import collections
import itertools
import datetime
from rdflib.namespace import NamespaceManager
from rdflib import Variable, BNode, Graph, ConjunctiveGraph, URIRef, Literal
from rdflib.term import Node
from parserutils import CompValue
import rdflib.plugins.sparql
from rdflib.plugins.sparql.compat import Mapping, MutableMapping
[docs]class SPARQLError(Exception):
[docs] def __init__(self, msg=None):
Exception.__init__(self, msg)
[docs]class NotBoundError(SPARQLError):
[docs] def __init__(self, msg=None):
SPARQLError.__init__(self, msg)
[docs]class AlreadyBound(SPARQLError):
"""Raised when trying to bind a variable that is already bound!"""
[docs] def __init__(self):
SPARQLError.__init__(self)
[docs]class SPARQLTypeError(SPARQLError):
[docs] def __init__(self, msg):
SPARQLError.__init__(self, msg)
[docs]class Bindings(MutableMapping):
"""
A single level of a stack of variable-value bindings.
Each dict keeps a reference to the dict below it,
any failed lookup is propegated back
In python 3.3 this could be a collections.ChainMap
"""
[docs] def __init__(self, outer=None, d=[]):
self._d = dict(d)
self.outer = outer
[docs] def __getitem__(self, key):
try:
return self._d[key]
except KeyError:
if not self.outer:
raise
return self.outer[key]
[docs] def __contains__(self, key):
try:
self[key]
return True
except KeyError:
return False
[docs] def __setitem__(self, key, value):
self._d[key] = value
[docs] def __delitem__(self, key):
raise Exception("DelItem is not implemented!")
[docs] def __len__(self):
i = 0
for x in self:
i += 1
return i
[docs] def __iter__(self):
d = self
while d is not None:
for i in dict.__iter__(d._d):
yield i
d = d.outer
[docs] def __str__(self):
return "Bindings({"+", ".join((k, self[k]) for k in self)+"})"
[docs] def __repr__(self):
return unicode(self)
[docs]class FrozenDict(Mapping):
"""
An immutable hashable dict
Taken from http://stackoverflow.com/a/2704866/81121
"""
[docs] def __init__(self, *args, **kwargs):
self._d = dict(*args, **kwargs)
self._hash = None
[docs] def __iter__(self):
return iter(self._d)
[docs] def __len__(self):
return len(self._d)
[docs] def __getitem__(self, key):
return self._d[key]
[docs] def __hash__(self):
# It would have been simpler and maybe more obvious to
# use hash(tuple(sorted(self._d.iteritems()))) from this discussion
# so far, but this solution is O(n). I don't know what kind of
# n we are going to run into, but sometimes it's hard to resist the
# urge to optimize when it will gain improved algorithmic performance.
if self._hash is None:
self._hash = 0
for key, value in self.iteritems():
self._hash ^= hash(key)
self._hash ^= hash(value)
return self._hash
[docs] def project(self, vars):
return FrozenDict(
(x for x in self.iteritems() if x[0] in vars))
[docs] def disjointDomain(self, other):
return not bool(set(self).intersection(other))
[docs] def compatible(self, other):
for k in self:
try:
if self[k] != other[k]:
return False
except KeyError:
pass
return True
[docs] def merge(self, other):
res = FrozenDict(
itertools.chain(self.iteritems(), other.iteritems()))
return res
[docs] def __str__(self):
return str(self._d)
[docs] def __repr__(self):
return repr(self._d)
[docs]class FrozenBindings(FrozenDict):
[docs] def __init__(self, ctx, *args, **kwargs):
FrozenDict.__init__(self, *args, **kwargs)
self.ctx = ctx
[docs] def __getitem__(self, key):
if not isinstance(key, Node):
key = Variable(key)
if not type(key) in (BNode, Variable):
return key
return self._d[key]
[docs] def project(self, vars):
return FrozenBindings(
self.ctx, (x for x in self.iteritems() if x[0] in vars))
[docs] def merge(self, other):
res = FrozenBindings(
self.ctx, itertools.chain(self.iteritems(), other.iteritems()))
return res
def _now(self):
return self.ctx.now
def _bnodes(self):
return self.ctx.bnodes
def _prologue(self):
return self.ctx.prologue
prologue = property(_prologue)
bnodes = property(_bnodes)
now = property(_now)
[docs] def forget(self, before, _except=None):
"""
return a frozen dict only of bindings made in self
since before
"""
if not _except : _except = []
# bindings from initBindings are newer forgotten
return FrozenBindings(self.ctx, (x for x in self.iteritems() if x[0] in _except or x[0] in self.ctx.initBindings or before[x[0]] is None))
[docs] def remember(self, these):
"""
return a frozen dict only of bindings in these
"""
return FrozenBindings(self.ctx, (x for x in self.iteritems() if x[0] in these))
[docs]class QueryContext(object):
"""
Query context - passed along when evaluating the query
"""
[docs] def __init__(self, graph=None, bindings=None, initBindings=None):
self.initBindings = initBindings
self.bindings = Bindings(d=bindings or [])
if initBindings: self.bindings.update(initBindings)
if isinstance(graph, ConjunctiveGraph):
self._dataset = graph
if rdflib.plugins.sparql.SPARQL_DEFAULT_GRAPH_UNION:
self.graph = self.dataset
else:
self.graph = self.dataset.default_context
else:
self._dataset = None
self.graph = graph
self.prologue = None
self.now = datetime.datetime.now()
self.bnodes = collections.defaultdict(BNode)
[docs] def clone(self, bindings=None):
r = QueryContext(
self._dataset if self._dataset is not None else self.graph, bindings or self.bindings, initBindings=self.initBindings)
r.prologue = self.prologue
r.graph = self.graph
r.bnodes = self.bnodes
return r
def _get_dataset(self):
if self._dataset is None:
raise Exception(
'You performed a query operation requiring ' +
'a dataset (i.e. ConjunctiveGraph), but ' +
'operating currently on a single graph.')
