From: Mark Kirkwood <markir@paradise.net.nz>
To: Merlin Moncure <merlin.moncure@rcsonline.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Hardware/OS recommendations for large databases (
Date: Tue, 29 Nov 2005 10:45:46 +1300
Message-ID: <438B7A8A.4020505@paradise.net.nz> (raw)
In-Reply-To: <6EE64EF3AB31D5448D0007DD34EEB3417DD97C@Herge.rcsinc.local>
References: <6EE64EF3AB31D5448D0007DD34EEB3417DD97C@Herge.rcsinc.local>
Merlin Moncure wrote:
>>It certainly makes quite a difference as I measure it:
>>
>>doing select(1) from a 181000 page table (completely uncached) on my
>
> PIII:
>
>>8.0 : 32 s
>>8.1 : 25 s
>>
>>Note that the 'fastcount()' function takes 21 s in both cases - so all
>>the improvement seems to be from the count overhead reduction.
>
>
> Are you running windows? There is a big performance improvement in
> count(*) on pg 8.0->8.1 on win32 that is not relevant to this debate...
>
No - FreeBSD 6.0 on a dual PIII 1 Ghz. The slow cpu means that the 8.1
improvements are very noticeable!
A point of interest - applying Niels palloc - avoiding changes to
NodeAgg.c and int8.c in 8.0 changes those results to:
8.0 + palloc avoiding patch : 27 s
(I am guessing the remaining 2 s could be shaved off if I backported
8.1's virtual tuples - however that looked like a lot of work)
Cheers
Mark
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Cc: markir@paradise.net.nz, merlin.moncure@rcsonline.com
Subject: Re: Hardware/OS recommendations for large databases (
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