Finding classes for property objects is slow

[karlisc]

Finding classes for property objects at least in some cases seem to work much slower on QLever Uniprot, than on Virtuoso Uniprot (these are the cases when the actual classes are not there).

SELECT ?class (COUNT(?x) as ?instances) WHERE {?x <http://xmlns.com/foaf/0.1/page> ?y. ?y <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?class. } GROUP BY ?class

SELECT DISTINCT ?class WHERE {?x <http://xmlns.com/foaf/0.1/page> ?y. ?y <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?class. }

One might wonder, if pre-computing some indexes for patterns [] ?p ?x. ?x ?q [] could help in speeding up the queries in general (I not know anything about the feasibility, especially in teh case of updates).