[JENA-2332] Bad optimization transform when modifers used in SERVICE

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Jena 4.5.0
• Fix Version/s: Jena 4.6.0
• Component/s: ARQ
• Assignee: Andy Seaborne
• Reporter: Andy Seaborne
• Created: 03/Jun/22 20:13
• Updated: 25/Aug/22 09:43
• Resolved: 04/Jun/22 09:55

Description

Report: https://lists.apache.org/thread/87wgds6c43j88829bscx4xkwsgcgq58p

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 }
}

produces

(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)))))

but this query can't be transformed because of ?s.

It needs to remain as a join.

Issue Links

• is related to: JENA-1813 Join optimization transform results in incorrect query results
• links to: GitHub Pull Request #1364