Re: planner with index scan cost way off actual cost,

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Jim C. Nasby wrote:
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.

I was going to recommend higher - but not knowing what else was running, kept it to quite conservative :-)... and given he's running java, the JVM could easily eat 512M all by itself!

Cheers

Mark


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