Thanks Ivan,
Out of all the samples, the 4th one in the previous email is the only
one I can't find any work around / alternative syntax for (alternative
to the second IN), if you do know of any alternate way of doing this in
the interim please do let me know :)
eg:
select distinct ?s ?p ?o WHERE {
?s foaf:page ?page .
FILTER( ?s
in(<http://dbpedia.org/resource/BBC>,<http://dbpedia.org/resource/Quantum_tunnelling>)
) .
?s ?p ?o . FILTER( isURI(?o) )
FILTER( ?o
in(<http://dbpedia.org/resource/United_Kingdom>,<http://dbpedia.org/resource/Category:Physics>)
)
}
Many Regards,
Nathan
Ivan Mikhailov wrote:
> Hello Nathan,
>
> I'll inspect what can be improved tonight. Single-element IN differs
> from "longer" IN because it becomes an equality and then the query is
> rewritten to, say,
> select distinct (<http://dbpedia.org/resource/BBC> as ?s) ?p ?o WHERE {
> <http://dbpedia.org/resource/BBC> ?p ?o .
> }
>
> so these cases differ.
>
> Best Regards,
>
> Ivan Mikhailov
> OpenLink Software
> http://virtuoso.openlinksw.com
>
> On Fri, 2010-02-12 at 19:58 +0000, Nathan wrote:
>> Further test cases:
>>
>> seems to be tied to the number of arguments inside the in() clause eg:
>>
>> this works:
>> select distinct ?s ?p ?o WHERE {
>> ?s ?p ?o . FILTER( ?s in (<http://dbpedia.org/resource/BBC>) )
>> }
>>
>> this doesn't (occasionally does but is exceptionally slow):
>> select distinct ?s ?p ?o WHERE {
>> ?s ?p ?o . FILTER( ?s in
>> (<http://dbpedia.org/resource/BBC>,<http://dbpedia.org/resource/Quantum_tunnelling>)
>> )
>> }
>>
>> and to ensure it's not a size of graph thing; the following queries
>> create a small result set which is then filtered using the second IN
>>
>> this works:
>> select distinct ?s ?p ?o WHERE {
>> ?s foaf:page ?page .
>> FILTER( ?s in
>> (<http://dbpedia.org/resource/BBC>,<http://dbpedia.org/resource/Quantum_tunnelling>)
>> ) .
>> ?s ?p ?o . FILTER( isURI(?o) )
>> FILTER( ?o in( <http://dbpedia.org/resource/United_Kingdom>) )
>> }
>>
>> this doesn't:
>>
>> select distinct ?s ?p ?o WHERE {
>> ?s foaf:page ?page .
>> FILTER( ?s in
>> (<http://dbpedia.org/resource/BBC>,<http://dbpedia.org/resource/Quantum_tunnelling>)
>> ) .
>> ?s ?p ?o . FILTER( isURI(?o) )
>> FILTER( ?o in(
>> <http://dbpedia.org/resource/United_Kingdom>,<http://dbpedia.org/resource/Category:Physics>
>> ) )
>> }
>>
>> regards!
>>
>> Nathan wrote:
>>> 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
>>>>
>>>>
>>>
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>
>
>
