server/rqlrewrite.py
author Arthur Lutz <arthur.lutz@logilab.fr>
Tue, 10 Feb 2009 18:12:43 +0100
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"""RQL rewriting utilities, used for read security checking
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:organization: Logilab
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:copyright: 2007-2008 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
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:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr
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"""
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from rql import nodes, stmts, TypeResolverException
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from cubicweb import Unauthorized, server, typed_eid
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from cubicweb.server.ssplanner import add_types_restriction
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def remove_solutions(origsolutions, solutions, defined):
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    """when a rqlst has been generated from another by introducing security
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    assertions, this method returns solutions which are contained in orig
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    solutions
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    """
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    newsolutions = []
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    for origsol in origsolutions:
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        for newsol in solutions[:]:
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            for var, etype in origsol.items():
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                try:
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                    if newsol[var] != etype:
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                        try:
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                            defined[var].stinfo['possibletypes'].remove(newsol[var])
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                        except KeyError:
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                            pass
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                        break
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                except KeyError,ex:
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                    # variable has been rewritten
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                    continue
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            else:
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                newsolutions.append(newsol)
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                solutions.remove(newsol)
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    return newsolutions
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class Unsupported(Exception): pass
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class RQLRewriter(object):
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    """insert some rql snippets into another rql syntax tree"""
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    def __init__(self, querier, session):
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        self.session = session
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        self.annotate = querier._rqlhelper.annotate
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        self._compute_solutions = querier.solutions
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        self.schema = querier.schema
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    def compute_solutions(self):
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        self.annotate(self.select)
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        try:
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            self._compute_solutions(self.session, self.select, self.kwargs)
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        except TypeResolverException:
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            raise Unsupported()
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        if len(self.select.solutions) < len(self.solutions):
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            raise Unsupported()
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    def rewrite(self, select, snippets, solutions, kwargs):
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        if server.DEBUG:
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            print '---- rewrite', select, snippets, solutions
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        self.select = select
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        self.solutions = solutions
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        self.kwargs = kwargs
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        self.u_varname = None
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        self.removing_ambiguity = False
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        self.exists_snippet = {}
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        # we have to annotate the rqlst before inserting snippets, even though
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        # we'll have to redo it latter
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        self.annotate(select)
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        self.insert_snippets(snippets)
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        if not self.exists_snippet and self.u_varname:
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            # U has been inserted than cancelled, cleanup
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            select.undefine_variable(select.defined_vars[self.u_varname])
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        # clean solutions according to initial solutions
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        newsolutions = remove_solutions(solutions, select.solutions,
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                                        select.defined_vars)
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        assert len(newsolutions) >= len(solutions), \
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               'rewritten rql %s has lost some solutions, there is probably something '\
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               'wrong in your schema permission (for instance using a '\
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              'RQLExpression which insert a relation which doesn\'t exists in '\
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               'the schema)\nOrig solutions: %s\nnew solutions: %s' % (
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            select, solutions, newsolutions)
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        if len(newsolutions) > len(solutions):
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            # the snippet has introduced some ambiguities, we have to resolve them
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            # "manually"
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            variantes = self.build_variantes(newsolutions)
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            # insert "is" where necessary
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            varexistsmap = {}
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            self.removing_ambiguity = True
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            for (erqlexpr, mainvar, oldvarname), etype in variantes[0].iteritems():
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                varname = self.rewritten[(erqlexpr, mainvar, oldvarname)]
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                var = select.defined_vars[varname]
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                exists = var.references()[0].scope
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                exists.add_constant_restriction(var, 'is', etype, 'etype')
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                varexistsmap[mainvar] = exists
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            # insert ORED exists where necessary
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            for variante in variantes[1:]:
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                self.insert_snippets(snippets, varexistsmap)
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                for (erqlexpr, mainvar, oldvarname), etype in variante.iteritems():
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                    varname = self.rewritten[(erqlexpr, mainvar, oldvarname)]
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                    try:
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                        var = select.defined_vars[varname]
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                    except KeyError:
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                        # not a newly inserted variable
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                        continue
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                    exists = var.references()[0].scope
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                    exists.add_constant_restriction(var, 'is', etype, 'etype')
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            # recompute solutions
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            #select.annotated = False # avoid assertion error
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            self.compute_solutions()
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            # clean solutions according to initial solutions
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            newsolutions = remove_solutions(solutions, select.solutions,
