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49 lines
1.6 KiB
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49 lines
1.6 KiB
Plaintext
.\" This is -*-nroff-*-
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.\" XXX standard disclaimer belongs here....
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.\" $Header: /cvsroot/pgsql/doc/man/Attic/notify.l,v 1.1.1.1 1996/08/18 22:14:26 scrappy Exp $
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.TH "NOTIFY" SQL 11/05/95 Postgres95 Postgres95
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.SH NAME
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notify \(em signal all frontends and backends listening on a class
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.SH SYNOPSIS
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.nf
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\fBnotify\fR class_name
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.fi
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.SH DESCRIPTION
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.BR notify
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is used to awaken all backends and consequently all frontends
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that have executed
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.IR listen (l)
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on
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.IR class_name .
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This can be used either within an instance-level rule as part of the
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action body or from a normal query. When used from within a normal
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query, this can be thought of as interprocess communication (IPC).
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When used from within a rule, this can be thought of as an alerter
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mechanism.
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.PP
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Notice that the mere fact that a
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.BR notify
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has been executed does not imply anything in particular about
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the state of the class (e.g., that it has been updated), nor
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does the notification protocol transmit any useful information
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other than the class name. Therefore, all
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.BR notify
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does is indicate that some backend wishes its peers to examine
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.IR class_name
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in some application-specific way.
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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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define rule(l),
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listen(l),
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libpq.
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