public void addPipelineDriverFactory(
      Operator operation, DriverContext driverContext, long estimatedMemorySize) {
    pipelineDriverFactories.add(
        new PipelineDriverFactory(operation, driverContext, estimatedMemorySize));
  }
Records the parent of each pipeline. The order of each list does not matter for now.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/LocalExecutionPlanContext.java