unlisten(7) [redhat man page]

UNLISTEN(7)							   SQL Commands 						       UNLISTEN(7)

NAME

       UNLISTEN - stop listening for a notification

SYNOPSIS

       UNLISTEN { notifyname | * }

   INPUTS
       notifyname
	      Name of previously registered notify condition.

       *      All current listen registrations for this backend are cleared.

   OUTPUTS
       UNLISTEN
	      Acknowledgment that statement has executed.

DESCRIPTION

       UNLISTEN  is  used to remove an existing NOTIFY registration.  UNLISTEN cancels any existing registration of the current PostgreSQL session
       as a listener on the notify condition notifyname.  The special condition wildcard * cancels all listener registrations for the current ses-
       sion.

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

   NOTES
       notifyname need not be a valid class name but can be any string valid as a name up to 64 characters long.

       The  backend  does  not	complain if you unlisten something you were not listening for.	Each backend will automatically execute UNLISTEN *
       when exiting.

USAGE

       To subscribe to an existing registration:

       LISTEN virtual;
       LISTEN
       NOTIFY virtual;
       NOTIFY
       Asynchronous NOTIFY 'virtual' from backend with pid '8448' received

       Once UNLISTEN has been executed, further NOTIFY commands will be ignored:

       UNLISTEN virtual;
       UNLISTEN
       NOTIFY virtual;
       NOTIFY
       -- notice no NOTIFY event is received

COMPATIBILITY

   SQL92
       There is no UNLISTEN in SQL92.

SQL - Language Statements					    2002-11-22							       UNLISTEN(7)

LISTEN(7)							   SQL Commands 							 LISTEN(7)

NAME

       LISTEN - listen for a notification

SYNOPSIS

       LISTEN name

DESCRIPTION

       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  cur-
       rently  listening  on that notification condition are notified, and each will in turn notify its connected client application. See the dis-
       cussion 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  PQno-
       tifies  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  docu-
       mentation for the interface you are using for more details.

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

PARAMETERS

       name   Name of a notify condition (any identifier).

EXAMPLES

       Configure and execute a listen/notify sequence from psql:

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

COMPATIBILITY

       There is no LISTEN statement in the SQL standard.

SEE ALSO

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

SQL - Language Statements					    2010-05-14								 LISTEN(7)