Index condition pushdown is not used with ref access of partitioned tables

create table t0 (

tp int, a int, b int, c varchar(12), index idx (a,b)

) engine=myisam;

insert into t0 values

(1,3,30,'yyzy'), (1,3,30,'yxxyy'), (1,3,30,'yyxy'), (1,3,30,'xxyy'),

(1,3,30,'yyxz'), (1,3,30,'yyzz'), (1,3,30,'xxyzy'), (1,3,30,'yyyy'),

(1,3,30,'yzzy'), (1,93,30,'zzzy'),

(2,3,40,'yxx'), (2,4,40,'xx'), (2,3,10,'zxz'),

(2,3,40,'yyx'), (2,4,40,'xxx'), (2,3,10,'zyyz'),

(2,3,40,'xzzzz'), (2,4,40,'yyyxx'), (2,3,10,'zyz'),

(2,3,40,'xxx'), (2,4,40,'xx'), (2,3,10,'zzz'),

(2,3,40,'yyxzx'), (2,4,40,'xyx'), (2,3,10,'xzz'),

(2,3,40,'xxxzz'), (2,4,40,'xxz'), (2,3,10,'zzzy'),

(2,3,40,'zzxxx'), (2,4,40,'zxx'), (2,3,10,'yzzz'),

(2,3,40,'xyyxx'), (2,4,40,'xzzzx'), (2,3,10,'zzxxz'),

(2,3,40,'yzxxx'), (2,4,40,'xxzy'), (2,3,10,'zzzyx'),

(2,93,40,'xzx'), (2,94,40,'xz'), (2,93,10,'zyyyz'),

(3,4,30,'yx'), (3,4,30,'yyxxx'), (3,4,30,'zzyy'), (3,4,30,'zxyy'),

(3,4,30,'xxyy'), (3,4,30,'yyzx'),  (3,4,30,'zyyy'), (3,4,30,'yzy'),

(3,4,30,'zzzyy'), (3,94,30,'yyz');

create table t1 (

tp int, a int, b int, c varchar(12), index idx (a,b)

) engine=myisam

partition by list (tp)

( partition p1 values in (1),

  partition p2 values in (2),

  partition p3 values in (3));

insert into t1 select * from t0;

create table t2 (a int, index idx(a)) engine=myisam;

insert into t2 values (1), (2), (3), (4), (5);

insert into t2 select a+10 from t2;

insert into t2 select a+20 from t2;

analyze table t0,t1,t2;

select * from t0,t2 where t2.a in (3,4) and t0.a=t2.a and (t0.b / 10) = 4;

MariaDB [test]> explain extended select * from t0,t2 where t2.a in (3,4) and t0.a=t2.a and (t0.b / 10) = 4;

+------+-------------+-------+-------+---------------+------+---------+-----------+------+----------+--------------------------+

| id   | select_type | table | type  | possible_keys | key  | key_len | ref       | rows | filtered | Extra                    |

+------+-------------+-------+-------+---------------+------+---------+-----------+------+----------+--------------------------+

|    1 | SIMPLE      | t2    | range | idx           | idx  | 5       | NULL      |    2 |   100.00 | Using where; Using index |

|    1 | SIMPLE      | t0    | ref   | idx           | idx  | 5       | test.t2.a |   13 |   100.00 | Using index condition    |

+------+-------------+-------+-------+---------------+------+---------+-----------+------+----------+--------------------------+

select * from t1,t2 where t2.a in (3,4) and t1.a=t2.a and (t1.b / 10) = 4;

MariaDB [test]> explain extended select * from t1,t2 where t2.a in (3,4) and t1.a=t2.a and (t1.b / 10) = 4;

+------+-------------+-------+-------+---------------+------+---------+-----------+------+----------+--------------------------+

| id   | select_type | table | type  | possible_keys | key  | key_len | ref       | rows | filtered | Extra                    |

+------+-------------+-------+-------+---------------+------+---------+-----------+------+----------+--------------------------+

|    1 | SIMPLE      | t2    | range | idx           | idx  | 5       | NULL      |    2 |   100.00 | Using where; Using index |

|    1 | SIMPLE      | t1    | ref   | idx           | idx  | 5       | test.t2.a |    5 |   100.00 | Using where              |

+------+-------------+-------+-------+---------------+------+---------+-----------+------+----------+--------------------------+