From: Josh Berkus <josh@agliodbs.com>
Reply-To: josh@agliodbs.com
Organization: Aglio Database Solutions
To: Greg Stark <gsstark@mit.edu>
Subject: Re: More thoughts about planner's cost estimates
Date: Fri, 2 Jun 2006 15:15:43 -0700
User-Agent: KMail/1.8
Cc: Tom Lane <tgl@sss.pgh.pa.us>, David Fetter <david@fetter.org>,
	pgsql-hackers@postgresql.org
References: <14821.1149104747@sss.pgh.pa.us> <10464.1149281016@sss.pgh.pa.us>
	<87k67zdymk.fsf@stark.xeocode.com>
In-Reply-To: <87k67zdymk.fsf@stark.xeocode.com>
MIME-Version: 1.0
Content-Type: text/plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <200606021515.44174.josh@agliodbs.com>

Greg, Tom,

> But for most users analyze doesn't really have to run as often as
> vacuum. One sequential scan per night doesn't seem like that big a deal
> to me.

Clearly you don't have any 0.5 TB databases.  

> > I'd still be worried about the CPU pain though.  ANALYZE can afford to
> > expend a pretty fair number of cycles per sampled tuple, but with a
> > whole-table sample that's going to add up.

Agreed.  Despite conventional wisdom, most PostgreSQL databases ... even 
those with high level OLTP or very large DW ... are CPU-bound.    We 
really don't want an ANALYZE which is an order-of-magnitude increase in 
CPU activity.

-- 
--Josh

Josh Berkus
PostgreSQL @ Sun
San Francisco