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Re: I/O on select count(*)

From: PFC <lists(at)peufeu(dot)com>
To: "Greg Smith" <gsmith(at)gregsmith(dot)com>, "Matthew Wakeling" <matthew(at)flymine(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: I/O on select count(*)
Date: 2008-05-19 17:14:48
Message-ID: op.ubeviyrgcigqcu@apollo13.peufeu.com (view raw or flat)
Thread:
Lists: pgsql-performance
> The real question in my mind is why this turns into a bottleneck before  
> the similar task of cleaning the 16MB XLOG segment does.  I expected  
> that one would need to be cracked before the CLOG switch time could  
> possibly be an issue, but reports from the field seem to suggest  
> otherwise.

	Hm, on current CPUs zeroing 8kB of RAM should take less than 2 us... now  
if it has to be written to disk, that's another story !

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