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planner: pre-refactor for join reorder conflict detection algorithm#68870

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planner: pre-refactor for join reorder conflict detection algorithm#68870
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@guo-shaoge guo-shaoge commented Jun 2, 2026

What problem does this PR solve?

Issue Number: close #66088

Problem Summary: manually cherry pick #66087

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

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

None

Summary by CodeRabbit

  • New Features

    • Support for nested LEADING(...) optimizer hints, preserving nested structure for parsing and planner use.
  • Improvements

    • Planner now respects structured LEADING hints when constructing join orders and applying join-method preferences.
  • Tests

    • Added parser and restore tests covering nested and mixed LEADING(...) forms to ensure correct round-trip rendering and parsing.

Signed-off-by: guo-shaoge <shaoge1994@163.com>
Signed-off-by: guo-shaoge <shaoge1994@163.com>
Signed-off-by: guo-shaoge <shaoge1994@163.com>
Signed-off-by: guo-shaoge <shaoge1994@163.com>
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ti-chi-bot Bot commented Jun 2, 2026

This cherry pick PR is for a release branch and has not yet been approved by triage owners.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick:

  1. It must be LGTMed and approved by the reviewers firstly.
  2. For pull requests to TiDB-x branches, it must have no failed tests.
  3. AFTER it has lgtm and approved labels, please wait for the cherry-pick merging approval from triage owners.
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@ti-chi-bot ti-chi-bot Bot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. sig/planner SIG: Planner labels Jun 2, 2026
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Run ID: 9c2b8656-adc6-4eb8-8b7c-aa33dffc2a20

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Reviewing files that changed from the base of the PR and between 6d4f992 and 0af91a8.

📒 Files selected for processing (1)
  • pkg/planner/core/rule_join_reorder.go
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📝 Walkthrough

Walkthrough

This PR adds nested LEADING(...) AST support and restoration, updates the hint parser and generated parser to produce structured *ast.LeadingList HintData (with legacy flattening), propagates the structured leading hint into PlanHints, introduces a new joinorder utilities package for join-order/hint handling, and integrates these helpers into planner code while adding Schema.Equal, InjectExpr, and minor cost helper adjustments.

Changes

LEADING Hint Parsing and Propagation

Layer / File(s) Summary
Schema equality comparison
pkg/expression/schema.go
Adds Schema.Equal() method comparing two schemas by nil-ness, column count, and per-position column equality without considering keys.
AST structures for nested LEADING hints
pkg/parser/ast/misc.go
Introduces LeadingList AST node, FlattenLeadingList helper to extract flat table list, LeadingList.RestoreWithQB for rendering nested LEADING with query-block awareness, and adjusts TableOptimizerHint.Restore QB handling.
Parser grammar for nested LEADING hints
pkg/parser/hintparser.y
Extends %union with leadingList/leadingElement and adds LeadingTableList/LeadingTableElement nonterminals to parse comma-separated and parenthesized nested table/list items; routes LEADING through dedicated production.
Generated parser code and symbol tables
pkg/parser/hintparser.go
Regenerated parsing tables, symbol names, and reductions to support nested LEADING construction; yyhintSymType carries leading element, HintData is set to *ast.LeadingList and Tables is populated via FlattenLeadingList for compatibility.
Parser test cases and restore tests
pkg/parser/hintparser_test.go, pkg/parser/parser_test.go, pkg/parser/ast/misc_test.go
Adds parse tests for nested LEADING forms and extends restore tests to validate nested rendering with proper quoting and QB behavior; TestOptimizerHints updated to assert HintData is *ast.LeadingList.
Hint propagation with structured LEADING data
pkg/util/hint/hint.go
Adds LeadingList *ast.LeadingList to PlanHints; ParsePlanHints extracts *ast.LeadingList from parsed hints when present and includes it in returned PlanHints.

