[Wikidata-bugs] [Maniphest] [Created] T153061: [Bug] SPARQL sub queries avoid timeouts

[Jonas]

Jonas created this task. Jonas added projects: Wikidata-Query-Service, Discovery. Herald added a subscriber: Aklapper. Herald added a project: Wikidata.

TASK DESCRIPTION

This query works

SELECT DISTINCT ?id ?label ?description WHERE {
  {
    SELECT ?id WHERE { ?i wdt:P31 ?id. }
  }
  ?id rdfs:label ?label.
  ?id schema:description ?description.
  FILTER((LANG(?label)) = "en")
  FILTER((LANG(?description)) = "en")
}
LIMIT 20

but this query times out

SELECT DISTINCT ?id ?label ?description WHERE {
  ?i wdt:P31 ?id. 
  ?id rdfs:label ?label.
  ?id schema:description ?description.
  FILTER((LANG(?label)) = "en")
  FILTER((LANG(?description)) = "en")
}
LIMIT 20

So as far as I understand those two queries are semantically the same and it might be a bug that a sub query must be used to avoid time outs.

TASK DETAIL

https://phabricator.wikimedia.org/T153061

EMAIL PREFERENCES

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To: Jonas
Cc: Jonas, Aklapper, EBjune, mschwarzer, Avner, debt, Gehel, D3r1ck01, FloNight, Xmlizer, Izno, jkroll, Smalyshev, Wikidata-bugs, Jdouglas, aude, Deskana, Manybubbles, Mbch331

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