@Override
        protected boolean collapse(RecordIdentifier recordIdentifier) {
          ((ReaderKey) recordIdentifier).setValues(
                  prevKey.getCurrentWriteId(),
                  prevKey.getBucketProperty(),
                  prevKey.getRowId(),
                  prevKey.getCurrentWriteId(),
                  true);
          return false;
        }
Return a RecordReader that is compatible with the Hive 0.12 reader
with NullWritable for the key instead of RecordIdentifier.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/OrcInputFormat.java