The pgloader parser reads the command language (a pgloader specific DSL) and produces lisp code as its output. The lisp code is then compiled at run-time and executed.
The generated lisp-code uses the generic API defined in src/sources.lisp and creates objects specifics to the kind of source that is being loaded.
It is possible to see the generated code for study or debug:
PARSER> (pprint
(with-monitor ()
(parse-commands-from-file
"/Users/dim/dev/pgloader/test/fixed.load")))