January 2002
Intermediate to advanced
640 pages
16h 39m
English
Content preview from Practical PostgreSQL
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Notify
Signals all backends that are listening for the specified notify event.
Synopsis
NOTIFY nameParameters
nameThe condition to be signaled.
Results
NOTIFYThe message returned when a notification is sent out correctly.
Description
The NOTIFY command is the counterpart of the LISTEN
command, which we covered earlier in this chapter. The two commands provide a simple
interprocess communication (IPC) implementation that can often prove useful if used
correctly.
Use NOTIFY to send out a notification with the specified name; if any
frontends have issued a LISTEN command with the same notification name,
they will be informed of the notification.
Note
The behavior of a frontend process after receiving a notification sent by the NOTIFY command is dependent upon its implementation of the feature, so it may not
respond immediately (or at all).
A notification is comprised of the notification’s name and the issuing backend’s process ID (PID). The original designer of the database specifies what notify condition names exist and how they function within the database.
The NOTIFY and LISTEN commands are most often used
to provide a way to notify frontend processes that tables have been modified; as such,
notification names are often set to the names of tables. This is the
common use of this feature, but it is not required that notification
names be table names.
Note
Automatic notification of table modifications ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.