planner: allow LEADING hint to match plan nodes with anonymous columns

[ghoshh]

What problem does this PR solve?

Issue Number: ref #65797

Problem Summary:

What changed and how does it work?

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

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None

[ti-chi-bot]

Hi @ghoshh. Thanks for your PR.

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[tiprow]

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[Copilot]

Pull request overview

Updates planner hint matching so LEADING can match plan nodes whose OutputNames() include anonymous/empty table-name columns (e.g., types.EmptyName), by ignoring those columns when extracting the table alias.

Changes:

• Adjust ExtractTableAlias to find the first non-empty table name and ignore columns with empty TblName during alias consistency checks.
• Preserve existing query-block offset adjustment logic while allowing alias extraction to succeed for plans with anonymous output columns.

[Copilot]

blockAsNames[qbOffset] can panic when qbOffset is negative (e.g. -1) or >= len(blockAsNames). This path is now reachable even when the first output name has an empty table name (because we scan for the first non-empty TblName), so it can introduce new panics compared to the previous early-return behavior. Add an explicit bounds check (and ensure qbOffset >= 0) before indexing blockAsNames.

Suggested change

	if qbOffset != parentOffset && blockAsNames != nil && blockAsNames[qbOffset].TableName.L != "" {
	if qbOffset != parentOffset &&
	blockAsNames != nil &&
	qbOffset >= 0 &&
	qbOffset < len(blockAsNames) &&
	blockAsNames[qbOffset].TableName.L != "" {

[hawkingrei]

/ok-to-test

[fixdb]

Can we add test cases?

[ghoshh]

I’ve added several new tests. The LEADING hint now takes effect, but it still emits a warning. The warning is generated during the plan-building phase (not join reordering), I think we can fix it in the future.
I'll try to add more test cases.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.3594%. Comparing base (5da5f2a) to head (c8de6a1).
⚠️ Report is 25 commits behind head on master.

⚠️ Current head c8de6a1 differs from pull request most recent head d99bca4

Please upload reports for the commit d99bca4 to get more accurate results.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #65837        +/-   ##
================================================
- Coverage   77.7956%   77.3594%   -0.4362%     
================================================
  Files          2000       1921        -79     
  Lines        545038     535107      -9931     
================================================
- Hits         424016     413956     -10060     
- Misses       119360     120889      +1529     
+ Partials       1662        262      -1400     

Flag	Coverage Δ
integration	41.4931% <100.0000%> (-6.6775%)	⬇️

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

Components	Coverage Δ
dumpling	56.7974% <ø> (ø)
parser	∅ <ø> (∅)
br	48.8044% <ø> (-12.1671%)	⬇️

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[Reminiscent]

/retest

[ti-chi-bot]

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[tiprow]

@ghoshh: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
fast_test_tiprow	d99bca4	link	true	/test fast_test_tiprow

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[ti-chi-bot]

@ghoshh: 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
pull-br-integration-test	a4ccddb	link	true	/test pull-br-integration-test
pull-lightning-integration-test	a4ccddb	link	true	/test pull-lightning-integration-test
pull-unit-test-ddlv1	a4ccddb	link	true	/test pull-unit-test-ddlv1
idc-jenkins-ci-tidb/check_dev	d99bca4	link	true	/test check-dev
idc-jenkins-ci-tidb/check_dev_2	d99bca4	link	true	/test check-dev2
pull-unit-test-next-gen	d99bca4	link	true	/test pull-unit-test-next-gen
idc-jenkins-ci-tidb/unit-test	d99bca4	link	true	/test unit-test

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