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Re: slow queries, possibly disk io

From: Josh Close <narshe(at)gmail(dot)com>
To: POSTGRES-PERFORMANCE <pgsql-performance(at)postgresql(dot)org>
Subject: Re: slow queries, possibly disk io
Date: 2005-05-27 12:52:16
Message-ID: 4a0cafe205052705526fccfe75@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
> Setting shared buffers above something like 10-30% of memory is counter
> productive.

What is the reason behind it being counter productive? If shared
buffers are at 30%, should effective cache size be at 70%? How do
those two relate?

> 
> Increasing sort_mem can help with various activities, but increasing it
> too much can cause you to swap, which kills performance. The caution is
> that you will likely use at least 1 sort_mem per connection, and can
> likely use more than one if the query is complicated.

I have a max of 100 connections and 2 gigs of mem. Right now the sort
mem is a 4 megs. How much higher could I put that?

-Josh

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Subject: slow queries, possibly disk io
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Subject: Re: Optimising queries involving unions

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