Re: planner with index scan cost way off actual cost, advices to tweak cost constants?

On Mon, Mar 20, 2006 at 09:35:14AM +0100, Guillaume Cottenceau wrote:
> > shared_buffer = 12000
> > effective_cache_size = 25000
> >
> > This would mean you are reserving 100M for Postgres to cache relation
> > pages, and informing the planner that it can expect ~200M available
> > from the disk buffer cache. To give a better recommendation, we need
>
> Ok, thanks. I wanted to investigate this field, but as the
> application is multithreaded and uses a lot of postgres clients,
> I wanted to make sure the shared_buffers values is globally for
> postgres, not just per (TCP) connection to postgres, before
> increasing the value, fearing to take the whole server down.

shared_buffer is for the entire 'cluster', not per-connection or
per-database.

Also, effective_cache_size of 25000 on a 1G machine seems pretty
conservative to me. I'd set it to at least 512MB, if not closer to
800MB.
--
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
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