Join-order Utility Library and Rule Refactoring

Layer / File(s) Summary
Join-order utilities package
pkg/planner/core/BUILD.bazel, pkg/planner/core/joinorder/BUILD.bazel, pkg/planner/core/joinorder/util.go
Creates new public joinorder library providing CheckAndGenerateLeadingHint, BuildLeadingTreeFromList (generic), FindAndRemovePlanByAstHint, IsDerivedTableInLeadingHint, and SetNewJoinWithHint.
Logical projection injection helper
pkg/planner/core/operator/logicalop/logical_projection.go
Adds exported InjectExpr helper that ensures a LogicalProjection exists above a plan, appends an expression, and returns the projected column.
Cost model helper extraction
pkg/planner/core/plan_cost_ver2.go
Replaces local cols2Exprs helper usage with expression.Column2Exprs for join-key expression derivation and removes the deleted helper.
Rule join reorder refactoring to use shared utilities
pkg/planner/core/rule_join_reorder.go
Refactors join-reorder to use joinorder.CheckAndGenerateLeadingHint, joinorder.SetNewJoinWithHint, and joinorder.JoinMethodHint mapping; removes local join-hint helpers and types; updates core BUILD deps to include joinorder.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

🐰 Twitch, twitch! A rabbit hops through nested LEADING hints,
Restructuring join orders with gleaming checklists,
Schema.Equal() whispers: both paths align,
Shared utilities bloom—join-reorder refines!
Binky!

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name Status Explanation Resolution
Description check ⚠️ Warning The PR description includes the linked issue reference (#66088), confirms unit tests were added, marks side effects as checked, and provides a release note section. However, the 'What changed and how does it work?' section is blank, which is a critical requirement for clarity. Add a detailed 'What changed and how does it work?' section explaining the refactoring changes, including the new joinorder package and schema equality logic introduced in this PR.
Docstring Coverage ⚠️ Warning Docstring coverage is 70.00% which is insufficient. The required threshold is 80.00%. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (3 passed)
Check name Status Explanation
Title check ✅ Passed The title 'planner: pre-refactor for join reorder conflict detection algorithm' clearly describes the main change and relates directly to the changeset's focus on refactoring join reorder logic and supporting infrastructure.
Linked Issues check ✅ Passed The code changes implement preparatory refactoring for join reorder conflict detection by introducing the joinorder package with utility functions for handling LEADING hints, schema comparison methods, and hint restoration logic—directly supporting the refactoring objective stated in issue #66088.
Out of Scope Changes check ✅ Passed All changes align with the pre-refactor objective: new joinorder package for join-order utilities, parser enhancements for LEADING hints, schema equality comparison, and integration with existing planner components. No extraneous changes detected.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.

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@guo-shaoge guo-shaoge changed the title Cp pre cdc impl planner: pre-refactor for join reorder conflict detection algorithm Jun 2, 2026
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Actionable comments posted: 3

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)
pkg/util/hint/hint.go (1)

955-983: ⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Clear LeadingList when LEADING is invalidated.

This branch invalidates conflicting LEADING hints by emptying LeadingJoinOrder, but it still returns the parsed LeadingList. The new join-order helpers read PlanHints.LeadingList directly, so LEADING + STRAIGHT_JOIN or multiple LEADING hints can still influence join-order selection after being marked invalid here.

Suggested fix
 	if leadingHintCnt > 1 || (leadingHintCnt > 0 && straightJoinOrder) {
 		// If there are more leading hints or the straight_join hint existes, all leading hints will be invalid.
 		leadingJoinOrder = leadingJoinOrder[:0]
+		leadingList = nil
 		if leadingHintCnt > 1 {
 			warnHandler.SetHintWarning("We can only use one leading hint at most, when multiple leading hints are used, all leading hints will be invalid")
 		} else if straightJoinOrder {
 			warnHandler.SetHintWarning("We can only use the straight_join hint, when we use the leading hint and straight_join hint at the same time, all leading hints will be invalid")
 		}
 	}
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@pkg/util/hint/hint.go` around lines 955 - 983, The code invalidates LEADING
by clearing leadingJoinOrder but still returns LeadingList, so
PlanHints.LeadingList remains populated and can affect join-order; update the
branch that checks leadingHintCnt and straightJoinOrder (the block manipulating
leadingJoinOrder and warnHandler.SetHintWarning) to also clear leadingList (or
set PlanHints.LeadingList to empty) when LEADING is deemed invalidated so the
returned PlanHints has LeadingList cleared alongside LeadingJoinOrder and the
same warning behavior is preserved.
🧹 Nitpick comments (1)
pkg/expression/schema.go (1)

86-100: ⚡ Quick win

Clarify that Equal only compares ordered columns.

