>
> It is still unclear to me why we should remember all these tricks (or add
> lots of extra little functions) when this elegantly can be expressed in a
> reduce operation with a simple one line lamba function.
>
I think you can do that too. KeyValueGroupedDataset has a reduceGroups
function. This probably won't be as fast though because you end up
creating objects where as the version I gave will get codgened to operate
on binary data the whole way though.
> The same applies to these Window functions. I had to read it 3 times to
> understand what it all means. Maybe it makes sense for someone who has been
> forced to use such limited tools in sql for many years but that's not
> necessary what we should aim for. Why can I not just have the sortBy and
> then an Iterator[X] => Iterator[Y] to express what I want to do?
>
We also have orderBy and mapPartitions.
> All these functions (rank etc.) can be trivially expressed in this, plus I
> can add other operations if needed, instead of being locked in like this
> Window framework.
>
I agree that window functions would probably not be my first choice for
many problems, but for people coming from SQL it was a very popular
feature. My real goal is to give as many paradigms as possible in a single
unified framework. Let people pick the right mode of expression for any
given job :)
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