| 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 |
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| 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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