public void addResultColumn(ResultColumn resultColumn) {
    resultColumns.add(resultColumn);
    ResultColumn.ColumnType columnType = resultColumn.getColumnType();
    if (columnType == ResultColumn.ColumnType.AGGREGATION) {
      hasBuiltInAggregationFunction = true;
    }
  }
This class maintains information of {@code SELECT} clause.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/statement/component/SelectComponent.java