At 07:55 PM 9/22/2010, Vick Khera wrote:
Here's how you do it: first, make sure you are not within a transaction or other Pg activity. Get the socket's file handle from the Pg connection handle. When you're ready to wait for a notify event, just do a select() system call on that file handle waiting until there is data to read on that socket. When you return from the select, just check for the notifications and you're ready to go. If you did not find a notification, return to the select() call. Of course, this assumes you've issued the necessary LISTEN command. This has worked for me (and is tested well) up thru Pg 8.3. I cannot imagine it would stop working as the wire line protocol doesn't really change.
How'd one get the socket file handle if using JDBC/ODBC? It seems possible if using perl DBD-Pg, but I haven't tested that to see if you can really get out of a transaction.
Given these issues I guess it would be easier to use a separate messaging server (despite that still not being that easy :) ). This would have the characteristic of not being DB specific, so apps wouldn't be locked in to postgresql. Whether this is a benefit or not depends on your POV ;).
Regards, Link. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
