tidb: update the default value of tidb_analyze_column_options

[0xPoe]

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ref pingcap/tidb#64994

Updated the default value of tidb_analyze_column_options to ALL.

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[gemini-code-assist]

Summary of Changes

Hello @0xPoe, 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 updates the documentation to reflect a significant change in the default behavior of the tidb_analyze_column_options system variable. By setting the default to ALL, TiDB will now collect statistics for all columns by default, which is generally beneficial for query optimization, especially in OLAP scenarios. The changes ensure that users are aware of this new default and its implications for statistics collection and performance.

Highlights

• Default Value Update: The default value for the tidb_analyze_column_options system variable has been updated from PREDICATE to ALL.
• Documentation Alignment: The documentation for tidb_analyze_column_options has been revised to reflect the new default behavior across different TiDB versions, specifically noting the change for v8.5.5 and later.
• Performance Tuning Guide Adjustment: A cautionary note in the performance tuning guide regarding increased resource usage when tidb_analyze_column_options is set to ALL has been removed, aligning with the new default recommendation.

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[Copilot]

Pull request overview

This PR updates the documentation for the tidb_analyze_column_options system variable to reflect a change in its default value from PREDICATE to ALL. This change aligns with TiDB PR #64994 and will apply to newly deployed TiDB clusters starting from v8.5.5, as well as v9.0 and master branches. The change means that by default, TiDB will now collect statistics for all columns rather than just predicate columns, which helps avoid suboptimal execution plans in OLAP query scenarios.

Key Changes:

• Updated the default value of tidb_analyze_column_options from PREDICATE to ALL in system variable documentation
• Added version-specific notes explaining the default behavior across different TiDB versions (v8.3.0-v8.5.4 vs v8.5.5+)
• Removed the resource usage warning from the performance tuning guide since ALL is now the default behavior

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
system-variables.md	Updated the default value to ALL and added detailed version history notes explaining when the default changed from PREDICATE to ALL for newly deployed clusters
tidb-performance-tuning-config.md	Removed the resource usage warning note and simplified the description since ALL is now the default value and the warning is no longer applicable

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[gemini-code-assist]

Code Review

This pull request correctly updates the default value of tidb_analyze_column_options to ALL and adjusts the documentation accordingly. My review includes a few suggestions to enhance clarity and restore important contextual information. I've recommended rephrasing the version history for better readability, clarifying a potentially confusing sentence about performance impact, and re-adding a note about the resource usage trade-off in the performance tuning guide.