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From Josh Wills <jwi...@cloudera.com>
Subject Re: Thoughts on supporting HBase 0.96
Date Thu, 17 Oct 2013 13:38:53 GMT
My feeling is that the consensus here is that adding a new PTypeFamily is a
bad idea. :)

The other idea I had would be to add a way for the Source and Target to
indicate that they were reading input data directly from the Hadoop
serialization framework, and thus did not need the input/output PTypes to
perform any additional transforms via getInputMapFn/getOutputMapFn. We
would still need different PTypes for working with the HBase objects (along
the lines that Gabriel mentioned earlier in the thread), but this approach
would solve the core issue w/o requiring a new PTypeFamily.


On Wed, Oct 16, 2013 at 7:17 PM, Micah Whitacre <mkwhit@gmail.com> wrote:

> If we created a new PTypeFamily we'd need to build in support to the Avros
> (and possibly Writables) class to support wrapping the HBaseTypeFamily
> types.
>
>
> On Wed, Oct 16, 2013 at 10:20 AM, Gabriel Reid <gabriel.reid@gmail.com
> >wrote:
>
> > Ok, makes sense. And yeah, going from a Put to bytes and then back to a
> > Put in order to write to HBase doesn't sound too awesome.
> >
> >
> > On Wed, Oct 16, 2013 at 5:10 PM, Josh Wills <josh.wills@gmail.com>
> wrote:
> >
> > > On Wed, Oct 16, 2013 at 8:02 AM, Gabriel Reid <gabriel.reid@gmail.com
> > > >wrote:
> > >
> > > > On Wed, Oct 16, 2013 at 4:34 PM, Josh Wills <jwills@cloudera.com>
> > wrote:
> > > >
> > > > > On Wed, Oct 16, 2013 at 12:15 AM, Gabriel Reid <
> > gabriel.reid@gmail.com
> > > > > >wrote:
> > > > >
> > > > > > Wouldn't a derived PType (like in o.a.c.types.PTypes) be a better
> > fit
> > > > > here?
> > > > > >
> > > > >
> > > > > That was my initial attempt, and in an ideal world, my preferred
> > > > solution--
> > > > > but I haven't figured out how to make it work. The question here
> is:
> > > what
> > > > > do I derive a KeyValue object to? What I really want, for purposes
> of
> > > > > reading it/writing it to one of our HBase IO formats, is to map it
> to
> > > > > itself, and not some subclass of Writable. Another option might be
> an
> > > > > extension of WritableType to handle these special case formats--
> I'll
> > > > take
> > > > > a crack at getting that to work.
> > > > >
> > > >
> > > > I'm sure I'm just missing something obvious, but I don't totally get
> > it.
> > > > What I had
> > > > in my head is that KeyValue, Put, Delete, Result, etc could all be
> > > derived
> > > > to byte
> > > > arrays, with the KeyValueSerialization, MutationSerialization, and
> > > > ResultSerialization
> > > > classes being used in the MapFns within the derived PType to go
> between
> > > the
> > > > type and its byte representation, i.e.
> > > >
> > > >    public static PType<KeyValue> keyValue(PTypeFamily ptf) {
> > > >       return ptf.derived(
> > > >          KeyValue.class,
> > > >          BYTES_TO_KEYVALUE_VIA_KVSERIALIZATION,
> > > >          KEYVALUE_TO_BYTES_VIA_KVSERIALIZATION,
> > > >          ptf.bytes());
> > > >    }
> > > >
> > > > I'm guessing this is the same thing you're talking about, which I
> > assume
> > > > means that
> > > > I'm missing something simple as to why that wouldn't just work, but
> I'm
> > > not
> > > > sure
> > > > what it is that I'm missing.
> > > >
> > > >
> > > The rub is the Input and Output formats, which don't expect bytes--
> they
> > > expect either subclasses of the Mutation interface (Put or Delete), or
> > > KeyValue (for HFile) or Result (for HTable) inputs. So we would need to
> > > change the input and output formats so that they would take in bytes as
> > > arguments and then convert them back to the objects that the HBase APIs
> > > expect, so something like:
> > >
> > > getOutputMapFn() -> OutputFormat
> > > Put -> bytes() -> Put
> > >
> > > That isn't the end of the world, it's just a little odd. We'd need to
> do
> > > something similar on the Input format side as well, so like:
> > >
> > > InputFormat -> getInputMapFn()
> > > Result -> bytes() -> Result
> > >
> > >
> > >
> > > >
> > >
> > > > >
> > > > >
> > > > > > A whole new PTypeFamily sounds like a lot of work (unless maybe
> if
> > it
> > > > > was a
> > > > > > subclass of one of the existing ones), and I think there's still
> a
> > > fair
> > > > > bit
> > > > > > of code
> > > > > > that assumes that Avro & Writable are the only two possible
> > > PTypeFamily
> > > > > > implementations.
> > > > > >
> > > > >
> > > > > For any kind of intermediate processing, that is still true. The
> > > > > HBaseTypeFamily would only ever really appear at the input or
> output
> > > for
> > > > a
> > > > > job.
> > > > >
> > > > >
> > > > True, although of course it would be nice if we wouldn't have that
> > > > limitation.
> > > >
> > > > - Gabriel
> > > >
> > >
> >
>



-- 
Director of Data Science
Cloudera <http://www.cloudera.com>
Twitter: @josh_wills <http://twitter.com/josh_wills>

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