On Tue, Jul 7, 2009 at 19:52, stack <[email protected]> wrote:
> 2009/7/7 Doğacan Güney <[email protected]>
>
> > ...
> > > What would you suggest Doğacan? Maybe we should add Marker interfaces
> to
> > > Put and Delete and then change TableReducer to take the Marker?
> > >
> >
> > Sure, that's a good idea.
> >
> > I haven't studied hadoop 0.20's API much yet so I am not sure if this can
> > be
> > done but can hbase have its own ReduceContext class? If this is possible,
> > then maybe we can just expose the HTable instance through the context and
> > allow user to do whatever he wants to do on the table (and throw an
> > exception if context.write is called) . I think this would be much more
> > simpler to understand than the write/collect() calls (e.g
> TableOutputFormat
> > ignores the collect-ed keys). Does this make sense?
>
>
> This is an interesting idea. Sketch more how it work. Currently the
> HTable
> is made in the TableOutputWriter. Would we then change the Reducer input
> so
> it took any Writable rather than IBW and Put?
>
Yes, so TableReducer would look something like this:
class TableReducer<K extends WritableComparable<?>, V extends Writable>
extends Reducer<K, V, WritableComparable, Writable> { /* ..... */ };
And in general, you would write your reduce method like this:
void reduce(K, V, HbaseContext context) {
Put put = new Put(row);
// ...........
// add stuff to put
// ...........
Delete delete = new Delete(row);
// ......
// add stuff to delete
// .......
context.putToTable(put);
context.deleteFromTable(delete);
// and context.write may raise an exception
}
Anyway, I guess we are close to 0.20 release. So if this is unnecessarily
complex, the solution you described works just fine for me.
>
> St.Ack
>
--
Doğacan Güney
