Re: range_agg

On Tue, Jul 9, 2019 at 12:24 PM Pavel Stehule <pavel.stehule@gmail.com> wrote:
> út 9. 7. 2019 v 21:10 odesílatel Pavel Stehule <pavel.stehule@gmail.com> napsal:
>> I afraid so with generic multiragetype there lot of array infrastructure will be duplicated
>
> on second hand - it is true so classic array concat is not optimal for set of ranges, so some functionality should be
redefinedevery time. 
>
> I don't know what is possible, but for me - multiranges is special kind (subset) of arrays and can be implement as
subsetof arrays. I remember other possible kind of arrays - "sets" without duplicates. It is similar case, I think. 
>
> Maybe introduction of multirages as new generic type is bad direction, and can be better and more enhanceable in
futureto introduce some like special kinds of arrays. So for example - unnest can be used directly for arrays and
multirangestoo - because there will be common base. 

Well I'm afraid of that too a bit, although I also agree it may be an
opportunity to share some common behavior and implementation. For
example in the discussion about string syntax, I think keeping it the
same as arrays is nicer for people and lets us share more between the
two types.

That said I don't think a multirange is a subtype of arrays (speaking
as a traditional object-oriented subtype), just something that shares
a lot of the same behavior. I'm inclined to maximize the overlap where
feasible though, e.g. string syntax, UNNEST, indexing, function naming
(`range_length`), etc. Something like Rust traits (or Java interfaces)
seems a closer mental model, not that we have to formalize that
somehow, particularly up front.

Yours,
Paul