Rob,
I've tried on my database (that is mix of dbpedia and few other
databases. Both queries return accurate results. So questions are:
1. What version of Virtuoso Open Source do you use?
2. What version of Virtuoso Open Source was used at the time you've
loaded the database?
3. Did you create any additional indexes in RDF_QUAD table?
4. What are the outputs of the following SQL commands:
explain ('sparql SELECT ?p ?o WHERE
{ <http://dbpedia.org/resource/Programmers> ?p ?o }');
explain ('sparql SELECT ?o WHERE
{ <http://dbpedia.org/resource/Programmers>
<http://dbpedia.org/property/redirect> ?o } ');
5. If index RDF_QUAD_OGPS is mentioned in the output of second explain()
but not in the output of the first explain(), then could you please
backup your database and try
checkpoint;
drop index RDF_QUAD_OGPS;
create bitmap index RDF_QUAD_OGPS on DB.DBA.RDF_QUAD (O, G, P, S)
checkpoint;
then re-try that queries?
Best Regards,
Ivan Mikhailov,
OpenLink Software.
On Thu, 2008-05-01 at 13:19 +0100, Hugh Williams wrote:
> Rob,
>
> Querying against the officially host Virtuoso DBpedia endpoint
> (http://dbpedia.org:8890/sparql), the second query does return a
> single result as you expect. So it would appear their is something
> wrong most probably with your DBpedia datasets loaded I would think.
> When you state having "a fairly complete en version of the DBpedia
> dataset loaded into Virtuoso OS" how complete is this are they some
> datasets you have not loaded ?
>
> Best Regards
> Hugh Williams
> Professional Serviced
> OpenLink Software
>
> On 30 Apr 2008, at 14:06, robl wrote:
>
> > Hi,
> >
> > I have a fairly complete en version of the DBpedia dataset loaded into
> > Virtuoso OS. I can perform the following query and it returns data as
> > expected :
> >
> > SELECT ?p ?o WHERE { <http://dbpedia.org/resource/Programmers> ?p ?o }
> >
> > Which returns one result :
> >
> > p : http://dbpedia.org/property/redirect
> > o : http://dbpedia.org/resource/Programmer
> >
> > When I execute this query however, there are no results returned :
> >
> > SELECT ?o WHERE { <http://dbpedia.org/resource/Programmers>
> > <http://dbpedia.org/property/redirect> ?o }
> >
> > I'd expect this to return :
> >
> > o : http://dbpedia.org/resource/Programmer
> >
> > Have I misunderstood something here or is my virtuoso installation/
> > data
> > flawed in some way ?
> >
> > Thanks,
> >
> > Rob
> >
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