support for deleting triples

_py4s.pxd

@@ -113,6 +113,9 @@ cdef extern from "frontend/import.h":
 	int fs_import_stream_data(fsp_link *link, unsigned char *data, size_t count)
 	int fs_import_stream_finish(fsp_link *link, int *count, int *errors)
 
+cdef extern from "frontend/update.h":
+	int fs_update(fsp_link *link, char *update, char **message, int unsafe)
+
 cdef extern from "glib/gslist.h":
 	ctypedef struct GSList:
 		char		*data

_py4s.pyx

@@ -51,7 +51,7 @@ cdef class FourStoreClient:
 	def cursor(self):
 		return _Cursor(self)
 
-cdef _n3(s):
+def _n3(s):
 	return " ".join([x.n3() for x in s])
 
 cdef class _Cursor:
@@ -144,6 +144,12 @@ cdef class _Cursor:
 			if transaction:
 				self.commit()
 
+	def update(self, query):
+		cdef char *message
+		py4s.fs_update(self._link, query, &message, 1)
+		if message != NULL:
+			raise FourStoreError("%s: -- %s" % (message, query))
+
 	def transaction(self, context="local:"):
 		if isinstance(context, Graph): context = context.identifier
 		content_type = "application/x-turtle"

py4s/__init__.py

@@ -2,7 +2,7 @@
 from rdflib.term import Variable
 from rdflib.store import Store, VALID_STORE, NO_STORE
 from rdflib.plugin import register
-from _py4s import FourStoreClient, FourStoreError
+from _py4s import FourStoreClient, FourStoreError, _n3
 
 __all__ = ["FourStore", "FourStoreError"]
 
@@ -33,9 +33,32 @@ def addN(self, slist, **kw):
 		"""Add a list of quads to the graph"""
 		for s,p,o,c in slist:
 			self.add((s,p,o), context=c, **kw)
-	def remove(self, *av, **kw):
-		"""Remove a triple from the graph (unimplemented)"""
-		raise FourStoreError("Triple Removal Not Implemented")
+	def remove(self, statement, context="local:"):
+		"""Remove a triple from the graph"""
+		if isinstance(context, Graph): _context = context.identifier
+		else: _context = context
+		s,p,o = statement
+		bindings = (
+			s or Variable("s"),
+			p or Variable("p"),
+			o or Variable("o")
+		)
+
+		construct = "CONSTRUCT { " + _n3(bindings) + " } WHERE { " 
+		if _context and _context != "local:": construct += "GRAPH <%s> { " % _context
+		construct += _n3(bindings)
+		if _context and _context != "local:": construct += " }"
+		construct += " }"
+
+		result = self.cursor().execute(construct)
+
+		delete = "DELETE { "
+		if _context and _context != "local:": delete += "GRAPH <%s> { " % _context
+		delete += " .\n".join(map(_n3, result.triples((None, None, None))))
+		if _context and _context != "local:": delete += " }"
+		delete += " }"
+
+		self.cursor().update(delete)
 
 	def __contains__(self, statement, context="local:"):
 		if isinstance(context, Graph): _context = context.identifier
@@ -47,6 +70,20 @@ def __contains__(self, statement, context="local:"):
 		query += " }"
 		return bool(self.cursor().execute(query))
 
+	def contexts(self, triple=None):
+		if triple is None: triple = (None,None,None)
+		s,p,o = triple
+		bindings = (
+			s or Variable("s"),
+			p or Variable("p"),
+			o or Variable("o")
+		)
+		query = "SELECT DISTINCT ?g WHERE { GRAPH ?g { "
+		query += " ".join([x.n3() for x in bindings])
+		query += " } }"
+		for g, in self.query(query):
+			yield Graph(self, identifier=g)
+
 	def triples(self, statement, context="local:", **kw):
 		"""Return triples matching (s,p,o) pattern"""
 

setup.py

@@ -115,6 +115,7 @@ def uniqify(l):
 		"src/frontend/query-data.c",
 		"src/frontend/order.c",
 		"src/frontend/import.c",
+		"src/frontend/update.c",
 		"py4s_helpers.c",
 	],
 	extra_compile_args=["-std=gnu99"],

tests/test_4store.py

@@ -2,10 +2,10 @@
 try:
 	from rdflib.term import URIRef, Literal
 	from rdflib.namespace import RDF, RDFS
-	from rdflib.graph import Graph
+	from rdflib.graph import Graph, ConjunctiveGraph
 except ImportError:
 	from rdflib import URIRef, RDF, RDFS, Literal
-	from rdflib.Graph import Graph
+	from rdflib.Graph import Graph, ConjunctiveGraph
 from StringIO import StringIO
 
 TEST_GRAPH = "http://example.org/"
@@ -35,10 +35,16 @@ def test_11_add_triple(self):
 		g.add(s)
 		for count, in store.query("SELECT DISTINCT COUNT(?s) AS c WHERE { graph <%s> { ?s ?p ?o } }" % TEST_GRAPH): pass
 		assert count == 3
-	def test_11_construct(self):
+	def test_20_remove(self):
+		assert store.query("ASK WHERE { ?s ?p ?o }")
+		g = ConjunctiveGraph(store)
+		for ctx in g.contexts():
+			store.remove((None,None,None), context=ctx)
+		assert not store.query("ASK WHERE { ?s ?p ?o }")
+	def test_13_construct(self):
 		g = store.query("CONSTRUCT { <http://foo> ?p ?o } WHERE { ?s ?p ?o } LIMIT 2")
 		assert len(g) == 2
-	def test_12_triples(self):
+	def test_14_triples(self):
 		g = Graph(store, identifier=TEST_GRAPH)
 		for s,p,o in g.triples((URIRef("http://irl.styx.org/foo"), None, None)):
 			## should only have one