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                                            select.defined_vars)
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        select.solutions = newsolutions
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        add_types_restriction(self.schema, select)
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        if server.DEBUG:
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            print '---- rewriten', select
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    def build_variantes(self, newsolutions):
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        variantes = set()
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        for sol in newsolutions:
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            variante = []
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            for (erqlexpr, mainvar, oldvar), newvar in self.rewritten.iteritems():
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                variante.append( ((erqlexpr, mainvar, oldvar), sol[newvar]) )
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            variantes.add(tuple(variante))
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        # rebuild variantes as dict
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        variantes = [dict(variante) for variante in variantes]
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        # remove variable which have always the same type
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        for erqlexpr, mainvar, oldvar in self.rewritten:
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            it = iter(variantes)
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            etype = it.next()[(erqlexpr, mainvar, oldvar)]
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            for variante in it:
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diff changeset
   130
                if variante[(erqlexpr, mainvar, oldvar)] != etype:
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parents:
diff changeset
   131
                    break
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parents:
diff changeset
   132
            else:
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parents:
diff changeset
   133
                for variante in variantes:
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parents:
diff changeset
   134
                    del variante[(erqlexpr, mainvar, oldvar)]
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parents:
diff changeset
   135
        return variantes
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parents:
diff changeset
   136
    
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parents:
diff changeset
   137
    def insert_snippets(self, snippets, varexistsmap=None):
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parents:
diff changeset
   138
        self.rewritten = {}
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parents:
diff changeset
   139
        for varname, erqlexprs in snippets:
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parents:
diff changeset
   140
            if varexistsmap is not None and not varname in varexistsmap:
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parents:
diff changeset
   141
                continue
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parents:
diff changeset
   142
            try:
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parents:
diff changeset
   143
                self.const = typed_eid(varname)
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parents:
diff changeset
   144
                self.varname = self.const
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parents:
diff changeset
   145
                self.rhs_rels = self.lhs_rels = {}
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parents:
diff changeset
   146
            except ValueError:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   147
                self.varname = varname
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parents:
diff changeset
   148
                self.const = None
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parents:
diff changeset
   149
                self.varstinfo = stinfo = self.select.defined_vars[varname].stinfo
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   150
                if varexistsmap is None:
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parents:
diff changeset
   151
                    self.rhs_rels = dict( (rel.r_type, rel) for rel in stinfo['rhsrelations'])
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parents:
diff changeset
   152
                    self.lhs_rels = dict( (rel.r_type, rel) for rel in stinfo['relations']
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parents:
diff changeset
   153
                                                  if not rel in stinfo['rhsrelations'])
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parents:
diff changeset
   154
                else:
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parents:
diff changeset
   155
                    self.rhs_rels = self.lhs_rels = {}
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   156
            parent = None
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   157
            inserted = False
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   158
            for erqlexpr in erqlexprs:
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parents:
diff changeset
   159
                self.current_expr = erqlexpr
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   160
                if varexistsmap is None:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   161
                    try:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   162
                        new = self.insert_snippet(varname, erqlexpr.snippet_rqlst, parent)
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   163
                    except Unsupported:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   164
                        continue
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   165
                    inserted = True
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   166
                    if new is not None:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   167
                        self.exists_snippet[erqlexpr] = new
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   168
                    parent = parent or new
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   169
                else:
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parents:
diff changeset
   170
                    # called to reintroduce snippet due to ambiguity creation,
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   171
                    # so skip snippets which are not introducing this ambiguity
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   172
                    exists = varexistsmap[varname]
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   173
                    if self.exists_snippet[erqlexpr] is exists:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   174
                        self.insert_snippet(varname, erqlexpr.snippet_rqlst, exists)
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   175
            if varexistsmap is None and not inserted:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   176
                # no rql expression found matching rql solutions. User has no access right
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   177
                raise Unauthorized()
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   178
            
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   179
    def insert_snippet(self, varname, snippetrqlst, parent=None):
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parents:
diff changeset
   180
        new = snippetrqlst.where.accept(self)
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   181
        if new is not None:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   182
            try:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   183
                var = self.select.defined_vars[varname]
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   184
            except KeyError:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   185
                # not a variable
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   186
                pass
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   187
            else:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   188
                if var.stinfo['optrelations']:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   189
                    # use a subquery
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   190
                    subselect = stmts.Select()
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   191
                    subselect.append_selected(nodes.VariableRef(subselect.get_variable(varname)))
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   192
                    subselect.add_restriction(new.copy(subselect))
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   193
                    aliases = [varname]
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   194
                    for rel in var.stinfo['relations']:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   195
                        rschema = self.schema.rschema(rel.r_type)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   196
                        if rschema.is_final() or (rschema.inlined and not rel in var.stinfo['rhsrelations']):
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   197
                            self.select.remove_node(rel)
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   198
                            rel.children[0].name = varname
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   199
                            subselect.add_restriction(rel.copy(subselect))
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   200
                            for vref in rel.children[1].iget_nodes(nodes.VariableRef):
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   201
