public byte[] getBytesForEquality() {
      if (inputSplit instanceof HashableInputSplit) {
        return ((HashableInputSplit) inputSplit).getBytesForHash();
      } else {
        byte[] pathBytes = getPath().toString().getBytes();
        byte[] allBytes = new byte[pathBytes.length + 8];
        System.arraycopy(pathBytes, 0, allBytes, 0, pathBytes.length);
        SerDeUtils.writeLong(allBytes, pathBytes.length, getStart());
        return allBytes;
      }
    }
The position of the first byte in the file to process.
ql/src/java/org/apache/hadoop/hive/ql/io/HiveInputFormat.java