@Override
    protected Boolean visitSearchedCaseExpression(SearchedCaseExpression node, Void context) {
      for (WhenClause whenClause : node.getWhenClauses()) {
        if (!process(whenClause.getOperand(), context)
            || !process(whenClause.getResult(), context)) {
          return false;
        }
      }

      return !node.getDefaultValue().isPresent() || process(node.getDefaultValue().get(), context);
    }
visitor returns true if all expressions are constant with respect to the group.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/analyzer/AggregationAnalyzer.java