static String getKeyIndexAsString(Reader reader) {
    try {
      ByteBuffer val =
          reader.getMetadataValue(OrcRecordUpdater.ACID_KEY_INDEX_NAME)
              .duplicate();
      return utf8Decoder.decode(val).toString();
    } catch (CharacterCodingException e) {
      throw new IllegalArgumentException("Bad string encoding for " +
          OrcRecordUpdater.ACID_KEY_INDEX_NAME, e);
    }
  }
Utility to check and fix the ACID key index of an ORC file if it has been written incorrectly
due to HIVE-18817.
The condition that will be checked in the ORC file will be if the number of stripes in the
acid key index matches the number of stripes in the ORC StripeInformation.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/FixAcidKeyIndex.java