fix optimisation with super session that may lead to integrity loss
at some point I've decided to stop ensuring ?1 cardinality was respected
when adding a new relation using a super session, to avoid the cost of
the delete query. That was yet discussable because it introduced unexpected
difference between execute and unsafe_execute, which is imo not worth it.
Also, now that rql() in migration script default to unsafe_execute, we
definitly don't want that implicit behaviour change (which already cause
bug when for instance adding another default workflow for an entity type:
without that fix we end up with *two* default workflows while the schema
tells we can have only one.
IMO we should go to the direction that super session skip all security
check, but nothing else, unless explicitly asked.
"""SPARQL -> RQL translator
:organization: Logilab
:copyright: 2010 LOGILAB S.A. (Paris, FRANCE), license is LGPL v2.
:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
:license: GNU Lesser General Public License, v2.1 - http://www.gnu.org/licenses
"""
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()
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()
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 == ('', 'a'):
# 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