Russell Smith wrote: > SELECT ... WHERE CASE WHEN x <> 0 THEN y/x > 1.5 ELSE false END; > > A CASE construct used in this fashion will defeat optimization attempts, > so it should only be done when necessary. (In this particular example, > it would be best to sidestep the problem by writing y > 1.5*x instead.) > > > In-equality transformations do not guarantee that y > 1.5x == y/x > > 1.5. This is only true for x>0
So the proper expression would be SELECT ... WHERE CASE WHEN x >= 0 THEN y > 1.5*x ELSE y < 1.5*x END; or SELECT ... WHERE (x >= 0 AND y > 1.5*x) OR y < 1.5*x; which obviously isn't simpler. So I suggest that we just delete the parenthetical note. -- Peter Eisentraut http://developer.postgresql.org/~petere/ ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
