hi all, I have performance problems with queries using property paths on a Fuseki 2.0.0 TDB with half a billion triples from Wikidata. Ramdom disk access does not seem to be the cause. I use a SSD and see low IO tps values during queries but high CPU usage. I tried with and without the automatically generated stats.opt.
Counting all birds takes ca. 8s if not called for the first time (no disk
access, everything in memory):
select count(*) where {
?d1 ( <http://www.wikidata.org/entity/P171s> /
<http://www.wikidata.org/entity/P171v> )+
<http://www.wikidata.org/entity/Q5113>
}
Counting all beetles does not seem to finish:
select count(*) where {
?d1 ( <http://www.wikidata.org/entity/P171s> /
<http://www.wikidata.org/entity/P171v> )+
<http://www.wikidata.org/entity/Q22671>
}
I tried with and without stats.opt and also with inverse paths (^property)
without success.
I guess this is not the "Counting Beyond a Yottabyte" problem?
http://www.w3.org/blog/SW/2012/04/19/no-more-counting-beyond-a-yottabyte-or-why-the-w3c-process-works/
https://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2012Apr/0003.html
If I do a count(distinct ?d1) in the Bird query, I get the same number so I
guess that the + makes the query "non-counting".
Any idea if this slow performance is to be expected and why?
Regards,
Michael Brunnbauer
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