________________________________________ From: Greg Sabino Mullane [greg@xxxxxxxxxxxx] Sent: Wednesday, November 28, 2012 10:26 AM To: pgsql-general@xxxxxxxxxxxxxx Subject: Re: pg_listening_channels() -----BEGIN PGP SIGNED MESSAGE----- Hash: RIPEMD160 Igor Neyman asked: [Postgres 9.2] > How (if it's even possible) can I get listening channels > for all sessions/ connections in the database? No, this is not possible. You can only see items from your own session. - -- IMHO, that's a step back comparing to "older" implementation of LISTEN/NOTIFY. Of course allowing "payload" to be attached to NOTIFY signal (instead of being passed through some user defined table) is a good thing. But, I (and probably many others) use LISTEN/NOTIFY mechanism to notify client program connected to postgres database about changes made in the database Implementation prior to PG 9.0: INTERESTED_CLIENT: LISTEN my_alert; SOME_OTHER_PROGRAM: INSERTS/UPDATES/DELETES table_client_interested_in; ON INSERT/UPDATE/DELETE TRIGGER: check if anyone listens on "my_alert" channel by querying pg_listener table, sends NOTIFY my_alert signal and inserts message into user_message_table; INTERESTED_CLIENT: upon receiving NOTIFY signal reads message from user_message_table; With PG 9.0 changes I lost ability to check if anyone is interested in the NOTIFY signal and payload I'm about to send. Seems like this change was not thought through completely. Regards, Igor Neyman -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
