On Mon, 15 Jan 2007, Neil Conway wrote: > On Mon, 2007-01-15 at 10:51 -0800, Richard Troy wrote: > > I therefore propose that the engine evaluate - > > benchmark, if you will - all functions as they are ingested, or > > vacuum-like at some later date (when valid data for testing may exist), > > and assign a cost relative to what it already knows - the built-ins, for > > example. > > That seems pretty unworkable. It is unsafe, for one: evaluating a > function may have side effects (inside or outside the database), so the > DBMS cannot just invoke user-defined functions at whim. Also, the > relationship between a function's arguments and its performance will > often be highly complex -- it would be very difficult, not too mention > computationally infeasible, to reconstruct that relationship > automatically, especially without any real knowledge about the > function's behavior. > > -Neil
Hi Neil, Tom had already proposed: > > I'm envisioning that the CREATE FUNCTION syntax would add optional > clauses > > COST function-name-or-numeric-constant > ROWS function-name-or-numeric-constant > > that would be used to fill these columns. I was considering these ideas in the mix; let the user provide either a numeric or a function, the distinction here being that instead of running that function at planning-time, it could be run "off-line", so to speak. Richard -- Richard Troy, Chief Scientist Science Tools Corporation 510-924-1363 or 202-747-1263 [EMAIL PROTECTED], http://ScienceTools.com/ ---------------------------(end of broadcast)--------------------------- TIP 2: Don't 'kill -9' the postmaster
