Re: problem with SPARQL query with GROUP_CONCAT

[Andy Seaborne]

Andrea,

It does not appear to be the GROUP_CONCAT.
I get "Connection reset by peer" when its commented out. Maybe there is 
some sort of intermediate process - if the GROUP_CONCAT with () is in a 
comment, it does not work; if it is omitted completely it does.

"Connection reset by peer" is something to take up with the operators of 
the service as is the different behaviour from different places.

    Andy

On 21/06/18 15:43, Andrea Turbati wrote:
Hi everyone,

I've found a strange behaviour when executing a SPARQL query having 
GROUP_CONCAT on a Jena-Fuseki SPARQL endpoint.

Executing, for example, the following query:


SELECT DISTINCT ?resource  (GROUP_CONCAT( ?singleLabel; separator=",") 
AS ?multiLabel )

WHERE {
     ?resource a <http://www.w3.org/2004/02/skos/core#Concept> .
     ?resource (<http://www.w3.org/2008/05/skos-xl#prefLabel> | 
<http://www.w3.org/2008/05/skos-xl#altLabel>) ?skosxlLabel .
     ?skosxlLabel <http://www.w3.org/2008/05/skos-xl#literalForm> 
?singleLabel .
     FILTER regex(str(?singleLabel), 'dog', 'i')

}
GROUP BY ?resource


on the AGROVOC SPARQL endpoint at 
http://agrovoc.uniroma2.it:3030/agrovoc/sparql  (it's using 
apache-jena-fuseki-3.6.0 and it has no GUI, so you need to use another 
GUI, for example http://yasgui.org/ ) you get no answer, unless you do 
such query from one of Tor Vergata IPs (Tor Vergata is hosting such 
SPARQL endpoint).

If I remove

(GROUP_CONCAT( ?singleLabel; separator=",") AS ?multiLabel )

then I'm able to execute such query from every where.


Does any of you know why I get such strange behaviour? How can I fix the 
problem (apart from doing a SPARQL query without the GROUP )


Thank you for your answer


Cheers


Andrea