public void updateGroupByLevelExpressions(Expression groupedExpression) {
    for (Expression groupedAggregationExpression :
        searchAggregationExpressions(groupedExpression)) {
      Set<Expression> groupedExpressionSet =
          groupedAggregationExpressionToRawExpressionsMap.get(groupedAggregationExpression);
      groupByLevelExpressions
          .computeIfAbsent(groupedAggregationExpression, key -> new HashSet<>())
          .addAll(groupedExpressionSet);
    }
  }
Only used to check whether one alisa is corresponding to only one column. i.e. Different
columns can't have the same alias.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/analyze/GroupByLevelHelper.java