Note that GC Disabling is a must despite Dumpling's auto extend feature

[Tetsuya3850]

What is changed, added or deleted? (Required)

I was reading the guide to migrate from TiDB to MySQL.
The guide advised to disable the GC before Dumpling is run.
However, I read in the Dumpling overview that this is now only necessary in certain conditions in the latest TiDB version.
If this section was potentially not up to date with that, I thought it will be nicer to note on that.

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.

• master (the latest development version)
• v7.6 (TiDB 7.6 versions)
• v7.5 (TiDB 7.5 versions)
• v7.4 (TiDB 7.4 versions)
• v7.3 (TiDB 7.3 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)
• v5.3 (TiDB 5.3 versions)
• v5.2 (TiDB 5.2 versions)
• v5.1 (TiDB 5.1 versions)
• v5.0 (TiDB 5.0 versions)

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

https://docs-archive.pingcap.com/tidb/v7.2/dumpling-overview#manually-set-the-tidb-gc-time
https://docs-archive.pingcap.com/tidb/v7.2/migrate-from-tidb-to-mysql

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

[ti-chi-bot]

Hi @Tetsuya3850. Thanks for your PR.

I'm waiting for a pingcap member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[Tetsuya3850]

@Oreoxmt Hi! Much appreciated if you can please take a look at your convenience 🙇

[Oreoxmt]

/ok

[Oreoxmt]

/ok-to-test

[Oreoxmt]

@wjhuang2016 Could you please help review this change? Thanks!

[lance6716]

Thanks for your contribution!

I think manually disabling GC is a must for this scenario. Dumpling can hold the GC when it is running. But after it has exited and before TiCDC starts, the GC may happen and cause TiCDC failing to read the data in the exact time of full migration snapshot.

[Tetsuya3850]

@lance6716
Thank you for your feedback! I understood the necessity now. So, I tried noting that so that people may not try to skip the step with similar misunderstanding as me.

[Tetsuya3850]

@Oreoxmt Thank you for the suggestion! Applied.

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-02-08 01:51:22.848063363 +0000 UTC m=+408008.414833237: ☑️ agreed by lance6716.
• 2024-02-08 04:27:43.123895883 +0000 UTC m=+417388.690665772: ☑️ agreed by Oreoxmt.

[Tetsuya3850]

@ran-huang Hi, I applied your suggestion. Thank you!

[Oreoxmt]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Oreoxmt

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.6: #16494.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #16495.