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https://issues.apache.org/jira/browse/JCR-3280?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13239717#comment-13239717
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Christian Stocker commented on JCR-3280:
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you're my hero. the queries are now fast.
Will report, if some issues pop up, but testsuite ran without problems
> SQL2 joins on empty sets are not efficient
> ------------------------------------------
>
> Key: JCR-3280
> URL: https://issues.apache.org/jira/browse/JCR-3280
> Project: Jackrabbit Content Repository
> Issue Type: Improvement
> Reporter: Alex Parvulescu
> Assignee: Alex Parvulescu
> Attachments: JCR-3280.patch
>
>
> It seems that in the cases where the LEFT side of the join doesn't contain
> any hits, the QueryEngine in unable to generate an efficient query for the
> RIGHT side, so it basically select all the possible nodes.
> See this discussion as context [0].
> Example:
> LEFT side has hits, RIGHT side select is fast given some conditions:
> > SQL2 JOIN LEFT SIDE took 18 ms. fetched 145 rows.
> > SQL2 JOIN RIGHT SIDE took 67 ms. fetched 0 rows.
> LEFT side has no hits, RIGHT select everything
> > SQL2 JOIN LEFT SIDE took 8 ms. fetched 0 rows.
> > SQL2 JOIN RIGHT SIDE took 845 ms. fetched 13055 rows.
> ...so it fetches 130k nodes and doesn't keep any of them.
> [0]
> http://jackrabbit.510166.n4.nabble.com/Strange-Search-Performance-problem-with-OR-td4507121.html
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