public static GroupNode deserialize(ByteBuffer byteBuffer) {
    OrderingScheme orderingScheme = OrderingScheme.deserialize(byteBuffer);
    int partitionColumnCount = ReadWriteIOUtils.readInt(byteBuffer);
    PlanNodeId planNodeId = PlanNodeId.deserialize(byteBuffer);
    return new GroupNode(planNodeId, null, orderingScheme, partitionColumnCount);
  }
orderingScheme may include two parts: PartitionKey and OrderKey. It marks the number of
PartitionKey.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/relational/planner/node/GroupNode.java