On Mon, 2010-02-15 at 12:59 +0100, Joachim Wieland wrote: > On Sun, Feb 14, 2010 at 11:44 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > > Next set of questions > > > > * Will this work during Hot Standby now? The barrier was that it wrote > > to a table and so we could not allow that. ISTM this new version can and > > should work with Hot Standby. Can you test that and if so, remove the > > explicit barrier code and change tests and docs to enable it? > > I have tested it already. The point where it currently fails is the > following line: > > qe->xid = GetCurrentTransactionId(); > > We record the TransactionId (of the notifying transaction) in the > notification in order to later check if this transaction has committed > successfully or not. If you tell me how we can find this out in HS, we > might be done... > > The reason why we are doing all this is because we fear that we can > not write the notifications to disk once we have committed to clog... > So we write them to disk before committing to clog and therefore need > to record the TransactionId.
That's a shame. So it will never work in Hot Standby mode unless you can think of a different way. > > * We also discussed the idea of having a NOTIFY command that would work > > from Primary to Standby. All this would need is some code to WAL log the > > NOTIFY if not in Hot Standby and for some recovery code to send the > > NOTIFY to any listeners on the standby. I would suggest that would be an > > option on NOTIFY to WAL log the notification: > > e.g. NOTIFY me 'with_payload' FOR STANDBY ALSO; > > What should happen if you wanted to replay a NOTIFY WAL record in the > standby but cannot write to the pg_notify/ directory? Same thing that happens to any action that cannot be replayed. Why should that be a problem? -- Simon Riggs www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
