mirror of
https://github.com/postgres/postgres.git
synced 2025-04-21 12:05:57 +03:00
45 lines
1.3 KiB
Plaintext
45 lines
1.3 KiB
Plaintext
.\" This is -*-nroff-*-
|
|
.\" XXX standard disclaimer belongs here....
|
|
.\" $Header: /cvsroot/pgsql/doc/man/Attic/listen.l,v 1.1.1.1 1996/08/18 22:14:25 scrappy Exp $
|
|
.TH "LISTEN" SQL 03/12/94 Postgres95 Postgres95
|
|
.SH NAME
|
|
listen \(em listen for notification on a relation
|
|
.SH SYNOPSIS
|
|
.nf
|
|
\fBlisten\fR class_name
|
|
.fi
|
|
.SH DESCRIPTION
|
|
.BR listen
|
|
is used to register the current backend as a listener on the relation
|
|
.IR class_name .
|
|
When the command
|
|
.BI notify " class_name"
|
|
is called either from within a rule or at the query level, the
|
|
frontend applications corresponding to the listening backends
|
|
are notified. When the backend process exits, this registration
|
|
is cleared.
|
|
.PP
|
|
This event notification is performed through the Libpq protocol
|
|
and frontend application interface. The application program
|
|
must explicitly poll a Libpq global variable,
|
|
.IR PQAsyncNotifyWaiting ,
|
|
and call the routine
|
|
.IR PQnotifies
|
|
in order to find out the name of the class to which a given
|
|
notification corresponds. If this code is not included in
|
|
the application, the event notification will be queued and
|
|
never be processed.
|
|
.SH "SEE ALSO"
|
|
create rule(l),
|
|
notify(l),
|
|
select(l),
|
|
libpq.
|
|
.SH BUGS
|
|
There is no way to un-\c
|
|
.BR listen
|
|
except to drop the connection (i.e., restart the backend server).
|
|
.PP
|
|
The
|
|
.IR monitor (1)
|
|
command does not poll for asynchronous events.
|