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Re: Abnormal performance difference between Postgres and MySQL

From: Farhan Husain <russoue(at)gmail(dot)com>
To: Akos Gabriel <akos(dot)gabriel(at)i-logic(dot)hu>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Abnormal performance difference between Postgres and MySQL
Date: 2009-02-25 22:08:36
Message-ID: 3df32b6d0902251408j48efcab7ke7d83208bd434c@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
I am trying to find the reason of the problem so going to Oracle or
something else is not the solution. I tried with several combinations of
those parameters before posting the problem here. I have read
http://www.postgresql.org/docs/current/interactive/runtime-config-resource.htmlbefore
and I think I understood what it said.

2009/2/25 Akos Gabriel <akos(dot)gabriel(at)i-logic(dot)hu>

> Wed, 25 Feb 2009 15:43:49 -0600 -n
> Farhan Husain <russoue(at)gmail(dot)com> írta:
>
> OK, you have two options:
>
> 1. Learn to read carefully, and differentiate between work_mem and
> shared_buffers options. Lower work_mem and rise shared_buffers as
> others wrote.
> 2. Leave Postgresql alone and go for Oracle or Microsoft SQL...
>
> Rgds,
> Akos
>
> > It was only after I got this high execution time when I started to
> > look into the configuration file and change those values. I tried
> > several combinations in which all those values were higher than the
> > default values. I got no improvement in runtime. The machine postgres
> > is running on has 4 GB of RAM.
> >
> > On Wed, Feb 25, 2009 at 3:40 PM, Robert Haas <robertmhaas(at)gmail(dot)com>
> > wrote:
> >
> > > >> > shared_buffers = 32MB                   # min 128kB or
> > > >> > max_connections*16kB
> > > >>
> > > >> That's REALLY small for pgsql.  Assuming your machine has at
> > > >> least 1G of ram, I'd set it to 128M to 256M as a minimum.
> > > >
> > > > As I wrote in a previous email, I had the value set to 1792MB (the
> > > highest I
> > > > could set) and had the same execution time. This value is not
> > > > helping me
> > > to
> > > > bring down the execution time.
> > >
> > > No, you increased work_mem, not shared_buffers.  You might want to
> > > go and read the documentation:
> > >
> > >
> > >
> http://www.postgresql.org/docs/current/interactive/runtime-config-resource.html
> > >
> > > But at any rate, the large work_mem was producing a very strange
> > > plan. It may help to see what the system does without that
> > > setting.  But changing shared_buffers will not change the plan, so
> > > let's not worry about that right now.
> > >
> > > ...Robert
> > >
> >
> >
> >
>
>
> --
> Üdvözlettel,
> Gábriel Ákos
> -=E-Mail :akos(dot)gabriel(at)i-logic(dot)hu|Web:  http://www.i-logic.hu=-
> -=Tel/fax:+3612367353            |Mobil:+36209278894         =-
>
> --
> Sent via pgsql-performance mailing list (pgsql-performance(at)postgresql(dot)org)
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>



-- 
Mohammad Farhan Husain
Research Assistant
Department of Computer Science
Erik Jonsson School of Engineering and Computer Science
University of Texas at Dallas

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