return self._dataset
dataset = property(_get_dataset, doc="current dataset")
[docs] def load(self, source, default=False, **kwargs):
def _load(graph, source):
try:
return graph.load(source, **kwargs)
except:
pass
try:
return graph.load(source, format='n3', **kwargs)
except:
pass
try:
return graph.load(source, format='nt', **kwargs)
except:
raise Exception(
"Could not load %s as either RDF/XML, N3 or NTriples" % (
source))
if not rdflib.plugins.sparql.SPARQL_LOAD_GRAPHS:
# we are not loading - if we already know the graph
# being "loaded", just add it to the default-graph
if default:
self.graph += self.dataset.get_context(source)
else:
if default:
_load(self.graph, source)
else:
_load(self.dataset, source)
[docs] def __getitem__(self, key):
# in SPARQL BNodes are just labels
if not type(key) in (BNode, Variable):
return key
try:
return self.bindings[key]
except KeyError:
return None
[docs] def get(self, key, default=None):
try:
return self[key]
except KeyError:
return default
[docs] def solution(self, vars=None):
"""
Return a static copy of the current variable bindings as dict
"""
if vars:
return FrozenBindings(
self, ((k, v)
for k, v in self.bindings.iteritems()
if k in vars))
else:
return FrozenBindings(self, self.bindings.iteritems())
[docs] def __setitem__(self, key, value):
if key in self.bindings and self.bindings[key] != value:
raise AlreadyBound()
self.bindings[key] = value
[docs] def pushGraph(self, graph):
r = self.clone()
r.graph = graph
return r
[docs] def push(self):
r = self.clone(Bindings(self.bindings))
return r
[docs] def clean(self):
return self.clone([])
# def pop(self):
# self.bindings = self.bindings.outer
# if self.bindings is None:
# raise Exception("We've bottomed out of the bindings stack!")
[docs] def thaw(self, frozenbindings):
"""
Create a new read/write query context from the given solution
"""
c = self.clone(frozenbindings)
return c
[docs]class Prologue(object):
"""
A class for holding prefixing bindings and base URI information
"""
[docs] def __init__(self):
self.base = None
self.namespace_manager = NamespaceManager(
Graph()) # ns man needs a store
[docs] def resolvePName(self, prefix, localname):
ns = self.namespace_manager.store.namespace(prefix or "")
if ns is None:
raise Exception('Unknown namespace prefix : %s' % prefix)
return URIRef(ns + (localname or ""))
[docs] def bind(self, prefix, uri):
self.namespace_manager.bind(prefix, uri, replace=True)
[docs] def absolutize(self, iri):
"""
Apply BASE / PREFIXes to URIs
(and to datatypes in Literals)
TODO: Move resolving URIs to pre-processing
"""
if isinstance(iri, CompValue):
if iri.name == 'pname':
return self.resolvePName(iri.prefix, iri.localname)
if iri.name == 'literal':
return Literal(
iri.string, lang=iri.lang,
datatype=self.absolutize(iri.datatype))
elif isinstance(iri, URIRef) and not ':' in iri:
return URIRef(iri, base=self.base)
return iri
[docs]class Query(object):
"""
A parsed and translated query
"""
[docs] def __init__(self, prologue, algebra):
self.prologue = prologue
self.algebra = algebra
