[Wikidata-bugs] [Maniphest] [Created] T175380: Queries with wikibase:statements or wikibase:sitelinks are slow

[Lucas_Werkmeister_WMDE]

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

TASK DESCRIPTION

I would expect this query to be very efficient:

SELECT ?item ?sitelinks WHERE {
  ?item wikibase:statements ?sitelinks.
}
ORDER BY DESC(?sitelinks)
LIMIT 10

But it times out. The same query with another numeric predicate, like wdt:P2067 (mass), is fairly efficient. I suspect Blazegraph for some reason doesn’t have an index for sorted wikibase:statements (or whatever the equivalent Blazegraph term is)… perhaps because it’s xsd:integer instead of xsd:decimal?

Same situation for wikibase:sitelinks.

Motivation: a Wikipedia user suggested searching for items wtih most sitelinks but no dewiki article. This query should find such items, but also times out:

SELECT ?item ?sitelinks WHERE {
  ?item wikibase:sitelinks ?sitelinks.
  MINUS {
    ?deArticle schema:about ?item;
               schema:isPartOf <https://de.wikipedia.org/>.
  }
}
ORDER BY DESC(?sitelinks)
LIMIT 10

TASK DETAIL

https://phabricator.wikimedia.org/T175380

EMAIL PREFERENCES

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To: Lucas_Werkmeister_WMDE
Cc: Aklapper, Smalyshev, Lucas_Werkmeister_WMDE, GoranSMilovanovic, QZanden, EBjune, merbst, Avner, debt, Gehel, Jonas, FloNight, Xmlizer, Izno, jkroll, Wikidata-bugs, Jdouglas, aude, Tobias1984, Manybubbles, Mbch331

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