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From David Whiting <d...@apache.org>
Subject Re: Alternative strategy for incorporating Java 8 lambdas into Crunch
Date Fri, 11 Dec 2015 21:20:24 GMT
Oops, my bad. Here's a Gist:
https://gist.github.com/DavW/e2588e42c45ad8c06038

On 11 December 2015 at 18:43, Josh Wills <josh.wills@gmail.com> wrote:

> I think it's kind of awesome, but the attachment didn't go through- PR or
> gist?
> On Fri, Dec 11, 2015 at 7:42 AM David Whiting <davw@apache.org> wrote:
>
> > While fixing the bug where the IFn version of mapValues on PGroupedTable
> > was missing, I got thinking that this is quite an inefficient way of
> > including support for lambdas and method references, and it still didn't
> > actually support quite a few of the features that would make it easy to
> > code against.
> >
> > Negative parts of existing lambda implementation:
> > 1) Explosion of already-crowded PCollection, PTable and PGroupedTable
> > interfaces, and having to implement those methods in all implementations.
> > 2) Not supporting flatMap to Optional or Stream types.
> > 3) Not exposing convenient types for reduce-type operations (Stream
> > instead of Iterable, for example).
> >
> > Something that would solve all three of these is to build lambda support
> > as a separate artifact (so we can use all java8 types), and instead of
> the
> > API being directly on the PSomething interfaces, we just have convenient
> > ways to wrap up lambdas into DoFns or MapFns via statically-imported
> > methods.
> >
> > The usage then becomes
> > import static org.apache.crunch.Lambda.*;
> > ...
> > someCollection.parallelDo(flatMap(d -> someFnOf(d)), pt)
> > ...
> > otherGroupedTable.mapValue(reduce(seq -> seq.mapToInt(i -> i).sum()),
> > ints())
> >
> > Where flatMap and reduce are static methods on Lambda, and Lambda goes in
> > it's own artifact (to preserve compatibility with 6 and 7 for the rest of
> > Crunch).
> > I've attached a basic proof-of-concept implementation which I've tested a
> > few things with, and I'm very happy to sketch out a more substantial
> > implementation if people here think it's a good idea in general.
> >
> > Thoughts? Ideas? Suggestions? Please tell me if this is crazy.
> >
> >
>

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