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Re: Proposal: vacuum and autovacuum parameters to control freezing

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>
Cc: pgsql-hackers(at)postgreSQL(dot)org, "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "Simon Riggs" <simon(at)2ndquadrant(dot)com>
Subject: Re: Proposal: vacuum and autovacuum parameters to control freezing
Date: 2006-11-05 16:29:06
Message-ID: 14247.1162744146@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
"Heikki Linnakangas" <heikki(at)enterprisedb(dot)com> writes:
> I think a global critical_age parameter is just fine. If you have one 
> huge table that takes a long time to vacuum, just adjust critical_age so 
> that there's enough time for the huge table vacuum to finish before 
> wrap-around. That means that other smaller tables are vacuumed more 
> frequently than would otherwise be necessary, but that's not a big deal 
> if the other tables really are much smaller.

Well, that's what you have to do right now, but as soon as we support
multiple autovac processes it'll be useful to do the other; so I figured
we might as well add the pg_autovacuum column while we're at it.

>> pg_autovacuum.freeze_distance: per-table vacuum_freeze_distance setting
>> for autovacuum to use.

> Shouldn't this be used for manual vacuums as well?

I thought about that but it seemed pretty dubious --- manual vacuums
don't look at pg_autovacuum for anything else, eg not for the cost
variables.

			regards, tom lane

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