getColumns()方法问题！！！

DatabaseMetaData dm = con.getMetaData();
  if (dm != null){
    rs = dm.getColumns("","DA","DOCUMENT_ARCHIVE","%");
    rs2 = dm.getPrimaryKeys("","DA","DOCUMENT_ARCHIVE");
    if (rs != null) {
      while (rs.next()) {
        System.out.println(rs.getString(4)+"\n"+rs.getString(6));
    }
   rs.close();
}请问：rs.getString(index i)方法中的i,对应数据库表中的什么值？？？
如：getString(4)为数据库“字段名”.