pg_listener system catalog table supports the
NOTIFY commands. A listener creates an entry in
pg_listener for each notification name it is listening for. A notifier scans and updates each matching entry to show that a notification has occurred. The notifier also sends a signal (using the PID recorded in the table) to awaken the listener from sleep.
This table is not currently used in HAWQ.
||name||Notify condition name. (The name need not match any actual relation in the database.|
||integer||PID of the server process that created this entry.|
||integer||Zero if no event is pending for this listener. If an event is pending, the PID of the server process that sent the notification.|