--disable_warnings drop table if exists t0,t1,t2,t3; --enable_warnings --echo # --echo # BUG#38049 incorrect rows estimations with references from preceding table --echo # create table t0 (a int); insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9); create table t1 (a varchar(32)); insert into t1 values ('owner'),('requester'),('admincc'),('cc'); CREATE TABLE t2 ( id int(11) NOT NULL, type varchar(32) default NULL, PRIMARY KEY (id) ); insert into t2 values (1,'owner'), (2,'admincc'); CREATE TABLE t3 ( id int(11) NOT NULL, domain varchar(32) default NULL, type varchar(32) default NULL, PRIMARY KEY (id) ); set @domain='system'; set @pk=0; INSERT INTO t3 select @pk:=@pk+1, 'system', t1.a from t1; INSERT INTO t3 select @pk:=@pk+1, 'queue', t1.a from t1, t0 where t0.a<3; INSERT INTO t3 select @pk:=@pk+1, 'ticket', t1.a from t1, t0 A, t0 B, t0 C; CREATE INDEX groups_d ON t3(domain); CREATE INDEX groups_t ON t3(type); CREATE INDEX groups_td ON t3(type, domain); CREATE INDEX groups_dt ON t3(domain, type); --echo For table g this must use ref(groups_dt) and #rows should be around 15 and not 335: explain SELECT STRAIGHT_JOIN g.id FROM t2 a, t3 g USE INDEX(groups_dt) WHERE g.domain = 'queue' AND g.type = a.type; drop table t0,t1,t2,t3;