How to fix KeyError in zc.relation catalog - plone

Question

One of our sites has a broken relations catalog and I don't know how to fix it.
This is what I see in the log:
2015-11-20T09:27:43 ERROR Zope.SiteErrorLog 1448018863.240.913599974037 http://www.example.com/folder/news-item/##edit
Traceback (innermost last):
Module ZPublisher.Publish, line 138, in publish
Module ZPublisher.mapply, line 77, in mapply
Module ZPublisher.Publish, line 48, in call_object
Module z3c.form.form, line 218, in __call__
Module collective.nitf.browser, line 64, in update
Module plone.dexterity.browser.edit, line 62, in update
Module plone.z3cform.fieldsets.extensible, line 59, in update
Module plone.z3cform.patch, line 30, in GroupForm_update
Module z3c.form.group, line 145, in update
Module plone.app.z3cform.csrf, line 21, in execute
Module z3c.form.action, line 98, in execute
Module z3c.form.button, line 315, in __call__
Module z3c.form.button, line 170, in __call__
Module plone.dexterity.browser.edit, line 26, in handleApply
Module z3c.form.group, line 126, in applyChanges
Module zope.event, line 31, in notify
Module zope.component.event, line 24, in dispatch
Module zope.component._api, line 136, in subscribers
Module zope.component.registry, line 321, in subscribers
Module zope.interface.adapter, line 585, in subscribers
Module zope.component.event, line 32, in objectEventNotify
Module zope.component._api, line 136, in subscribers
Module zope.component.registry, line 321, in subscribers
Module zope.interface.adapter, line 585, in subscribers
Module z3c.relationfield.event, line 76, in updateRelations
Module zc.relation.catalog, line 546, in unindex
Module zc.relation.catalog, line 556, in unindex_doc
Module zc.relation.catalog, line 622, in _remove
KeyError: 304600783
I already tried the code in The dreaded plone.relations IntId KeyError, written by #martijn-pieters some years ago, but seems is no longer valid as I can't find any interfaces named IComplexRelationshipContainer.
Any hints?

Answer 1

Verify if plone.relations are installed.
See here http://davidjb.com/blog/2010/10/bad-relationships-relationchoice-relationcatalog-and-removed-dexterity-content-in-plone, may be the solution for this problem.
Eg.
from zope.component.hooks import setSite
from AccessControl.SecurityManagement import newSecurityManager
from AccessControl.SecurityManager import setSecurityPolicy
from Testing.makerequest import makerequest
from Products.CMFCore.tests.base.security import PermissiveSecurityPolicy, OmnipotentUser
from zope.component import getUtility
from zope.intid.interfaces import IIntIds
from zc.relation.interfaces import ICatalog
_policy=PermissiveSecurityPolicy()
_oldpolicy=setSecurityPolicy(_policy)
newSecurityManager(None, OmnipotentUser().__of__(app.acl_users))
portal = makerequest(app['Plone'])
setSite(portal)
intids = getUtility(IIntIds)
catalog = getUtility(ICatalog)
print [x.from_object for x in sorted(catalog.findRelations({}))]

Answer 2

I think some years ago I stumpled upon something similar.
I launched this and everything worked fine later:
from Products.Five.browser import BrowserView
from Products.CMFCore.utils import getToolByName
from z3c.relationfield.event import updateRelations
from z3c.relationfield.interfaces import IHasRelations
from zc.relation.interfaces import ICatalog
from zope.component import getUtility
class View(BrowserView):
def __call__(self):
rcatalog = getUtility(ICatalog)
# Clear the relation catalog to fix issues with interfaces that don't exist anymore.
# This actually fixes the from_interfaces_flattened and to_interfaces_flattened indexes.
rcatalog.clear()
pc = getToolByName(self.context, 'portal_catalog')
brains = pc.searchResults(object_provides=IHasRelations.__identifier__)
for brain in brains:
obj = brain.getObject()
updateRelations(obj, None)
return "Catalog rebuilt for %s objects" % len(brains)