@Override
    public void writeValue(RandomAccessOutput dest) throws SerDeException {
      if (!(value instanceof BinaryComparable)) {
        throw new SerDeException("Unexpected type " + value.getClass().getCanonicalName());
      }
      BinaryComparable b = (BinaryComparable)value;
      dest.write(b.getBytes(), 0, b.getLength());
    }
If we received data with tags from ReduceSinkOperators, no keys will match. This should
not happen, but is important enough that we want to find out and work around it if some
optimized change causes RSO to pass on tags.
ql/src/java/org/apache/hadoop/hive/ql/exec/persistence/MapJoinBytesTableContainer.java