public static String makePartName(List<String> partCols, List<String> vals) {
    return makePartName(partCols, vals, null);
  }
Returns a relative path wrt the parent path.
@param parentPath the parent path.
@param childPath the child path.
@return childPath relative to parent path.
standalone-metastore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/utils/FileUtils.java