Add docs for Analyze Embedded in DDL and new system variable

[hfxsd]

Introduces the 'Analyze Embedded in DDL' feature documentation and adds a new page describing its behavior for index creation and reorganization. Updates TOC to include the new doc and documents the 'tidb_stats_update_during_ddl' system variable, which controls this feature.

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• This PR is translated from:Add docs for Analyze Embedded in DDL and new system variable docs-cn#21031
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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 adds new documentation for TiDB's 'Analyze Embedded in DDL' feature, which is designed to improve query plan stability and performance. By automatically collecting statistics for new or reorganized indexes during DDL operations, the feature ensures that the optimizer has accurate and up-to-date information immediately, preventing suboptimal query plans that could arise from missing statistics. The documentation details the feature's purpose, use cases, and how it's controlled by the new tidb_stats_update_during_ddl system variable.

Highlights

• New Feature Documentation: Introduced comprehensive documentation for the 'Analyze Embedded in DDL' feature, which automatically collects statistics during index creation and reorganization.
• New System Variable: Added documentation for the new system variable tidb_stats_update_during_ddl, which controls the DDL-embedded Analyze behavior.
• Table of Contents Update: The Table of Contents (TOC) has been updated to include the new documentation page for 'Analyze Embedded in DDL'.

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[gemini-code-assist]

Code Review

This pull request introduces documentation for the 'Analyze Embedded in DDL' feature and its corresponding system variable. The documentation is well-structured and informative. I've provided a few suggestions to correct some typos in the examples and to align the text with the repository's style guide, primarily concerning the formatting of command names.

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[qiancai]

Rest LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-11-07 10:26:28.379496409 +0000 UTC m=+438637.822526288: ☑️ agreed by qiancai.

[hfxsd]

/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hfxsd

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #22035.