[jira] [Resolved] (JENA-109) Optimise ORDER BY + OFFSET + LIMIT queries

["Paolo Castagna (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/JENA-109?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Paolo Castagna resolved JENA-109.
---------------------------------

    Resolution: Fixed

> 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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