Update system-variables tidb_ddl_reorg_batch_size and tidb_ddl_reorg_…

[Frank945946]

…worker_cnt

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What is changed, added or deleted? (Required)

Update system-variables tidb_ddl_reorg_batch_size and tidb_ddl_reorg_worker_cnt

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• v8.1 (TiDB 8.1 versions)
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-09-22 14:05:08.303600538 +0000 UTC m=+279118.374094222: ☑️ agreed by tangenta.
• 2025-09-24 06:44:01.119080686 +0000 UTC m=+425451.189574358: ☑️ agreed by hfxsd.

[hfxsd]

/approve

[ti-chi-bot]

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #20949.