message: fix: a bug when handling DISTINCT clause
diff: @@ -837,7 +837,7 @@ void GeneralEvaluation::getFinalResult(ResultSet &ret_result)
  useful += this->temp_result->results[i].getAllVarset();
  }
  - if ((int)this->temp_result->results.size() > 1)
  + if ((int)this->temp_result->results.size() > 1 || this->query_tree.getProjectionModifier() == QueryTree::Modifier_Distinct)
  {
  TempResultSet *new_temp_result = new TempResultSet();
  