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From Andy Seaborne <a...@apache.org>
Subject Re: Equivalent query and performances
Date Thu, 07 Mar 2019 20:09:33 GMT
It might be going to the network though as far as I can tell,
http://givingsense.eu/datamusee/onto/contextgraph18022019
does not have any triples.

In order to do FROM, the query engine has to create create a different 
dataset and that can imped some TDB features. Have you tried:


  where {
       ?s a <http://dbpedia.org/ontology/Painter>
       ?s a ?t;
  }

also - what happens if you remove the "?s a ?t" because with the 
DISTINCT, it does not change the results.

     Andy

On 07/03/2019 17:47, Zachary Whitley wrote:
> I believe that the first query with the "from" will make a network call and
> add what is returned to to default graph while the second one will query
> the data already loaded in the named graph. If I'm correct that would
> explain the difference and wouldn't be surprised to see the results you're
> getting.
> 
> https://jena.apache.org/tutorials/sparql_datasets.html
> 
> On Thu, Mar 7, 2019 at 11:56 AM Jean-Claude Moissinac <jcmoissinac@gmail.com>
> wrote:
> 
>> Hello
>>
>> I'm using jena-fuseki 3.6.0
>> I've tried two queries which, for me seems equivalent:
>> select  (count(distinct ?s) as ?c)
>> from <http://givingsense.eu/datamusee/onto/contextgraph18022019>
>> where {
>>      ?s a ?t;
>>         a <http://dbpedia.org/ontology/Painter>
>> }
>> and
>> select  (count(distinct ?s) as ?c)
>> where {
>>      graph <http://givingsense.eu/datamusee/onto/contextgraph18022019> {
>>       ?s a ?t;
>>         a <http://dbpedia.org/ontology/Painter>
>>    }
>> }
>>
>> The second is much muck quickest than the first; for example, 42712 ms for
>> the first one and 524 ms for the second
>> It's a penalty because I would like sometimes to use several graphs and the
>> from version seems to be the good way.
>>
>> Any advices or comments?
>> --
>> Jean-Claude Moissinac
>>
> 

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