Bruno Wolff III <[EMAIL PROTECTED]> writes: > Tom Lane <[EMAIL PROTECTED]> wrote: >> Can anyone suggest a more general rule?
> I think it makes sense to guess that a smaller fraction of the rows will > be returned when a column value is bounded above and below than if it > is only bounded on one side, even if the bounds aren't fixed. You can > certainly be wrong. Yeah, the whole thing is only a heuristic anyway. I've been coming around to the view that relation membership shouldn't matter, because of cases like WHERE a.x > b.y AND a.x < 42 which surely should be taken as a range constraint. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match