Do not merge until v8.5.4: distribute-table: support to scatter the region distribution of the given table and engine (#20345)

[ti-chi-bot]

This is an automated cherry-pick of #20345

First-time contributors' checklist

• I've signed Contributor License Agreement that's required for repo owners to accept my contribution.

What is changed, added or deleted? (Required)

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

Tips for choosing the affected version(s):

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)
• v8.4 (TiDB 8.4 versions)
• v8.3 (TiDB 8.3 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)?

• This PR is translated from: distribute-table: support to scatter the region distribution of the given table and engine  docs-cn#19534
• 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 @ti-chi-bot, 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 enhances TiDB's data distribution capabilities by introducing a suite of new SQL statements. These statements empower users to actively manage and monitor the scattering of table regions across different storage engines like TiKV and TiFlash. The primary goal is to ensure a more balanced data distribution, thereby optimizing performance and preventing hotspots, with explicit commands for initiating, canceling, and observing these critical operations.

Highlights

• New SQL Statement: DISTRIBUTE TABLE: Introduced the DISTRIBUTE TABLE statement, which allows users to explicitly redistribute and reschedule Regions of a specified table to achieve balanced distribution across TiFlash or TiKV nodes. This feature is currently experimental and aims to prevent uneven region distribution.
• New SQL Statement: CANCEL DISTRIBUTION JOB: Added the CANCEL DISTRIBUTION JOB statement, enabling users to cancel ongoing Region scheduling tasks that were initiated by the DISTRIBUTE TABLE statement.
• New SQL Statement: SHOW DISTRIBUTION JOBS: Implemented the SHOW DISTRIBUTION JOBS statement, providing visibility into all current Region distribution jobs, including their status, associated tables, engines, and rules.
• New SQL Statement: SHOW TABLE DISTRIBUTION: Included the SHOW TABLE DISTRIBUTION statement, which displays detailed Region distribution information for a specified table, helping users monitor how data is spread across the cluster.
• Documentation Updates: The TOC.md file has been updated to include links to the new documentation pages for CANCEL DISTRIBUTION JOB, DISTRIBUTE TABLE, SHOW DISTRIBUTION JOBS, and SHOW TABLE DISTRIBUTION.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request adds documentation for several new SQL statements related to table data distribution: DISTRIBUTE TABLE, CANCEL DISTRIBUTION JOB, SHOW DISTRIBUTION JOBS, and SHOW TABLE DISTRIBUTION. The changes look good overall. I've added several comments with suggestions to improve clarity, accuracy, and consistency, following the repository's style guide. My feedback includes correcting an inaccurate description, fixing a broken SQL example, and suggesting adding descriptions for output columns to make the documentation more complete for users.

[gemini-code-assist]

The description is slightly inaccurate. The statement shows all created jobs, including finished and cancelled ones, not just "current" jobs as the example output shows. Consider rephrasing for accuracy.¹

Suggested change

	The `SHOW DISTRIBUTION JOBS` statement shows all current Region distribution jobs.
	The `SHOW DISTRIBUTION JOBS` statement shows all Region distribution jobs that have been created.

Style Guide References

Footnotes

1. Repository Style Guide, line 16: Technical accuracy and terminology consistency ↩

[gemini-code-assist]

The word "current" is inaccurate here, as the command shows historical jobs as well. It's better to remove it.¹

Suggested change

	Show all current Region distribution jobs:
	Show all Region distribution jobs:

Style Guide References

Footnotes

1. Repository Style Guide, line 16: Technical accuracy and terminology consistency ↩

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please ask for approval from qiancai. For more information see the Code Review Process.
Please ensure that each of them provides their approval before proceeding.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

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

In response to this:

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.