load: fix load data with non-utf8 will succeed (#26054)

[ti-srebot]

cherry-pick #26054 to release-4.0
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/26142

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git push git@github.com:ti-srebot/tidb.git pr/26142:release-4.0-d070f708cd62

---

Signed-off-by: ailinkid 314806019@qq.com

What problem does this PR solve?

Issue Number: close #25979

What is changed and how it works?

How it Works:

Refer: https://dev.mysql.com/doc/refman/8.0/en/load-data.html
With IGNORE or LOCAL, data-interpretation errors become warnings and the load operation continues, even if the SQL mode is restrictive. For examples, see Column Value Assignment.

Reason:
load data into t: CAST(BINARY(X'c2c2c2c2') -> CHAR(2);
the returned truncated value is X'c2c2' which is still invalid without right utf8 encode.

That's is because the loaddata statement's TruncateAsWarning doesn't follow the strict sql mode when keyword ignore and local is turned on.

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch

Check List

Tests

• Manual test (add detailed scripts or steps below)

Using the real TiKV nodes with TiUP

create table t( `a` varchar(12) DEFAULT NUL);
load data local infile "/home/arenatlx/下载/1111.txt" into table t FIELDS TERMINATED BY '||' LINES TERMINATED BY '\n' (@`a`) set `a` = NULLif(@a,'');

analyze table t // shouldn't have a error here.

1111.txt

Release note

• load: fix load data with non-utf8 can succeed

[ti-srebot]

/run-all-tests

[ti-srebot]

@AilinKid you're already a collaborator in bot's repo.

[bb7133]

/lgtm

[AilinKid]

/merge

[ti-chi-bot]

@AilinKid: /merge in this pull request requires 2 approval(s).

In response to this:

/merge

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[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• jackysp
• wjhuang2016

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[AilinKid]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 1d2d4a6