server/sources/pyrorql.py
changeset 8354 a9984ceebc26
parent 8244 c7d89541e3c5
child 8545 eb7a171cec72
--- a/server/sources/pyrorql.py	Wed Apr 04 10:57:03 2012 +0200
+++ b/server/sources/pyrorql.py	Wed Apr 04 17:47:58 2012 +0200
@@ -21,298 +21,56 @@
 _ = unicode
 
 import threading
-from os.path import join
-from time import mktime
-from datetime import datetime
-from base64 import b64decode
-
 from Pyro.errors import PyroError, ConnectionClosedError
 
 from logilab.common.configuration import REQUIRED
-from logilab.common.optik_ext import check_yn
-
-from yams.schema import role_name
-
-from rql.nodes import Constant
-from rql.utils import rqlvar_maker
 
-from cubicweb import dbapi, server
-from cubicweb import ValidationError, BadConnectionId, UnknownEid, ConnectionError
-from cubicweb.schema import VIRTUAL_RTYPES
-from cubicweb.cwconfig import register_persistent_options
-from cubicweb.server.sources import (AbstractSource, ConnectionWrapper,
-                                     TimedCache, dbg_st_search, dbg_results)
-from cubicweb.server.msplanner import neged_relation
+from cubicweb import dbapi
+from cubicweb import ConnectionError
+from cubicweb.server.sources import ConnectionWrapper
 
-def uidtype(union, col, etype, args):
-    select, col = union.locate_subquery(col, etype, args)
-    return getattr(select.selection[col], 'uidtype', None)
-
+from cubicweb.server.sources.remoterql import RemoteSource
 
-class ReplaceByInOperator(Exception):
-    def __init__(self, eids):
-        self.eids = eids
-
-class PyroRQLSource(AbstractSource):
+class PyroRQLSource(RemoteSource):
     """External repository source, using Pyro connection"""
 
-    # boolean telling if modification hooks should be called when something is
-    # modified in this source
-    should_call_hooks = False
-    # boolean telling if the repository should connect to this source during
-    # migration
-    connect_for_migration = False
+    CNX_TYPE = 'pyro'
 
-    options = (
+    options = RemoteSource.options + (
         # XXX pyro-ns host/port
         ('pyro-ns-id',
          {'type' : 'string',
           'default': REQUIRED,
           'help': 'identifier of the repository in the pyro name server',
-          'group': 'pyro-source', 'level': 0,
-          }),
-        ('cubicweb-user',
-         {'type' : 'string',
-          'default': REQUIRED,
-          'help': 'user to use for connection on the distant repository',
-          'group': 'pyro-source', 'level': 0,
-          }),
-        ('cubicweb-password',
-         {'type' : 'password',
-          'default': '',
-          'help': 'user to use for connection on the distant repository',
-          'group': 'pyro-source', 'level': 0,
-          }),
-        ('base-url',
-         {'type' : 'string',
-          'default': '',
-          'help': 'url of the web site for the distant repository, if you want '
-          'to generate external link to entities from this repository',
-          'group': 'pyro-source', 'level': 1,
-          }),
-        ('skip-external-entities',
-         {'type' : 'yn',
-          'default': False,
-          'help': 'should entities not local to the source be considered or not',
-          'group': 'pyro-source', 'level': 0,
+          'group': 'remote-source', 'level': 0,
           }),
         ('pyro-ns-host',
          {'type' : 'string',
           'default': None,
           'help': 'Pyro name server\'s host. If not set, default to the value \
 from all_in_one.conf. It may contains port information using <host>:<port> notation.',
-          'group': 'pyro-source', 'level': 1,
+          'group': 'remote-source', 'level': 1,
           }),
         ('pyro-ns-group',
          {'type' : 'string',
           'default': None,
           'help': 'Pyro name server\'s group where the repository will be \
 registered. If not set, default to the value from all_in_one.conf.',
-          'group': 'pyro-source', 'level': 2,
+          'group': 'remote-source', 'level': 2,
           }),
-        ('synchronization-interval',
-         {'type' : 'time',
-          'default': '5min',
-          'help': 'interval between synchronization with the external \
-repository (default to 5 minutes).',
-          'group': 'pyro-source', 'level': 2,
-          }),
-
     )
 
-    PUBLIC_KEYS = AbstractSource.PUBLIC_KEYS + ('base-url',)
-    _conn = None
-
-    def __init__(self, repo, source_config, eid=None):
-        AbstractSource.__init__(self, repo, source_config, eid)
-        self.update_config(None, self.check_conf_dict(eid, source_config,
-                                                      fail_if_unknown=False))
-        self._query_cache = TimedCache(1800)
-
-    def update_config(self, source_entity, processed_config):
-        """update configuration from source entity"""
-        # XXX get it through pyro if unset
-        baseurl = processed_config.get('base-url')
-        if baseurl and not baseurl.endswith('/'):
-            processed_config['base-url'] += '/'
-        self.config = processed_config
