Re: Abnormal performance difference between Postgres and MySQL

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
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