public static List<String> getSamzaSqlCompositeKeyFieldNames(List<String> fieldNames,
      List<Integer> nameIds) {
    List<String> keyPartNames = new ArrayList<>();
    for (int idx : nameIds) {
      keyPartNames.add(fieldNames.get(idx));
    }
    return keyPartNames;
  }
Get composite key field names.
@param fieldNames list of field names to extract the key names from.
@param nameIds indices within the field names.
@return list of composite key field names
samza-sql/src/main/java/org/apache/samza/sql/data/SamzaSqlRelMessage.java