Re: [RFC] GSoC Work on readonly queries done so far - Mailing list pgsql-hackers

On Wed, 2007-06-06 at 22:36 +0100, Simon Riggs wrote:
> >   .) Transactions are assigned a dummy xid ReadOnlyTransactionId, that
> >      is considered to be "later" than any other xid.
> 
> So you are bumping FirstNormalTransactionId up by one for this?
> 
> You're assuming then that we will "freeze" replay while we run a query?
> Otherwise doing this will mean the snapshot changes as a query executes.

Is it possible to put a normal xmax for the snapshot?

It wouldn't be a real transaction on the slave, and also the master will
use that ID for a real transaction itself. However, I don't see a real
problem on the slave because it would only be used for the purpose of
the snapshot we need at that moment.

Regards,Jeff Davis