As long as you don't have to split up a fully optimized index, or
one with the wrong number of segments for the division you
want to do, that would be useful. Of course, sometimes you
need to split up the big segments into smaller ones too, but
the only way I've done that in the past is basically:
We have a way to merges indexes together with IW.addIndexes,
however not the opposite, split up an index with multiple
segments. I think I can simply manufacture a new segmentinfos in
a new directory, copy over the segments files from those
segments, delete the copied segments from the source, and
