ddl: scattering truncated tables without pre-split option (#22787)

[ti-srebot]

cherry-pick #22787 to release-4.0
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---

Signed-off-by: Shuaipeng Yu jackysp@gmail.com

What problem does this PR solve?

Issue Number: close #xxx

Problem Summary:
The current truncate table statement could not scatter regions for tables without pre-split option.

What is changed and how it works?

Proposal: xxx

What's Changed:
Make scattering regions for truncated tables without pre-split option.

How it Works:

Check List

Tests

• Manual test (add detailed scripts or steps below)
  • start a cluster
  • truncate some tables which have no pre-split option
  • grep the log files of pd server for 'add operator', it will have 'transfer leader' and 'mv light peer' (will not see mv operator because misuse ScatterRegions api in pdclient, see Scatter region when creating tables is not work #22788).

Release note

• Scattering truncated tables without pre-split option.

[ti-srebot]

/run-all-tests

[ti-srebot]

@jackysp you're already a collaborator in bot's repo.

[jackysp]

PTAL @bb7133 @tiancaiamao @crazycs520

[tiancaiamao]

/LGTM

[bb7133]

/lgtm

[ti-chi-bot]

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• bb7133
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[bb7133]

/merge

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 41d56f3

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