str_to_date() Microseconds with leading zeros are not converted correctly in tiflash

[wshwsh12]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Similar to pingcap/tidb#30078

use test;
drop table t;
create table t(a varchar(30));
insert into t values("2003-01-02 10:11:12.0012");
alter table t set tiflash replica 1;
set tidb_enforce_mpp=1; set tidb_isolation_read_engines='tiflash';
select str_to_date(a, "%Y-%m-%d %H:%i:%S.%f") from t;

2. What did you expect to see? (Required)

MySQL [test]> select str_to_date(a, "%Y-%m-%d %H:%i:%S.%f") from t;
+----------------------------------------+
| str_to_date(a, "%Y-%m-%d %H:%i:%S.%f") |
+----------------------------------------+
| 2003-01-02 10:11:12.001200             |
+----------------------------------------+
1 row in set (0.000 sec)

3. What did you see instead (Required)

[tidb]> select str_to_date(a, "%Y-%m-%d %H:%i:%S.%f") from t;
+----------------------------------------+
| str_to_date(a, "%Y-%m-%d %H:%i:%S.%f") |
+----------------------------------------+
| 2003-01-02 10:11:12.120000             |
+----------------------------------------+
1 row in set (0.004 sec)

4. What is your TiFlash version? (Required)

master, 5.3, 5.2, 5.1, 5.0

[fuzhe1989]

#3557