# copyright 2003-2010 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of CubicWeb.
#
# CubicWeb is free software: you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option)
# any later version.
#
# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with CubicWeb. If not, see <http://www.gnu.org/licenses/>.
"""SPARQL -> RQL translator"""
from logilab.common import make_domains
from rql import TypeResolverException
from fyzz.yappsparser import parse
from fyzz import ast
from cubicweb.xy import xy
class UnsupportedQuery(Exception): pass
def order_limit_offset(sparqlst):
addons = ''
if sparqlst.orderby:
sortterms = ', '.join('%s %s' % (var.name.upper(), ascdesc.upper())
for var, ascdesc in sparqlst.orderby)
addons += ' ORDERBY %s' % sortterms
if sparqlst.limit:
addons += ' LIMIT %s' % sparqlst.limit
if sparqlst.offset:
addons += ' OFFSET %s' % sparqlst.offset
return addons
class QueryInfo(object):
"""wrapper class containing necessary information to generate a RQL query
from a sparql syntax tree
"""
def __init__(self, sparqlst):
self.sparqlst = sparqlst
if sparqlst.selected == ['*']:
self.selection = [var.upper() for var in sparqlst.variables]
else:
self.selection = [var.name.upper() for var in sparqlst.selected]
self.possible_types = {}
self.infer_types_info = []
self.union_params = []
self.restrictions = []
self.literals = {}
self._litcount = 0
def add_literal(self, value):
key = chr(ord('a') + self._litcount)
self._litcount += 1
self.literals[key] = value
return key
def set_possible_types(self, var, varpossibletypes):
"""set/restrict possible types for the given variable.
:return: True if something changed, else false.
:raise: TypeResolverException if no more type allowed
"""
varpossibletypes = set(varpossibletypes)
try:
ctypes = self.possible_types[var]
nbctypes = len(ctypes)
ctypes &= varpossibletypes
if not ctypes:
raise TypeResolverException('No possible type')
return len(ctypes) != nbctypes
except KeyError:
self.possible_types[var] = varpossibletypes
return True
def infer_types(self):
# XXX should use something similar to rql.analyze for proper type inference
modified = True
# loop to infer types until nothing changed
while modified:
modified = False
for yams_predicates, subjvar, obj in self.infer_types_info:
nbchoices = len(yams_predicates)
# get possible types for the subject variable, according to the
# current predicate
svptypes = set(s for s, r, o in yams_predicates)
if not '*' in svptypes:
if self.set_possible_types(subjvar, svptypes):
modified = True
# restrict predicates according to allowed subject var types
if subjvar in self.possible_types:
yams_predicates[:] = [(s, r, o) for s, r, o in yams_predicates
if s == '*' or s in self.possible_types[subjvar]]
if isinstance(obj, ast.SparqlVar):
# make a valid rql var name
objvar = obj.name.upper()
# get possible types for the object variable, according to
# the current predicate
ovptypes = set(o for s, r, o in yams_predicates)
if not '*' in ovptypes:
if self.set_possible_types(objvar, ovptypes):
modified = True
# restrict predicates according to allowed object var types
if objvar in self.possible_types:
yams_predicates[:] = [(s, r, o) for s, r, o in yams_predicates
if o == '*' or o in self.possible_types[objvar]]
# ensure this still make sense
if not yams_predicates:
raise TypeResolverException('No yams predicate')
if len(yams_predicates) != nbchoices:
modified = True
def build_restrictions(self):
# now, for each predicate
for yams_predicates, subjvar, obj in self.infer_types_info:
rel = yams_predicates[0]
# if there are several yams relation type equivalences, we will have
# to generate several unioned rql queries
for s, r, o in yams_predicates[1:]:
if r != rel[1]:
self.union_params.append((yams_predicates, subjvar, obj))
break
# else we can simply add it to base rql restrictions
else:
restr = self.build_restriction(subjvar, rel[1], obj)
self.restrictions.append(restr)
def build_restriction(self, subjvar, rtype, obj):
if isinstance(obj, ast.SparqlLiteral):
key = self.add_literal(obj.value)
objvar = '%%(%s)s' % key
else:
assert isinstance(obj, ast.SparqlVar)
# make a valid rql var name
objvar = obj.name.upper()
# else we can simply add it to base rql restrictions
return '%s %s %s' % (subjvar, rtype, objvar)
def finalize(self):
"""return corresponding rql query (string) / args (dict)"""
for varname, ptypes in self.possible_types.iteritems():
if len(ptypes) == 1:
self.restrictions.append('%s is %s' % (varname, iter(ptypes).next()))
unions = []
for releq, subjvar, obj in self.union_params:
thisunions = []
for st, rt, ot in releq:
thisunions.append([self.build_restriction(subjvar, rt, obj)])
if st != '*':
thisunions[-1].append('%s is %s' % (subjvar, st))
if isinstance(obj, ast.SparqlVar) and ot != '*':
objvar = obj.name.upper()
thisunions[-1].append('%s is %s' % (objvar, objvar))
if not unions:
unions = thisunions
else:
unions = zip(*make_domains([unions, thisunions]))
selection = 'Any ' + ', '.join(self.selection)
sparqlst = self.sparqlst
if sparqlst.distinct:
selection = 'DISTINCT ' + selection
if unions:
baserql = '%s WHERE %s' % (selection, ', '.join(self.restrictions))
rqls = ['(%s, %s)' % (baserql, ', '.join(unionrestrs))
for unionrestrs in unions]
rql = ' UNION '.join(rqls)
if sparqlst.orderby or sparqlst.limit or sparqlst.offset:
rql = '%s%s WITH %s BEING (%s)' % (
selection, order_limit_offset(sparqlst),
', '.join(self.selection), rql)
else:
rql = '%s%s WHERE %s' % (selection, order_limit_offset(sparqlst),
', '.join(self.restrictions))
return rql, self.literals
class Sparql2rqlTranslator(object):
def __init__(self, yschema):
self.yschema = yschema
def translate(self, sparql):
sparqlst = parse(sparql)
if sparqlst.type != 'select':
raise UnsupportedQuery()
qi = QueryInfo(sparqlst)
for subj, predicate, obj in sparqlst.where:
if not isinstance(subj, ast.SparqlVar):
raise UnsupportedQuery()
# make a valid rql var name
subjvar = subj.name.upper()
if predicate in [('', 'a'),
('http://www.w3.org/1999/02/22-rdf-syntax-ns#', 'type')]:
# special 'is' relation
if not isinstance(obj, tuple):
raise UnsupportedQuery()
# restrict possible types for the subject variable
qi.set_possible_types(
subjvar, xy.yeq(':'.join(obj), isentity=True))
else:
# 'regular' relation (eg not 'is')
if not isinstance(predicate, tuple):
raise UnsupportedQuery()
# list of 3-uple
# (yams etype (subject), yams rtype, yams etype (object))
# where subject / object entity type may '*' if not specified
yams_predicates = xy.yeq(':'.join(predicate))
qi.infer_types_info.append((yams_predicates, subjvar, obj))
if not isinstance(obj, (ast.SparqlLiteral, ast.SparqlVar)):
raise UnsupportedQuery()
qi.infer_types()
qi.build_restrictions()
return qi