<brook@biology.nmsu.edu> writes:
> - How can I introduce a new variable (e.g., XXX) to the system so that
> for example SET XXX=1 will work?
The basic thing is to add an appropriate table entry to guc.c. You
might try searching the sources for all references to one of the
lesser-used GUC variables, perhaps default_statistics_target, to get
a feeling for what's involved.
regards, tom lane