LISTEN

    Description

    registers the current session as a listener on the notification channel named <channel>. If the current session is already registered as a listener for this notification channel, nothing is done.

    Whenever the command NOTIFY <channel> is invoked, either by this session or another one connected to the same database, all the sessions currently listening on that notification channel are notified, and each will in turn notify its connected client application.

    A session can be unregistered for a given notification channel with the UNLISTEN command. A session’s listen registrations are automatically cleared when the session ends.

    NOTIFY contains a more extensive discussion of the use of LISTEN and NOTIFY.

    channel

    The name of a notification channel (any identifier).

    Notes

    A transaction that has executed LISTEN cannot be prepared for two-phase commit.

    Configure and execute a listen/notify sequence from psql:

    1. LISTEN virtual;
    2. Asynchronous notification "virtual" received from server process with PID 8448.

    Compatibility

    There is no LISTEN statement in the SQL standard.

    Parent topic: SQL Commands