executor: fix wrong result of delete multiple tables using left join

[guo-shaoge]

Signed-off-by: guo-shaoge [email protected]

What problem does this PR solve?

Issue Number: close #31321

Problem Summary:
delete from t1, t2 using t1 left join t2 on t1.c1 = t2.c1;

row of t1: (1)
row of t2: (2)
The join result will be (1, null). 1 in t1 is matched, and no row in t2 is matched. So row in t1 should be deleted, while no row in t2 should be deleted.

But the original implementation didn't check if the row in t2 is matched or not, just delete it directly, which cause the wrong result.

What is changed and how it works?

If a row is not matched in outer join, the rowid of the join result will be NULL, we use this to decide if we can delete row.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

executor: fix wrong result of delete multiple tables using left join

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• winoros
• wshwsh12

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[guo-shaoge]

/cc @wshwsh12

[winoros]

I just raise a question.

In the case you mentioned, the t2's columns are filled with NULL. How did we get its row id value so that unwanted deletion happened?

[guo-shaoge]

I just raise a question.

In the case you mentioned, the t2's columns are filled with NULL. How did we get its row id value?

As we discussed, the rowid is NULL, but it's value is zero, So the row whose primary key is zero will be deleted.

[wshwsh12]

LGTM

[guo-shaoge]

/merge

[ti-chi-bot]

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

Commit hash: e92141e

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/3956c7d920d6638ecc7d1197fb1dda00d339bec2

[ti-srebot]

cherry pick to release-4.0 in PR #33118

[ti-srebot]

cherry pick to release-5.0 in PR #33119

[ti-srebot]

cherry pick to release-5.1 in PR #33120

[ti-srebot]

cherry pick to release-5.2 in PR #33121

[ti-srebot]

cherry pick to release-5.3 in PR #33122

[ti-srebot]

cherry pick to release-5.4 in PR #33123