The implementation is narrower than the name/comment suggest: it ignores Keys and UniqueKeys. That is fine for the new join-reorder caller, but the exported contract should say so explicitly or use a more specific name to avoid future misuse.

As per coding guidelines, "Keep exported-symbol doc comments, and prefer semantic constraints over name restatement".

🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@pkg/expression/schema.go` around lines 86 - 100, The Schema.Equal method
currently only compares ordered Columns and ignores Keys and UniqueKeys, which
is narrower than its name suggests; update the exported doc comment for
Schema.Equal to explicitly state it compares only the ordered Columns (and not
Keys or UniqueKeys) or rename the method to a more specific name (e.g.,
EqualColumnsOrdered) to avoid misuse; locate the method by the symbol
Schema.Equal and modify its comment to describe the exact contract (ordered
column-wise equality) and, if renaming, update all call sites to use the new
name.
🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@pkg/parser/ast/misc.go`:
- Around line 3967-4005: The bug is that when the first LeadingList item is
itself a nested LeadingList, RestoreWithQB pushes the hint-level QB into the
child causing LEADING((`@qb` a, b), c) instead of LEADING(`@qb` (a, b), c); modify
LeadingList.RestoreWithQB so that in the case "case *LeadingList" if i == 0 and
currentQBName.L != "" and !qbOnTable you emit the "@<qb>"
(ctx.WriteKeyWord("@"); ctx.WriteName(currentQBName.String()); ctx.WritePlain("
")) before restoring the child and then call t.RestoreWithQB with an empty
model.CIStr for qbName (so the child does not receive the QB), afterwards clear
currentQBName; otherwise keep the existing behavior of passing currentQBName
into the child.

In `@pkg/parser/hintparser_test.go`:
- Around line 369-474: The LEADING hint test cases use ast.NewCIStr but NewCIStr
is defined in the model package; update the LEADING test block to replace all
ast.NewCIStr(...) occurrences with model.NewCIStr(...). Specifically modify the
HintName fields and all HintTable.TableName constructors in the
TableOptimizerHint / LeadingList test cases so they use model.NewCIStr, leaving
the surrounding structures (TableOptimizerHint, LeadingList, HintTable,
HintName, Tables) unchanged.

In `@pkg/planner/core/joinorder/util.go`:
- Around line 221-225: The fallback path in util.go currently computes dbMatch
as "astTbl.DBName.L == '' || astTbl.DBName.L == blockName.DBName.L", which drops
the "*" DB wildcard semantics; update the dbMatch logic used in the blockOffset
> 1 fallback so it treats "*" as a wildcard (e.g., accept when astTbl.DBName.L
== "*" or blockName.DBName.L == "*") in addition to the empty or exact-match
cases, keeping tableMatch unchanged; modify the dbMatch check near variables
blockOffset, queryBlockNames, blockName, astTbl, dbMatch so LEADING(*.alias)
still matches derived-table aliases in this fallback path.

---

Outside diff comments:
In `@pkg/util/hint/hint.go`:
- Around line 955-983: The code invalidates LEADING by clearing leadingJoinOrder
but still returns LeadingList, so PlanHints.LeadingList remains populated and
can affect join-order; update the branch that checks leadingHintCnt and
straightJoinOrder (the block manipulating leadingJoinOrder and
warnHandler.SetHintWarning) to also clear leadingList (or set
PlanHints.LeadingList to empty) when LEADING is deemed invalidated so the
returned PlanHints has LeadingList cleared alongside LeadingJoinOrder and the
same warning behavior is preserved.

---

Nitpick comments:
In `@pkg/expression/schema.go`:
- Around line 86-100: The Schema.Equal method currently only compares ordered
Columns and ignores Keys and UniqueKeys, which is narrower than its name
suggests; update the exported doc comment for Schema.Equal to explicitly state
it compares only the ordered Columns (and not Keys or UniqueKeys) or rename the
method to a more specific name (e.g., EqualColumnsOrdered) to avoid misuse;
locate the method by the symbol Schema.Equal and modify its comment to describe
the exact contract (ordered column-wise equality) and, if renaming, update all
call sites to use the new name.
🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

  • Push a commit to this branch (recommended)
  • Create a new PR with the fixes

ℹ️ Review info
⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 362404df-e24a-4cdb-ab10-6a67cd93d0ba

📥 Commits

Reviewing files that changed from the base of the PR and between e198e2d and 153d1cc.

