Add new session variable "tidb_opt_partial_ordered_index_for_topn"

[qiancai]

First-time contributors' checklist

• I've signed the Contributor License Agreement, which is required for the repository owners to accept my contribution.

What is changed, added or deleted? (Required)

Explain the new session variable "tidb_opt_partial_ordered_index_for_topn" in sys-var doc

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

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By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions (in Chinese).

• 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)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)

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

Related issue: pingcap/tidb#65813

• This PR is translated from: Add new session variable "tidb_opt_partial_ordered_index_for_topn" docs-cn#21318
• Other reference link(s):

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

[gemini-code-assist]

Summary of Changes

Hello @qiancai, 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 aims to document the new "tidb_opt_partial_ordered_index_for_topn" session variable within the TiDB system variable documentation. While the current patch includes a temporary file, the primary goal is to provide clear information for this new configuration option, ensuring users understand its purpose and usage.

Highlights

• Documentation Update: Prepared documentation for the new session variable "tidb_opt_partial_ordered_index_for_topn", which will be added to the system variable documentation.

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Changelog

• temp.md
  • Added a new temporary file.

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[gemini-code-assist]

Code Review

This pull request is intended to add documentation for the tidb_opt_partial_ordered_index_for_topn session variable. However, the current changes only add a file named temp.md with placeholder content. The actual documentation changes appear to be missing. Please update the pull request to include the correct files.

I am having trouble creating individual review comments. Click here to see my feedback.

temp.md (1)

It is a common convention for text files to end with a newline character. This prevents potential issues with some command-line tools and version control systems.

This is a test file.

[qiancai]

/cc @qw4990

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-04-03 04:04:42.481986075 +0000 UTC m=+497087.687346122: ☑️ agreed by Oreoxmt.

[ti-chi-bot]

@qw4990: adding LGTM is restricted to approvers and reviewers in OWNERS files.

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[qiancai]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

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• OWNERS [qiancai]

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #22737.