On Thu, Nov 12, 2009 at 11:30 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Joachim Wieland <j...@mcknight.de> writes: >> However I share Greg's concerns that people are trying to use NOTIFY >> as a message queue which it is not designed to be. > > Yes. Particularly those complaining that they want to have very large > payload strings --- that's pretty much a dead giveaway that it's not > being used as a condition signal. > > Now you might say that yeah, that's the point, we're trying to enable > using NOTIFY in a different style. The problem is that if you are > trying to use NOTIFY as a queue, you will soon realize that it has > the wrong semantics for that --- in particular, losing notifies across > a system crash or client crash is OK for a condition notification, > not so OK for a message queue. The difference is that the former style > assumes that the authoritative data is in a table somewhere, so you can > still find out what you need to know after reconnecting. If you are > doing messaging you are likely to think that you don't need any backing > store for the system state. > > So while a payload string for NOTIFY has been on the to-do list since > forever, I have to think that Greg's got a good point questioning > whether it is actually a good idea.
I think there could be cases where the person writing the code can know, extrinsic to the system, that lost notifications are OK, and still want to deliver a payload. But I think the idea of enabling a huge payload is not wise, as it sounds like it will sacrifice performance for a feature that is by definition not essential to anyone who is using this now. A small payload seems like a reasonable compromise. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers