def remove(self, statement, context=None):
"""Remove a triple from the graph"""
log.debug("remove(%s) from %s" % (statement, context))
_context = _get_context(context)
s,p,o = skolemise(statement)
bindings = (
s or Variable("s"),
p or Variable("p"),
o or Variable("o")
)
construct = u"CONSTRUCT { " + _n3(bindings) + u" } WHERE { "
if _context != "local:": construct += u"GRAPH <%s> { " % _context
construct += _n3(bindings)
if _context != "local:": construct += u" }"
construct += u" }"
result = self.cursor().execute(construct)
_skg = SkolemGraph(result)
print result.serialize(format="n3")
if len(result) > 0:
delete = u"DELETE DATA { "
if _context != "local:": delete += u"GRAPH <%s> {\n" % _context
delete += _skg.serialize(format="nt")
if _context != "local:": delete += u"}"
delete += u" }"
print delete
self.cursor().update(delete)
def triples(self, statement, context=None, **kw):
"""Return triples matching (s,p,o) pattern"""
## shortcut if we are just checking the existence
if all(statement):
if self.__contains__(statement, context):
yield statement, context
return
_context = _get_context(context)
s,p,o = skolemise(statement)
bindings = (
s or Variable("s"),
p or Variable("p"),
o or Variable("o")
)
query = u"SELECT DISTINCT " + u" ".join([x.n3() for x in bindings if isinstance(x, Variable)])
query += u" WHERE { "
if _context != "local:": query += u"GRAPH <%s> { " % _context
query += u" ".join([x.n3() for x in bindings])
if _context != "local:": query += u" }"
query += u" }"
results = self.cursor().execute(query, **kw)
for row in results:
triple = []
for b in bindings:
if isinstance(b, Variable):
triple.append(row[b])
else:
triple.append(b)
yield (deskolemise(triple), context)
def add(self, statement, context=None, **kw):
"""Add triples to the graph"""
context = _get_context(context)
if not self.exists(statement, context):
cursor = self.cursor()
g = Graph(identifier=context)
g.add(skolemise(statement))
cursor.add_graph(g, replace=False)
def addN(self, slist, **kw):
"""Add a list of quads to the graph"""
graphs = {}
for s,p,o,c in slist:
c = _get_context(c)
g = graphs.get(c, Graph(identifier=c))
if not self.exists((s,p,o), c):
g.add(skolemise((s,p,o)))
cursor = self.cursor()
for g in graphs.values():
cursor.add_graph(g, replace=False)
def exists(self, statement, context=None):
context = _get_context(context)
s,p,o = skolemise(statement)
q = u"ASK WHERE { GRAPH <%s> { %s %s %s } }" % (context, s.n3(), p.n3(), o.n3())
return bool(self.query(q))
