Re: default_stats_target WAS: Simple postgresql.conf wizard

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От Aidan Van Dyk
Тема Re: default_stats_target WAS: Simple postgresql.conf wizard
Дата
Msg-id 20081202211035.GR26596@yugib.highrise.ca
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Ответ на Re: default_stats_target WAS: Simple postgresql.conf wizard  (Josh Berkus <josh@agliodbs.com>)
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* Josh Berkus <josh@agliodbs.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@highrise.ca                                       command like a king,
http://www.highrise.ca/                                   work like a slave.

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