Re: MAX/MIN optimization via rewrite (plus query rewrites

Tom Lane wrote:

>
>A more radical way of handling it would be to detect the relevance of an
>indexscan in indxpath.c and generate a special kind of Path node; this
>would not generalize to other sorts of things as you were hoping, but
>I'm unconvinced that the mechanism is going to be very general-purpose
>anyway. The major advantage is that this would work conveniently for
>comparing the cost of a rewritten query to a non-rewritten one.
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I like this point - it makes sense to check that the rewritten query is
less costly to execute than the original!

>How are you planning to represent the association between MIN/MAX and
>particular index orderings in the system catalogs?
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That is the next item to think on, we could have a rewrite catalog that
holds possible transformations for certain functions (certain aggregates
at this stage I guess). This is a bit like Alvaro's idea - however it
may be better to represent it the way he suggested!

regards

Mark