ddl: fix alter index visibility suffix collision

[idle-lab]

What problem does this PR solve?

Issue Number: close #70049

Problem Summary:

ALTER TABLE ... ALTER INDEX ... VISIBLE/INVISIBLE could incorrectly change the visibility of other indexes whose names shared the same underscore-delimited prefix. For example, altering idx_k also affected idx_k_copy, because normal indexes were incorrectly treated as temporary indexes created during a column change.

What changed and how does it work?

The visibility update now matches an index by its original name only when it is an actual temporary changing index. It checks both IsChanging() and isTempIndex() before comparing the original index name.

Regression tests cover:

• Changing an index to INVISIBLE.
• Changing an index to VISIBLE.
• Numeric and non-numeric underscore suffixes, such as idx_k_1 and idx_k_copy.

These similarly named indexes now retain their original visibility

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

• Bug Fixes
  • Fixed index visibility changes for indexes with underscore-delimited names.
  • Improved visibility updates while indexes are being renamed or modified.
  • Added regression coverage to ensure only the targeted index is marked visible or invisible.

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[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 Plus

Run ID: d6b21044-cf00-4eee-ba14-944bcffb8bd9

📥 Commits

Reviewing files that changed from the base of the PR and between 231dad5 and 96e56c7.

📒 Files selected for processing (2)

• pkg/ddl/db_change_test.go
• pkg/ddl/index.go

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📝 Walkthrough

Walkthrough

setIndexVisibility now avoids treating ordinary underscore-suffixed indexes as temporary indexes, and TestParallelAlterIndex adds regression coverage confirming only the named index changes visibility.

Changes

Index visibility behavior

Layer / File(s)	Summary
Visibility matching and regression coverage pkg/ddl/index.go, pkg/ddl/db_change_test.go	Visibility updates require a changing temporary index before comparing its origin name, while regression tests verify suffixed ordinary indexes remain unaffected.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: lcwangchao

Poem

A rabbit checked the index row,
And watched the named one hide below.
Its suffix friend stayed bright and clear,
No stray visibility changes here.
Hop, hop—issue fixed with cheer!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise and accurately describes the main change: fixing ALTER INDEX visibility handling for suffix collisions.
Description check	✅ Passed	The description includes the issue number, problem summary, implementation details, tests, and release note placeholder, matching the template well.
Linked Issues check	✅ Passed	The code and regression tests address issue #70049 by preventing unrelated suffix-matched indexes from being treated as changing indexes.
Out of Scope Changes check	✅ Passed	The changes are scoped to the reported ALTER INDEX visibility bug and its regression tests, with no clear unrelated additions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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