@Override
    protected Boolean visitExpression(Expression node, Void context) {
      throw new UnsupportedOperationException(
          "aggregation analysis not yet implemented for: " + node.getClass().getName());
    }
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