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 <[email protected]> wrote: > On Wed, Oct 16, 2013 at 8:02 AM, Gabriel Reid <[email protected] > >wrote: > > > On Wed, Oct 16, 2013 at 4:34 PM, Josh Wills <[email protected]> wrote: > > > > > On Wed, Oct 16, 2013 at 12:15 AM, Gabriel Reid <[email protected] > > > >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 > > >
