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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