presto-main/src/main/java/io/prestosql/operator/OrderByOperator.java/OrderByOperator/addInput
class OrderByOperator:    @Override
    public void addInput(Page page)
    {
        checkState(state == State.NEEDS_INPUT, "Operator is already finishing");
        requireNonNull(page, "page is null");
        checkSuccess(spillInProgress, "spilling failed");

        pageIndex.addPage(page);
        updateMemoryUsage();
    }