> "Mark Woodward" <[EMAIL PROTECTED]> writes:
>> The analyzer, at least the last time I checked, does not recognize these
> The analyzer is imperfect but arguing from any particular imperfection is
> 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
> 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
> a) they're simply too complex to ever expect to be able to find
> 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
> 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
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.
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TIP 6: explain analyze is your friend