The benefits of
JENA-89 gets lost as soon as someone uses OFFSET, even for low values.
Maybe we can assume users will not hit 'next page' too many times.
We can increase the TOPN_LIMIT_THRESHOLD in TransformTopN to 100000 and apply the same TopN optimization we discussed in
JENA-89 even when we have OFFSET (when OFFSET + LIMIT < TOPN_LIMIT_THRESHOLD).
In QueryIterTopN we simply return IteratorArray.create(y, offset, offset+limit) instead of IteratorArray.create.
This way we can avoid total sort for a few number of small pages (all within the 100000 threshold).