listen/notify vs. sequence-model

for a caching-application I need to implement an indicator if my table
has been changed.

I will create three rules (insert, update, delete) and then imho there
are two ways to continue:

I could simply send notifies on changes and my application listen to
the notify or I could increment a sequence and the application queries
and memorize the value of the sequence.

The solution with the sequence would have the big advantage that the
application must not keep the db-handle open all the time. (the
solution would work with cgi also and not only with mod_perl in my
case)

My question is, if the sequence-model has very poor performance
compared to the listen/notify-modell.

I need three rules in both models. In the first case I need to send
and listen a notify.
In the second case I need to update and query a sequence.

thnx,
peter

ps: are rules executed when the current transaction is closed or
immediately after the corresponding statement ?

--
mag. peter pilsl
IT-Consulting
tel: +43-699-1-3574035
fax: +43-699-4-3574035
pilsl(at)goldfisch(dot)at
http://www.goldfisch.at