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| author | Marc G. Fournier | 1996-08-18 22:14:33 +0000 |
|---|---|---|
| committer | Marc G. Fournier | 1996-08-18 22:14:33 +0000 |
| commit | 69b655f481c0696064466bcee8e09c7844aff382 (patch) | |
| tree | 07c9f640637884cdded35df571ae6d03f6674d18 /doc/man/notify.l | |
Support Docs & ContribPG95-DIST
Diffstat (limited to 'doc/man/notify.l')
| -rw-r--r-- | doc/man/notify.l | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/doc/man/notify.l b/doc/man/notify.l new file mode 100644 index 0000000000..a986e9a454 --- /dev/null +++ b/doc/man/notify.l @@ -0,0 +1,48 @@ +.\" This is -*-nroff-*- +.\" XXX standard disclaimer belongs here.... +.\" $Header$ +.TH "NOTIFY" SQL 11/05/95 Postgres95 Postgres95 +.SH NAME +notify \(em signal all frontends and backends listening on a class +.SH SYNOPSIS +.nf +\fBnotify\fR class_name +.fi +.SH DESCRIPTION +.BR notify +is used to awaken all backends and consequently all frontends +that have executed +.IR listen (l) +on +.IR class_name . +This can be used either within an instance-level rule as part of the +action body or from a normal query. When used from within a normal +query, this can be thought of as interprocess communication (IPC). +When used from within a rule, this can be thought of as an alerter +mechanism. +.PP +Notice that the mere fact that a +.BR notify +has been executed does not imply anything in particular about +the state of the class (e.g., that it has been updated), nor +does the notification protocol transmit any useful information +other than the class name. Therefore, all +.BR notify +does is indicate that some backend wishes its peers to examine +.IR class_name +in some application-specific way. +.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" +define rule(l), +listen(l), +libpq. |