tiflash: Add warnings about LOCATION LABELS on ALTER TABLE ... SET TIFLASH REPLICA (#21692) #21697
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…LICA Signed-off-by: JaySon-Huang <[email protected]>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Signed-off-by: JaySon-Huang <[email protected]>
Co-authored-by: xixirangrang <[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 primarily updates the TiDB documentation related to TiFlash replica configuration. It addresses a known issue where the LOCATION LABELS clause in ALTER TABLE ... SET TIFLASH REPLICA does not function as expected for multiple labels, by adding a clear warning and simplifying the syntax examples. Additionally, it provides improved SQL-based methods for users to verify their TiFlash replica distribution.
Highlights
- Documentation Update for TiFlash Replicas: The documentation for configuring TiFlash replicas has been updated to remove the LOCATION LABELS clause from the ALTER TABLE ... SET TIFLASH REPLICA syntax examples.
- Warning on LOCATION LABELS Usage: A new warning note has been added to clarify that the LOCATION LABELS clause in ALTER TABLE ... SET TIFLASH REPLICA does not correctly parse multiple labels, advising users not to use it for configuring TiFlash replicas.
- Improved Replica Verification Method: The method for verifying the distribution of TiFlash replicas has been updated from using pd-ctl to providing SQL queries against information_schema.tikv_region_status, offering a more direct way to check replica placement.
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Code Review
This pull request updates the documentation for creating TiFlash replicas to warn users against using the LOCATION LABELS clause, as it doesn't parse multiple labels correctly. The changes remove LOCATION LABELS from the recommended syntax and add an explicit warning note. My review focuses on improving the clarity of this new warning note to ensure users fully understand the issue.
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/approve |
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: hfxsd 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 #21692
First-time contributors' checklist
What is changed, added or deleted? (Required)
According to the discussion with @JmPotato , the current implementation of
LOCATION LABELSis not correct and may acts does not meet the user want. Fixing the behavior requires manpower, and there is currently no plan or demand from users. So just add warnings about it.For example, if the user set
LOCATION LABELSwith the similar string as placement-rule-in-SQL does: https://docs.pingcap.com/zh/tidb/stable/placement-rules-in-sql/#%E6%8C%87%E5%AE%9A%E7%94%9F%E5%AD%98%E5%81%8F%E5%A5%BDthen the generated placement-rule in PD is
{ "group_id": "tiflash", ... "start_key": "748000000000055fff795f720000000000fa", "end_key": "748000000000055fff7a00000000000000f8", "role": "learner", "count": 2, "label_constraints": [ { "key": "engine", "op": "in", "values": ["tiflash"] } ], "location_labels": [ "[region, zone, host]" ], }but not
{ "group_id": "tiflash", ... "start_key": "748000000000055fff795f720000000000fa", "end_key": "748000000000055fff7a00000000000000f8", "role": "learner", "count": 2, "label_constraints": [ { "key": "engine", "op": "in", "values": ["tiflash"] } ], "location_labels": [ "region", "zone", "host" ], }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).
What is the related PR or file link(s)?
Do your changes match any of the following descriptions?