@Override
    public void write(DataOutput out) throws IOException {
      int keyLen = PrivateCellUtil.estimatedSerializedSizeOfKey(kv);
      int valueLen = 0; // We avoid writing value here. So just serialize as if an empty value.
      out.writeInt(keyLen + valueLen + KeyValue.KEYVALUE_INFRASTRUCTURE_SIZE);
      out.writeInt(keyLen);
      out.writeInt(valueLen);
      PrivateCellUtil.writeFlatKey(kv, out);
    }
Import data written by {@link Export}.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/Import.java