📒 Files selected for processing (14)
  • pkg/expression/schema.go
  • pkg/parser/ast/misc.go
  • pkg/parser/ast/misc_test.go
  • pkg/parser/hintparser.go
  • pkg/parser/hintparser.y
  • pkg/parser/hintparser_test.go
  • pkg/parser/parser_test.go
  • pkg/planner/core/BUILD.bazel
  • pkg/planner/core/joinorder/BUILD.bazel
  • pkg/planner/core/joinorder/util.go
  • pkg/planner/core/operator/logicalop/logical_projection.go
  • pkg/planner/core/plan_cost_ver2.go
  • pkg/planner/core/rule_join_reorder.go
  • pkg/util/hint/hint.go

Comment thread pkg/parser/ast/misc.go
Comment on lines +3967 to +4005
func (lt *LeadingList) RestoreWithQB(ctx *format.RestoreCtx, qbName model.CIStr, needParen bool, isTop bool, qbOnTable bool) error {
if lt == nil || len(lt.Items) == 0 {
return nil
}
if needParen {
ctx.WritePlain("(")
}

currentQBName := qbName // hint level QBName

for i, item := range lt.Items {
if i > 0 {
ctx.WritePlain(", ")
}

switch t := item.(type) {
case *HintTable:
if i == 0 && currentQBName.L != "" && !qbOnTable {
ctx.WriteKeyWord("@")
ctx.WriteName(currentQBName.String())
ctx.WritePlain(" ")
t.Restore(ctx)
currentQBName = model.CIStr{}
} else {
t.Restore(ctx)
}
case *LeadingList:
if err := t.RestoreWithQB(ctx, currentQBName, true, false, qbOnTable); err != nil {
return err
}
currentQBName = model.CIStr{}
default:
return fmt.Errorf("unexpected type in LeadingList: %T", t)
}
}
if needParen {
ctx.WritePlain(")")
}
return nil
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⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Preserve the hint-level QB before a parenthesized first LEADING group.

When the first LEADING element is nested, Line 3994 pushes QBName into the child list, so Restore emits LEADING((@QB a, b), c) instead of LEADING(@QB (a, b), c). That breaks restore/parse round-tripping for valid hints with a hint-level query block.

Suggested fix
 	case *LeadingList:
-		if err := t.RestoreWithQB(ctx, currentQBName, true, false, qbOnTable); err != nil {
+		childQBName := currentQBName
+		if i == 0 && childQBName.L != "" && !qbOnTable {
+			ctx.WriteKeyWord("@")
+			ctx.WriteName(childQBName.String())
+			ctx.WritePlain(" ")
+			childQBName = model.CIStr{}
+		}
+		if err := t.RestoreWithQB(ctx, childQBName, true, false, qbOnTable); err != nil {
 			return err
 		}
 		currentQBName = model.CIStr{}
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@pkg/parser/ast/misc.go` around lines 3967 - 4005, The bug is that when the
first LeadingList item is itself a nested LeadingList, RestoreWithQB pushes the
hint-level QB into the child causing LEADING((`@qb` a, b), c) instead of
LEADING(`@qb` (a, b), c); modify LeadingList.RestoreWithQB so that in the case
"case *LeadingList" if i == 0 and currentQBName.L != "" and !qbOnTable you emit
the "@<qb>" (ctx.WriteKeyWord("@"); ctx.WriteName(currentQBName.String());
ctx.WritePlain(" ")) before restoring the child and then call t.RestoreWithQB
with an empty model.CIStr for qbName (so the child does not receive the QB),
afterwards clear currentQBName; otherwise keep the existing behavior of passing
currentQBName into the child.

Comment thread pkg/parser/hintparser_test.go
Comment on lines +221 to +225
if blockOffset > 1 && blockOffset < len(queryBlockNames) {
blockName := queryBlockNames[blockOffset]
dbMatch := astTbl.DBName.L == "" || astTbl.DBName.L == blockName.DBName.L
tableMatch := astTbl.TableName.L == blockName.TableName.L
if dbMatch && tableMatch {
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⚠️ Potential issue | 🟠 Major | ⚡ Quick win

Preserve * DB wildcard in the subquery-alias fallback.

