Message-ID: <4410BF88.5080001@bigpond.net.au>
Date: Fri, 10 Mar 2006 09:51:36 +1000
From: David Brown <time@bigpond.net.au>
User-Agent: Mozilla Thunderbird 1.0RC1 (Windows/20041201)
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To: Andre Felipe Machado <andremachado@techforce.com.br>
CC: pgsql-performance@postgresql.org
Subject: Re: firebird X postgresql 8.1.2 windows, performance comparison
References: <20060307162842.M37264@techforce.com.br>
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Andre Felipe Machado wrote:

>It seems that Firebird windows can use adequately as much ram it finds
>and postgresql windows can not.
>  
>
PostgreSQL relies on the OS cache to utilize RAM. Make sure that most of 
the RAM is 'available' so Windows can do its thing.

effective_cache_size should be set correspondingly high - at least 65535.

shared_buffers should be as low as you can get away with (allowing for 
multiple users). 16384 is 12.5% of your RAM and far too high.

AFAIK, PostgreSQL still doesn't differentiate between index blocks and 
data blocks.

>work_mem reduced time almost 66%.
>But work_mem easily can exhaust ram with many users connected, as each
>connection query will use this amount of memory (if I can remember).
>How much it can grow at this 1 gbram win machine?
>  
>

work_mem has to be just big enough to allow hash joins to operate 
efficiently. This varies from query to query and can be set in your code 
accordingly. However, the 1024 default is just too low for most 
applications and you'll probably find even 4096 is a huge improvement. 
You need to find the minimum that delivers acceptable performance in 
most queries and boost it for selected queries as required.

BTW, which version of Firebird is this?