segmentStart = finalOut.getPos();
RawKeyValueIterator kvIter = sorter.merge(segmentList, new Path(getTaskId()));
SequenceFile.Writer writer = SequenceFile.createWriter(job, finalOut,
job.getMapOutputKeyClass(), job.getMapOutputValueClass(),
compressionType, codec);
sorter.writeFile(kvIter, writer);
//close the file - required esp. for block compression to ensure
//partition data don't span partition boundaries
writer.close();
//when we write the offset/length to the final index file, we write
//longs for both. This helps us to reliably seek directly to the