presto-main/src/main/java/io/prestosql/operator/LookupJoinOperator.java/JoinProcessor/addInput
class JoinProcessor:        private void addInput(Page page, SpillInfoSnapshot spillInfoSnapshot)
        {
            requireNonNull(spillInfoSnapshot, "spillInfoSnapshot is null");

            if (spillInfoSnapshot.hasSpilled()) {
                page = spillAndMaskSpilledPositions(page, spillInfoSnapshot.getSpillMask());
                if (page.getPositionCount() == 0) {
                    return;
                }
            }

            // create probe
            inputPageSpillEpoch = spillInfoSnapshot.getSpillEpoch();
            probe = joinProbeFactory.createJoinProbe(page);

            // initialize to invalid join position to force output code to advance the cursors
            joinPosition = -1;
        }