cubicweb #343007 rql query planner problem ? [rejected]

I am running a script that fetches data from my crm app. Here is a query with a part commented out:

def get_projets_concernent(self, login):
    rql = ('DISTINCT Any W WHERE U login %(x)s, '
           '(U responsible_for W) OR (U looks_after W), '# OR (U concerned_by W), '
           'W is Workcase, W in_state S, S eid %(seid)s')
    return list(self.execute(rql, {'x':login, 'seid': self.ENCOURS}).entities())

if I uncomment (U concerned_by W), the query takes ages. If I replace looks_after with concerned_by, it takes ages too. If I keep only concerned_by and forget about the others, the query returns results immediately.

done in3.2.1
load left0.000
closed by<not specified>