EVOLUTION-MANAGER

Edit File: myisam_mrr.result

drop table if exists t0, t1, t2, t3; set @myisam_mrr_tmp=@@optimizer_switch; set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on'; set @mrr_buffer_size_save= @@mrr_buffer_size; set mrr_buffer_size=79; Warnings: Warning 1292 Truncated incorrect mrr_buffer_size value: '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-1012=w filler c-1013=w filler c-1014=w filler c-1015=w filler c-1011=w filler-1 c-1012=w filler-1 c-1013=w filler-1 c-1014=w filler-1 c-1015=w filler-1 c-1011=w filler-2 c-1012=w filler-2 c-1013=w filler-2 c-1014=w filler-2 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-1012=w filler c-1013=w filler c-1014=w filler c-1015=w filler c-1011=w filler-1 c-1012=w filler-1 c-1013=w filler-1 c-1014=w filler-1 c-1015=w filler-1 c-1011=w filler-2 c-1012=w filler-2 c-1013=w filler-2 c-1014=w filler-2 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-1012=w filler c-1013=w filler c-1014=w filler c-1015=w filler c-1011=w filler-1 c-1012=w filler-1 c-1013=w filler-1 c-1014=w filler-1 c-1015=w filler-1 c-1011=w filler-2 c-1012=w filler-2 c-1013=w filler-2 c-1014=w filler-2 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-1012=w filler c-1013=w filler c-1014=w filler c-1015=w filler c-1011=w filler-1 c-1012=w filler-1 c-1013=w filler-1 c-1014=w filler-1 c-1015=w filler-1 c-1011=w filler-2 c-1012=w filler-2 c-1013=w filler-2 c-1014=w filler-2 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-1012=w filler c-1013=w filler c-1014=w filler c-1015=w filler c-1011=w filler-1 c-1012=w filler-1 c-1013=w filler-1 c-1014=w filler-1 c-1015=w filler-1 c-1011=w filler-2 c-1012=w filler-2 c-1013=w filler-2 c-1014=w filler-2 c-1015=w filler-2 c-1013=w inserted 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 drop table if exists t4; 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 index condition; Using where; Rowid-ordered scan 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 index condition; Using where; Rowid-ordered scan 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); Warnings: Warning 1062 Duplicate entry '6-6' for key 'a' 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; set @@mrr_buffer_size= @mrr_buffer_size_save; 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) ) ENGINE=MyISAM 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 index condition 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 19 Using index condition; 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 index condition drop table t0, t1; # # Part of MWL#67: DS-MRR backport: add an @@optimizer_switch flag for # index_condition pushdown: # - engine_condition_pushdown does not affect ICP select @@optimizer_switch like '%index_condition_pushdown=on%'; @@optimizer_switch like '%index_condition_pushdown=on%' 1 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; A query that will use ICP: explain select * from t1 where a < 20; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range a a 5 NULL 20 Using index condition; Rowid-ordered scan set @save_optimizer_switch=@@optimizer_switch; set optimizer_switch='index_condition_pushdown=off'; explain select * from t1 where a < 20; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range a a 5 NULL 20 Using where; Rowid-ordered scan set optimizer_switch='index_condition_pushdown=on'; explain select * from t1 where a < 20; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range a a 5 NULL 20 Using index condition; Rowid-ordered scan set optimizer_switch=@save_optimizer_switch; # # BUG#629684: Unreachable