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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 Extra
1 SIMPLE a ALL NULL NULL NULL NULL 2 Using where
1 SIMPLE g ref groups_dt groups_dt 70 const,test.a.type 13 Using index condition
drop table t0,t1,t2,t3;
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