unexpected duplicate error when replace into clustered primary key with prefix column with default value

[lysu]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table test1(c1 varchar(100) not null default 'xyza', c2 int, primary key(c1(3)) clustered);
replace into test1(c2) values(1);
replace into test1(c2) values(1);

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

two replace successed

3. What did you see instead (Required)

last replace failed with

replace into test1(c2) values(1);
ERROR 1062 (23000): Duplicate entry 'xyz' for key 'PRIMARY'

4. What is your TiDB version? (Required)

Release Version: v4.0.0-beta.2-2243-g7daf7436d
Edition: Community
Git Commit Hash: 7daf7436da5de4e5fea3895e892d10d3790e9102
Git Branch: master
UTC Build Time: 2021-03-03 06:18:37
GoVersion: go1.15
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[lysu]

insert on duplicate without default value also have same problem

create table test3(c1 varchar(100), c2 int, primary key(c1(1)) clustered);
insert into test3 values('ab', 1) on duplicate key update c2 = 100;
insert into test3 values('ab', 1) on duplicate key update c2 = 100;
ERROR 1062 (23000): Duplicate entry 'a' for key 'PRIMARY'

[ti-srebot]

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Bug

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5. Affected versions

master

6. Fixed versions

master