[JENA-109] Optimise ORDER BY + OFFSET + LIMIT queries

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Done
• Fix Version/s: Jena 2.11.0
• Component/s: ARQ
• Labels: optimization sparql
• Assignee: Paolo Castagna
• Reporter: Paolo Castagna
• Created: 02/Sep/11 23:30
• Updated: 01/Feb/15 19:11
• Resolved: 01/Feb/15 19:11

Description

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).

Issue Links

• is related to: JENA-89 Avoid a total sort for ORDER BY + LIMIT queries