-        self._skip_externals = processed_config['skip-external-entities']
-        if source_entity is not None:
-            self.latest_retrieval = source_entity.latest_retrieval
-
-    def reset_caches(self):
-        """method called during test to reset potential source caches"""
-        self._query_cache = TimedCache(1800)
-
-    def init(self, activated, source_entity):
-        """method called by the repository once ready to handle request"""
-        self.load_mapping(source_entity._cw)
-        if activated:
-            interval = self.config['synchronization-interval']
-            self.repo.looping_task(interval, self.synchronize)
-            self.repo.looping_task(self._query_cache.ttl.seconds/10,
-                                   self._query_cache.clear_expired)
-            self.latest_retrieval = source_entity.latest_retrieval
-
-    def load_mapping(self, session=None):
-        self.support_entities = {}
-        self.support_relations = {}
-        self.dont_cross_relations = set(('owned_by', 'created_by'))
-        self.cross_relations = set()
-        assert self.eid is not None
-        self._schemacfg_idx = {}
-        self._load_mapping(session)
-
-    etype_options = set(('write',))
-    rtype_options = set(('maycross', 'dontcross', 'write',))
-
-    def _check_options(self, schemacfg, allowedoptions):
-        if schemacfg.options:
-            options = set(w.strip() for w in schemacfg.options.split(':'))
-        else:
-            options = set()
-        if options - allowedoptions:
-            options = ', '.join(sorted(options - allowedoptions))
-            msg = _('unknown option(s): %s' % options)
-            raise ValidationError(schemacfg.eid, {role_name('options', 'subject'): msg})
-        return options
-
-    def add_schema_config(self, schemacfg, checkonly=False):
-        """added CWSourceSchemaConfig, modify mapping accordingly"""
-        try:
-            ertype = schemacfg.schema.name
-        except AttributeError:
-            msg = schemacfg._cw._("attribute/relation can't be mapped, only "
-                                  "entity and relation types")
-            raise ValidationError(schemacfg.eid, {role_name('cw_for_schema', 'subject'): msg})
-        if schemacfg.schema.__regid__ == 'CWEType':
-            options = self._check_options(schemacfg, self.etype_options)
-            if not checkonly:
-                self.support_entities[ertype] = 'write' in options
-        else: # CWRType
-            if ertype in ('is', 'is_instance_of', 'cw_source') or ertype in VIRTUAL_RTYPES:
-                msg = schemacfg._cw._('%s relation should not be in mapped') % ertype
-                raise ValidationError(schemacfg.eid, {role_name('cw_for_schema', 'subject'): msg})
-            options = self._check_options(schemacfg, self.rtype_options)
-            if 'dontcross' in options:
-                if 'maycross' in options:
-                    msg = schemacfg._("can't mix dontcross and maycross options")
-                    raise ValidationError(schemacfg.eid, {role_name('options', 'subject'): msg})
-                if 'write' in options:
-                    msg = schemacfg._("can't mix dontcross and write options")
-                    raise ValidationError(schemacfg.eid, {role_name('options', 'subject'): msg})
-                if not checkonly:
-                    self.dont_cross_relations.add(ertype)
-            elif not checkonly:
-                self.support_relations[ertype] = 'write' in options
-                if 'maycross' in options:
-                    self.cross_relations.add(ertype)
-        if not checkonly:
-            # add to an index to ease deletion handling
-            self._schemacfg_idx[schemacfg.eid] = ertype
-
-    def del_schema_config(self, schemacfg, checkonly=False):
-        """deleted CWSourceSchemaConfig, modify mapping accordingly"""
-        if checkonly:
-            return
-        try:
-            ertype = self._schemacfg_idx[schemacfg.eid]
-            if ertype[0].isupper():
-                del self.support_entities[ertype]
-            else:
-                if ertype in self.support_relations:
-                    del self.support_relations[ertype]
-                    if ertype in self.cross_relations:
-                        self.cross_relations.remove(ertype)
-                else:
-                    self.dont_cross_relations.remove(ertype)
-        except Exception:
-            self.error('while updating mapping consequently to removal of %s',
-                       schemacfg)
-
-    def local_eid(self, cnx, extid, session):
-        etype, dexturi, dextid = cnx.describe(extid)
-        if dexturi == 'system' or not (
-            dexturi in self.repo.sources_by_uri or self._skip_externals):
-            assert etype in self.support_entities, etype
-            eid = self.repo.extid2eid(self, str(extid), etype, session)
-            if eid > 0:
-                return eid, True
-        elif dexturi in self.repo.sources_by_uri:
