IS NULL GROUP BY t2.pk ); 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 2 SUBQUERY t2 ref int_key int_key 5 const 1 100.00 Using where Warnings: Note 1003 /* select#1 */ select min(`test`.`t1`.`pk`) AS `MIN(t1.pk)` from `test`.`t1` where 0 DROP TABLE t1, t2; # # BUG#42048 Discrepancy between MyISAM and Maria's ICP implementation # create table t0 (a int); insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); create table t1 (a int, b char(20), filler char(200), key(a,b(10))); insert into t1 select A.a + 10*(B.a + 10*C.a), 'bbb','filler' from t0 A, t0 B, t0 C; update t1 set b=repeat(char(65+a), 20) where a < 25; This must show range + using index condition: explain select * from t1 where a < 10 and b = repeat(char(65+a), 20); id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range a a 5 NULL x Using where select * from t1 where a < 10 and b = repeat(char(65+a), 20); a b filler 0 AAAAAAAAAAAAAAAAAAAA filler 1 BBBBBBBBBBBBBBBBBBBB filler 2 CCCCCCCCCCCCCCCCCCCC filler 3 DDDDDDDDDDDDDDDDDDDD filler 4 EEEEEEEEEEEEEEEEEEEE filler 5 FFFFFFFFFFFFFFFFFFFF filler 6 GGGGGGGGGGGGGGGGGGGG filler 7 HHHHHHHHHHHHHHHHHHHH filler 8 IIIIIIIIIIIIIIIIIIII filler 9 JJJJJJJJJJJJJJJJJJJJ filler drop table t0,t1; # # BUG#41136: ORDER BY + range access: EXPLAIN shows "Using MRR" while MRR is actually not used # create table t0 (a int); insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); create table t1 (a int, b int, key(a)); insert into t1 select A.a + 10 *(B.a + 10*C.a), A.a + 10 *(B.a + 10*C.a) from t0 A, t0 B, t0 C; This mustn't show "Using MRR": explain select * from t1 where a < 20 order by a; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range a a 5 NULL 20 Using where drop table t0, t1; set @read_rnd_buffer_size_save= @@read_rnd_buffer_size; set read_rnd_buffer_size=64; create table t1(a int); insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); create table t2(a char(8), b char(8), c char(8), filler char(100), key k1(a,b,c) ); insert into t2 select concat('a-', 1000 + A.a, '-a'), concat('b-', 1000 + B.a, '-b'), concat('c-', 1000 + C.a, '-c'), 'filler' from t1 A, t1 B, t1 C; EXPLAIN select count(length(a) + length(filler)) from t2 force index (k1) where a>='a-1000-a' and a <'a-1001-a'; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t2 range k1 k1 9 NULL 92 Using where; Using MRR select count(length(a) + length(filler)) from t2 force index (k1) where a>='a-1000-a' and a <'a-1001-a'; count(length(a) + length(filler)) 100 drop table t2; create table t2 (a char(100), b char(100), c char(100), d int, filler char(10), key(d), primary key (a,b,c)); insert into t2 select A.a, B.a, B.a, A.a, 'filler' from t1 A, t1 B; explain select * from t2 force index (d) where d < 10; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t2 range d d 5 NULL # Using where; Using MRR drop table t2; drop table t1; set @@read_rnd_buffer_size= @read_rnd_buffer_size_save; create table t1 (f1 int not null, f2 int not null,f3 int not null, f4 char(1), primary key (f1,f2), key ix(f3)); select * from t1 where (f3>=5 and f3<=10) or (f3>=1 and f3<=4); f1 f2 f3 f4 1 1 1 A 10 10 10 A 2 2 2 A 3 3 3 A 4 4 4 A 5 5 5 A 6 6 6 A 7 7 7 A 8 8 8 A 9 9 9 A drop table t1; BUG#37977: Wrong result returned on GROUP