The catalog pg_listener
supports the
LISTEN and
NOTIFY
commands. A listener creates an entry in
pg_listener
for each notification name
it is listening for. A notifier scans pg_listener
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.
Table 43.22. pg_listener
Columns
Name | Type | References | Description |
---|---|---|---|
relname |
name |
Notify condition name. (The name need not match any actual
relation in the database; the name relname is historical.)
|
|
listenerpid |
int4 |
PID of the server process that created this entry | |
notification |
int4 |
Zero if no event is pending for this listener. If an event is pending, the PID of the server process that sent the notification |