Triggers called twice, triggers debugging

Hi all,

I'm quite new to postgresql, so please forgive me if these are stupid
questions, but I couldn't find answers.

I'm using versione 7.3.4 (i can't upgrade, sorry).

I've written a trigger function using C to export update query results
to a Java program. The trigger seems to work except that it's being
called twice for each tuple updated.

This is what I used

CREATE TRIGGER myTrig AFTER UPDATE on myTable FOR EACH ROW EXECUTE
PROCEDURE trigFunction();

The trigger is quite simple right now, but it's going to become
complex, so I'd like to know how to deug it, I've tried to attach to
postmaster process and to psql without succeding, is there any guide
for triggers debugging?