planner: fix prepared plan cache after table rename

[tiancaiamao]

What problem does this PR solve?

Issue Number: close #71041

Problem Summary:
A prepared plan cache entry can retain stale table metadata after a table is renamed. If a new table is created with the original name and the renamed table is later dropped, executing the prepared statement can incorrectly return error 8113 for the dropped table.

This is a regression introduced by the metadata-lock support for plan cache:

• Original upstream PR: #51897, commit 70a825397f3b
• The v7.5 backport is #52957, commit 84e2926684
• Equivalent backports include *: add metadata lock when using the plan cache (#51897) #52955 for v8.1, *: add metadata lock when using the plan cache (#51897) #52956 for v6.5, and *: add metadata lock when using the plan cache (#51897) #52958 for v7.1.

What changed and how does it work?

After a schema change, re-preprocess the prepared AST with a fresh resolve context and rebuild the schema-dependent metadata.

The metadata-lock/cache-key table set is rebuilt from the complete StmtCtx.RelatedTableIDs dependency set after a fresh plan-builder dependency-discovery pass. This preserves dependencies expanded from views and other resolved plan inputs; the AST-only stmt.tables list is retained only for AST-derived plan-cache information. The table metadata conversion is shared with initial plan-cache construction.

This fixes the rename/drop/create sequence while preserving the original metadata-lock behavior introduced by #51897. The additional discovery build runs only on the schema-change reprepare path.

Regression and release impact

The introducing change is present through equivalent commits in the following code lines, so the rename regression should be considered affected unless this fix is backported:

• v7.5: 84e2926684 is present from v7.5.2 onward in the inspected tags.
• v8.1: equivalent backport e39969afee49 / *: add metadata lock when using the plan cache (#51897) #52955 is present.
• v8.2 and v8.5: the original master-line commit 70a825397f3b is in the release lineage; the pre-fix reprepare path is present in inspected tags.
• v9.x: the same metadata-lock/revision and reprepare code path is present in inspected tags; this is a code-path assessment, not a claim that the exact 84e object was cherry-picked there.
• v26.3: the next-gen code still has the corresponding ID/name fallback and reprepare behavior without this metadata rebuild, so it is likely affected based on static inspection; runtime confirmation on that line is still needed.
• 25.10: no 25.10 tag or branch exists in the repository snapshot used for this analysis, so its impact cannot be confirmed here.

No inspected release ref contains this fix yet.

Check List

Tests

• Unit test
  • go test -tags=intest ./pkg/executor/test/plancache -run '^TestPreparedPlanCacheRenameCreateDropOldName$' -count=1
  • go test -tags=intest ./pkg/executor/test/plancache -count=1
• 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.

bugfix: fix prepared plan cache metadata after table rename

Summary by CodeRabbit

• Bug Fixes

  • Improved prepared statement handling after tables are renamed, recreated, or dropped.
  • Prepared statements now refresh schema information and use the current table definition after schema changes.
  • Reduced stale table references during subsequent prepared statement executions.

• Tests

  • Added coverage for prepared statements across table rename, recreation, and removal scenarios.
  • Verified statements continue executing correctly after the original table is replaced.

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📥 Commits

Reviewing files that changed from the base of the PR and between 6cc78f4 and bfcb20b.

📒 Files selected for processing (1)

• pkg/planner/core/plan_cache.go

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📝 Walkthrough

Walkthrough

The schema-change path resets and rebuilds prepared statement metadata. A shared helper collects current table information. A test covers rename, recreate, and drop operations. The test target shard count increases from 8 to 9.

Changes

Prepared plan cache schema refresh

Layer / File(s)	Summary
Rebuild schema-dependent metadata pkg/planner/core/plan_cache.go, pkg/planner/core/plan_cache_utils.go	The schema-change path clears stale metadata, reprocesses the statement, discovers related tables, and collects current database names, table descriptors, and schema versions through collectPlanCacheTableInfo.
Validate rename and recreate flow pkg/executor/test/plancache/plan_cache_test.go, pkg/executor/test/plancache/BUILD.bazel	A test verifies that a prepared query uses the recreated t table after t is renamed to bak, and continues to execute after bak is dropped. The test target shard count increases from 8 to 9.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to bfcb2

The schema-refresh change includes coverage for the rename, replacement, and old-table drop flow. No unresolved merge-blocking issue is identified.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 4 files.	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 is concise, specific, and accurately describes the main change: fixing prepared plan cache behavior after a table rename.
Description check	✅ Passed	The description includes the required issue number, problem summary, implementation details, tests, side effects, documentation impact, and release note. It is complete and aligned with the pull reque…
Linked Issues check	✅ Passed	The changes satisfy issue #71041. planCachePreprocess clears schema-dependent metadata, reprocesses the resolved AST, collects the refreshed related table IDs, and rebuilds table metadata. This prev…
Out of Scope Changes check	✅ Passed	The changes stay within issue #71041. The production changes repair stale prepared plan cache metadata after a table rename. The helper extraction preserves table metadata collection and error handlin…

✨ Finishing Touches 💡 2

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🛠️ Fix failing CI checks 💡

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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/prepared-rename-regression

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_{A rabbit checks the table trail
Fresh plans hop where old names fail
t returns, while bak sleeps
The cache guards its schema peeps
Tests thump softly: all rows keep}

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[codecov]

Codecov Report

❌ Patch coverage is 59.37500% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.4458%. Comparing base (419f965) to head (083097d).
⚠️ Report is 9 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #71042        +/-   ##
================================================
- Coverage   76.3176%   72.4458%   -3.8718%     
================================================
  Files          2041       2102        +61     
  Lines        556081     596713     +40632     
================================================
+ Hits         424388     432294      +7906     
- Misses       130793     163131     +32338     
- Partials        900       1288       +388     

Flag	Coverage Δ
integration	40.7368% <59.3750%> (+1.0692%)	⬆️

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

Components	Coverage Δ
dumpling	58.8716% <ø> (ø)
parser	∅ <ø> (∅)
br	46.5879% <ø> (-16.1200%)	⬇️

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[tiancaiamao]

/test check-dev2

[tiancaiamao]

/test check-dev2