code in multi_range_read.cc in maria-5.3-dsmrr-cpk # delete from t0 where a > 2; insert into t0 values (NULL),(NULL); insert into t1 values (NULL, 1234), (NULL, 5678); set @save_join_cache_level=@@join_cache_level; set @@join_cache_level=6; explain select * from t0, t1 where t0.a<=>t1.a; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t0 ALL NULL NULL NULL NULL 5 1 SIMPLE t1 ref a a 5 test.t0.a 1 Using index condition(BKA); Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan select * from t0, t1 where t0.a<=>t1.a; a a b 0 0 0 1 1 1 2 2 2 NULL NULL 1234 NULL NULL 1234 NULL NULL 5678 NULL NULL 5678 set @@join_cache_level=@save_join_cache_level; drop table t0, t1; # # BUG#625841: Assertion `!table || (!table->read_set || bitmap_is_set # (table->read_set, field_index))' on REPLACE ... SELECT with MRR # create table t0 (a int); insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); create table t1 ( key1 varchar(10), col1 char(255), col2 char(255), col3 char(244), col4 char(255), key(key1) ); create table t2 like t1; insert into t1 select 1000+A.a+100*B.a + 10*C.a, 'col1val', 'col2val', 'col3val', 'col4val' from t0 A, t0 B, t0 C; REPLACE INTO t2(col2,col3,col4) SELECT col2,col3,col4 FROM t1 WHERE `key1` LIKE CONCAT( LEFT( '1' , 7 ) , '%' ) ORDER BY col1 LIMIT 7; drop table t0, t1, t2; # # BUG#670417: Diverging results in maria-5.3-mwl128-dsmrr-cpk with join buffer (incremental, BKA join) # set @save_join_cache_level = @@join_cache_level; set join_cache_level = 6; set @save_join_buffer_size=@@join_buffer_size; set join_buffer_size = 136; CREATE TABLE t1 ( pk int(11) NOT NULL AUTO_INCREMENT, col_int_key int(11) NOT NULL, col_varchar_key varchar(1) NOT NULL, col_varchar_nokey varchar(1) NOT NULL, PRIMARY KEY (pk), KEY col_varchar_key (col_varchar_key,col_int_key) ); INSERT INTO t1 VALUES (10,8,'v','v'),(11,8,'f','f'), (12,5,'v','v'), (13,8,'s','s'),(14,8,'a','a'),(15,6,'p','p'), (16,7,'z','z'),(17,2,'a','a'),(18,5,'h','h'), (19,7,'h','h'),(20,2,'v','v'),(21,9,'v','v'), (22,142,'b','b'),(23,3,'y','y'),(24,0,'v','v'), (25,3,'m','m'),(26,5,'z','z'),(27,9,'n','n'), (28,1,'d','d'),(29,107,'a','a'); INSERT INTO t1 VALUES (110,8,'v','v'),(111,8,'f','f'), (112,5,'v','v'), (113,8,'s','s'),(114,8,'a','a'),(115,6,'p','p'), (116,7,'z','z'),(117,2,'a','a'),(118,5,'h','h'), (119,7,'h','h'),(120,2,'v','v'),(121,9,'v','v'), (122,142,'b','b'),(123,3,'y','y'),(124,0,'v','v'), (125,3,'m','m'),(126,5,'z','z'),(127,9,'n','n'), (128,1,'d','d'),(129,107,'a','a'); SELECT COUNT(*) FROM t1 AS table2, t1 AS table3 where table3.col_varchar_key = table2.col_varchar_key AND table3.col_varchar_key = table2.col_varchar_nokey AND table3.pk<>0; COUNT(*) 200 EXPLAIN SELECT COUNT(*) FROM t1 AS table2, t1 AS table3 where table3.col_varchar_key = table2.col_varchar_key AND table3.col_varchar_key = table2.col_varchar_nokey AND table3.pk<>0; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE table2 ALL col_varchar_key NULL NULL NULL 40 Using where 1 SIMPLE table3 ref PRIMARY,col_varchar_key col_varchar_key 3 test.table2.col_varchar_key 5 Using where; Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan set join_cache_level= @save_join_cache_level; set join_buffer_size= @save_join_buffer_size; drop table t1; # # BUG#730133: Wrong result with jkl = 7, BKA, ICP in maria-5.3 + compound index # set @tmp_730133_jcl= @@join_cache_level; set join_cache_level = 7; set @tmp_730133_os= @@optimizer_switch; set optimizer_switch= 'join_cache_hashed=off,join_cache_bka=on,index_condition_pushdown=on,optimize_join_buffer_size=on'; CREATE TABLE t1 (f1 int, f2 