From: | Aidan Van Dyk <aidan(at)highrise(dot)ca> |
---|---|
To: | Josh Berkus <josh(at)agliodbs(dot)com> |
Cc: | Mark Wong <markwkm(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: default_stats_target WAS: Simple postgresql.conf wizard |
Date: | 2008-12-02 21:10:35 |
Message-ID: | 20081202211035.GR26596@yugib.highrise.ca |
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Lists: | pgsql-hackers |
* Josh Berkus <josh(at)agliodbs(dot)com> [081202 15:54]:
> Do you have any idea how skewed the distribution of data for DBT3 is? If
> values are being generated in relatively equal proportion, I'd expect
> increasing DST to have little effect. The databases where higher DST is
> useful is ones with skewed data distribution.
>
> Unfortunately, all the data examples I could point to are proprietary
> customer databases :-(
But no body's asking anybody to point out "skewed" data... I think it's
*unanimous* that on skewed data, a higher stats target is needed for the
skewed columns.
The question is how much of a penalty the (majority of?) users with "normal"
data columns will have to pay in stats/planning overhead to accomidate a
blanket increase in DST for the (few?) skewed columns.
I think Marks started to try and show that overhead/difference with real
numbers.
My (probably unsubstantiated) bias is showing, but nobody else has (yet)
showed otherwise ;-)
a.
--
Aidan Van Dyk Create like a god,
aidan(at)highrise(dot)ca command like a king,
http://www.highrise.ca/ work like a slave.
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