Hi Bernhard,
What Jena version was used to compile your sample as using Jena 2.5.4 I get the
following error trying to compile it :
$ /usr/bin/javac -classpath
"lib/arq.jar:lib/iri.jar:lib/jena.jar:./virtuoso_driver:."
SPARQLDescribePerformance.java
SPARQLDescribePerformance.java:129: cannot find symbol
symbol : method getURI()
location: interface com.hp.hpl.jena.rdf.model.RDFNode
uri =
node.as(Resource.class).getURI();
^
SPARQLDescribePerformance.java:131: cannot find symbol
symbol : method getLexicalForm()
location: interface com.hp.hpl.jena.rdf.model.RDFNode
uri =
node.as(Literal.class).getLexicalForm();
^
2 errors
Best Regards
Hugh Williams
Professional Services
OpenLink Software
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On 21 Dec 2009, at 16:09, Bernhard Haslhofer wrote:
> Hi,
>
> I am currently performing some data analysis on our local DBpedia dataset
> running on a Virtuoso 6 server. For that I need to execute a large amount of
> SPARQL DESCRIBE queries against the local Virtuoso SPARQL endpoint - in a
> single run approx. 400.000 queries. I know that this will take some time, but
> that's not the problem if the execution time for a single query remains
> constant.
>
> The problem I am experiencing right now is that with an increasing number of
> DESCRIBE queries executed against a single SPARQL endpoint, the response time
> for a single DESCRIBE queries goes up almost linear. The first hundred
> queries take a few ms, the queries > 3000 take a few hundred ms in our local
> environment.
>
> I have tested this also against the public DBpedia endpoint and noticed a
> similar behavior.
>
> I've attached a code snippet that illustrates the problem. Can
> anybody<SPARQLDescribePerformance.java> tell me if the problem is on the
> client or the server side? Maybe I have missed sth... Are there any
> db-parameters to increase the performance of DESCRIBE queries?
>
> Thx,
> Bernhard
>
>
> ______________________________________________________
> Research Group Multimedia Information Systems
> Department of Distributed and Multimedia Systems
> Faculty of Computer Science
> University of Vienna
>
> Postal Address: Liebiggasse 4/3-4, 1010 Vienna, Austria
> Phone: +43 1 42 77 39635 Fax: +43 1 4277 39649
> E-Mail: [email protected]
> WWW: http://www.cs.univie.ac.at/bernhard.haslhofer
>
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