Hi Ivan / All,
I've checked, checked and checked a hundred+ times; there's definitely a
performance issue with *only* the following query (where a,b,c can be
any URIs, and where * can be * or ?s ?p ?o ):
SELECT * WHERE {
?s ?p ?o . FILTER( ?s in( a,b,c ) )
}
I can skirt around the performance issue by rewriting the query as a
UNION or by either of the following (which requires me to know a
predicate at least all of the subjects share in common):
SELECT ?s ?p ?o WHERE {
?s foaf:page ?skip ; ?p ?o . FILTER( ?s in( a,b,c ) )
}
SELECT ?s ?p ?o WHERE {
?s foaf:page ?skip . FILTER( ?s in( a,b,c ) ) . ?s ?p ?o
}
I'm also sure that it's not down to server performance as every other
query I run (many of them v complex) run without any problems, in fact
they run very quickly (which is great! good work).
Please do see and test for yourself at the following address:
http://webr3.org:8890/sparql?default-graph-uri=http%3A%2F%2Fdbpedia.org&query=SELECT+*+WHERE+{%0D%0A+%3Fs+%3Fp+%3Fo+.+FILTER%28+%3Fs+in%28%3Chttp%3A%2F%2Fdbpedia.org%2Fresource%2FRDFa%3E%2C%3Chttp%3A%2F%2Fdbpedia.org%2Fresource%2FSemantic_Web%3E+%29+%29%0D%0A}&format=text%2Fhtml&debug=on&timeout=
Many Regards,
Nathan
Ivan Mikhailov wrote:
> Hello Nathan,
>
> I've checked the compilation of the query and it seems the same for old
> and new versions, so I have no clue. I can't say anything about the
> speed of dbpedia.org endpoint, but it runs Virtuoso Cluster Edition that
> is not yet released and it has no relation to your local installation.
>
> What about the speed of same queries but with the graph specified? BTW
> how many graphs does the database contain? What is the database size,
> number of buffers and the hardware (most important, amount of RAM)?
>
> Best Regards,
> Ivan Mikhailov
> http://virtuoso.openlinksw.com
>
> On Tue, 2010-02-09 at 22:14 +0000, Nathan wrote:
>> Hi,
>>
>> I'm pretty sure that the performance of in() seems to have downgraded
>> somewhat with the new 6.1.0.3126 release of virtuoso; I'm struggling to
>> run even very simple queries such as the following without them timing
>> out, on both my own 6.1 and dbpedia.org's instance:
>>
>> SELECT * WHERE {
>> ?s ?p ?o . FILTER( ?s in(<http://dbpedia.org/resource/RDFa>,
>> <http://dbpedia.org/resource/Semantic_Web> ) )
>> }
>>
>> Pretty sure this is a new issue as I can run similar queries (all be it
>> on a smaller dataset) on 6.0.1-pre1.3124 without any problems, and
>> likewise I've tested on the bio2rdf.org sparql endpoint and performance
>> is nice and fast as expected.
>>
>> Regardless even if the above versioning detail is incorrect, the in()
>> performance definitely appears to be an issue on 6.1.1.0.3126
>>
>> Many Regards,
>>
>> Nathan
>
>
>
>
