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https://issues.apache.org/jira/browse/JENA-2332?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17550066#comment-17550066
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Claus Stadler edited comment on JENA-2332 at 6/5/22 12:56 AM:
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It turns out its not as bad as I thought - For plain ARQ I could work around it
with a custom algebra transformer (based on TransformJoinStrategy) together
with a custom optimizer factory that injects the transform. [Working
example|https://github.com/Aklakan/jena/blob/8c2c4d197da658caea4c602a004dcafbac3bb613/jena-examples/src/main/java/arq/examples/service/CustomServiceExecutor.java#L144].
I guess that could be made part of the eventual jena-extra module in the end.
was (Author: aklakan):
It turns out its not as bad as I thought - For plain ARQ I could work around it
with a custom algebra transformer (based on TransformJoinStrategy) together
with a custom optimizer factory that injects the transform. [Working
example|https://github.com/Aklakan/jena/blob/8793a0b0dc6685fddee2e929a2cac5413d271845/jena-examples/src/main/java/arq/examples/service/CustomServiceExecutor.java#L148].
I guess that could be made part of the eventual jena-extra module in the end.
> Bad optimization transform when modifers used in SERVICE
> --------------------------------------------------------
>
> Key: JENA-2332
> URL: https://issues.apache.org/jira/browse/JENA-2332
> Project: Apache Jena
> Issue Type: Bug
> Components: ARQ
> Affects Versions: Jena 4.5.0
> Reporter: Andy Seaborne
> Assignee: Andy Seaborne
> Priority: Major
> Fix For: Jena 4.6.0
>
>
> Report: https://lists.apache.org/thread/87wgds6c43j88829bscx4xkwsgcgq58p
> {noformat}
> SELECT * {
> SERVICE <https://dbpedia.org/sparql> { SELECT * { ?s a
> <http://dbpedia.org/ontology/MusicalArtist> } LIMIT 5 }
> SERVICE <https://dbpedia.org/sparql> { SELECT * { ?s
> <http://www.w3.org/2000/01/rdf-schema#label> ?x } LIMIT 1 }
> }
> {noformat}
> produces
> {noformat}
> (sequence
> (service <https://dbpedia.org/sparql>
> (slice _ 5
> (bgp (triple ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
> <http://dbpedia.org/ontology/MusicalArtist>))))
> (service <https://dbpedia.org/sparql>
> (slice _ 1
> (bgp (triple ?s <http://www.w3.org/2000/01/rdf-schema#label> ?x)))))
> {noformat}
> but this query can't be transformed because of {{?s}}.
> It needs to remain as a join.
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