Re: NOTIFY/LISTEN in Postgresql

On 10/15/2012 08:54 PM, P. Broennimann wrote:
> Hi there
>
> 1) Can a Pg/SQL function "listen" for a notification sent from an
> external instance?

No, it's the other way around. A client can `LISTEN` for a `NOTIFY` sent
by another client, either directly or via a PL/PgSQL function.

What you want is a NOTIFY callback or NOTIFY trigger, something that
invokes a function without any client action when a NOTIFY comes in. No
such feature exists.

> I would like my stored function to pause/wait and continue its execution
> once an external event (NOTIFY event) occurs.

Use an advisory lock, they're ideal for that job:

http://www.postgresql.org/docs/current/static/explicit-locking.html#ADVISORY-LOCKS

> 2) In Pg/SQL I can implement a loop (until something happens) to
> pause/wait. This costs CPU time -> Is there another solution?

Depends on what you're waiting for. Details?

Again, an advisory lock may be a candidate.

--
Craig Ringer