Re: [Virtuoso-users] execution time error when running SPARQL query on DBPEDIA endpoint

[Ivan Mikhailov]

Hello Lorenz,

The query

SELECT * WHERE { <http://dbpedia.org/ontology/Place> 
<http://www.w3.org/2002/07/owl#unionOf> ?o0.  { OPTIONAL { ?o0 ?p1 ?o1. 
}} }

as it is written, with redundant braces around { optional {..}}, means "select 
whole dbpedia into
?o0 ?p1 ?o1 and join it with { <http://dbpedia.org/ontology/Place> 
<http://www.w3.org/2002/07/owl#unionOf> ?o0 } , then filter by equality on ?o0 
bindings".
The optimizer has failed to prove that the result of such a join is always 
identical to the result of much cheaper

SELECT * WHERE { <http://dbpedia.org/ontology/Place> 
<http://www.w3.org/2002/07/owl#unionOf> ?o0. OPTIONAL { ?o0 ?p1 ?o1. 
} }

so it reported an error. The variant without extra braces return the expected 
empty result set instantly.

Best Regards,

Ivan Mikhailov
OpenLink Software
http://virtuoso.openlinksw.com


On Tue, 2009-09-22 at 22:03 +0200, Lorenz wrote:
> Hello,
> 
> when i'm executing the query below on the DBPEDIA endpoint 
> http://dbpedia.org/sparql, i get an error according to a negative 
> execution time.
> 
> Error message:
> 
> 42000 Error The estimated execution time -742267904 (sec) exceeds the limit 
> of 1200 (sec).
> in
> signal:(BIF),
>         __01 => '42000',
>         __02 => 'The estimated execution time -742267904 (sec) exceeds the 
> limit of 1200 (sec).'
> 
> 
> 
> 
> 
> 
> SPARQL query:
> SELECT * WHERE { <http://dbpedia.org/ontology/Place> 
> <http://www.w3.org/2002/07/owl#unionOf> ?o0.  { OPTIONAL { ?o0 ?p1 ?o1. 
> }} }
> 
> 
> 
> 
> Kind regards,
> 
> Lorenz
> 
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