Hello Hugh,
if you set the default graph to http://dbpedia.org at
http://lod.openlinksw.com/sparql the same behaviour that Claus spotted
at DBpedia occurs, which is also strange because it needs much more time
on a smaller graph compared to the whole LOd Cloud.
Kind regards,
Lorenz
Hi Claus,
I see the behaviour you report running the two queries again
http://dbpedia.org/sparql , but running against
http://lod.openlinksw.com/sparql the roles are reversed with the
bif:contains query completing in about 1 sec :
http://lod.openlinksw.com/sparql/?default-graph-uri=&qtxt=Select+%3Fx+%7B%0D%0A++%3Fx+%3Chttp%3A%2F%2Fwww.w3.org%2F1999%2F02%2F22-rdf-syntax-ns%23type%3E+%3Chttp%3A%2F%2Fwww.w3.org%2F2002%2F07%2Fowl%23Class%3E+.%0D%0A++%3Fx+%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23label%3E+%3Fv_3+.%0D%0A++Filter%28%3Cbif%3Acontains%3E%28%3Fv_3%2C+%22airport%22%29%29+.%0D%0A++Filter%28langMatches%28lang%28%3Fv_3%29%2C+%22en%22%29%29+.%0D%0A%7D++Limit+10&format=text%2Fhtml&CXML_redir_for_subjs=121&CXML_redir_for_hrefs=&timeout=30000&debug=on
and the regex query taking 20+ secs to complete:
http://lod.openlinksw.com/sparql/?default-graph-uri=&qtxt=Select+%3Fx+%7B%0D%0A++%3Fx+%3Chttp%3A%2F%2Fwww.w3.org%2F1999%2F02%2F22-rdf-syntax-ns%23type%3E+%3Chttp%3A%2F%2Fwww.w3.org%2F2002%2F07%2Fowl%23Class%3E+.%0D%0A++%3Fx+%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23label%3E+%3Fv_3+.%0D%0A++Filter%28regex%28%3Fv_3%2C+%22airport%22%2C+%22i%22%29%29+.%0D%0A++Filter%28langMatches%28lang%28%3Fv_3%29%2C+%22en%22%29%29+.%0D%0A%7D++Limit+10&format=text%2Fhtml&CXML_redir_for_subjs=121&CXML_redir_for_hrefs=&timeout=30000&debug=on
So something to look into against the dbpedia endpoint , but not
against lod ...
Best Regards
Hugh Williams
Professional Services
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On 19 Aug 2014, at 12:20, Claus Stadler
<cstad...@informatik.uni-leipzig.de
<mailto:cstad...@informatik.uni-leipzig.de>> wrote:
Hi,
I noticed the following issue on the DBpedia endpoint and the LOD
cache (http://dbpedia.org/sparql, http://lod.openlinksw.com/sparql):
I did not have time to try it against a develop7 git branch.
The following query works as expected and returns fast: It apparently
scans the approx. 600 classes and filters them by their label
matching the regex:
Select ?x {
?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://www.w3.org/2002/07/owl#Class> .
?x <http://www.w3.org/2000/01/rdf-schema#label> ?v_3 .
Filter(regex(?v_3, "airport", "i")) .
Filter(langMatches(lang(?v_3), "en")) .
} Limit 10
The following query takes very long to complete. Apparently the query
planner decides to start with bif:contains, thereby scanning all
instances that have 'airport' in their name - which is a much larger
set than filtering just by the classes first:
Select ?x {
?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://www.w3.org/2002/07/owl#Class> .
?x <http://www.w3.org/2000/01/rdf-schema#label> ?v_3 .
Filter(<bif:contains>(?v_3, "airport")) .
Filter(langMatches(lang(?v_3), "en")) .
} Limit 10
I am wordering if there are already planned enhancements for this issue.
Cheers,
Claus
--
Dipl. Inf. Claus Stadler
Department of Computer Science, University of Leipzig
Research Group: http://aksw.org/
Workpage & WebID: http://aksw.org/ClausStadler
Phone: +49 341 97-32260
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