presto-main/src/main/java/io/prestosql/operator/WorkProcessorPipelineSourceOperator.java/WorkProcessorPipelineSourceOperator/addSplit
class WorkProcessorPipelineSourceOperator:    @Override
    public Supplier<Optional<UpdatablePageSource>> addSplit(Split split)
    {
        if (sourceOperator == null) {
            return Optional::empty;
        }

        Object splitInfo = split.getInfo();
        if (splitInfo != null) {
            operatorContext.setInfoSupplier(() -> new SplitOperatorInfo(splitInfo));
        }

        pendingSplits.add(split);
        blockedOnSplits.set(null);

        return sourceOperator.getUpdatablePageSourceSupplier();
    }