int, f3 int, f4 int, f5 int, KEY (f4,f3)); INSERT IGNORE INTO t1 VALUES ('2','9','5','0','0'),('4','7','0','0','0'), ('6','97','190','0','0'),('7','3','6','0','0'),('11','101','186','0','0'), ('14','194','226','0','0'),('15','148','133','0','0'), ('16','9','6','0','0'),('17','9','3','0','0'),('18','1','8','0','0'), ('19','1','5','0','0'),('20','5','7','0','0'); explain SELECT COUNT(alias2.f2) FROM t1 STRAIGHT_JOIN t1 AS alias3 STRAIGHT_JOIN t1 AS alias2 FORCE KEY (f4) WHERE alias2.f4=alias3.f5 AND alias2.f3 > alias3.f1; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 index NULL f4 10 NULL 12 Using index 1 SIMPLE alias3 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join) 1 SIMPLE alias2 ref f4 f4 5 test.alias3.f5 2 Using index condition(BKA); Using join buffer (incremental, BKA join); Key-ordered Rowid-ordered scan SELECT COUNT(alias2.f2) FROM t1 STRAIGHT_JOIN t1 AS alias3 STRAIGHT_JOIN t1 AS alias2 FORCE KEY (f4) WHERE alias2.f4=alias3.f5 AND alias2.f3 > alias3.f1; COUNT(alias2.f2) 768 set @@join_cache_level= @tmp_730133_jcl; set @@optimizer_switch= @tmp_730133_os; drop table t1; # # Test of MRR handler counters # flush status; show status like 'Handler_mrr%'; Variable_name Value Handler_mrr_init 0 Handler_mrr_key_refills 0 Handler_mrr_rowid_refills 0 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, filler char(200), key(a)); insert into t1 select A.a+10*B.a+100*C.a+1000*D.a, 123,'filler' from t0 A, t0 B, t0 C, t0 D; explain select sum(b) from t1 where a < 10; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range a a 5 NULL 8 Using index condition; Rowid-ordered scan # This should show one MRR scan and no re-fills: flush status; select sum(b) from t1 where a < 10; sum(b) 1230 show status like 'handler_mrr%'; Variable_name Value Handler_mrr_init 1 Handler_mrr_key_refills 0 Handler_mrr_rowid_refills 0 set @mrr_buffer_size_save= @@mrr_buffer_size; set mrr_buffer_size=128; explain select sum(b) from t1 where a < 1600; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t1 range a a 5 NULL 1380 Using index condition; Rowid-ordered scan # This should show one MRR scan and one extra rowid sort: flush status; select sum(b) from t1 where a < 1600; sum(b) 196800 show status like 'handler_mrr%'; Variable_name Value Handler_mrr_init 1 Handler_mrr_key_refills 0 Handler_mrr_rowid_refills 1 set @@mrr_buffer_size= @mrr_buffer_size_save; #Now, let's check BKA: set @join_cache_level_save= @@join_cache_level; set @join_buffer_size_save= @@join_buffer_size; set join_cache_level=6; explain select sum(t1.b) from t0,t1 where t0.a=t1.a; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t0 ALL NULL NULL NULL NULL 10 Using where 1 SIMPLE t1 ref a a 5 test.t0.a 1 Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan flush status; select sum(t1.b) from t0,t1 where t0.a=t1.a; sum(t1.b) 1230 show status like 'handler_mrr%'; Variable_name Value Handler_mrr_init 1 Handler_mrr_key_refills 0 Handler_mrr_rowid_refills 0 set join_buffer_size=10; explain select sum(t1.b) from t0,t1 where t0.a=t1.a; id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE t0 ALL NULL NULL NULL NULL 10 Using where 1 SIMPLE t1 ref a a 5 test.t0.a 1 Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan flush status; select sum(t1.b) from t0,t1 where t0.a=t1.a; sum(t1.b) 1230 show status like 'handler_mrr%'; Variable_name Value Handler_mrr_init ok Handler_mrr_key_refills ok Handler_mrr_rowid_refills ok set join_cache_level= @join_cache_level_save; set join_buffer_size= @join_buffer_size_save; drop table t0, t1; set optimizer_switch= @myisam_mrr_tmp;