drop table if exists t0,t1,t2,t3;## BUG#38049 incorrect rows estimations with references from preceding table#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);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;id select_type table type possible_keys key key_len ref rows Extra1 SIMPLE a ALL NULL NULL NULL NULL 2 Using where1 SIMPLE g ref groups_dt groups_dt 70 const,test.a.type 13 Using index conditiondrop table t0,t1,t2,t3;