planner: fix null-safe equality partition pruning

[hawkingrei]

What problem does this PR solve?

Issue Number: close #65991

Problem Summary:

Queries can panic with invalid input parameternulleq when partition pruning sees a constant-left null-safe equality predicate such as 1 <=> partition_col. The failing issue query derives that shape from a correlated tuple IN predicate over partitioned tables.

What changed and how does it work?

opposite() now treats ast.NullEQ as symmetric when partition pruning normalizes constant-left predicates into column-left predicates. This keeps <=> unchanged after operand flipping instead of falling through to the panic path.

The regression test covers both PARTITION BY RANGE and PARTITION BY RANGE COLUMNS, including non-NULL and NULL constants.

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.

Manual test:

go test -tags=intest,deadlock ./pkg/planner/core/issuetest -run TestPlannerIssueRegressions -count=1
go test -tags=intest,deadlock ./pkg/planner/core/rule -run Test -count=1
make bazel_prepare
git diff --check

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

Fix a panic that could occur during partition pruning for constant-left null-safe equality predicates.

Summary by CodeRabbit

• Bug Fixes

  • Fixed handling of null-safe equality operator in partition-pruned queries.

• Tests

  • Added regression test validating partition pruning behavior with null-safe equality operator.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 4e187246-663a-4c3e-9421-0001265bac5e

📥 Commits

Reviewing files that changed from the base of the PR and between dd8253c and 014fa0f.

📒 Files selected for processing (2)

• pkg/planner/core/issuetest/planner_issue_test.go
• pkg/planner/core/rule/rule_partition_processor.go

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📝 Walkthrough

Walkthrough

This PR fixes an invalid-parameter panic in partition range pruning when the null-safe equality operator (<=>) is encountered. The opposite() function in the partition processor now treats null-safe equality as symmetric (returning itself when operands are flipped) instead of falling through to the panic path. A regression test validates the fix across both range and range columns partitioning.

Changes

Null-safe equality partition pruning

Layer / File(s)	Summary
Null-safe equality symmetry in opposite() pkg/planner/core/rule/rule_partition_processor.go	opposite() adds explicit handling for ast.NullEQ so that null-safe equality returns the same operator when operands are flipped, preventing panic in partition pruning logic.
Regression test for constant-left null-safe equality pkg/planner/core/issuetest/planner_issue_test.go	New cascades test validates partition pruning with null-safe equality on the left side, covering both range and range columns partitioning with NULL values.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested labels

sig/planner, size/M

Suggested reviewers

• AilinKid
• winoros
• guo-shaoge

Poem

🐰 Null-safe hops through partition plans,
Symmetric equals, no more panics and cans,
Range pruning blooms where <=> would fall,
Tests verify the fix works for all!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'planner: fix null-safe equality partition pruning' directly and clearly summarizes the main change—fixing partition pruning for null-safe equality operators.
Description check	✅ Passed	The description follows the template well, including issue number, problem summary, explanation of changes, test checklist with unit and manual tests marked, manual test commands, and a clear release note.
Linked Issues check	✅ Passed	The PR successfully addresses issue #65991 by fixing the panic caused by null-safe equality in partition pruning; the opposite() function now correctly handles ast.NullEQ, resolving the 'invalid input parameternulleq' error.
Out of Scope Changes check	✅ Passed	All changes are directly in scope: a fix to the opposite() function and a corresponding regression test case for partition pruning with null-safe equality operators.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.7244%. Comparing base (dd8253c) to head (014fa0f).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #68425        +/-   ##
================================================
- Coverage   77.2764%   75.7244%   -1.5521%     
================================================
  Files          2010       2008         -2     
  Lines        555481     563986      +8505     
================================================
- Hits         429256     427075      -2181     
- Misses       125305     136752     +11447     
+ Partials        920        159       -761     

Flag	Coverage Δ
integration	41.1499% <0.0000%> (+1.3559%)	⬆️

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

Components	Coverage Δ
dumpling	60.4888% <ø> (ø)
parser	∅ <ø> (∅)
br	49.9725% <ø> (-13.0354%)	⬇️

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, qw4990

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Details

Needs approval from an approver in each of these files:

• pkg/planner/OWNERS [AilinKid,qw4990]

Approvers can indicate their approval by writing /approve in a comment
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-05-18 09:03:51.49352243 +0000 UTC m=+168560.997653096: ☑️ agreed by AilinKid.
• 2026-05-18 09:04:15.55988851 +0000 UTC m=+168585.064019186: ☑️ agreed by qw4990.

[hawkingrei]

/retest