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Re: More thoughts about planner's cost estimates

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, David Fetter <david(at)fetter(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: More thoughts about planner's cost estimates
Date: 2006-06-02 22:15:43
Message-ID: 200606021515.44174.josh@agliodbs.com (view raw or flat)
Thread:
Lists: pgsql-hackers
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

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