1 files changed, 35 insertions, 0 deletions
diff --git a/mysql-test/main/index_merge_myisam.test b/mysql-test/main/index_merge_myisam.test
index d265007431e..75beb9bd883 100644
--- a/mysql-test/main/index_merge_myisam.test
+++ b/mysql-test/main/index_merge_myisam.test
@@ -243,3 +243,38 @@ DROP TABLE t1;
 
 set optimizer_switch= @optimizer_switch_save;
 
+--echo #
+--echo # MDEV-16695: Estimate for rows of derived tables is very high when we are using index_merge union
+--echo #
+
+create table t0
+(
+  key1 int not null,
+  INDEX i1(key1)
+);
+
+insert into t0 values (1),(2),(3),(4),(5),(6),(7),(8);
+let $1=7;
+set @d=8;
+while ($1)
+{
+  eval insert into t0 select key1+ @d from t0;
+  eval set @d=@d*2;
+  dec $1;
+}
+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;
+
+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;
+select * from (select * from t0 where key1 = 3 or key2 =3) as Z where Z.key8 > 5;
+set optimizer_use_condition_selectivity=2;
+explain select * from (select * from t0 where key1 = 3 or key2 =3) as Z where Z.key8 > 5;
+select * from (select * from t0 where key1 = 3 or key2 =3) as Z where Z.key8 > 5;
+set @@optimizer_switch= @optimizer_switch_save;
+drop table t0;