The fallback path drops the wildcard DB semantics that direct matching already supports. LEADING(*.alias) can match a derived-table alias in step 1, but the same binding stops matching in step 2 because dbMatch only accepts empty or exact DB names here.

Suggested fix
-			dbMatch := astTbl.DBName.L == "" || astTbl.DBName.L == blockName.DBName.L
+			dbMatch := astTbl.DBName.L == "" || astTbl.DBName.L == blockName.DBName.L || astTbl.DBName.L == "*"
🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@pkg/planner/core/joinorder/util.go` around lines 221 - 225, The fallback path
in util.go currently computes dbMatch as "astTbl.DBName.L == '' ||
astTbl.DBName.L == blockName.DBName.L", which drops the "*" DB wildcard
semantics; update the dbMatch logic used in the blockOffset > 1 fallback so it
treats "*" as a wildcard (e.g., accept when astTbl.DBName.L == "*" or
blockName.DBName.L == "*") in addition to the empty or exact-match cases,
keeping tableMatch unchanged; modify the dbMatch check near variables
blockOffset, queryBlockNames, blockName, astTbl, dbMatch so LEADING(*.alias)
still matches derived-table aliases in this fallback path.

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codecov Bot commented Jun 2, 2026

Codecov Report

❌ Patch coverage is 18.38565% with 182 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release-8.5@53d8056). Learn more about missing BASE report.

⚠️ Current head 6d4f992 differs from pull request most recent head 0af91a8

Please upload reports for the commit 0af91a8 to get more accurate results.

Additional details and impacted files
@@               Coverage Diff                @@
##             release-8.5     #68870   +/-   ##
================================================
  Coverage               ?   42.2591%           
================================================
  Files                  ?       1536           
  Lines                  ?     429701           
  Branches               ?          0           
================================================
  Hits                   ?     181588           
  Misses                 ?     231936           
  Partials               ?      16177           
Flag Coverage Δ
integration 42.2591% <18.3856%> (?)

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

Components Coverage Δ
dumpling ∅ <0.0000%> (?)
parser ∅ <0.0000%> (?)
br 0.1790% <0.0000%> (?)
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@ti-chi-bot ti-chi-bot Bot added the needs-1-more-lgtm Indicates a PR needs 1 more LGTM. label Jun 2, 2026
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ti-chi-bot Bot commented Jun 2, 2026

[LGTM Timeline notifier]

Timeline:

  • 2026-06-02 08:00:52.95991249 +0000 UTC m=+255754.030229880: ☑️ agreed by AilinKid.

…_impl

Signed-off-by: guo-shaoge <shaoge1994@163.com>
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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@pkg/planner/core/rule_join_reorder.go`:
- Around line 449-474: Remove the dead duplicate function
checkAndGenerateLeadingHint from this file: the project already uses
joinorder.CheckAndGenerateLeadingHint(joinOrderHintInfo) (see usage at the other
call site), so delete the local checkAndGenerateLeadingHint definition to avoid
duplicate/unreferenced code; ensure no other local references to
checkAndGenerateLeadingHint remain and run tests/compile to confirm nothing else
relied on this duplicate.
🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

  • Push a commit to this branch (recommended)
  • Create a new PR with the fixes

ℹ️ Review info
⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 7a9ba0bb-3c35-4ac1-913e-5b9d4467fa69

📥 Commits

Reviewing files that changed from the base of the PR and between 153d1cc and 6d4f992.

📒 Files selected for processing (4)
  • pkg/parser/hintparser.y
  • pkg/parser/parser_test.go
  • pkg/planner/core/BUILD.bazel
  • pkg/planner/core/rule_join_reorder.go
🚧 Files skipped from review as they are similar to previous changes (2)
  • pkg/planner/core/BUILD.bazel
  • pkg/parser/parser_test.go

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Caution

Inline review comments failed to post. This is likely due to GitHub's internal server error or limits when posting large numbers of comments. If you are seeing this consistently it is likely a permissions issue. Please check "Moderation" -> "Code review limits" under your organization settings.

