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https://issues.apache.org/jira/browse/JENA-109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13096943#comment-13096943
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Paolo Castagna commented on JENA-109:
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> Setting the window to 100000 interacts with JENA-44, which gives parallelism
> in the sort. I suggest a more cautious limit of a few hundred items.
Ok.
Even if the interaction is one exclude the other rather than causing problems
or wrong results.
Maybe, the window for JENA-89 and JENA-109 should be configurable via ARQ
symbols as it will be the threshold for JENA-44. This way, users can tune their
systems as they wish. Not an excuse to come up with sensible and reasonable
defaults though.
> There's no need to change (TopN). [...] put a slice over the "top"
Ok, it's much simpler this way. I'll do that.
> Optimise ORDER BY + OFFSET + LIMIT queries
> ------------------------------------------
>
> Key: JENA-109
> URL: https://issues.apache.org/jira/browse/JENA-109
> Project: Jena
> Issue Type: Improvement
> Components: ARQ
> Reporter: Paolo Castagna
> Assignee: Paolo Castagna
> Priority: Minor
> Labels: optimization, sparql
> Attachments: JENA-109_ARQ_r1164652.patch
>
>
> 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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