Hackers,
Currently the only way that I know of to consume async notifications
via SQL (as opposed to a client application) is via dblink_get_notify.
This method isn't very good; it requires some extra support coding,
eats a connection and a backend, and doesn't have any timeout
facilities. The lack a good facility to do this will become more
troublesome if/when Peter's recent fantastic work to implement stored
procedures in the database gets accepted; asynchronous notifications
could be a more efficient mechanic for backend processes to signal
each other than the current method of signalling via fields in a
table.
A good interface might look something like:
pg_get_notifications( TimeOut INT DEFAULT 0, notify_name OUT TEXT, payload OUT TEXT, pid OUT INT) RETURNS SETF RECORD
AS...
The function would return immediately by default, or until TimeOut
seconds transpired. We'd still have to poll internally, so that
signals could be checked etc, but this would be a nice way to consume
notifications without any dependencies -- what do you think?
merlin