I think, it should be new node in executor. Planner select classic
index scan or new functional index scan.
2011/9/25, Tom Lane <tgl@sss.pgh.pa.us>:
> =?ISO-8859-2?Q?pasman_pasma=F1ski?= <pasman.p@gmail.com> writes:
>> My english is not perfect, by accumulative i think about monotonically
>> increasing function.
>
> Oh, I see how that would work. I can't get real excited about it
> though. The use-case seems a bit narrow, and the amount of complexity
> added to the btree search mechanism (thereby slowing down all btree
> searches) would be significant. Furthermore, unless f() is pretty cheap
> to evaluate, you'd end up preferring an index on f(x) anyway, because
> that can be searched without any new evaluations of f().
>
> regards, tom lane
>
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pasman