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Re: Autovacuum loose ends

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From:	Alvaro Herrera
Subject:	Re: Autovacuum loose ends
Date:	July 22, 2005 , 22:54:03
Msg-id:	20050722225432.GA2734@alvh.no-ip.org (view: Whole thread, Raw)
In response to:	Autovacuum loose ends (Tom Lane)
Responses:	Re: Autovacuum loose ends (Tom Lane)
List:	pgsql-hackers

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Autovacuum loose ends (Tom Lane, 14 July 2005, 14:53:05 )
Re: Autovacuum loose ends ("Matthew T. O'Connor", 14 July 2005, 16:58:06 )
Re: Autovacuum loose ends (Tom Lane, 14 July 2005, 18:13:02 )
Re: Autovacuum loose ends ("Matthew T. O'Connor", 14 July 2005, 18:30:38 )
Re: Autovacuum loose ends (Greg Stark, 14 July 2005, 19:42:21 )
Re: Autovacuum loose ends (Hannu Krosing, 14 July 2005, 20:30:32 )
Re: Autovacuum loose ends (Ron Mayer, 16 July 2005, 22:29:35 )
Re: Autovacuum loose ends (Tom Lane, 17 July 2005, 04:43:30 )
Re: Autovacuum loose ends (Alvaro Herrera <-ip.org>, 14 July 2005, 17:06:35 )
Re: Autovacuum loose ends (Tom Lane, 14 July 2005, 18:05:17 )
Re: Autovacuum loose ends (Tom Lane, 14 July 2005, 19:07:32 )
Re: Autovacuum loose ends (Alvaro Herrera <-ip.org>, 22 July 2005, 22:54:03 )
Re: Autovacuum loose ends (Tom Lane, 22 July 2005, 23:38:05 )
Re: Autovacuum loose ends (Alvaro Herrera <-ip.org>, 23 July 2005, 01:15:41 )

On Thu, Jul 14, 2005 at 10:52:56AM -0400, Tom Lane wrote:

Hey,

> * Or actually, it would vacuum template0, except that since no regular
> backend ever connects to template0, there will be no stats DB entry for
> it and so the loop in AutoVacMain will ignore it.  This is definitely
> BAD as it means that a database that's not been touched since postmaster
> start will never be vacuumed, not even for XID wraparound prevention.
> That test needs to be weakened.

I've hacked the whole thing enough that I fixed most of the issues.
However this one I don't know how to handle.  What I need to do is
compare each database's frozen Xid with the current transaction Id.
I can get the frozenxid from the flatfile -- however I don't have
anything with which to compare it.  I tried ReadNewTransactionId(), but
it doesn't work because it tries to acquire a LWLock, which isn't
possible because we don't have a PGPROC before connecting to a database.

I guess I could the Xid from pg_control.  This seems unclean however.
Opinions about doing that?  Better ideas?

-- 
Alvaro Herrera (<alvherre[a]alvh.no-ip.org>)
"Crear es tan difícil como ser libre" (Elsa Triolet)

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