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From: Greg Smith <greg@2ndquadrant.com>
To: Craig James <craig_james@emolecules.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: Occasional giant spikes in CPU load
Date: Fri, 25 Jun 2010 12:55:17 -0400
Message-ID: <4C24DF75.4060502@2ndquadrant.com> (raw)
In-Reply-To: <4C24D679.7030701@emolecules.com>
References: <k2pda0294261004061437p9cd3810dqe9ce528b6ddb0873@mail.gmail.com>
	<m2m603c8f071004071413w1f2d2497hbbe07d9c6491848f@mail.gmail.com>
	<4BBCFB12.1010306@emolecules.com>
	<y2r72dbd3151004071556j22244233l8fa1db295b7f9cd3@mail.gmail.com>
	<r2q603c8f071004071747n3e56d12bo11c49885b8c2eb2e@mail.gmail.com>
	<4BBD3A17.90209@emolecules.com>
	<y2l72dbd3151004071950kfe09a98fqf0c9a136375260e2@mail.gmail.com>
	<v2u603c8f071004072007t323fe469lfdd8fa5f2a283890@mail.gmail.com>
	<4C23FD52.40508@emolecules.com>
	<23596.1277438692@sss.pgh.pa.us>
	<4C24B3BB.3070901@emolecules.com>
	<2286.1277477230@sss.pgh.pa.us>
	<4C24D679.7030701@emolecules.com>

Craig James wrote:
> if I upgrade a bloated database using the upgrade-in-place feature, 
> will 8.4.4 recover the bloat and return it to the OS, or do I still 
> have to recover the space manually (like vacuum-full/reindex, or 
> cluster, or copy/drop a table)?

There's no way for an upgrade in place to do anything about bloat.  The 
changes in 8.4 reduce the potential sources for new bloat (like running 
out of a FSM pages), and the overhead of running VACUUM drops some due 
to things like the "Partial VACUUM" changes.  But existing bloated 
tables and indexes are moved forward to the new version without any change.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com   www.2ndQuadrant.us




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