Hi Martin,
The default indexes should do, i don't see wrong plan or similar. So it's
better to send us the execution plan so we can see how this query compiles on
your site; to do this put the query in explain ('sparql ...query here ..') and
execute via command line ISQL tool.
When doing explain note that query should begin with SPARQL keyword.
Also what are INI settings in Parameters section specifically NumberOfBuffers,
how large is working set? Check the staistics with status () command again with
ISQL tool.
Best Regards,
Mitko
On Apr 22, 2010, at 12:45 PM, Martin Gerlach wrote:
> Hi,
>
> The following SPARQL Query returns approx. 10000 results out of 35
> million triples.
>
> select [distinct] ?conflict ?metadata [from
> <http://example.com/mygraph>] where {
> ?conflict a <http://dbpedia.org/ontology/MilitaryConflict> .
> ?conflict ?p <http://dbpedia.org/ontology/Event> .
> ?p rdfs:subPropertyOf rdf:type .
> ?p <http://example.com/mymetadata> ?metadata .
> }
>
> There are only 4 graphs including the Virtuoso default graphs and all
> triples concerned are in <http://example.com/mygraph>. RDF_QUAD has the
> following default indexes: GS, OP, POGS, SP.
>
> Now the given query seems to be really slow. With FROM clause it is even
> slower than without. Using DISTINCT or not does not seem to have much
> impact.
>
> Which indexes could help? I would think the query triple "?conflict ?p
> <Event>" could be the cause for the delay - shouldn't an index on just
> "O", "O,S", or "G,O,S" help? I tried each of the three without much of
> an effect.
> Are there other tables which need to be indexed in order to increase
> SPARQL perfomance?
>
> (Background: We have subclassed rdf:type dynamically for each ?s a
> <Event> triple in order to annotate metadata, e.g. provenance, source,
> time, ...)
>
> Any ideas?
>
> Thanks and cheers,
> Martin
>
>
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> Research
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--
Mitko Iliev
Developer Virtuoso Team
OpenLink Software
http://www.openlinksw.com/virtuoso
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