Re: Q: Executing functions at connect/disconnect?

Just as i thought...
I have only one solution then; to have a cleanup function which is executed every now and then...

Cleanup function:
1. Look in the Session table to find out which sessions are registered.
2. Determine if some of these sessions are "dead".
3. Update all those items/objects/rows held by the dead session(s) as "unused".
4. Unregister the session.

I see two problems with this:
A. How do I know if a session is dead or still connected? I need to get that information from the postmaster or my backend in some way, but I don't know how to do that.
B. If this function is exeuted by a cron job or something, then some rows will be marked as "in use" and unavailable to other clients for some time... I would have to run this frequently to be sure that no objects are left behind for too long. Besides, it is an ugly solution. :/

/Mattias

>From: "Darko Prenosil" <darko(dot)prenosil(at)finteh(dot)hr>
> I had same question before about two months, but I'm afraid, there is no
> simple way. I tried to add some code to the "backend", but have broken all my
> teeth trying to get it work. Such code goes deeply into PostgreSQL internals,
> and I'm afraid only few people can do it(Tom,Bruce,Jan...).
> Hoverer if You succeed ,please let me know because I'm interested in this
> feature too.
>
> Regards !

> On Thursday 03 July 2003 17:28, Mattias Kregert wrote:
> > Is there a way to automagically execute a function at connect/disconnect?
> > I was thinking about the possibility to have some kind of automatic cleanup
> > when the client disconnects.
> >
> > I would like to:
> > - Register a session id at connect time. (INSERT into sessions(sessId,
> > user, host, ...) ...) - Use the session id to mark some objects as "in use"
> > (UPDATE tbl SET usedBy=<sessionid> WHERE...). - Automatically update all
> > rows with this session-id as "unused" when the client disconnects from the
> > backend.
> >
> > I can not trust the client to exit cleanly all the time, so the cleanup
> > function must be executed by the backend when the connection is lost. The
> > client could exit nicely or crash or have a power failure or whatever. I
> > don't expect bad things to happen very often, but if/when they do i want to
> > be sure that no rows are "in use".
> >
> > Any ideas?
> >