[Virtuoso-users] Another query complexity question

[Sebastian Trüg]

Ok, my confusion with query complexity does not stop:

Please compare the following two queries (all on V6.1.1.3127):

$ nepomukcmd query "select distinct ?r where { { { ?r a ?v1 . ?v1 \
   rdfs:subClassOf pimo:Thing . } UNION \
   { ?r a ?v2 . ?v2 rdfs:subClassOf nao:Tag . } . \
     ?r nao:prefLabel ?v3 . ?v3 bif:contains \"test\" . } . }"

r -> <nepomuk:/res/fdda2f95-c674-42b1-9cc9-22103addbe79>
r -> <nepomuk:/0GDPmnDdyvTBmt1vya6b>
r -> <nepomuk:/FinishandtestSopranoservermultithreadpatch>
r -> <nepomuk:/res/94d9a84b-c2f2-4594-894f-230a5dee4c5c>
r -> <nepomuk:/res/4ee75a14-6cea-4ed0-bce3-ddcb9966c530>
r -> <nepomuk:/res/fe5e4211-98d0-478f-8ba8-d994f2c294d5>
r -> <nepomuk:/XYmkFlBSvczgG6S1yxqt>
r -> <nepomuk:/rJ6mzwHB1QJyX670pCWc>
r -> <nepomuk:/B8z7pBUi5YpkPPxiaJI1>
r -> <nepomuk:/VsaaFgtwyjCNvw57hrcC>

Total results: 10
Execution time: 00:00:07.191


$ nepomukcmd query "select distinct ?r where { { { ?r a ?v1 . ?v1 \
     rdfs:subClassOf pimo:Thing . } UNION \
     { ?r a ?v2 . ?v2 rdfs:subClassOf nao:Tag . } . \
     { ?r ?v3 ?v4 . ?v4 bif:contains \"test\" . } UNION \
     { ?r ?v3 ?v5 . ?v5 ?v6 ?v4 . ?v6 rdfs:subPropertyOf rdfs:label . \
       ?v4 bif:contains \"test\" . } . } . }"

r -> <nepomuk:/res/fdda2f95-c674-42b1-9cc9-22103addbe79>
r -> <nepomuk:/0GDPmnDdyvTBmt1vya6b>
r -> <nepomuk:/FinishandtestSopranoservermultithreadpatch>
r -> <nepomuk:/res/94d9a84b-c2f2-4594-894f-230a5dee4c5c>
r -> <nepomuk:/res/4ee75a14-6cea-4ed0-bce3-ddcb9966c530>
r -> <nepomuk:/res/fe5e4211-98d0-478f-8ba8-d994f2c294d5>
r -> <nepomuk:/XYmkFlBSvczgG6S1yxqt>
r -> <nepomuk:/rJ6mzwHB1QJyX670pCWc>
r -> <nepomuk:/B8z7pBUi5YpkPPxiaJI1>
r -> <nepomuk:/VsaaFgtwyjCNvw57hrcC>
r -> <nepomuk:/LqCrjm7lKHm7IXla7VUF>
r -> <nepomuk:/cTY7XppxJtr0EPGlhgqy>
r -> <nepomuk:/res/fb3e377f-be57-4173-9f80-13314528402e>

Total results: 13
Execution time: 00:00:00.572


As you can see the second query (while to me way more complex) is very
fast while the first one takes "forever".

I would very much like to know why that is so I can maybe adjust my
query creator to create "better" queries.

Cheers,
Sebastian