@Override
  public Operator visitOutput(OutputNode node, LocalExecutionPlanContext context) {
    return node.getChild().accept(this, context);
  }
This Visitor is responsible for transferring Table PlanNode Tree to Table Operator Tree.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/TableOperatorGenerator.java