Query Progress Estimator

Hi
I am trying to implement Query Progress estimator in postgres for 
queries with long run time.I am looking for info regarding the number of 
tuples already processsed by a running query .
I would be very thankful if someone can suggest where can i find it or 
the data structure that holds the value.      Right now I am exploring postgres using ddd ( debugger ).Can 
anyone suggest a better utility /editor/tool for exploring the same in a 
better way ?
I am working Fedora core 3 Linux
Thanks and regards
Anuj Tripathi