*: add slow log control variables (tidb_slow_log_rules, tidb_slow_log_max_per_sec) and hint WRITE_SLOW_LOG

[hfxsd]

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• This PR is translated from: *: add slow log control variables (tidb_slow_log_rules, tidb_slow_log_max_per_sec) and hint WRITE_SLOW_LOG docs-cn#21009
• Other reference link(s): Slow Log Enhancement: Multi-Dimensional Triggering and Dynamic Scope Control tidb#62959

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[gemini-code-assist]

Summary of Changes

Hello @hfxsd, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the control and management of slow query logging in TiDB. It introduces tidb_slow_log_rules to allow for more sophisticated, rule-based logging criteria, moving beyond a simple time threshold. To prevent excessive logging when using these new rules, tidb_slow_log_max_per_sec is added to provide a rate-limiting mechanism. Furthermore, a WRITE_SLOW_LOG hint offers a direct way to ensure specific queries are logged for debugging or analysis. The accompanying documentation has been thoroughly updated to explain these new functionalities and improve overall clarity.

Highlights

• New Slow Log Control Variables: Introduced tidb_slow_log_rules for flexible, multi-dimensional slow query logging triggers and tidb_slow_log_max_per_sec to cap the rate of slow log entries, both new in v9.0.0.
• WRITE_SLOW_LOG Hint: Added a new SQL hint to explicitly force any statement to be recorded in the slow query log, bypassing defined thresholds.
• Documentation Enhancement: Updated documentation to reflect these new features and ensure consistent terminology (e.g., "slow query log" instead of "slow log").

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[gemini-code-assist]

Code Review

This pull request introduces documentation for new slow log control variables (tidb_slow_log_rules, tidb_slow_log_max_per_sec) and the WRITE_SLOW_LOG hint. It also improves consistency by standardizing the term "slow query log". My review focuses on enhancing the clarity, conciseness, and formatting of the new content to align with the style guide. I've provided suggestions to rephrase sentences, correct capitalization, ensure proper use of backticks for technical terms, and fix a broken link.

[ti-chi-bot]

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