Single Query Performance Regression in Group BY

select    a13.id_vehicule  id_vehicule,

                a12.id_energie  id_energie,

                sum(a11.num_jo_dans_mois)  WJXBFS1,

                sum(a11.num_jo_dans_annee)  WJXBFS2

from      `T_CALENDRIER`              a11

                cross join            `T_ENERGIE`      a12

                cross join            `T_VEHICULE`    a13

where  (a11.Id_Calendrier in (20131231)

and a13.id_genre in (45))

group by             a13.id_vehicule,

                a12.id_energie;