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From Joseph Adler <joseph.ad...@gmail.com>
Subject Re: extending crunch
Date Thu, 15 Nov 2012 15:58:36 GMT
Personally, I'd love to see Crunch mixed with Clojure. I was thinking about
this myself, but I'd rather see someone who really knows Clojure take this
on.

Just don't call it Clunch.

-- Joe


On Thu, Nov 15, 2012 at 5:04 AM, Victor Iacoban <victor.iacoban@gmail.com>wrote:

> Thanks Josh, will give this a try
>
>
> On Wed, Nov 14, 2012 at 9:54 PM, Josh Wills <josh.wills@gmail.com> wrote:
>
> > I'm always glad to help people to extend Crunch in ways that are useful
> for
> > them. I think that most things that involve type-related extensions can
> be
> > handled using the PTypes.derived() function, which can be used to create
> > custom PTypes that are mapped to underlying serialized types, so that you
> > could do something like
> >
> > // Forgive my syntax errors, I'm doing this w/o an IDE
> > PType<Object> objectType = PTypes.derived(Object.class, new
> > InputMapFn<BytesWritable, Object>(), new OutputMapFn<Object,
> > BytesWritable>(), Writables.writables(BytesWritable.class));
> >
> > ...which is essentially how Scrunch works: the PTypes { } functionality
> in
> > Scrunch maps from Scala types to Java types using the derived
> > functionality.
> >
> > The Converter stuff is internal to Avro and Writable, I can't think of a
> > case where that would need to be exposed outside the package (i.e., once
> > you've decided on whether to use Writables or Avro as your serialization
> > framework, the choice of Converter is fixed.)
> >
> > If you have a use case where the derived type can't handle the conversion
> > or is a poor choice for whatever reason, I'm all about having a
> discussion
> > and trying out different designs.
> >
> > Josh
> >
> >
> > On Wed, Nov 14, 2012 at 6:18 PM, Victor Iacoban <
> victor.iacoban@gmail.com
> > >wrote:
> >
> > > Hi,
> > >
> > > I'm very interested in writing a wrapper library around Apache Crunch
> for
> > > Clojure, something similar to existing Scrunch.
> > > How do you recommend to start?
> > >
> > > I was looking through Crunch code and it looks like I can pretty easily
> > > integrate it in clojure by adding some custom WritableType type.
> > > Something like WritableType<Object, ByteWritable> with a custom
> converter
> > > or inputFn/outputFn functions.
> > >
> > > Regretfully there are several issues with this approach and instead I'd
> > > have to duplicate all those type classes for a new type set
> > > * WritableType has a package visible constructor so I cannot extend it
> > and
> > > cannot instantiate it
> > > * Converter is instantiated inside WritableType constructor so in case
> I
> > > need a different converter I'm stuck
> > > * Writables has a factory method for WritableType but it's private
> > > * it looks like there is an attempt to support additional WritableTypes
> > > through EXTENSIONS in Writables but it would only work for cases where
> in
> > > WritableType<T, W> both T and W are hadoop writables
> > >
> > > So what do you think is a best solution, is it possible to open up the
> > api
> > > to support custom WritableTypes or the only option for me is to
> > implement a
> > > new ClojurePType and all related classes?
> > >
> > > Hope I'm not too detailed, but at this stage you all are probably very
> > > familiar with the code
> > >
> > > Thanks,
> > > Victor
> > >
> >
>

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