Re: cost-based vacuum

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От Tom Lane
Тема Re: cost-based vacuum
Дата
Msg-id 24553.1120844902@sss.pgh.pa.us
обсуждение исходный текст
Ответ на cost-based vacuum  (Ian Westmacott <ianw@intellivid.com>)
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Ian Westmacott <ianw@intellivid.com> writes:
> If I make the single configuration change of setting
> vacuum_cost_delay=1000, each iteration in analyze_thread takes
> much longer, of course.  But what I also see is that the CPU
> usage of the connections for writer_thread and reader_thread
> spike up to well over 80% each (this is a dualie) and latency
> drops to 8-10s, during the ANALYZEs.

[ scratches head... ]  That doesn't make any sense at all.

> I don't understand why this would be.  I don't think there
> are any lock issues, and I don't see any obvious I/O issues.
> Am I missing something?  Is there any way to get some
> insight into what those connections are doing?

Profiling maybe?  Can you put together a self-contained test case
that replicates this behavior, so other people could look?

            regards, tom lane

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