Re: Last modification time

On Sat, Feb 11, 2006 at 09:26:57PM +0100, Johan Vromans wrote:

> Doug McNaught <doug@mcnaught.org> writes:
> > Yeah, LISTEN/NOTIFY is definitely a lighter-weight solution--I didn't
> > think of that before.
>
> LISTEN/NOTIFY looks like a synchronisation mechanism. You can notify a
> subscriber that something happened. But in my case, the report
> generating program runs only occasionally and will not be permanently
> running subscribed. I'm not sure how to use LISTEN/NOTIFY for that.

You add ON INSERT/UPDATE/NOTIFY triggers to the tables you
are interested in which fire a given NOTIFY. The report
generator would LISTEN for that while connected.

However, given your above description why does it not
suffice to regenerate the report whenever the report
generator connects ? If you want to do so only when the
table has actually changed you might add a last_modified
timestamp column with a default of now(), remember that in
the report generator and later do

 select exists(select 1 from <table> where last_modified > <old_last_modified>)

to check whether you need to regenerate the report.

Karsten
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