public byte[] getConstantAsBytes(Writable writable) throws SerDeException {
    if (pCompare instanceof StringCompare) {
      return writable.toString().getBytes();
    } else if (pCompare instanceof DoubleCompare) {
      byte[] bts = new byte[8];
      double val = ((DoubleWritable) writable).get();
      ByteBuffer.wrap(bts).putDouble(val);
      return bts;
    } else if (pCompare instanceof IntCompare) {
      byte[] bts = new byte[4];
      int val = ((IntWritable) writable).get();
      ByteBuffer.wrap(bts).putInt(val);
      return bts;
    } else if (pCompare instanceof LongCompare) {
      byte[] bts = new byte[8];
      long val = ((LongWritable) writable).get();
      ByteBuffer.wrap(bts).putLong(val);
      return bts;
    } else {
      throw new SerDeException("Unsupported primitive category: " + pCompare.getClass().getName());
    }
  }
@return byte [] value from writable.
@throws SerDeException
accumulo-handler/src/java/org/apache/hadoop/hive/accumulo/predicate/PushdownTuple.java