Re: How is random_page_cost=4 ok?

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Greg Smith <gsmith(at)gregsmith(dot)com>
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>, Postgres <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: How is random_page_cost=4 ok?
Date: 2008-10-10 21:56:48
Message-ID: 48EFCFA0.4050201@agliodbs.com
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> I don't think random_page_cost actually corresponds with any real number
> anymore. I just treat it as an uncalibrated knob you can turn and
> benchmark the results at.

And, frankly, not a useful knob. You get much more useful results out
of effective_cache_size and cpu_* costs than you get out of messing with
random_page_cost, unless you're running on SSD or something which would
justify a lower RPC, or if you're compensating for our poor n-distinct
estimation for very large tables.

--Josh

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