pg_listen creates, changes, or cancels a
request to listen for asynchronous notification messages from the
PostgreSQL server. With a
callbackCommand parameter, the request is
established, or the command string of an already existing request
is replaced. With no callbackCommand parameter, a
prior request is canceled.
pg_listen request is established, the
specified command string is executed whenever a notification
message bearing the given name arrives from the server. This
occurs when any PostgreSQL client
application issues a
NOTIFY command referencing that name. The
command string is executed from the Tcl idle loop. That is the
normal idle state of an application written with Tk. In non-Tk Tcl
shells, you can execute
vwait to cause the idle loop to be entered.
You should not invoke the SQL statements LISTEN
or UNLISTEN directly when using
takes care of issuing those statements for you. But if you want to
send a notification message yourself, invoke the SQL
NOTIFY statement using
The handle of the connection on which to listen for notifications.
The name of the notification condition to start or stop listening to.
If present, provides the command string to execute when a matching notification arrives.