tidb-functions: clarify TIDB_ENCODE_INDEX_KEY parameters

[hfxsd]

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• This PR is translated from:tidb-functions: clarify TIDB_ENCODE_INDEX_KEY parameters docs-cn#21278
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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 focuses on improving the clarity and completeness of the documentation for the TIDB_ENCODE_INDEX_KEY and TIDB_ENCODE_RECORD_KEY functions. The changes provide explicit syntax, detailed parameter descriptions, and illustrative examples, particularly clarifying how different primary key types influence the handle_columns argument. This enhancement aims to help users better understand and correctly utilize these TiDB functions.

Highlights

• Enhanced TIDB_ENCODE_INDEX_KEY Documentation: The documentation for TIDB_ENCODE_INDEX_KEY has been significantly expanded to include its full syntax, detailed explanations for each parameter (including db_name, table_name, index_name, index_columns, and handle_columns), and specific rules for determining handle_columns based on primary key types (e.g., _tidb_rowid, single integer CLUSTERED, composite CLUSTERED).
• New Examples for TIDB_ENCODE_INDEX_KEY: Several new SQL examples have been added to illustrate the usage of TIDB_ENCODE_INDEX_KEY with composite secondary indexes and different primary key configurations, making its application clearer for users.
• Improved TIDB_ENCODE_RECORD_KEY Documentation: The TIDB_ENCODE_RECORD_KEY function's documentation now includes its syntax and detailed parameter descriptions, with a clear reference to the comprehensive handle_columns explanation provided for TIDB_ENCODE_INDEX_KEY.
• Example Data Consistency: Minor updates were made to example INSERT statements and SELECT calls for both functions to ensure consistency and accuracy in the provided code snippets.

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[gemini-code-assist]

Code Review

This pull request significantly clarifies the parameters for the TIDB_ENCODE_INDEX_KEY and TIDB_ENCODE_RECORD_KEY functions, which is a great improvement for the documentation. My review includes a few minor suggestions to enhance readability and consistency, such as using consistent list formatting and making descriptions more concise.

[ti-chi-bot]

@fzzf678: adding LGTM is restricted to approvers and reviewers in OWNERS files.

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[Oreoxmt]

Rest LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-01-19 03:50:45.108391449 +0000 UTC m=+379472.722348306: ☑️ agreed by Oreoxmt.

[hfxsd]

/approve

[ti-chi-bot]

[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: #22344.