ddl, executor: fix clustered prefix primary key truncation

[tangenta]

What problem does this PR solve?

Problem Summary:

• In UpdateRecord, the updating common handle should be truncated. Otherwise, the update-ignore statement fails to throw a warning.

drop table if exists t;
set tidb_enable_clustered_index=1;
create table t(a varchar(255), b int, primary key (a(2)));
insert into t values ('aaa', 1), ('bbb', 1);
update ignore t set a = 'aaaaa' where a = 'bbb';
show warnings;

Expected

+---------+------+----------------------------------------+
| Level   | Code | Message                                |
+---------+------+----------------------------------------+
| Warning | 1062 | Duplicate entry 'aa' for key 'PRIMARY' |
+---------+------+----------------------------------------+

Got

+-------+------+---------+
| Level | Code | Message |
+-------+------+---------+

What is changed and how it works?

What's Changed: Truncate the updating common handle if necessary.

How it Works: Omitted.

Related changes

N/A

Check List

Tests

• Unit test
• Integration test

Side effects

N/A

Release note

• No release note

[coocood]

LGTM

[lzmhhh123]

LGTM

[lzmhhh123]

/merge

[ti-srebot]

/run-all-tests

[ti-srebot]

/run-all-tests

[ti-srebot]

@tangenta merge failed.