Encoding failed when comparing the type of char and hex

[lilinghai]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

CREATE TABLE `t` (
  `a` char(10) DEFAULT NULL
);
insert into t values('h');
select * from t where a> 0x67; -- successfully
select * from t where a> 0x88; -- encoding failed

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

successfully

3. What did you see instead (Required)

ERROR 1105 (HY000): encoding failed

4. What is your TiDB version? (Required)

Release Version: v4.0.0-beta.2-2561-g9c75cfa4e
Edition: Community
Git Commit Hash: 9c75cfa
Git Branch: master
UTC Build Time: 2021-04-02 18:50:29
GoVersion: go1.13
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[xiongjiwei]

it is the same reason with #23506

[wshwsh12]

Duplicate of #23506

[ti-srebot]

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