From: Joe Conway <mail@joeconway.com>
To: mladen.gogala@vmsinfo.com
Cc: Neil Whelchel <neil.whelchel@gmail.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Slow count(*) again...
Date: Sat, 09 Oct 2010 19:10:38 -0700
Message-ID: <4CB1209E.9000706@joeconway.com> (raw)
In-Reply-To: <4CB11CC7.8070300@vmsinfo.com>
References: <201010091626.18636.neil.whelchel@gmail.com>
<4CB11CC7.8070300@vmsinfo.com>
On 10/09/2010 06:54 PM, Mladen Gogala wrote:
> In another database, whose name I will not mention, there is a parameter
> db_file_multiblock_read_count which specifies how many blocks will be
> read by a single read when doing a full table scan. PostgreSQL is in
> dire need of something similar and it wouldn't even be that hard to
> implement.
You're correct in that it isn't particularly difficult to implement for
sequential scans. But I have done some testing with aggressive read
ahead, and although it is clearly a big win with a single client, the
benefit was less clear as concurrency was increased.
Joe
--
Joe Conway
credativ LLC: http://www.credativ.us
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To: pgsql-performance@postgresql.org
Cc: mail@joeconway.com, mladen.gogala@vmsinfo.com, neil.whelchel@gmail.com
Subject: Re: Slow count(*) again...
In-Reply-To: <4CB1209E.9000706@joeconway.com>
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