public void setUpstream(TEndPoint endPoint, FragmentInstanceId instanceId, PlanNodeId nodeId) {
    this.upstreamEndpoint = endPoint;
    this.upstreamInstanceId = instanceId;
    this.upstreamPlanNodeId = nodeId;
  }
Exchange needs to know which child of IdentitySinkNode/ShuffleSinkNode it matches
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/node/process/ExchangeNode.java