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