presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/storage/OrcStorageManager.java/OrcStorageManager/shardDelta
class OrcStorageManager:    private static Collection<Slice> shardDelta(UUID oldShardUuid, Optional<ShardInfo> shardInfo)
    {
        List<ShardInfo> newShards = shardInfo.map(ImmutableList::of).orElse(ImmutableList.of());
        ShardDelta delta = new ShardDelta(ImmutableList.of(oldShardUuid), newShards);
        return ImmutableList.of(Slices.wrappedBuffer(SHARD_DELTA_CODEC.toJsonBytes(delta)));
    }