BY + OR + Innodb CREATE TABLE t1 ( `pk` int(11) NOT NULL AUTO_INCREMENT, `int_nokey` int(11) NOT NULL, `int_key` int(11) NOT NULL, `date_key` date NOT NULL, `date_nokey` date NOT NULL, `time_key` time NOT NULL, `time_nokey` time NOT NULL, `datetime_key` datetime NOT NULL, `datetime_nokey` datetime NOT NULL, `varchar_key` varchar(5) DEFAULT NULL, `varchar_nokey` varchar(5) DEFAULT NULL, PRIMARY KEY (`pk`), KEY `int_key` (`int_key`), KEY `date_key` (`date_key`), KEY `time_key` (`time_key`), KEY `datetime_key` (`datetime_key`), KEY `varchar_key` (`varchar_key`) ); INSERT INTO t1 VALUES (1,5,5,'2009-10-16','2009-10-16','09:28:15','09:28:15','2007-09-14 05:34:08','2007-09-14 05:34:08','qk','qk'), (2,6,6,'0000-00-00','0000-00-00','23:06:39','23:06:39','0000-00-00 00:00:00','0000-00-00 00:00:00','j','j'), (3,10,10,'2000-12-18','2000-12-18','22:16:19','22:16:19','2006-11-04 15:42:50','2006-11-04 15:42:50','aew','aew'), (4,0,0,'2001-09-18','2001-09-18','00:00:00','00:00:00','2004-03-23 13:23:35','2004-03-23 13:23:35',NULL,NULL), (5,6,6,'2007-08-16','2007-08-16','22:13:38','22:13:38','2004-08-19 11:01:28','2004-08-19 11:01:28','qu','qu'); select pk from t1 WHERE `varchar_key` > 'kr' group by pk; pk 1 5 select pk from t1 WHERE `int_nokey` IS NULL OR `varchar_key` > 'kr' group by pk; pk 1 5 drop table t1; # # BUG#39447: Error with NOT NULL condition and LIMIT 1 # CREATE TABLE t1 ( id int(11) NOT NULL, parent_id int(11) DEFAULT NULL, name varchar(10) DEFAULT NULL, PRIMARY KEY (id), KEY ind_parent_id (parent_id) ); insert into t1 (id, parent_id, name) values (10,NULL,'A'), (20,10,'B'), (30,10,'C'), (40,NULL,'D'), (50,40,'E'), (60,40,'F'), (70,NULL,'J'); SELECT id FROM t1 WHERE parent_id IS NOT NULL ORDER BY id DESC LIMIT 1; id 60 This must show type=index, extra=Using where explain SELECT * FROM t1 WHERE parent_id IS NOT NULL ORDER BY id DESC LIMIT 1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index ind_parent_id PRIMARY 4 NULL 1 Using where SELECT * FROM t1 WHERE parent_id IS NOT NULL ORDER BY id DESC LIMIT 1; id parent_id name 60 40 F drop table t1; # # Bug#50381 "Assertion failing in handler.h:1283: # void COST_VECT::add_io(double, double)" # CREATE TABLE t1 ( c1 INT NOT NULL, c2 VARCHAR(1) DEFAULT NULL, PRIMARY KEY (c1) ); CREATE TABLE t2 ( c1 INT NOT NULL, c2 VARCHAR(1) DEFAULT NULL, PRIMARY KEY (c1) ); INSERT INTO t2 VALUES (10,'v'); INSERT INTO t2 VALUES (11,'r'); SELECT t1.c2 FROM t2 STRAIGHT_JOIN t1 ON t1.c1 < t2.c1; c2 DROP TABLE t1, t2; # # Bug#58463: Error Can't find record on SELECT with JOIN and ORDER BY # CREATE TABLE t1 ( pk INT NOT NULL, PRIMARY KEY (pk) ) ENGINE=MyISAM; INSERT INTO t1 VALUES (2); CREATE TABLE t2 ( pk INT NOT NULL, i1 INT NOT NULL, i2 INT NOT NULL, c1 VARCHAR(1024) CHARACTER SET utf8, PRIMARY KEY (pk), KEY k1 (i1) ); INSERT INTO t2 VALUES (3, 9, 1, NULL); EXPLAIN SELECT i1 FROM t1 LEFT JOIN t2 ON t1.pk = t2.i2 WHERE t2.i1 > 5 AND t2.pk IS NULL ORDER BY i1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE noticed after reading const tables SELECT i1 FROM t1 LEFT JOIN t2 ON t1.pk = t2.i2 WHERE t2.i1 > 5 AND t2.pk IS NULL ORDER BY i1; i1 DROP TABLE t1, t2; # # Bug#12321461: CRASH IN DSMRR_IMPL::DSMRR_INIT ON SELECT STRAIGHT_JOIN # set @save_optimizer_switch = @@optimizer_switch; set optimizer_switch='block_nested_loop=off,batched_key_access=off'; CREATE TABLE t1 ( pk INTEGER, c1 VARCHAR(1) NOT NULL, PRIMARY KEY (pk) ); CREATE TABLE t2 ( c1 VARCHAR(1) NOT NULL ); INSERT INTO t2 VALUES ('v'), ('c'); EXPLAIN SELECT STRAIGHT_JOIN t1.c1 FROM t1 RIGHT OUTER JOIN t2 ON t1.c1 = t2.c1 WHERE t1.pk > 176; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t2 ALL NULL NULL NULL NULL 2 NULL 1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 1 Using where; Using MRR SELECT STRAIGHT_JOIN t1.c1 FROM t1 RIGHT OUTER JOIN t2 ON t1.c1 = t2.c1 WHERE t1.pk > 176; c1 DROP TABLE t1,t2; set optimizer_switch= @save_optimizer_switch; # # Bug#13249966 MRR: RANDOM ERROR DUE TO UNINITIALIZED RES WITH # SMALL READ_RND_BUFFER_SIZE # set @read_rnd_buffer_size_save= @@read_rnd_buffer_size; set read_rnd_buffer_size=1; select @@read_rnd_buffer_size; @@read_rnd_buffer_size 1 CREATE TABLE t1 ( i1 INTEGER NOT NULL, i2 INTEGER NOT NULL, KEY (i2) ); INSERT INTO t1 VALUES (0,1),(1,2),(2,3); EXPLAIN SELECT i1 FROM t1 WHERE i2 > 2; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range i2 i2 4 NULL 2 Using where SELECT i1 FROM t1 WHERE i2 > 2; i1 2 DROP TABLE t1; set @@read_rnd_buffer_size= @read_rnd_buffer_size_save; select @@read_rnd_buffer_size; @@read_rnd_buffer_size 79 # # Bug 12365385 STRAIGHT_JOIN QUERY QUICKLY EXHAUSTS SYSTEM+VIRT. # MEMORY LEADING TO SYSTEM CRASH # CREATE TABLE ten (a INTEGER); INSERT INTO ten VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); CREATE TABLE t1 ( pk INTEGER NOT NULL, i1 INTEGER NOT NULL, c1 VARCHAR(10) NOT NULL, PRIMARY KEY (pk) ); INSERT INTO t1 SELECT a, 1, 'MySQL' FROM ten; CREATE TABLE t2 ( pk INTEGER NOT NULL, c1 VARCHAR(10) NOT NULL, c2 varchar(10) NOT NULL, PRIMARY KEY (pk) ); INSERT INTO t2 SELECT a, 'MySQL', 'MySQL' FROM ten; CREATE TABLE t3 ( pk INTEGER NOT NULL, c1 VARCHAR(10) NOT NULL, PRIMARY KEY (pk) ); INSERT INTO t3 SELECT a, 'MySQL' FROM ten; CREATE TABLE t4 ( pk int(11) NOT NULL, c1_key varchar(10) CHARACTER SET utf8 NOT NULL, c2 varchar(10) NOT NULL, c3 varchar(10) NOT NULL, PRIMARY KEY (pk), KEY k1 (c1_key) ); CREATE TABLE t5 ( pk INTEGER NOT NULL, c1 VARCHAR(10) NOT NULL, PRIMARY KEY (pk) ); INSERT INTO t5 SELECT a, 'MySQL' FROM ten; EXPLAIN SELECT STRAIGHT_JOIN * FROM (t1 LEFT JOIN (t2 LEFT JOIN (t3 LEFT OUTER JOIN t4 ON t3.c1 <= t4.c1_key) ON t2.c1 = t4.c3) ON t1.c1 = t4.c2) RIGHT OUTER JOIN t5 ON t2.c2 <= t5.c1 WHERE t1.i1 = 1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t5 ALL NULL NULL NULL NULL 10 NULL 1 SIMPLE t1 ALL NULL NULL NULL NULL 10 Using where; Using join buffer (Block Nested Loop) 1 SIMPLE t2 ALL NULL NULL NULL NULL 10 Using where; Using join buffer (Block Nested Loop) 1 SIMPLE t3 ALL NULL NULL NULL NULL 10 Using join buffer (Block Nested Loop) 1 SIMPLE t4 ALL k1 NULL NULL NULL 0 Range checked for each record (index map: 0x2) SELECT STRAIGHT_JOIN * FROM (t1 LEFT JOIN (t2 LEFT JOIN (t3 LEFT OUTER JOIN t4 ON t3.c1 <= t4.c1_key) ON t2.c1 = t4.c3) ON t1.c1 = t4.c2) RIGHT OUTER JOIN t5 ON t2.c2 <= t5.c1 WHERE t1.i1 = 1; pk i1 c1 pk c1 c2 pk c1 pk c1_key c2 c3 pk c1 DROP TABLE ten, t1, t2, t3, t4, t5; set @@read_rnd_buffer_size= @read_rnd_buffer_size_save; set optimizer_switch=default;