private String removeTrailingSpaces(String value) {
      if (value == null) {
        return null;
      }
      String regex = "\\s+$";
      return value.replaceAll(regex, "");
    }
@param op         consists of EQUALS, NULL_SAFE_EQUALS, LESS_THAN, LESS_THAN_EQUALS, IS_NULL
@param literal
@param columnName
@param columnType
@return
ql/src/java/org/apache/hadoop/hive/ql/io/parquet/LeafFilterFactory.java