Re: Prepared transactions vs novice DBAs, again

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