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Re: Prepared transactions vs novice DBAs, again

From: Jeff Davis <pgsql(at)j-davis(dot)com>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Prepared transactions vs novice DBAs, again
Date: 2009-04-22 18:55:27
Message-ID: 1240426527.26999.114.camel@monkey-cat.sm.truviso.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, 2009-04-22 at 13:53 -0400, Alvaro Herrera wrote:
> Another thing we could do is make autovacuum log something about those,
> similar to what it does to temp tables.  And if one of them gets too
> near Xid wraparound, kill it.

As I said in my reply to Joshua, I don't think killing a prepared
transaction is consistent with the safety people expect from 2PC.
However, if it's near wraparound time, that could be considered an
exceptional case I suppose, and if we don't have a better way to avoid
getting the system in a very bad state, it might be acceptable.

I like the idea of logging some kind of warning a long time before it
becomes a real problem. Should the staleness of a prepared transaction
be measured in time or xid age or both? Maybe have a reasonable default
of a few minutes or a couple thousand transactions before it starts
issuing warnings?

Regards,
	Jeff Davis


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