tracking postgres

hi all
    I am tracking  the psql and postgres recently.After psql sends the
query to the backend,I cann't continue to track.I don't know  how the
postgres puts the results into the conn. Because the psql gets results
of query afetr it sends query.
    If I   do "gdb postgres" , because of the variable dset=debug, I
cann't find the process of setting PGResult where dest=Local or Remote.
    who can tell me the way to solve the bored problem?
    Thanks.
                                     Guo Ge
                                      yanjia@nudt.edu.cn
                                       April  21