@Override
  public Operator visitCountMerge(
      final CountSchemaMergeNode node, final LocalExecutionPlanContext context) {
    final OperatorContext operatorContext =
        context
            .getDriverContext()
            .addOperatorContext(
                context.getNextOperatorId(),
                node.getPlanNodeId(),
                CountMergeOperator.class.getSimpleName());
    final List<Operator> children = new ArrayList<>(node.getChildren().size());
    for (final PlanNode child : node.getChildren()) {
      children.add(this.process(child, context));
    }
    return new CountMergeOperator(operatorContext, children);
  }
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