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From: Andrew Sullivan <ajs@commandprompt.com>
To: pgsql-performance@postgresql.org
Subject: Re: ??: Postgresql update op is very very slow
Date: Thu, 26 Jun 2008 09:55:01 -0400
Message-ID: <20080626135501.GF6918@commandprompt.com> (raw)
In-Reply-To: <486396A9.1030208@postnewspapers.com.au>
References: <473587.97248.qm@web32701.mail.mud.yahoo.com>
	<op.uc83c7m2cigqcu@apollo13.peufeu.com>
	<004b01c8d671$3dec1630$0544000a@hz.ali.com>
	<486219B6.7050003@enterprisedb.com>
	<005101c8d773$ff81b2c0$0644000a@hz.ali.com>
	<48638939.5080500@enterprisedb.com>
	<pan.2008.06.26.12.40.59.151500@wizards.de>
	<486396A9.1030208@postnewspapers.com.au>

On Thu, Jun 26, 2008 at 09:16:25PM +0800, Craig Ringer wrote:

> I think Pg already does in place updates, or close, if the tuples being 
> replaced aren't referenced by any in-flight transaction. I noticed a while 
> ago that if I'm doing bulk load/update work, if there aren't any other 
> transactions no MVCC bloat seems to occur and updates are faster.

Are you on 8.3?  That may be HOT working for you.  MVCC doesn't get
turned off if there are no other transactions (it can't: what if
another transaction starts part way through yours?).

A

-- 
Andrew Sullivan
ajs@commandprompt.com
+1 503 667 4564 x104
http://www.commandprompt.com/



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