It seems that the problem comes from SERVICE wikibase:label. As said in another discussion, ...
I noticed I could also specify AUTO_LANGUAGE in the filter, and it is still a quick query:
SELECT ?istanza_di ?instanza_diLabel WHERE { ?istanza_di wdt:P31 wd:Q13442814. ?istanza_di rdfs:label ?instanza_diLabel. FILTER((LANG(?instanza_diLabel)) IN ("[AUTO_LANGUAGE]","en")) }
Yet all the examples at query.wikidata.org use this style:
SELECT ?istanza_di ?istanza_diLabel WHERE { ?istanza_di wdt:P31 wd:Q13442814. SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". } }
The first (quick) query is actually returning more rows, but can be easily filtered to return the same data as the second. So is this a known bug just waiting for someone to fix it? Or a more complicated issue?
BTW, the first way is also easier to understand (IMHO), so I would prefer it if it was written that way in the examples!
Darren