Chris Cleveland <ccleve+github(at)dieselpoint(dot)com> writes:
> I'd like to add some keywords/clauses to the SELECT statement.
Yeah, you'll have to modify gram.y (and a pile of other places)
if you want to do that. That's certainly something we do all
the time, but bison doesn't provide any way to add grammar
productions on-the-fly, so it does imply core-code mods.
> ... The new SELECT would return multiple result sets.
And that sounds like you'd also be redefining the wire protocol,
hence having to touch client-side code as well as the server.
regards, tom lane