Add more description about SHARD_ROW_ID_BITS (#21467) #21599
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Co-authored-by: Aolin <[email protected]>
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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 the documentation for SHARD_ROW_ID_BITS by providing a more comprehensive explanation of its internal structure and practical guidance for its configuration. The updates aim to help users better understand how _tidb_rowid is constructed and how to optimally set SHARD_ROW_ID_BITS to mitigate hotspot issues and improve performance in TiDB clusters.
Highlights
- Detailed
_tidb_rowidStructure: The documentation now clearly outlines the internal structure of_tidb_rowidwhenSHARD_ROW_ID_BITSis set, detailing how it's composed of a sign bit,Sshard bits, and63-Sauto-increment bits. - Auto-increment Bit Behavior and Value Range: New information explains how auto-increment bits are stored in TiKV, allocated sequentially to ensure global uniqueness, and warns about potential allocation failures if the maximum value is reached. The maximum value for
_tidb_rowidis also specified as(2^63)-1. - Best Practices for
SHARD_ROW_ID_BITSSelection: Best practices for selecting theSHARD_ROW_ID_BITSvalue are introduced, advising users to balance randomness with available auto-increment space. A specific recommendation is provided: set shard bits tolog(2, x)wherexis the number of TiKV nodes, to evenly distribute bulk write loads.
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Code Review
This pull request adds a detailed explanation of SHARD_ROW_ID_BITS and its effect on _tidb_rowid, which is very helpful for users. I've provided a few suggestions to improve the clarity and formatting of the new content, ensuring it's easy to understand and adheres to the documentation style guide.
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/approve |
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: qiancai The full list of commands accepted by this bot can be found here. The pull request process is described here
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This is an automated cherry-pick of #21467
What is changed, added or deleted? (Required)
Add notice about setting the value of SHARD_ROW_ID_BITS
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.
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What is the related PR or file link(s)?
Do your changes match any of the following descriptions?