clustered index + new collation + old row format got wrong result

[lysu]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

start a tidb with the new collation enabled and MUST started with TiKV(because unistore only support new format- -)

set global tidb_row_format_version=1;

reconnect a new session

create table t2(col_1 varchar(132) CHARACTER SET utf8 COLLATE utf8_unicode_ci, primary key(col_1) clustered);
insert into t2 select 'aBc';
select * from t2 where col_1 = 'aBc';

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

aBc

3. What did you see instead (Required)

mysql> select * from t2 where col_1 = 'aBc';
+--------+
| col_1  |
+--------+
| 3J` |
+--------+
1 row in set (0.01 sec)

4. What is your TiDB version? (Required)

v5.0.1 tidb + tikv

master 5460b5c

[ti-srebot]

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