Re: Subtransaction commits and Hot Standby

On Tue, 2008-09-16 at 17:01 +0300, Heikki Linnakangas wrote:
> Simon Riggs wrote:
> > Subtransactions cause a couple of problems for Hot Standby:
> 
> Do we need to treat subtransactions any differently from normal 
> transactions? Just treat all subtransactions as top-level transactions 
> until commit, and mark them all as committed when you see the commit 
> record for the top-level transaction.

If we do that, snapshots become infinitely sized objects though, which
then requires us to invent some way of scrolling it to disk. So having
removed the need for subtrans, I then need to reinvent something similar
(or at least something like a multitrans entry).

Perhaps it is sufficient to throw an error if the subxid cache
overflows? But I suspect that may not be acceptable...

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support