                                subselect.append_selected(vref.copy(subselect))
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   202
                                aliases.append(vref.name)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   203
                    if self.u_varname:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   204
                        # generate an identifier for the substitution
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   205
                        argname = subselect.allocate_varname()
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   206
                        while argname in self.kwargs:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   207
                            argname = subselect.allocate_varname()
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   208
                        subselect.add_constant_restriction(subselect.get_variable(self.u_varname),
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   209
                                                        'eid', unicode(argname), 'Substitute')
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   210
                        self.kwargs[argname] = self.session.user.eid
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   211
                    add_types_restriction(self.schema, subselect, subselect, solutions=self.solutions)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   212
                    assert parent is None
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   213
                    myunion = stmts.Union()
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   214
                    myunion.append(subselect)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   215
                    aliases = [nodes.VariableRef(self.select.get_variable(name, i))
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   216
                               for i, name in enumerate(aliases)]
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   217
                    self.select.add_subquery(nodes.SubQuery(aliases, myunion), check=False)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   218
                    self._cleanup_inserted(new)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   219
                    try:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   220
                        self.compute_solutions()
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   221
                    except Unsupported:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   222
                        # some solutions have been lost, can't apply this rql expr
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   223
                        self.select.remove_subquery(new, undefine=True)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   224
                        raise
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   225
                    return
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   226
            new = nodes.Exists(new)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   227
            if parent is None:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   228
                self.select.add_restriction(new)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   229
            else:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   230
                grandpa = parent.parent
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   231
                or_ = nodes.Or(parent, new)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   232
                grandpa.replace(parent, or_)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   233
            if not self.removing_ambiguity:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   234
                try:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   235
                    self.compute_solutions()
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   236
                except Unsupported:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   237
                    # some solutions have been lost, can't apply this rql expr
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   238
                    if parent is None:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   239
                        self.select.remove_node(new, undefine=True)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   240
                    else:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   241
                        parent.parent.replace(or_, or_.children[0])
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   242
                        self._cleanup_inserted(new)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   243
                    raise 
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   244
            return new
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   245
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   246
    def _cleanup_inserted(self, node):
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   247
        # cleanup inserted variable references
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   248
        for vref in node.iget_nodes(nodes.VariableRef):
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   249
            vref.unregister_reference()
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   250
            if not vref.variable.stinfo['references']:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   251
                # no more references, undefine the variable
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   252
                del self.select.defined_vars[vref.name]
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   253
        
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   254
    def _visit_binary(self, node, cls):
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   255
        newnode = cls()
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   256
        for c in node.children:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   257
            new = c.accept(self)
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   258
            if new is None:
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   259
                continue
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   260
            newnode.append(new)
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        if len(newnode.children) == 0:
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            return None
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        if len(newnode.children) == 1:
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   264
            return newnode.children[0]
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        return newnode
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    def _visit_unary(self, node, cls):
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        newc = node.children[0].accept(self)
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        if newc is None:
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            return None
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        newnode = cls()
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        newnode.append(newc)
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        return newnode 
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    def visit_and(self, et):
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        return self._visit_binary(et, nodes.And)
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    def visit_or(self, ou):
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   279
        return self._visit_binary(ou, nodes.Or)
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    def visit_not(self, node):
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   282
        return self._visit_unary(node, nodes.Not)
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    def visit_exists(self, node):
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   285
        return self._visit_unary(node, nodes.Exists)
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   286
   
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   287
    def visit_relation(self, relation):
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   288
        lhs, rhs = relation.get_variable_parts()
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   289
        if lhs.name == 'X':
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   290
            # on lhs
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   291
            # see if we can reuse this relation
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   292
            if relation.r_type in self.lhs_rels and isinstance(rhs, nodes.VariableRef) and rhs.name != 'U':
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   293
                if self._may_be_shared(relation, 'object'):
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   294
                    # ok, can share variable
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   295
                    term = self.lhs_rels[relation.r_type].children[1].children[0]
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   296
                    self._use_outer_term(rhs.name, term)
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   297
                    return
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   298
        elif isinstance(rhs, nodes.VariableRef) and rhs.name == 'X' and lhs.name != 'U':
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   299
            # on rhs
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   300
            # see if we can reuse this relation
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   301
            if relation.r_type in self.rhs_rels and self._may_be_shared(relation, 'subject'):
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   302
                # ok, can share variable
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   303
                term = self.rhs_rels[relation.r_type].children[0]
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   304
                self._use_outer_term(lhs.name, term)            
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   305
