docs: public Reader getCharacterStream(long pos, long length) throws SQLException {
      String val = toString();
      if (val.length() < (int) pos - 1 + length) {
        throw ExceptionMapper
            .getSqlException("pos + length is greater than the number of characters in the Clob");
      }
      String sub = val.substring((int) pos - 1, (int) pos - 1 + (int) length);
      return new StringReader(sub);
    }