From: "Martin J. Laubach" <mjl@CSlab.tuwien.ac.at>

Subject: [HACKERS] Patch: SET var TO 'val'

  Here is a patch that adds a "SET variable TO 'somevalue'" capability
to the parser, and then calls the SetPGVariable() function (which does
just issue a elog(NOTICE) to see whether it works).

  That's the framework for adding timezone/date format/language/...
stuff.