                return
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   306
        rel = nodes.Relation(relation.r_type, relation.optional)
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   307
        for c in relation.children:
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   308
            rel.append(c.accept(self))
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   309
        return rel
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   310
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   311
    def visit_comparison(self, cmp):
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   312
        cmp_ = nodes.Comparison(cmp.operator)
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   313
        for c in cmp.children:
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   314
            cmp_.append(c.accept(self))
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   315
        return cmp_
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   316
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   317
    def visit_mathexpression(self, mexpr):
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diff changeset
   318
        cmp_ = nodes.MathExpression(cmp.operator)
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   319
        for c in cmp.children:
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diff changeset
   320
            cmp_.append(c.accept(self))
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diff changeset
   321
        return cmp_
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diff changeset
   322
        
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   323
    def visit_function(self, function):
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   324
        """generate filter name for a function"""
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diff changeset
   325
        function_ = nodes.Function(function.name)
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diff changeset
   326
        for c in function.children:
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diff changeset
   327
            function_.append(c.accept(self))
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diff changeset
   328
        return function_
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   329
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   330
    def visit_constant(self, constant):
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diff changeset
   331
        """generate filter name for a constant"""
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diff changeset
   332
        return nodes.Constant(constant.value, constant.type)
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diff changeset
   333
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   334
    def visit_variableref(self, vref):
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diff changeset
   335
        """get the sql name for a variable reference"""
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diff changeset
   336
        if vref.name == 'X':
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diff changeset
   337
            if self.const is not None:
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diff changeset
   338
                return nodes.Constant(self.const, 'Int')
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diff changeset
   339
            return nodes.VariableRef(self.select.get_variable(self.varname))
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diff changeset
   340
        vname_or_term = self._get_varname_or_term(vref.name)
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diff changeset
   341
        if isinstance(vname_or_term, basestring):
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diff changeset
   342
            return nodes.VariableRef(self.select.get_variable(vname_or_term))
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diff changeset
   343
        # shared term
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diff changeset
   344
        return vname_or_term.copy(self.select)
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diff changeset
   345
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   346
    def _may_be_shared(self, relation, target):
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diff changeset
   347
        """return True if the snippet relation can be skipped to use a relation
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   348
        from the original query
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diff changeset
   349
        """
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diff changeset
   350
        # if cardinality is in '?1', we can ignore the relation and use variable
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   351
        # from the original query
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diff changeset
   352
        rschema = self.schema.rschema(relation.r_type)
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diff changeset
   353
        if target == 'object':
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diff changeset
   354
            cardindex = 0
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diff changeset
   355
            ttypes_func = rschema.objects
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diff changeset
   356
            rprop = rschema.rproperty
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diff changeset
   357
        else: # target == 'subject':
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diff changeset
   358
            cardindex = 1
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diff changeset
   359
            ttypes_func = rschema.subjects
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diff changeset
   360
            rprop = lambda x,y,z: rschema.rproperty(y, x, z)
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diff changeset
   361
        for etype in self.varstinfo['possibletypes']:
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diff changeset
   362
            for ttype in ttypes_func(etype):
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diff changeset
   363
                if rprop(etype, ttype, 'cardinality')[cardindex] in '+*':
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parents:
diff changeset
   364
                    return False
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diff changeset
   365
        return True
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diff changeset
   366
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diff changeset
   367
    def _use_outer_term(self, snippet_varname, term):
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diff changeset
   368
        key = (self.current_expr, self.varname, snippet_varname)
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diff changeset
   369
        if key in self.rewritten:
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diff changeset
   370
            insertedvar = self.select.defined_vars.pop(self.rewritten[key])
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diff changeset
   371
            for inserted_vref in insertedvar.references():
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diff changeset
   372
                inserted_vref.parent.replace(inserted_vref, term.copy(self.select))
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diff changeset
   373
        self.rewritten[key] = term
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diff changeset
   374
        
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diff changeset
   375
    def _get_varname_or_term(self, vname):
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diff changeset
   376
        if vname == 'U':
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diff changeset
   377
            if self.u_varname is None:
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diff changeset
   378
                select = self.select
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diff changeset
   379
                self.u_varname = select.allocate_varname()
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diff changeset
   380
                # generate an identifier for the substitution
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diff changeset
   381
                argname = select.allocate_varname()
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   382
                while argname in self.kwargs:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   383
                    argname = select.allocate_varname()
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   384
                # insert "U eid %(u)s"
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parents:
diff changeset
   385
                var = select.get_variable(self.u_varname)
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parents:
diff changeset
   386
                select.add_constant_restriction(select.get_variable(self.u_varname),
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parents:
diff changeset
   387
                                                'eid', unicode(argname), 'Substitute')
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   388
                self.kwargs[argname] = self.session.user.eid
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   389
            return self.u_varname
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   390
        key = (self.current_expr, self.varname, vname)
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   391
        try:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
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   392
            return self.rewritten[key]
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
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   393
        except KeyError:
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Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
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   394
            self.rewritten[key] = newvname = self.select.allocate_varname()
b97547f5f1fa Showtime !
Adrien Di Mascio <Adrien.DiMascio@logilab.fr>
parents:
diff changeset
   395
            return newvname