Hi Maciej,

Thanks for noticing the error in the ticket provided. I did a search on "Linked Data Fragments endpoint returns IllegalStateException" and found the correct ticket:

https://phabricator.wikimedia.org/T270476 (looks like the last two digits got chomped in Guillaume's message)

I don't see the ticket assigned/triaged at the moment so I'll try to make sure it gets looked at in our next planning cycle. Sorry for the delay.

Ryan

On Tue, Jan 12, 2021 at 8:29 AM Maciej Gawinecki <mgawinecki@gmail.com> wrote:

Hi Guillaume,

Thanks for reporting the issue in the bug tracker. Is the link you have provided, https://phabricator.wikimedia.org/T2704, correct?

The last activity in that ticket was in 2014...

Thanks,

Maciej Gawinecki

czw., 17 gru 2020 o 16:05 Maciej Gawinecki <mgawinecki@gmail.com> napisał(a):

Hi,

I am trying to get alternative names of given names in WikiData with the following simple query:

    PREFIX ps: <http://www.wikidata.org/prop/direct/>
    PREFIX wd: <http://www.wikidata.org/entity/>
    PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
    CONSTRUCT {?s rdfs:label ?o}
    WHERE { ?s ps:P31 wd:Q202444. ?s rdfs:label ?o}
    LIMIT 1000

Initially, the query was much more complex, but I was getting time-outs on the public WikiData SPARQL endpoint. I decided to use Linked Data Fragments to offload some filtering from the server to the client.

    comunica-sparql "https://query.wikidata.org/bigdata/ldf" -f query > given_names.n3

(where "query" is a file with the SPARQL query shown above). Unfortunately, the client tries to get output from the 3rd page, I am getting the following error:

    Could not retrieve https://query.wikidata.org/bigdata/ldf?subject=http%3A%2F%2Fwww.wikidata.org%2Fentity%2FQ21147790&predicate=http%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23label&page=3 (500: unknown error)

Following the link in fact returns HTTP 500 error with

    Error details
    java.lang.IllegalStateException

The link points to the 3rd page. It works if you try to go the second page: https://query.wikidata.org/bigdata/ldf?subject=http%3A%2F%2Fwww.wikidata.org%2Fentity%2FQ21147790&predicate=http%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23label&page=2
 
Is this a bug or a limitation of a service?

With kind regards,

Maciej Gawinecki

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