presto-main/src/main/java/io/prestosql/sql/planner/NodePartitionMap.java/NodePartitionMap/asBucketNodeMap
class NodePartitionMap:    public BucketNodeMap asBucketNodeMap()
    {
        ImmutableList.Builder<InternalNode> bucketToNode = ImmutableList.builder();
        for (int partition : bucketToPartition) {
            bucketToNode.add(partitionToNode.get(partition));
        }
        return new FixedBucketNodeMap(splitToBucket, bucketToNode.build());
    }