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Re: BUG #5722: vacuum full does not update last_vacuumstatistics

From: Joshua Tolley <eggyknap(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Jochen Erwied <jochen(at)pgsql(dot)erwied(dot)eu>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #5722: vacuum full does not update last_vacuumstatistics
Date: 2010-10-26 16:31:24
Message-ID: 4cc7026a.a26fe50a.7c0f.2536@mx.google.com (view raw or flat)
Thread:
Lists: pgsql-bugs
On Mon, Oct 25, 2010 at 11:03:07AM -0400, Tom Lane wrote:
> Perhaps.  The new implementation of VACUUM FULL is really more like a
> CLUSTER, or one of the rewriting variants of ALTER TABLE.  Should all
> of those operations result in an update of last_vacuum?  From an
> implementation standpoint it's difficult to say that only some of them
> should, because all of them result in a table that has no immediate
> need for vacuuming.  The only argument I can see for having only VACUUM
> FULL update the timestamp is that it's called VACUUM and the others
> aren't.  Which is an argument, but not a terribly impressive one IMO.

I agree it's an unimpressive argument; perhaps it's worth considering that
last_vacuum doesn't really indicate how much a particular table needs
vacuuming, either. Without the update/delete statistics telling you how much
updating and deleting has happened since the last vacuum, there's really no
way of guessing how vacuum-needy something might be based only on available
statistics. last_vacuum is just a nice way of verifying that [auto]vacuum
happens on the table sometimes, and influencing an administrator's WAGs about
what needs vacuuming. 

--
Joshua Tolley / eggyknap
End Point Corporation
http://www.endpoint.com

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