Optimise ORDER BY + OFFSET + LIMIT queries
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Key: JENA-109
URL: https://issues.apache.org/jira/browse/JENA-109
Project: Jena
Issue Type: Improvement
Components: ARQ
Reporter: Paolo Castagna
Priority: Minor
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(y).
This way we can avoid total sort for a few number of small pages (all within
the 100000 threshold).
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