docs:document optimization(#11106)

[DiligenceLai]

What is the purpose of the change

document optimization

Brief changelog

Note When using the built-in data source in cluster mode, you must specify this parameter explicitly.

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[CLAassistant]

All committers have signed the CLA.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.