presto-main/src/main/java/io/prestosql/operator/OuterLookupSource.java/OuterLookupSource/SharedLookupOuterPositionIterator
class OuterLookupSource:        public SharedLookupOuterPositionIterator(LookupSource lookupSource, boolean[] visitedPositions)
        {
            this.lookupSource = requireNonNull(lookupSource, "lookupSource is null");
            this.visitedPositions = requireNonNull(visitedPositions, "visitedPositions is null");
            checkArgument(lookupSource.getJoinPositionCount() == visitedPositions.length);
        }