presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/RaptorSplitManager.java/RaptorSplitManager/createBucketSplit
class RaptorSplitManager:        private ConnectorSplit createBucketSplit(int bucketNumber, Set<ShardNodes> shards)
        {
            // Bucket splits contain all the shards for the bucket
            // and run on the node assigned to the bucket.

            String nodeId = bucketToNode.get().get(bucketNumber);
            Node node = nodesById.get(nodeId);
            if (node == null) {
                throw new PrestoException(NO_NODES_AVAILABLE, "Node for bucket is offline: " + nodeId);
            }

            Set<UUID> shardUuids = shards.stream()
                    .map(ShardNodes::getShardUuid)
                    .collect(toSet());
            HostAddress address = node.getHostAndPort();

            return new RaptorSplit(shardUuids, bucketNumber, address, transactionId);
        }