Re: Does VACUUM reorder tables on clustered indices

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Martin Marques <martin(at)bugs(dot)unl(dot)edu(dot)ar>, frank church <pgsql(at)adontendev(dot)net>, pgsql-sql(at)postgresql(dot)org
Subject: Re: Does VACUUM reorder tables on clustered indices
Date: 2005-12-19 04:29:36
Message-ID: 20051219042935.GA5692@surnet.cl
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Tom Lane escribió:
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> > Note that while reordering, CLUSTER also gets rid of dead tuples, so if
> > you cluster you don't need to vacuum.
>
> Just for the record, that behavior is seriously broken: it violates
> MVCC if any of the deleted tuples are still visible to anyone else.

Well, FWIW, the fact that the CLUSTER command exists at all is broken
IMHO ... but meanwhile, are you suggesting that CLUSTER should be fixed
to retain tuples that are visible to running transactions?

--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

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