executor: group_concat aggr panic when session.group_concat_max_len is small (#23131)

[ti-srebot]

cherry-pick #23131 to release-4.0
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---

Signed-off-by: guo-shaoge shaoge1994@163.com

What problem does this PR solve?

Issue Number: close #23129

Problem Summary:

drop table if exists t1;
create table t1(cid int, sname varchar(100));
insert into t1 values(1, 'Bob'), (1, 'Alice');
insert into t1 values(3, 'Ace');
set @@group_concat_max_len=5;
select group_concat(sname order by sname) from t1 group by cid;

What is changed and how it works?

What's Changed: when concat all strings from a group(AppendFinalResult2Chunk), we add the last separator to result, and then truncate to sesssion.group_concat_max_len. But we forgot to check if the concated string is shorter than sesssion.group_concat_max_len. So program panic.

PS: Another compatible bug found when fixing this bug, but it's not critical. Will fix in another issue.

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Integration test: Add test in aggregate_test.go::TestGroupConcatAggr()

Side effects: no

Release note

• group_concat aggr panic when session.group_concat_max_len is small.

[ti-srebot]

/run-all-tests

[ti-srebot]

@guo-shaoge you're already a collaborator in bot's repo.

[XuHuaiyu]

/LGTM

[guo-shaoge]

/run-unit-test

[zhouqiang-cl]

/merge

[ti-chi-bot]

@zhouqiang-cl: /merge in this pull request requires 2 /lgtm.

In response to this:

/merge

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[wshwsh12]

/lgtm

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• XuHuaiyu
• wshwsh12

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[XuHuaiyu]

/merge

[ti-chi-bot]

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

Commit hash: 7526894

[guo-shaoge]

/run-unit-test

[ti-chi-bot]

@ti-srebot: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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