Is map-reduce-merge coming?

[Ding, Hui]

Just read the map-reduce-merge paper by the Yahoo! folks.  It seems
there's nothing fancy:just combined two map-reduce together and use a
merge for coordination.
But still, it would be great to see how it works.  I'm wondering if
there is on-going effort to put this into the hbase impl? Or does hadoop
has this already?