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@pkg/planner/core/rule_join_reorder.go`:
- Around line 449-474: Remove the dead duplicate function
checkAndGenerateLeadingHint from this file: the project already uses
joinorder.CheckAndGenerateLeadingHint(joinOrderHintInfo) (see usage at the other
call site), so delete the local checkAndGenerateLeadingHint definition to avoid
duplicate/unreferenced code; ensure no other local references to
checkAndGenerateLeadingHint remain and run tests/compile to confirm nothing else
relied on this duplicate.
🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

  • Push a commit to this branch (recommended)
  • Create a new PR with the fixes

ℹ️ Review info
⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 7a9ba0bb-3c35-4ac1-913e-5b9d4467fa69

📥 Commits

Reviewing files that changed from the base of the PR and between 153d1cc and 6d4f992.

📒 Files selected for processing (4)
  • pkg/parser/hintparser.y
  • pkg/parser/parser_test.go
  • pkg/planner/core/BUILD.bazel
  • pkg/planner/core/rule_join_reorder.go
🚧 Files skipped from review as they are similar to previous changes (2)
  • pkg/planner/core/BUILD.bazel
  • pkg/parser/parser_test.go
🛑 Comments failed to post (1)
pkg/planner/core/rule_join_reorder.go (1)

449-474: ⚠️ Potential issue | 🟡 Minor | ⚡ Quick win

Dead code: local checkAndGenerateLeadingHint duplicates joinorder.CheckAndGenerateLeadingHint and is never called.

Line 342 uses joinorder.CheckAndGenerateLeadingHint(joinOrderHintInfo), while this local function has an identical implementation and signature but is never invoked.

🧹 Remove dead code
-// checkAndGenerateLeadingHint used to check and generate the valid leading hint.
-// We are allowed to use at most one leading hint in a join group. When more than one,
-// all leading hints in the current join group will be invalid.
-// For example: select /*+ leading(t3) */ * from (select /*+ leading(t1) */ t2.b from t1 join t2 on t1.a=t2.a) t4 join t3 on t4.b=t3.b
-// The Join Group {t1, t2, t3} contains two leading hints includes leading(t3) and leading(t1).
-// Although they are in different query blocks, they are conflicting.
-// In addition, the table alias 't4' cannot be recognized because of the join group.
-func checkAndGenerateLeadingHint(hintInfo []*h.PlanHints) (*h.PlanHints, bool) {
-	leadingHintNum := len(hintInfo)
-	var leadingHintInfo *h.PlanHints
-	hasDiffLeadingHint := false
-	if leadingHintNum > 0 {
-		leadingHintInfo = hintInfo[0]
-		// One join group has one leading hint at most. Check whether there are different join order hints.
-		for i := 1; i < leadingHintNum; i++ {
-			if hintInfo[i] != hintInfo[i-1] {
-				hasDiffLeadingHint = true
-				break
-			}
-		}
-		if hasDiffLeadingHint {
-			leadingHintInfo = nil
-		}
-	}
-	return leadingHintInfo, hasDiffLeadingHint
-}
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.


🤖 Prompt for AI Agents
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@pkg/planner/core/rule_join_reorder.go` around lines 449 - 474, Remove the
dead duplicate function checkAndGenerateLeadingHint from this file: the project
already uses joinorder.CheckAndGenerateLeadingHint(joinOrderHintInfo) (see usage
at the other call site), so delete the local checkAndGenerateLeadingHint
definition to avoid duplicate/unreferenced code; ensure no other local
references to checkAndGenerateLeadingHint remain and run tests/compile to
confirm nothing else relied on this duplicate.

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ti-chi-bot Bot commented Jun 4, 2026

@guo-shaoge: 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/unit-test 6d4f992 link true /test unit-test
idc-jenkins-ci-tidb/build 6d4f992 link true /test build
idc-jenkins-ci-tidb/check_dev_2 6d4f992 link true /test check-dev2

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tiprow Bot commented Jun 4, 2026

@guo-shaoge: 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_for_release 6d4f992 link true /test fast_test_tiprow_for_release

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…_impl

Signed-off-by: guo-shaoge <shaoge1994@163.com>
Signed-off-by: guo-shaoge <shaoge1994@163.com>
@ti-chi-bot ti-chi-bot Bot added size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. and removed size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. labels Jun 4, 2026
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ti-chi-bot Bot commented Jun 4, 2026

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: AilinKid
Once this PR has been reviewed and has the lgtm label, please assign windtalker for approval. For more information see the Code Review Process.
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