Source code for rdflib.plugins.sparql.sparql

import collections
import itertools
import datetime

import isodate

from rdflib.compat import Mapping, MutableMapping
from rdflib.namespace import NamespaceManager
from rdflib import Variable, BNode, Graph, ConjunctiveGraph, URIRef, Literal
from rdflib.term import Node

from rdflib.plugins.sparql.parserutils import CompValue

import rdflib.plugins.sparql


[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): if key in self._d: return self._d[key] if not self.outer: raise KeyError() 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) -> int: i = 0 d = self while d is not None: i += len(d._d) d = d.outer return i # type: ignore[unreachable]
[docs] def __iter__(self): d = self while d is not None: yield from d._d d = d.outer
[docs] def __str__(self): return "Bindings({" + ", ".join((k, self[k]) for k in self) + "})"
[docs] def __repr__(self): return str(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.items()))) 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.items(): self._hash ^= hash(key) self._hash ^= hash(value) return self._hash
[docs] def project(self, vars): return FrozenDict((x for x in self.items() 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.items(), other.items())) 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 isinstance(key, (BNode, Variable)): return key if key not in self._d: return self.ctx.initBindings[key] else: return self._d[key]
[docs] def project(self, vars): return FrozenBindings(self.ctx, (x for x in self.items() if x[0] in vars))
[docs] def merge(self, other): res = FrozenBindings(self.ctx, itertools.chain(self.items(), other.items())) return res
@property def now(self): return self.ctx.now @property def bnodes(self): return self.ctx.bnodes @property def prologue(self): return self.ctx.prologue
[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.items() 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.items() 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 = None self.bnodes = collections.defaultdict(BNode)
@property def now(self) -> datetime.datetime: if self._now is None: self._now = datetime.datetime.now(isodate.tzinfo.UTC) return self._now
[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
@property def dataset(self): """ "current dataset""" 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
[docs] def load(self, source, default=False, **kwargs): def _load(graph, source): try: return graph.parse(source, format="turtle", **kwargs) except Exception: pass try: return graph.parse(source, format="xml", **kwargs) except Exception: pass try: return graph.parse(source, format="n3", **kwargs) except Exception: pass try: return graph.parse(source, format="nt", **kwargs) except Exception: 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 isinstance(key, (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.items() if k in vars) ) else: return FrozenBindings(self, self.bindings.items())
[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([])
[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: """ 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: """ A parsed and translated query """
[docs] def __init__(self, prologue, algebra): self.prologue = prologue self.algebra = algebra