Problem with async notifications of table updates

Hi,

I am trying to set up a PostGreSQL database to send asynchronous
notifications when certain inserts or updates are performed on the
tables. The idea is I want to have publish / subscirbe model with the
database in the centre as the information hub. An application will
insert a record into a table and then a notification message is sent to
all registered subscribers telling them that record number X has been
added to table Y. Each subscriber can then chose to retrieve the record
or ignore the notification. This should be near real-time (< 0.5 sec
from insert / update to notification reception).

To do the notification I have ported the Spread (www.spread.org)
interface for MySQL to Postgres (actually only the send_mesg() part of
it). I then have a trigger function which calls the send_mesg() function
on an insert or update to the table. All good -- except that when
another application receives the message and queries the table the
record that caused the notification is not there. It would appear that
it only becomes available AFTER the trigger function that fired the
message returns.

So the question is - how can I get my trigger function to flush the row
so that I can be sure it is available for use prior to the return of the
trigger function? Alternatively - how can I tell the trigger function to
only execute the send_mesg() after the row is available?

I have not used the LISTEN / NOTIFY interface because:
a) It does not easily support sending any information (yes I know you
can set up another table and insert a pointer to the record however that
is far from ideal)
b) There is no guarantee on message delivery. Spread allows you to
ensure that message is delivered.

Thanks in advance - Mark

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