presto-main/src/main/java/io/prestosql/operator/LookupJoinOperator.java/JoinProcessor/pageTail
class JoinProcessor:        private Page pageTail(Page currentPage, int startAtPosition)
        {
            verify(currentPage.getPositionCount() - startAtPosition >= 0);
            return currentPage.getRegion(startAtPosition, currentPage.getPositionCount() - startAtPosition);
        }