remote sparql queries always use POST

[lalewis1]

Hi All,

Looks like the logic in the way that the _buildQueryStringForServiceCall function gets called is flawed.
code here:

rdflib/rdflib/plugins/sparql/evaluate.py

Line 404 in 500ec25

parser.parseQuery(service_query)

The function only gets passed the inner text from the SERVICE query and then the sparql parser tries to parse it which fails. This then results in a bunch of prefixes being added to the query. making the query always longer than 600 characters.

In turn this then means that a POST request is always used, due to the logic here:

rdflib/rdflib/plugins/sparql/evaluate.py

Line 363 in 500ec25

if len(service_query) < 600:

[lalewis1]

More Info.

This works as expected because the internal service query is valid sparql on its own.

...
    service <my-service> {
        select ?s ?p ?o
        where {
                ?s ?p ?o
        }
    }
...

This results in a POST request because the internal service query is not valid on its own

...
    service <my-service> {
        ?s ?p ?o
    }
...

However, the above is still valid sparql, and is how Federated queries are documented by the W3C

Suggested Solution
Only bind required prefixes to the query if necessary.