void deserializePartitionIndex(long[] shuffleSplitRelation) {
    int prefixParams = 3;
    this.totalParallelism = (int) shuffleSplitRelation[0];
    this.totalSplitNum = (int) shuffleSplitRelation[1];
    this.currentMaskOfTreeNode = shuffleSplitRelation[2] == -1 ? null : shuffleSplitRelation[2];

    for (int i = prefixParams; i < shuffleSplitRelation.length; i++) {
      partitionIndexSubtaskMap.put(shuffleSplitRelation[i], (int) shuffleSplitRelation[++i]);
    }
  }
Key is subtaskId, Value is the queue of unAssigned mixed-format splits.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/read/hybrid/assigner/ShuffleSplitAssigner.java