@Override
      public int compareTo(CompressedOwid other) {
        // When comparing the CompressedOwid, the one with the lesser value is smaller.
        if (originalWriteId != other.originalWriteId) {
          return originalWriteId < other.originalWriteId ? -1 : 1;
        }
        if(bucketProperty != other.bucketProperty) {
          return bucketProperty < other.bucketProperty ? -1 : 1;
        }
        return 0;
      }
A CompressedOwid class stores a compressed representation of the original
write ids (owids) read from the delete delta files. Since the record ids
are sorted by (owid, rowId) and owids are highly likely to be repetitive, it is
efficient to compress them as a CompressedOwid that stores the fromIndex and
the toIndex. These fromIndex and toIndex reference the larger vector formed by
concatenating the correspondingly ordered rowIds.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/VectorizedOrcAcidRowBatchReader.java