> > "Mark Woodward" <[EMAIL PROTECTED]> writes: > >> The analyzer, at least the last time I checked, does not recognize these >> relationships. > > The analyzer is imperfect but arguing from any particular imperfection is > weak > because someone will just come back and say we should work on that problem > -- > though I note nobody's actually volunteering to do so whereas they appear > to > be for hints. > > I think the stronger argument is to say that there are some statistical > properties that the analyzer _cannot_ be expected to figure out. Either > because > > a) they're simply too complex to ever expect to be able to find > automatically, > > b) too expensive to make it worthwhile in the general case, or > > c) because of some operational issue such as the data changing frequently > enough that the analyzes that would be necessary to keep the statistics > up > to date would become excessively expensive or even be impossible to > perform rapidly enough.
Well, from a purely data domain standpoint, it is impossible to charactize the exact nature of a data set without enough information to recreate it. Anything less must be designed for a fixed set of assumptions. There is no way that every specific trend can be covered by a fixed number of assumptions. The argument that all we need is better statistics completely misses the point. There will *always* be a number cases where the planner will not work optimally. I would say that a "simpler" planner with better hints will always be capable of creating a better query plan. ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
