The type of year operation with the type of date is wrong

[lilinghai]

create table t(a year,b date);
insert into t values(2005,"2004-10-10"),(2015,"2018-03-27");
alter table t set tiflash replica 1;
select * from t where a>b;

expect

+------+------------+
| a    | b          |
+------+------------+
| 2005 | 2004-10-10 |
+------+------------+

but got

+------+------------+
| a    | b          |
+------+------------+
| 2005 | 2004-10-10 |
| 2015 | 2018-03-27 |
+------+------------+

[mengxin9014]

pingcap/tidb#26215