От: Dave Held
Тема: Re: speed of querry?
Дата: ,
Msg-id: 49E94D0CFCD4DB43AFBA928DDD20C8F9026184B2@asg002.asg.local
(см: обсуждение, исходный текст)
Ответ на: speed of querry?  ("Joel Fradkin")
Ответы: Re: speed of querry?  ("Joel Fradkin")
Список: pgsql-performance

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speed of querry?  ("Joel Fradkin", )
 Re: speed of querry?  (Richard Huxton, )
  Re: speed of querry?  ("Joel Fradkin", )
  Re: speed of querry?  (Tom Lane, )
   Re: speed of querry?  ("Joel Fradkin", )
    Re: speed of querry?  (Dawid Kuroczko, )
     Re: speed of querry?  ("Joel Fradkin", )
      Re: speed of querry?  (Dawid Kuroczko, )
       Re: speed of querry?  (Tom Lane, )
        Re: speed of querry?  ("Joel Fradkin", )
         Re: speed of querry?  ("Joel Fradkin", )
 Re: speed of querry?  ("Dave Held", )
  Re: speed of querry?  ("Joel Fradkin", )
   Re: speed of querry?  (Tom Lane, )
    Re: speed of querry?  ("Joel Fradkin", )
     Re: speed of querry?  (Tom Lane, )
 Re: speed of querry?  ("Dave Page", )
  Re: speed of querry?  ("Joel Fradkin", )

> -----Original Message-----
> From: Joel Fradkin [mailto:]
> Sent: Thursday, April 14, 2005 11:39 AM
> To: 'Tom Lane'; 'Dawid Kuroczko'
> Cc: 'PERFORM'
> Subject: Re: [PERFORM] speed of querry?
>
>
> I did as described to alter table and did not see any
> difference in speed. I am trying to undo the symbolic
> link to the data array and set it up on raid 5 disks in
> the machine just to test if there is an issue with the
> config of the raid 10 array or a problem with the controller.
>
> I am kinda lame at Linux so not sure I have got it yet still
> testing. Still kind puzzled why it chose tow different option,
> but one is running windows version of postgres, so maybe that
> has something to do with it.

That sounds like a plausible explanation.  However, it could
simply be that the statistics gathered on each box are
sufficiently different to cause different plans.

> The data bases and configs (as far as page cost) are the same.

Did you do as Dawid suggested?

> [...]
> Then do a query couple of times (EXPLAIN ANALYZE also :)), then
> do:
> SET enable_seqscan = off;
> and rerun the query -- if it was significantly faster, you will
> want to do:
> SET enable_seqscan = on;
> and tweak:
> SET random_page_cost = 2.1;
> ...and play with values.  When you reach the random_page_cost
> which suits your data, you will want to put it into
> postgresql.conf
> [...]

This is above and beyond toying with the column statistics.  You
are basically telling the planner to use an index.  Try this,
and post the EXPLAIN ANALYZE for the seqscan = off case on the
slow box if it doesn't speed things up for you.

__
David B. Held
Software Engineer/Array Services Group
200 14th Ave. East,  Sartell, MN 56377
320.534.3637 320.253.7800 800.752.8129


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