Aborting transactions

Hi,

we use postgres for student's education and others.

Now we had an issue with some SQL statement in connection with some
triggers, that probably caused an infinite loop in processing for at
least 10 hours or so on some two to ten line tables.

Unfortunately, the students used the phpPgAdmin web interface, so
they could not abort the running SQL statement. They could not even
continue to work with the database from phpPgAdmin.

So the question arose, how to abort running statements at least
via the postgres account. I remember some methods from Ingres "some"
years ago, but I did not find anything similar in postgresql.

Is there any chance to monitor the current transactions and abort them,
in case of need?

Thanks,
Thomas Mack
TU Braunschweig, Institut für Informationssysteme