-            source = self.repo.sources_by_uri[dexturi]
-            cnx = session.cnxset.connection(source.uri)
-            eid = source.local_eid(cnx, dextid, session)[0]
-            return eid, False
-        return None, None
-
-    def synchronize(self, mtime=None):
-        """synchronize content known by this repository with content in the
-        external repository
-        """
-        self.info('synchronizing pyro source %s', self.uri)
-        cnx = self.get_connection()
-        try:
-            extrepo = cnx._repo
-        except AttributeError:
-            # fake connection wrapper returned when we can't connect to the
-            # external source (hence we've no chance to synchronize...)
-            return
-        etypes = self.support_entities.keys()
-        if mtime is None:
-            mtime = self.latest_retrieval
-        updatetime, modified, deleted = extrepo.entities_modified_since(
-            etypes, mtime)
-        self._query_cache.clear()
-        repo = self.repo
-        session = repo.internal_session()
-        source = repo.system_source
-        try:
-            for etype, extid in modified:
-                try:
-                    eid = self.local_eid(cnx, extid, session)[0]
-                    if eid is not None:
-                        rset = session.eid_rset(eid, etype)
-                        entity = rset.get_entity(0, 0)
-                        entity.complete(entity.e_schema.indexable_attributes())
-                        source.index_entity(session, entity)
-                except Exception:
-                    self.exception('while updating %s with external id %s of source %s',
-                                   etype, extid, self.uri)
-                    continue
-            for etype, extid in deleted:
-                try:
-                    eid = self.repo.extid2eid(self, str(extid), etype, session,
-                                              insert=False)
-                    # entity has been deleted from external repository but is not known here
-                    if eid is not None:
-                        entity = session.entity_from_eid(eid, etype)
-                        repo.delete_info(session, entity, self.uri,
-                                         scleanup=self.eid)
-                except Exception:
-                    if self.repo.config.mode == 'test':
-                        raise
-                    self.exception('while updating %s with external id %s of source %s',
-                                   etype, extid, self.uri)
-                    continue
-            self.latest_retrieval = updatetime
-            session.execute('SET X latest_retrieval %(date)s WHERE X eid %(x)s',
-                            {'x': self.eid, 'date': self.latest_retrieval})
-            session.commit()
-        finally:
-            session.close()
-
     def _get_connection(self):
         """open and return a connection to the source"""
         nshost = self.config.get('pyro-ns-host') or self.repo.config['pyro-ns-host']
         nsgroup = self.config.get('pyro-ns-group') or self.repo.config['pyro-ns-group']
         self.info('connecting to instance :%s.%s for user %s',
                   nsgroup, self.config['pyro-ns-id'], self.config['cubicweb-user'])
-        #cnxprops = ConnectionProperties(cnxtype=self.config['cnx-type'])
         return dbapi.connect(database=self.config['pyro-ns-id'],
                              login=self.config['cubicweb-user'],
                              password=self.config['cubicweb-password'],
                              host=nshost, group=nsgroup,
-                             setvreg=False) #cnxprops=cnxprops)
+                             setvreg=False)
 
     def get_connection(self):
         try:
@@ -333,373 +91,5 @@
         except AttributeError:
             # inmemory connection
             pass
-        if not isinstance(cnx, ConnectionWrapper):
-            try:
-                cnx.check()
-                return # ok
-            except (BadConnectionId, ConnectionClosedError):
-                pass
-        # try to reconnect
-        return self.get_connection()
-
-    def syntax_tree_search(self, session, union, args=None, cachekey=None,
-                           varmap=None):
-        assert dbg_st_search(self.uri, union, varmap, args, cachekey)
-        rqlkey = union.as_string(kwargs=args)
-        try:
-            results = self._query_cache[rqlkey]
-        except KeyError:
-            results = self._syntax_tree_search(session, union, args)
-            self._query_cache[rqlkey] = results
-        assert dbg_results(results)
-        return results
-
-    def _syntax_tree_search(self, session, union, args):
-        """return result from this source for a rql query (actually from a rql
-        syntax tree and a solution dictionary mapping each used variable to a
-        possible type). If cachekey is given, the query necessary to fetch the
-        results (but not the results themselves) may be cached using this key.
