planner: constant folding to isnull(not null column) | tidb-test=pr/2559

[ti-chi-bot]

This is an automated cherry-pick of #62046

What problem does this PR solve?

Issue Number: close #62050 ref #7973

Problem Summary:

What changed and how does it work?

When we process the outer join, we remove the not-null flag. However, during predicate pushdown, this causes the flag to differ from the original one, and as a result, predicate simplification cannot be performed when handling the data source.

Check List

Tests

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

  • I checked and no code files have been changed.

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

@hawkingrei This PR has conflicts, I have hold it.
Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (release-8.5@6f8a5f8). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.5     #62163   +/-   ##
================================================
  Coverage               ?   57.1849%           
================================================
  Files                  ?       1777           
  Lines                  ?     630650           
  Branches               ?          0           
================================================
  Hits                   ?     360637           
  Misses                 ?     245839           
  Partials               ?      24174           

Flag	Coverage Δ
integration	37.1420% <100.0000%> (?)
unit	72.8010% <100.0000%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.9278% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	52.7007% <0.0000%> (?)

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[fixdb]

+1

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, fixdb

The full list of commands accepted by this bot can be found here.

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Needs approval from an approver in each of these files:

• pkg/planner/OWNERS [AilinKid,fixdb]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-07-11 04:02:41.833687705 +0000 UTC m=+2231614.556866688: ☑️ agreed by AilinKid.
• 2025-07-11 04:54:48.791203969 +0000 UTC m=+2234741.514382953: ☑️ agreed by fixdb.

[AilinKid]

/unhold

[AilinKid]

/test mysql-test

[tiprow]

@AilinKid: No presubmit jobs available for pingcap/[email protected]

In response to this:

/test mysql-test

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[hawkingrei]

/retest

[hawkingrei]

/retest

[hawkingrei]

/retest

[hawkingrei]

/retest