debugging with gdb in postgres

hi,

I am trying to learn how postgresql implements the join algorithms.

So I am trying to learn about the source code of the executor precisely the
file nodenestloop.c .

In the executor file I have nodenestloop.o but no binary executor file.

I am using helios eclipse to edit the source code.

I want to use gdb for debugging that file, but for that gdb needs a
executor file.

I want to Debug that file using gdb and attach the postgress process file.

Could anyone help me with how to debug that file using gdb and attach a
process, I know that we can find out about the pid of the process by using
this command in psql, *select pg_backend_pid* , but how exactly are we
going to give this pid to gdb.

any help or related links wwould be grateful.

Thank you