-        """
-        if not args is None:
-            args = args.copy()
-        # get cached cursor anyway
-        cu = session.cnxset[self.uri]
-        if cu is None:
-            # this is a ConnectionWrapper instance
-            msg = session._("can't connect to source %s, some data may be missing")
-            session.set_shared_data('sources_error', msg % self.uri, txdata=True)
-            return []
-        translator = RQL2RQL(self)
-        try:
-            rql = translator.generate(session, union, args)
-        except UnknownEid, ex:
-            if server.DEBUG:
-                print '  unknown eid', ex, 'no results'
-            return []
-        if server.DEBUG & server.DBG_RQL:
-            print '  translated rql', rql
-        try:
-            rset = cu.execute(rql, args)
-        except Exception, ex:
-            self.exception(str(ex))
-            msg = session._("error while querying source %s, some data may be missing")
-            session.set_shared_data('sources_error', msg % self.uri, txdata=True)
-            return []
-        descr = rset.description
-        if rset:
-            needtranslation = []
-            rows = rset.rows
-            for i, etype in enumerate(descr[0]):
-                if (etype is None or not self.schema.eschema(etype).final
-                    or uidtype(union, i, etype, args)):
-                    needtranslation.append(i)
-            if needtranslation:
-                cnx = session.cnxset.connection(self.uri)
-                for rowindex in xrange(rset.rowcount - 1, -1, -1):
-                    row = rows[rowindex]
-                    localrow = False
-                    for colindex in needtranslation:
-                        if row[colindex] is not None: # optional variable
-                            eid, local = self.local_eid(cnx, row[colindex], session)
-                            if local:
-                                localrow = True
-                            if eid is not None:
-                                row[colindex] = eid
-                            else:
-                                # skip this row
-                                del rows[rowindex]
-                                del descr[rowindex]
-                                break
-                    else:
-                        # skip row if it only contains eids of entities which
-                        # are actually from a source we also know locally,
-                        # except if some args specified (XXX should actually
-                        # check if there are some args local to the source)
-                        if not (translator.has_local_eid or localrow):
-                            del rows[rowindex]
-                            del descr[rowindex]
-            results = rows
-        else:
-            results = []
-        return results
-
-    def _entity_relations_and_kwargs(self, session, entity):
-        relations = []
-        kwargs = {'x': self.repo.eid2extid(self, entity.eid, session)}
-        for key, val in entity.cw_attr_cache.iteritems():
-            relations.append('X %s %%(%s)s' % (key, key))
-            kwargs[key] = val
-        return relations, kwargs
-
-    def add_entity(self, session, entity):
-        """add a new entity to the source"""
-        raise NotImplementedError()
-
-    def update_entity(self, session, entity):
-        """update an entity in the source"""
-        relations, kwargs = self._entity_relations_and_kwargs(session, entity)
-        cu = session.cnxset[self.uri]
-        cu.execute('SET %s WHERE X eid %%(x)s' % ','.join(relations), kwargs)
-        self._query_cache.clear()
-        entity.cw_clear_all_caches()
-
-    def delete_entity(self, session, entity):
-        """delete an entity from the source"""
-        if session.deleted_in_transaction(self.eid):
-            # source is being deleted, don't propagate
-            self._query_cache.clear()
-            return
-        cu = session.cnxset[self.uri]
-        cu.execute('DELETE %s X WHERE X eid %%(x)s' % entity.__regid__,
-                   {'x': self.repo.eid2extid(self, entity.eid, session)})
-        self._query_cache.clear()
-
-    def add_relation(self, session, subject, rtype, object):
-        """add a relation to the source"""
-        cu = session.cnxset[self.uri]
-        cu.execute('SET X %s Y WHERE X eid %%(x)s, Y eid %%(y)s' % rtype,
-                   {'x': self.repo.eid2extid(self, subject, session),
-                    'y': self.repo.eid2extid(self, object, session)})
-        self._query_cache.clear()
-        session.entity_from_eid(subject).cw_clear_all_caches()
-        session.entity_from_eid(object).cw_clear_all_caches()
-
-    def delete_relation(self, session, subject, rtype, object):
