Re: two queries and dual cpu (perplexed)

From: Jeff
Subject: Re: two queries and dual cpu (perplexed)
Date: ,
Msg-id: 8c459b7b96e6c310d641cebdfa8dcab6@torgo.978.org
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In response to: two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)")
Responses: Re: two queries and dual cpu (perplexed)  (Gavin Sherry)
Re: two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)")
Re: two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)")
Re: two queries and dual cpu (perplexed)  (Kenneth Marshall)
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two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)", )
 Re: two queries and dual cpu (perplexed)  (Jeff, )
  Re: two queries and dual cpu (perplexed)  (Gavin Sherry, )
  Re: two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)", )
   Re: two queries and dual cpu (perplexed)  (Russell Smith, )
    Re: two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)", )
     Re: two queries and dual cpu (perplexed)  (John A Meinel, )
      Re: two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)", )
       Re: two queries and dual cpu (perplexed)  (Gavin Sherry, )
       Re: two queries and dual cpu (perplexed)  (Jeff, )
      Re: two queries and dual cpu (perplexed)  (Tom Lane, )
       Re: two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)", )
        Re: two queries and dual cpu (perplexed)  (John A Meinel, )
   Re: two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)", )
  Re: two queries and dual cpu (perplexed)  ("Shoaib Burq (VPAC)", )
  Re: two queries and dual cpu (perplexed)  (Kenneth Marshall, )
 Re: two queries and dual cpu (perplexed)  (Daniel Schuchardt, )
 Re: two queries and dual cpu (perplexed)  ("Dave Held", )

On Apr 21, 2005, at 7:49 AM, Shoaib Burq (VPAC) wrote:

> Now I have not touch the $PGDATA/postgresql.conf (As I know very little
> about memory tuning) Have run VACCUM & ANALYZE.
>
You should really, really bump up shared_buffers and given you have 8GB
of ram this query would likely benefit from more work_mem.

> and the time taken is *twice* that for the original. The modification
> was
> minor. The queries do make use of both CPUs:
>
Is this an IO intensive query?  If running both in parellel results in
2x the run time and you have sufficient cpus it would (to me) indicate
you don't have enough IO bandwidth to satisfy the query.

Can we see an explain analyze of the query?  Could be a bad plan and a
bad plan will never give good performance.

--
Jeff Trout <>
http://www.jefftrout.com/
http://www.stuarthamm.net/



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