presto-hive/src/main/java/io/prestosql/plugin/hive/BackgroundHiveSplitLoader.java/BackgroundHiveSplitLoader/start
class BackgroundHiveSplitLoader:    @Override
    public void start(HiveSplitSource splitSource)
    {
        this.hiveSplitSource = splitSource;
        for (int i = 0; i < loaderConcurrency; i++) {
            ListenableFuture<?> future = ResumableTasks.submit(executor, new HiveSplitLoaderTask());
            addExceptionCallback(future, hiveSplitSource::fail); // best effort; hiveSplitSource could be already completed
        }
    }