-        """delete a relation from the source"""
-        if session.deleted_in_transaction(self.eid):
-            # source is being deleted, don't propagate
-            self._query_cache.clear()
-            return
-        cu = session.cnxset[self.uri]
-        cu.execute('DELETE X %s Y WHERE X eid %%(x)s, Y eid %%(y)s' % rtype,
-                   {'x': self.repo.eid2extid(self, subject, session),
-                    'y': self.repo.eid2extid(self, object, session)})
-        self._query_cache.clear()
-        session.entity_from_eid(subject).cw_clear_all_caches()
-        session.entity_from_eid(object).cw_clear_all_caches()
-
-
-class RQL2RQL(object):
-    """translate a local rql query to be executed on a distant repository"""
-    def __init__(self, source):
-        self.source = source
-        self.repo = source.repo
-        self.current_operator = None
-
-    def _accept_children(self, node):
-        res = []
-        for child in node.children:
-            rql = child.accept(self)
-            if rql is not None:
-                res.append(rql)
-        return res
-
-    def generate(self, session, rqlst, args):
-        self._session = session
-        self.kwargs = args
-        self.need_translation = False
-        self.has_local_eid = False
-        return self.visit_union(rqlst)
-
-    def visit_union(self, node):
-        s = self._accept_children(node)
-        if len(s) > 1:
-            return ' UNION '.join('(%s)' % q for q in s)
-        return s[0]
+        return super(PyroRQLSource, self).check_connection(cnx)
 
-    def visit_select(self, node):
-        """return the tree as an encoded rql string"""
-        self._varmaker = rqlvar_maker(defined=node.defined_vars.copy())
-        self._const_var = {}
-        if node.distinct:
-            base = 'DISTINCT Any'
-        else:
-            base = 'Any'
-        s = ['%s %s' % (base, ','.join(v.accept(self) for v in node.selection))]
-        if node.groupby:
-            s.append('GROUPBY %s' % ', '.join(group.accept(self)
-                                              for group in node.groupby))
-        if node.orderby:
-            s.append('ORDERBY %s' % ', '.join(self.visit_sortterm(term)
-                                              for term in node.orderby))
-        if node.limit is not None:
-            s.append('LIMIT %s' % node.limit)
-        if node.offset:
-            s.append('OFFSET %s' % node.offset)
-        restrictions = []
-        if node.where is not None:
-            nr = node.where.accept(self)
-            if nr is not None:
-                restrictions.append(nr)
-        if restrictions:
-            s.append('WHERE %s' % ','.join(restrictions))
-
-        if node.having:
-            s.append('HAVING %s' % ', '.join(term.accept(self)
-                                             for term in node.having))
-        subqueries = []
-        for subquery in node.with_:
-            subqueries.append('%s BEING (%s)' % (','.join(ca.name for ca in subquery.aliases),
-                                                 self.visit_union(subquery.query)))
-        if subqueries:
-            s.append('WITH %s' % (','.join(subqueries)))
-        return ' '.join(s)
-
-    def visit_and(self, node):
-        res = self._accept_children(node)
-        if res:
-            return ', '.join(res)
-        return
-
-    def visit_or(self, node):
-        res = self._accept_children(node)
-        if len(res) > 1:
-            return ' OR '.join('(%s)' % rql for rql in res)
-        elif res:
-            return res[0]
-        return
-
-    def visit_not(self, node):
-        rql = node.children[0].accept(self)
-        if rql:
-            return 'NOT (%s)' % rql
-        return
-
-    def visit_exists(self, node):
-        rql = node.children[0].accept(self)
-        if rql:
-            return 'EXISTS(%s)' % rql
-        return
-
-    def visit_relation(self, node):
-        try:
-            if isinstance(node.children[0], Constant):
-                # simplified rqlst, reintroduce eid relation
-                try:
-                    restr, lhs = self.process_eid_const(node.children[0])
-                except UnknownEid:
-                    # can safely skip not relation with an unsupported eid
-                    if neged_relation(node):
-                        return
-                    raise
-            else:
-                lhs = node.children[0].accept(self)
-                restr = None
-        except UnknownEid:
-            # can safely skip not relation with an unsupported eid
-            if neged_relation(node):
-                return
-            # XXX what about optional relation or outer NOT EXISTS()
-            raise
-        if node.optional in ('left', 'both'):
-            lhs += '?'
