@Override
  public List<WritePlanNode> splitByPartition(IAnalysis analysis) {
    Map<TRegionReplicaSet, Map<PartialPath, ViewExpression>> splitMap = new HashMap<>();
    for (Map.Entry<PartialPath, ViewExpression> entry : this.viewPathToSourceMap.entrySet()) {
      // for each entry in the map for target path to source expression,
      // build a map from TRegionReplicaSet to this entry.
      // Please note that getSchemaRegionReplicaSet needs a device path as parameter.
      TRegionReplicaSet regionReplicaSet =
          analysis
              .getSchemaPartitionInfo()
              .getSchemaRegionReplicaSet(
                  new MeasurementPath(entry.getKey().getNodes()).getIDeviceID());

      // create a map if the key(regionReplicaSet) is not exists,
      // then put this entry into this map(from regionReplicaSet to this entry)
      splitMap
          .computeIfAbsent(regionReplicaSet, k -> new HashMap<>())
          .put(entry.getKey(), entry.getValue());
    }

    // split this node into several nodes according to their regionReplicaSet
    List<WritePlanNode> result = new ArrayList<>();
    int maxSingleRequestSize =
        IoTDBDescriptor.getInstance().getConfig().getMaxMeasurementNumOfInternalRequest();
    for (Map.Entry<TRegionReplicaSet, Map<PartialPath, ViewExpression>> entry :
        splitMap.entrySet()) {
      // for each entry in splitMap, create a plan node.
      if (entry.getValue().size() > maxSingleRequestSize) {
        for (Map<PartialPath, ViewExpression> splitRequest :
            splitRequest(entry.getValue(), maxSingleRequestSize)) {
          result.add(new CreateLogicalViewNode(getPlanNodeId(), splitRequest, entry.getKey()));
        }
      } else {
        result.add(new CreateLogicalViewNode(getPlanNodeId(), entry.getValue(), entry.getKey()));
      }
    }
    return result;
  }
This variable will be set in function splitByPartition() according to analysis. And it will be
set when creating new split nodes.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/plan/node/metadata/write/view/CreateLogicalViewNode.java