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Re: Query Performance SQL Server vs. Postgresql

From: Merlin Moncure <mmoncure(at)gmail(dot)com>
To: Humair Mohammed <humairm(at)hotmail(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Query Performance SQL Server vs. Postgresql
Date: 2010-11-23 14:20:05
Message-ID: AANLkTinNLVJ_ypOAML4UmfZhKCz+eqstSQWaYbq390iJ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Mon, Nov 22, 2010 at 7:12 PM, Humair Mohammed <humairm(at)hotmail(dot)com> wrote:
> I did some further analysis and here are the results:
> work_mem;response_time
> 1MB;62 seconds
> 2MB;2 seconds
> 4MB;700 milliseconds
> 8MB;550 milliseconds
> In all cases shared_buffers were set to the default value of 32MB. As you
> can see the 1 to 2 MB jump on the work_mem does wonders. I probably don't
> need this to be any higher than 8 or 16 MB. Thanks to all for help!
> Humair

work_mem directly affects how the query is planned, because certain
types of plans (hash joins ans large sorts) require memory. raising or
lowering shared_buffers OTOH is very subtle and is not something you
tune to improve the execution of a single query...

merlin

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