sql-statements: say that optimistic constraint checks are deferred until the transaction is committed (#24027)

[ti-chi-bot]

This is an automated cherry-pick of #24027

What is changed, added, or deleted? (Required)

In sql-statements/sql-statement-commit.md, the MySQL compatibility section says that with optimistic locking, UNIQUE and PRIMARY KEY constraint checks "are deferred until statement commit". The checks are deferred until the transaction commits, which is why the COMMIT statement can fail. The same behavior is described that way elsewhere:

• constraints.md: "the unique check was deferred until the transaction is committed".
• transaction-overview.md: "These checks are instead performed on transaction COMMIT".

This PR changes "until statement commit" to "until the transaction is committed". It was flagged by CodeRabbit on the Japanese translation PR #24017, which inherited it from EN.

Which TiDB version(s) do your changes apply to? (Required)

• master (the latest development version)
• v9.0 (TiDB 9.0 versions)
• v8.5 (TiDB 8.5 versions)
• v8.1 (TiDB 8.1 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)

What is the related PR or file link(s)?

• Related code change PR links (if applicable): N/A
• This PR is translated from: N/A
• Other reference link(s): i18n(ja): fix translation defects in sql-statements docs (alter-table-compact to create-table-like) #24017

AI agent involvement

• The changes in this PR were primarily made by an AI agent on behalf of the PR author.

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Clarified that, with Optimistic Locking enabled, MySQL UNIQUE and PRIMARY KEY constraint checks occur at transaction commit and may cause COMMIT to fail. The note also describes how tidb_constraint_check_in_place=ON affects this behavior.

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between b3ad43c and ab50afb.

📒 Files selected for processing (1)

• sql-statements/sql-statement-commit.md

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📝 Walkthrough

Walkthrough

The MySQL compatibility note now states that, with Optimistic Locking enabled, UNIQUE and PRIMARY KEY checks are deferred until transaction commit. It retains the possible COMMIT failure and the tidb_constraint_check_in_place=ON setting.

Changes

MySQL compatibility note

Layer / File(s)	Summary
Constraint check timing sql-statements/sql-statement-commit.md	The note changes the deferral point for UNIQUE and PRIMARY KEY checks from statement commit to transaction commit. It retains the possible COMMIT failure and the tidb_constraint_check_in_place=ON setting.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~2 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to ab50a

The note clarifies when checks occur while retaining the COMMIT failure and setting exception; no material merge risk is evident.

Architecture Summary

Architecture risk: 🔵 Low · up to ab50a

The change affects 1 system.

Changed systems: sql-statements

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — sql-statements (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

• observed — Modified behavior in sql-statements/sql-statement-commit.md: The compatibility note changes the stated deferral point for UNIQUE and PRIMARY KEY checks from statement commit to transaction commit; the possible COMMIT failure and the tidb_constraint_check_in_place=ON setting remain unchanged.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the documentation file and the main change: clarifying that optimistic constraint checks are deferred until transaction commit.
Description check	✅ Passed	The description covers the required change, affected versions, reference PR, AI involvement, and change-category checklist. It also explains the reason for the wording change and its relation to the a…
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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[qiancai]

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