Tom Lane wrote:
> Er, why not just finish out the scan at the reduced I/O rate?  Any sort

Sometimes, you may need to vacuum large table in maintenance window and
hot table in the service time. If vacuum for hot table does not eat two
much foreground resource, then you can vacuum large table with a lower
IO rate outside maintenance window; but if vacuum for hot table is
overeating the system resource, then launcher had better to stop the
long running vacuum outside maintenance window.

But I am not insisting on the stop-start feature at this moment.
Changing the cost delay dynamically sounds more reasonable. We can use
it to balance total I/O of workers in service time or maintenance time.
It is not so difficult to achieve this by leveraging the share memory of

Best Regards
Galy Lee

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