presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/storage/BucketBalancer.java/BucketAssignment/BucketAssignment
class BucketAssignment:        public BucketAssignment(long distributionId, int bucketNumber, String nodeIdentifier)
        {
            this.distributionId = distributionId;
            this.bucketNumber = bucketNumber;
            this.nodeIdentifier = requireNonNull(nodeIdentifier, "nodeIdentifier is null");
        }