presto-main/src/main/java/io/prestosql/operator/LookupJoinOperator.java/JoinProcessor/joinCurrentPosition
class JoinProcessor:        private boolean joinCurrentPosition(LookupSource lookupSource, DriverYieldSignal yieldSignal)
        {
            // while we have a position on lookup side to join against...
            while (joinPosition >= 0) {
                if (lookupSource.isJoinPositionEligible(joinPosition, probe.getPosition(), probe.getPage())) {
                    currentProbePositionProducedRow = true;

                    pageBuilder.appendRow(probe, lookupSource, joinPosition);
                    joinSourcePositions++;
                }

                // get next position on lookup side for this probe row
                joinPosition = lookupSource.getNextJoinPosition(joinPosition, probe.getPosition(), probe.getPage());

                if (yieldSignal.isSet() || tryBuildPage()) {
                    return false;
                }
            }
            return true;
        }