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https://issues.apache.org/jira/browse/JENA-294?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13438928#comment-13438928
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Andy Seaborne commented on JENA-294:
------------------------------------
This is making it a moving target.
Please provide tests for jena-arq/testing/ARQ/OptFilterEquality/ so there is a
fixed target to aim for.
and surely the query is equivalent in outcome to the more conventional:
SELECT *
{
?x :p ?o2
OPTIONAL { ?x :q ?o }
FILTER(?x = :x)
}
Optimization has a degree of pragmatism - more conventional cases get better
treatment. All queries get the correct results.
)
> TransformFilterEquality does not handle starting OPTIONAL well
> --------------------------------------------------------------
>
> Key: JENA-294
> URL: https://issues.apache.org/jira/browse/JENA-294
> Project: Apache Jena
> Issue Type: Improvement
> Components: ARQ
> Affects Versions: Jena 2.7.4
> Reporter: Simon Helsen
> Assignee: Andy Seaborne
> Fix For: ARQ 2.9.4
>
> Attachments: jena-294-afs-1.patch, patch.txt, patch.txt,
> test-filter-equality.zip
>
>
> There was one other case where our tests were stuck on a very slow query
> execution because transformFilterEquality failed to optimize. The problem is
> that the optimizer gives up whenever the WHERE clause starts with an OPTIONAL
> clause. The reason is that the generated algebraic formula starts with a
> TableUnit and this is not handled correctly.
> I have attached a patch which fixes the problem
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