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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