Provided by: postgresql-client-8.4_8.4.11-1_amd64 bug


       LISTEN - listen for a notification


       LISTEN name


       LISTEN registers the current session as a listener on the notification condition name.  If
       the current session is already registered as a listener for this  notification  condition,
       nothing is done.

       Whenever  the  command  NOTIFY  name  is  invoked,  either  by this session or another one
       connected to the same database, all the sessions currently listening on that  notification
       condition are notified, and each will in turn notify its connected client application. See
       the discussion of NOTIFY for more information.

       A session can be unregistered for a given notify condition with the  UNLISTEN  command.  A
       session's listen registrations are automatically cleared when the session ends.

       The  method  a  client application must use to detect notification events depends on which
       PostgreSQL application  programming  interface  it  uses.  With  the  libpq  library,  the
       application  issues LISTEN as an ordinary SQL command, and then must periodically call the
       function PQnotifies to find out whether any notification events have been received.  Other
       interfaces  such  as  libpgtcl  provide  higher-level  methods for handling notify events;
       indeed, with libpgtcl the application programmer should not even issue LISTEN or  UNLISTEN
       directly. See the documentation for the interface you are using for more details.

       NOTIFY [notify(7)] contains a more extensive discussion of the use of LISTEN and NOTIFY.


       name   Name of a notify condition (any identifier).


       Configure and execute a listen/notify sequence from psql:

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


       There is no LISTEN statement in the SQL standard.


       NOTIFY [notify(7)], UNLISTEN [unlisten(7)]