App freezes on SPARQL SERVICE request

[webhart]

Steps to reproduce:
Run the following SPARQL query:

select * where { 
    SERVICE <https://query.wikidata.org/bigdata/namespace/wdq/sparql>{
		?s ?p ?o .
    }
} limit 10

[JannisGrundmann]

Trying to access https://query.wikidata.org/bigdata/namespace/wdq/sparql throws

com.google.gson.stream.MalformedJsonException: Unterminated string at line 30356959 column 1 path $.results.bindings[2309719].o.value 

It seems to work with

select * where { 
    SERVICE <https://dbpedia.org/sparql> {
		?s ?p ?o .
    }
} limit 10

[webhart]

According to https://www.wikidata.org/wiki/Wikidata:SPARQL_query_service:
The result is returned as XML by default, or as JSON if either the query parameter format=json or the header Accept: application/sparql-results+json are provided
Do we need to configure Jena accordingly?

[Lexachoc]

I download the RDF data from the endpoint and upload to FUSEKI, then the query works.

I started to doubt that the query on the server side is too large, which is causing the problem. I verify this by changing this line:

ontodocker/fastapi_app/app/triplestore/jena.py

Line 77 in dfe94de

return await client.get(self.server, params={"query": query}, headers=FusekiConnection._header)

into

return await client.post("https://query.wikidata.org/bigdata/namespace/wdq/sparql", params={'query': query, 'format': 'json'})

and type:

SELECT * WHERE {
  ?sub ?pred ?obj .
} LIMIT 10

to the YASGUI editor

Directly query to the endpoint works.

It turns out that the data is way too large to process and your LIMIT 10 is not passed to the wikidata server.

Using below query will fix the issue:

select * where { 
    SERVICE <https://query.wikidata.org/bigdata/namespace/wdq/sparql> {
    {
      SELECT * WHERE {
        ?s ?p ?o .
      } LIMIT 10
    }
    }
}

The result:

So we don't need to configure Fuseki. Fuseki/ontodocker can parse the results.