Re: Simple postgresql.conf wizard

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Dann Corbit" <DCorbit(at)connx(dot)com>
Cc: "Gregory Stark" <stark(at)enterprisedb(dot)com>, "Decibel!" <decibel(at)decibel(dot)org>, "Robert Haas" <robertmhaas(at)gmail(dot)com>, "Bruce Momjian" <bruce(at)momjian(dot)us>, "Mark Wong" <markwkm(at)gmail(dot)com>, "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, "Josh Berkus" <josh(at)agliodbs(dot)com>, "Greg Smith" <gsmith(at)gregsmith(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Simple postgresql.conf wizard
Date: 2008-11-26 01:33:23
Message-ID: 24578.1227663203@sss.pgh.pa.us
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"Dann Corbit" <DCorbit(at)connx(dot)com> writes:
> I also do not believe that there is any value that will be the right
> answer. But a table of data might be useful both for people who want to
> toy with altering the values and also for those who want to set the
> defaults. I guess that at one time such a table was generated to
> produce the initial estimates for default values.

Sir, you credit us too much :-(. The actual story is that the current
default of 10 was put in when we first implemented stats histograms,
replacing code that kept track of only a *single* most common value
(and not very well, at that). So it was already a factor of 10 more
stats than we had experience with keeping, and accordingly conservatism
suggested not boosting the default much past that.

So we really don't have any methodically-gathered evidence about the
effects of different stats settings. It wouldn't take a lot to convince
us to switch to a different default, I think, but it would be nice to
have more than none.

regards, tom lane

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