private String analyzeAlias(
      String resultColumnAlias,
      Expression rawExpression,
      Expression normalizedExpression,
      QueryStatement queryStatement) {
    if (resultColumnAlias != null) {
      // use alias as output symbol
      return resultColumnAlias;
    }

    if (queryStatement.isCountTimeAggregation()) {
      return COUNT_TIME_HEADER;
    }

    if (!Objects.equals(normalizedExpression, rawExpression)) {
      return rawExpression.getOutputSymbol();
    }

    return null;
  }
process select component for align by device.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/analyze/AnalyzeVisitor.java