SPARQLUpdateStore should use SPARQLWrapper instead of custom httplib.HTTPConnection

[olberger]

I'm fighting with a SPARQL update syntax issue when using SPARQLUpdateStore to add triples to a virtuoso store. The requests apparently succeds, silently discarding the SPARQL syntax error reported by the server.

I'm quite sure there'd be a lot of improvement if SPARQLUpdateStore used SPARQLWrapper's query() to talk to the server instead of its own httplib.HTTPConnection connection.

[uholzer]

Definitely. As far as I remember, back when I worked on SPARQLUpdateStore, SPARQLWrapper wasn't advanced enough to do updates in a meaningful way. I think the situation has changed. So, contributions are welcome.

[olberger]

Something along these lines should do :

class MyResponse(StringIO.StringIO):
    """Fakes a httplib.HTTPResponse which is always correct, for MySPARQLUpdateStore::_do_update()"""
    status = 200

class MySPARQLUpdateStore(SPARQLUpdateStore):
    """Overload SPARQLUpdateStore::_do_update() to use SPARQLWrapper::query()"""
    def _do_update(self, update):
        if myconfig.VERBOSE:
            handler = urllib2.HTTPHandler(debuglevel=1)
            opener = urllib2.build_opener(handler)
            urllib2.install_opener(opener)

            print update

        sparql = SPARQLWrapper(self.update_endpoint)
        sparql.setQuery(update)
        sparql.setMethod(POST)
        sparql.setReturnFormat(JSON)
        # Hack for Virtuoso
        #sparql.queryType= SELECT

        result = sparql.query()

        response = MyResponse(result.response.read())
        return response

At least here, it seems to work