executor: wrong result of nullif expr when used with is null expr. (#23170)

[ti-srebot]

cherry-pick #23170 to release-5.0-rc
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git pr https://github.com/pingcap/tidb/pull/23278

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

What problem does this PR solve?

Issue Number: close #23157

Problem Summary:

drop table t;
create table t(a int primary key);
insert into t values(1),(2);
select * from t where nullif(a,a) is null;

The result of Nullif expr is unexpected, same reason as #23102 .

What is changed and how it works?

Proposal: xxx

What's Changed: In TiDB, we rewrite Nullif(e1, e2) as If(e1 = e2, NULL, e2), so we need to change InferType4ControlFuncs()(which will be call in ifFunctionClass::getFunction), unset NotNullFlag if any argument is NULL.

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Integration test: TestNullifWithIsNull()

Side effects:no

Release note

• wrong result of nullif expr when used with is null expr

[ti-chi-bot]

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[ti-srebot]

/run-all-tests

[ti-srebot]

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

[guo-shaoge]

depend this pr: #23135