Merlin Moncure <mmonc...@gmail.com> writes: > On Thu, Feb 18, 2010 at 12:58 PM, Simon Riggs <si...@2ndquadrant.com> wrote: >> I thought a bit more about this and don't really understand why we need >> an xid at all. When we discussed this before the role of a NOTIFY was to >> remind us to refresh a cache, not as a way of delivering a transactional >> payload. If the cache refresh use case is still the objective why does >> it matter whether we commit or not when we issue a NOTIFY? Surely, the >> rare case where we actually abort right at the end of the transaction >> will just cause an unnecessary cache refresh.
> notifications serve many more purposes than cache refreshes...it's a > generic 'wake up and do something' to the client. The point to my mind is that the previous implementation guaranteed that failed transactions would not send notifies. I don't think we can just drop that semantic consistency statement and not break applications. Also, as Josh notes, even for cache refresh uses it is *critical* that the notifies not be delivered to listeners till after the sender commits; else you have race conditions where the listeners look for changes before they can see them. So it's difficult to make it much simpler than this anyhow. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers