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planner: fix wrong TopN's ByItem with expression.ScalarFunction when to PushDownTopN (#60822)#61005

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planner: fix wrong TopN's ByItem with expression.ScalarFunction when to PushDownTopN (#60822)#61005
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This is an automated cherry-pick of #60822

What problem does this PR solve?

Issue Number: close #60655

Problem Summary:

In the #40593,

There is a column in topN.ByItems is generated by proj, when topN is pushed down below proj, topN cannot obtain the column from datasource, to fix this, we can check whether topN.ByItems contains a column(with ID=0) generated by proj, if so, proj will prevent the optimizer from pushing topN down.

  1. A column with ID=0 indicates that the column cannot be resolved by data source.
  2. To determine whether a column is generated by projection, we can check whether the child of proj contains the column.

What changed and how does it work?

If you find that the TopN you can push down cannot actually be pushed down, you should use the original TopN to assemble into a structure of TopN -> Projection, rather than using the processed TopN to assemble.

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.

planner: fix wrong TopN's ByItem with expression.ScalarFunction when to PushDownTopN

修复在 TopN 下推过程中错误生成带表达式的TopN排序项 

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>
@ti-chi-bot ti-chi-bot added do-not-merge/hold Indicates that a PR should not merge because someone has issued a /hold command. release-note Denotes a PR that will be considered when it comes time to generate release notes. sig/planner SIG: Planner size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. type/cherry-pick-for-release-8.1 This PR is cherry-picked to release-8.1 from a source PR. labels May 8, 2025
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ti-chi-bot Bot commented May 8, 2025

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
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@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.

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ti-chi-bot Bot commented May 8, 2025

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name Commit Details Required Rerun command
idc-jenkins-ci-tidb/build 6292e27 link true /test build
idc-jenkins-ci-tidb/unit-test 6292e27 link true /test unit-test
idc-jenkins-ci-tidb/check_dev 6292e27 link true /test check-dev
idc-jenkins-ci-tidb/check_dev_2 6292e27 link true /test check-dev2

Full PR test history. Your PR dashboard.

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@ti-chi-bot ti-chi-bot Bot added cherry-pick-approved Cherry pick PR approved by release team. and removed do-not-merge/cherry-pick-not-approved labels Jun 25, 2025
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