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

От: Jeff
Тема: Re: Major differences between oracle and postgres performance - what can I do ?
Дата: ,
Msg-id: 082CB838-C121-11D8-810C-000D9366F0C4@torgo.978.org
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Ответ на: Major differences between oracle and postgres performance - what can I do ?  (Gary Cowell)
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Major differences between oracle and postgres performance - what can I do ?  (Gary Cowell, )
 Re: Major differences between oracle and postgres performance  (Richard Huxton, )
 Re: Major differences between oracle and postgres performance - what can I do ?  (Paul Thomas, )
 Re: Major differences between oracle and postgres performance - what can I do ?  (Jeff, )
 Re: Major differences between oracle and postgres performance  (Shridhar Daithankar, )
 Re: Major differences between oracle and postgres performance - what can I do ?  (Gary Cowell, )
  Re: Major differences between oracle and postgres performance  (pginfo, )
  Re: Major differences between oracle and postgres performance  (Richard Huxton, )
  Re: Major differences between oracle and postgres performance - what can I do ?  (Tom Lane, )
   Re: Major differences between oracle and postgres performance - what can I do ?  (Stephen Frost, )
    Re: Major differences between oracle and postgres performance - what can I do ?  (Tom Lane, )
     Re: Major differences between oracle and postgres performance - what can I do ?  (Stephen Frost, )
      Re: Major differences between oracle and postgres performance - what can I do ?  (Stephen Frost, )
  Re: Major differences between oracle and postgres performance  (pginfo, )
  Re: Major differences between oracle and postgres performance - what can I do ?  ("Mischa Sandberg", )
 Re: Major differences between oracle and postgres performance - what can I do ?  (Gary Cowell, )
  Re: Major differences between oracle and postgres performance - what can I do ?  (Tom Lane, )
   Re: Major differences between oracle and postgres performance - what can I do ?  (Gary Cowell, )

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 <>
http://www.jefftrout.com/
http://www.stuarthamm.net/



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