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Re: Major differences between oracle and postgres performance - what can I do ?

From: Jeff <threshar(at)torgo(dot)978(dot)org>
To: Gary Cowell <gary_cowell(at)yahoo(dot)co(dot)uk>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Major differences between oracle and postgres performance - what can I do ?
Date: 2004-06-18 12:14:22
Message-ID: 082CB838-C121-11D8-810C-000D9366F0C4@torgo.978.org (view raw or flat)
Thread:
Lists: pgsql-performance
On Jun 18, 2004, at 7:31 AM, Gary Cowell wrote:

> The explain output on postgres shows the same
> execution with a scan on vers and a sort but the query
> time is 78.6 seconds.
>

Does it run just as slow if you run it again?
It could be a case of the caches being empty

> Oracle but I think I've configured comparible
> buffering and sort area sizes, certainly there isn't
> much physical IO going on in either case.
>

Configuring PG like Oracle isn't the best thing in the world.  The 
general PG philosophy is to let the OS do all the caching & buffering  
- this is reversed in the Oracle world.  In 7.4 the rule of thumb is no 
more than 10k shared_buffers.. beyond that the overhead of maintaining 
it becomes excessive.  (This isn't really the case in 7.5)

Curiously, what are your sort_mem and shared_buffers settings?


--
Jeff Trout <jeff(at)jefftrout(dot)com>
http://www.jefftrout.com/
http://www.stuarthamm.net/


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