junior walter ramos diaz junior walter ramos diaz - 3 months ago 15
Java Question

Why hibernate add to my query cross join at the end

I am constructing and running a query via this Hibernate-based code:

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Tuple> criteria = cb.createTupleQuery();
Root<hisaVO> hisa = criteria.from(hisaVO.class);
Root<EstablecVO> establec = criteria.from(EstablecVO.class);
Root<DisaVO> disa = criteria.from(DisaVO.class);
Root<RedVO> red1 = criteria.from(RedVO.class);
Root<MicroredVO> microred = criteria.from(MicroredVO.class);
Root<Unidad_EjecutoraVO> ue1 = criteria.from(Unidad_EjecutoraVO.class);
Join<hisaVO,EstablecVO> j1 = hisa.join("estab");
Join<EstablecVO,DisaVO> j2 = j1.join("disa") ;
Join<EstablecVO,RedVO> j3 = j1.join("red") ;
Join<EstablecVO,MicroredVO> j4 = j1.join("microred") ;
Join<EstablecVO,Unidad_EjecutoraVO> j5 = j1.join("ue") ;

criteria.multiselect(j3.get("red_nombre"), cb.count(hisa))
.groupBy(red1.get("red_nombre"));

return em.createQuery(criteria).getResultList();


The log shows Hibernate is implementing that via this corresponding SQL:

select
redvo3_.red_nombre as col_0_0_,
count(hisavo0_.id) as col_1_0_
from
hisa hisavo0_
inner join establec establecvo6_
on hisavo0_.cod_estab=establecvo6_.COD_ESTAB
inner join disa disavo7_
on establecvo6_.cod_disa=disavo7_.id
inner join red redvo8_
on establecvo6_.cod_red=redvo8_.id
inner join microred microredvo9_
on establecvo6_.cod_mic=microredvo9_.id
inner join unidad_ejecutora unidad_eje10_
on establecvo6_.cod_ue=unidad_eje10_.id
cross join establec establecvo1_
cross join disa disavo2_
cross join red redvo3_
cross join microred microredvo4_
cross join unidad_ejecutora unidad_eje5_
group by redvo3_.red_nombre


It seems to be adding extra, unexpected
cross join
s at the end of the query. Why is it doing that?

Answer

You give your query multiple roots via multiple invocations of CriteriaQuery.from(). Each one after the first is reflected in the final query via a cross join. That's roughly what it means to be a query root.

You do not need to (and should not) use CriteriaQuery.from() to add entities to the query that you mean to be associated via inner joins -- those you connect via a Join used as the Selection when you run your query.