message: debug the bug
diff: @@ -3421,6 +3421,7 @@ void query_thread(bool update_flag, string db_name, string format, string db_que
  int ret_val;
  //catch exception when this is an update query and has no update privilege
  try{
  + cout << "begin query..." << endl;
  ret_val = current_database->query(sparql, rs, output, update_flag);
  }catch(string exception_msg){
  