From: Chris Browne <cbbrowne@acm.org>
To: pgsql-sql@postgresql.org
Subject: Re: Does VACUUM reorder tables on clustered indices
Date: Wed, 21 Dec 2005 18:36:45 -0500
Message-ID: <60d5jqja42.fsf@dba2.int.libertyrms.com> (raw)
References: <1134940325.43a5d0a5a882e@webmail.adontendev.net>
<Pine.LNX.4.61.0512181840350.20029@bugs.unl.edu.ar>
<20051218220139.GA1651@surnet.cl>
<20051220214124.GR28771@pervasive.com>
<00e001c605bd$e23ca1a0$0600000a@d505>
<20051221003339.GB72143@pervasive.com>
jnasby@pervasive.com ("Jim C. Nasby") writes:
> On Wed, Dec 21, 2005 at 12:34:12AM +0100, ipv@tinet.org wrote:
>> Hi,
>>
>> Utilize <b>CLUSTER;</b> (after vacuum) to reorder the data.
>
> Why would you vacuum when cluster is just going to wipe out the dead
> tuples anyway?
There is one reason to VACUUM before running CLUSTER...
That is that VACUUM will be *guaranteed* to draw all the pages into memory.
Subsequently, you can be certain that the pages are in cache, and that
the CLUSTER should need to do minimal I/O to read data into memory.
If I'm considering clustering the Slony-I "sl_log_1" table, forcing it
into memory *is* something I'll consider doing in order to minimize
the time that would-be writers are blocked from writing...
--
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To: pgsql-sql@postgresql.org
Cc: cbbrowne@acm.org
Subject: Re: Does VACUUM reorder tables on clustered indices
In-Reply-To: <60d5jqja42.fsf@dba2.int.libertyrms.com>
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