-        if node.r_type == 'eid' or not self.source.schema.rschema(node.r_type).final:
-            self.need_translation = True
-            self.current_operator = node.operator()
-            if isinstance(node.children[0], Constant):
-                self.current_etypes = (node.children[0].uidtype,)
-            else:
-                self.current_etypes = node.children[0].variable.stinfo['possibletypes']
-        try:
-            rhs = node.children[1].accept(self)
-        except UnknownEid:
-            # can safely skip not relation with an unsupported eid
-            if neged_relation(node):
-                return
-            # XXX what about optional relation or outer NOT EXISTS()
-            raise
-        except ReplaceByInOperator, ex:
-            rhs = 'IN (%s)' % ','.join(eid for eid in ex.eids)
-        self.need_translation = False
-        self.current_operator = None
-        if node.optional in ('right', 'both'):
-            rhs += '?'
-        if restr is not None:
-            return '%s %s %s, %s' % (lhs, node.r_type, rhs, restr)
-        return '%s %s %s' % (lhs, node.r_type, rhs)
-
-    def visit_comparison(self, node):
-        if node.operator in ('=', 'IS'):
-            return node.children[0].accept(self)
-        return '%s %s' % (node.operator.encode(),
-                          node.children[0].accept(self))
-
-    def visit_mathexpression(self, node):
-        return '(%s %s %s)' % (node.children[0].accept(self),
-                               node.operator.encode(),
-                               node.children[1].accept(self))
-
-    def visit_function(self, node):
-        #if node.name == 'IN':
-        res = []
-        for child in node.children:
-            try:
-                rql = child.accept(self)
-            except UnknownEid, ex:
-                continue
-            res.append(rql)
-        if not res:
-            raise ex
-        return '%s(%s)' % (node.name, ', '.join(res))
-
-    def visit_constant(self, node):
-        if self.need_translation or node.uidtype:
-            if node.type == 'Int':
-                self.has_local_eid = True
-                return str(self.eid2extid(node.value))
-            if node.type == 'Substitute':
-                key = node.value
-                # ensure we have not yet translated the value...
-                if not key in self._const_var:
-                    self.kwargs[key] = self.eid2extid(self.kwargs[key])
-                    self._const_var[key] = None
-                    self.has_local_eid = True
-        return node.as_string()
-
-    def visit_variableref(self, node):
-        """get the sql name for a variable reference"""
-        return node.name
-
-    def visit_sortterm(self, node):
-        if node.asc:
-            return node.term.accept(self)
-        return '%s DESC' % node.term.accept(self)
-
-    def process_eid_const(self, const):
-        value = const.eval(self.kwargs)
-        try:
-            return None, self._const_var[value]
-        except Exception:
-            var = self._varmaker.next()
-            self.need_translation = True
-            restr = '%s eid %s' % (var, self.visit_constant(const))
-            self.need_translation = False
-            self._const_var[value] = var
-            return restr, var
-
-    def eid2extid(self, eid):
-        try:
-            return self.repo.eid2extid(self.source, eid, self._session)
-        except UnknownEid:
-            operator = self.current_operator
-            if operator is not None and operator != '=':
-                # deal with query like "X eid > 12"
-                #
-                # The problem is that eid order in the external source may
-                # differ from the local source
-                #
-                # So search for all eids from this source matching the condition
-                # locally and then to replace the "> 12" branch by "IN (eids)"
-                #
-                # XXX we may have to insert a huge number of eids...)
-                sql = "SELECT extid FROM entities WHERE source='%s' AND type IN (%s) AND eid%s%s"
-                etypes = ','.join("'%s'" % etype for etype in self.current_etypes)
-                cu = self._session.system_sql(sql % (self.source.uri, etypes,
-                                                      operator, eid))
-                # XXX buggy cu.rowcount which may be zero while there are some
-                # results
-                rows = cu.fetchall()
-                if rows:
-                    raise ReplaceByInOperator((b64decode(r[0]) for r in rows))
-            raise
-