Listen for a notification event.
The name of the notify condition for which you want the backend to listen.
The message returned when a command is successful, and the backend process is listening for notification.
NOTICE: Async_Listen: We are already listening on
The notice returned if the backend is already listening for the specified notify condition
LISTEN commands work together to
create a system for PostgreSQL components to communicate between themselves. Use the
LISTEN command to start the backend process listening for a notification named
name. Notifications are passed by the
NOTIFY command, which is usually placed in rules related to changes of various
database components; in this way, notifications are sent out to listeners when things are
All running backend processes that are listening for a specific notification are sent
that notification when a
NOTIFY command is issued for it by any of the
processes. When a backend process receives a notification, that notification is sent to the
client application (such as psql), which then handles the notification in
whatever manner it is written for. For more information about this method of IPC
(inter-process communication), see the reference entry titled “NOTIFY.”
You can use any valid string no longer than 31 characters for the name of the
notification to listen for (this is also true for the
NOTIFY command). To stop a backend process from ...