A subclass of rdflib SPARQLUpdateStore with BNode support, for Virtuoso

vsparqlstore.py

from rdflib import BNode, URIRef
from rdflib.plugins.stores.sparqlstore import SPARQLUpdateStore, _node_to_sparql, _node_from_result, SPARQL_NS
from uuid import uuid4

def _virtuoso_compatible_generator():
    return unicode(uuid4().int % 2**61)

# monkey patch BNode to make it virtuoso compatible
BNode.__new__.func_defaults = (None, _virtuoso_compatible_generator, 'b')


def _virtuoso_node_to_sparql(node):
    if isinstance(node, BNode):
        return '<nodeID://{}>'.format(node)
    else:
        return node.n3()

def _virtuoso_node_from_result(element):
    if element.tag == '{%s}bnode' % SPARQL_NS:
        return BNode(element.text[9:])
    else:
        return _node_from_result(element)


class VSPARQLStore(SPARQLUpdateStore):
    def __init__(self, endpoint, username, password, **kwargs):

        SPARQLUpdateStore.__init__(self, endpoint, endpoint,
                                   node_to_sparql=_virtuoso_node_to_sparql,
                                   node_from_result=_virtuoso_node_from_result,
                                   **kwargs)
        self.setHTTPAuth('digest')
        self.setCredentials(username, password)


if __name__ == "__main__":
    from rdflib import Namespace, Graph, Literal
    from rdflib.collection import Collection
    EX = Namespace('http://example.org/')
    store = VSPARQLStore('http://localhost:8890/sparql-auth', 'dba', 'dba')
    g = Graph(store, EX.g)
    g.remove((None, None, None))
    print(len(g))

    bn = BNode()
    g.add((EX.s, EX.pb, bn))
    g.add((bn, EX.pb, Literal("foo")))

    lh = BNode()
    g.add((EX.s, EX.pl, lh))
    lst = Collection(g, lh, map(Literal, [1,2,3]))

    print(len(g))
    print(g.serialize(format="turtle"))
    
    g.remove((None, None, None))

Ok, I found a way to get rid of the global mapping table (revision 2).

It involves an ugly hack (monkeypatching the default parameters of BNode.__new__), and is not 100% robust (it will break with BNodes created with an explicit ID, for example those generated by some parsers). So I have mixed feelings about it.

... you seem to like living in the danger zone 😄

Monkeypatching obviously isn't that optimal, but to be honest i currently don't see a better way to do this (so being able to also configure BNode creation from a SPARQLStore in a way that doesn't have the potential to break things outside of it) ...

so, suggestions welcome, but till then 👍