Merge branch '10.4' into 10.4-mdev16188

1 files changed, 50 insertions, 0 deletions

diff --git a/mysql-test/main/index_merge_myisam.result b/mysql-test/main/index_merge_myisam.result
index 992e1d831b5..725a888c914 100644
--- a/mysql-test/main/index_merge_myisam.result
+++ b/mysql-test/main/index_merge_myisam.result
@@ -1715,3 +1715,53 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	PRIMARY,c1,i,c2	NULL	NULL	NULL	69	Using where
 DROP TABLE t1;
 set optimizer_switch= @optimizer_switch_save;
+#
+# MDEV-16695: Estimate for rows of derived tables is very high when we are using index_merge union
+#
+create table t0
+(
+key1 int not null,
+INDEX i1(key1)
+);
+insert into t0 values (1),(2),(3),(4),(5),(6),(7),(8);
+set @d=8;
+insert into t0 select key1+ @d from t0;
+set @d=@d*2;
+insert into t0 select key1+ @d from t0;
+set @d=@d*2;
+insert into t0 select key1+ @d from t0;
+set @d=@d*2;
+insert into t0 select key1+ @d from t0;
+set @d=@d*2;
+insert into t0 select key1+ @d from t0;
+set @d=@d*2;
+insert into t0 select key1+ @d from t0;
+set @d=@d*2;
+insert into t0 select key1+ @d from t0;
+set @d=@d*2;
+alter table t0 add key2 int not null, add index i2(key2);
+alter table t0 add key3 int not null, add index i3(key3);
+alter table t0 add key8 int not null, add index i8(key8);
+update t0 set key2=key1,key3=key1,key8=1024-key1;
+analyze table t0;
+Table	Op	Msg_type	Msg_text
+test.t0	analyze	status	OK
+set @optimizer_switch_save=@@optimizer_switch;
+set optimizer_switch='derived_merge=off,derived_with_keys=off';
+explain select * from (select * from t0 where key1 = 3 or key2 =3) as Z where Z.key8 > 5;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	Using where
+2	DERIVED	t0	index_merge	i1,i2,i8	i1,i2	4,4	NULL	2	Using union(i1,i2); Using where
+select * from (select * from t0 where key1 = 3 or key2 =3) as Z where Z.key8 > 5;
+key1	key2	key3	key8
+3	3	3	1021
+set optimizer_use_condition_selectivity=2;
+explain select * from (select * from t0 where key1 = 3 or key2 =3) as Z where Z.key8 > 5;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	Using where
+2	DERIVED	t0	index_merge	i1,i2,i8	i1,i2	4,4	NULL	2	Using union(i1,i2); Using where
+select * from (select * from t0 where key1 = 3 or key2 =3) as Z where Z.key8 > 5;
+key1	key2	key3	key8
+3	3	3	1021
+set @@optimizer_switch= @optimizer_switch_save;
+drop table t0;