Bene created this task. Bene added subscribers: Bene, JanZerebecki, Lucie, hoo, Smalyshev, Manybubbles. Bene added projects: Wikidata, Wikidata-Query-Service. Restricted Application added a subscriber: Aklapper.
TASK DESCRIPTION Blazegraph's query optimizer orders operations in a way that leads to a timeout in some cases where disabling the optimizer returns a result within seconds. The query where we stumbled on this is: ``` PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> PREFIX skos: <http://www.w3.org/2004/02/skos/core#> PREFIX wikibase: <http://wikiba.se/ontology#> SELECT DISTINCT ?result WHERE { { { ?subject0 rdfs:label "United States"@en . } UNION { ?subject0 skos:altLabel "United States"@en . } } { { ?predicate1 rdfs:label "president"@en . } UNION { ?predicate1 skos:altLabel "president"@en . } } ?predicate1 a wikibase:Property . ?predicate1 wikibase:directClaim ?directPredicate2 . ?subject0 ?directPredicate2 ?result . } ``` This url helped us identify what problem caused the timeout. [[ http://wdqs-beta.wmflabs.org/bigdata/namespace/wdq/sparql?query=PREFIX+rdfs%3A+%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23%3E%0D%0APREFIX+skos%3A+%3Chttp%3A%2F%2Fwww.w3.org%2F2004%2F02%2Fskos%2Fcore%23%3E%0D%0APREFIX+wikibase%3A+%3Chttp%3A%2F%2Fwikiba.se%2Fontology%23%3E%0D%0A%0D%0ASELECT+DISTINCT+%3Fresult+WHERE+{%0D%0A%09{+%0D%0A%09%09{+%3Fsubject0+rdfs%3Alabel+%22United+States%22%40en+.+}+UNION+{+%3Fsubject0+skos%3AaltLabel+%22United+States%22%40en+.+}%0D%0A%09}%0D%0A%09{%0D%0A%09%09{+%3Fpredicate1+rdfs%3Alabel+%22president%22%40en+.+}+UNION+{+%3Fpredicate1+skos%3AaltLabel+%22president%22%40en+.+}%0D%0A%09}%0D%0A%09%3Fpredicate1+a+wikibase%3AProperty+.%0D%0A%09%3Fpredicate1+wikibase%3AdirectClaim+%3FdirectPredicate2+.%0D%0A%09%3Fsubject0+%3FdirectPredicate2+%3Fresult+.%0D%0A}&explain | Blazegraph explain feature ]] The query works with optimizer disabled: ``` PREFIX hint: <http://www.bigdata.com/queryHints#> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> PREFIX skos: <http://www.w3.org/2004/02/skos/core#> PREFIX wikibase: <http://wikiba.se/ontology#> SELECT DISTINCT ?result WHERE { hint:Query hint:optimizer "None" . { { ?subject0 rdfs:label "United States"@en . } UNION { ?subject0 skos:altLabel "United States"@en . } } { { ?predicate1 rdfs:label "president"@en . } UNION { ?predicate1 skos:altLabel "president"@en . } } ?predicate1 a wikibase:Property . ?predicate1 wikibase:directClaim ?directPredicate2 . ?subject0 ?directPredicate2 ?result . } ``` TASK DETAIL https://phabricator.wikimedia.org/T100235 EMAIL PREFERENCES https://phabricator.wikimedia.org/settings/panel/emailpreferences/ To: Bene Cc: Manybubbles, Smalyshev, hoo, Lucie, JanZerebecki, Bene, Aklapper, jkroll, Wikidata-bugs, Jdouglas, aude, daniel _______________________________________________ Wikidata-bugs mailing list Wikidata-bugs@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-bugs
