presto-main/src/main/java/io/prestosql/operator/index/UpdateRequest.java/UpdateRequest/getFinishedIndexSnapshot
class UpdateRequest:    public IndexSnapshot getFinishedIndexSnapshot()
    {
        checkState(indexSnapshotFuture.isDone(), "Update request is not finished");
        return MoreFutures.getFutureValue(indexSnapshotFuture);
    }