After upgrading Hibernate from 3.2.4 to 4.1.7 we are facing some unneeded joins that are, in some cases, compromising performance. Let's show an example:

Let's say we have the following bidirectional one-to-many relationship : A (1)----->(*) B

Whenever we write an hql like this, hibernate makes two joins with the same entities (note that the HQL has a.b in projection)

- HQL

- select a.b from A a where a.b.name = 'entity_B'

- SQL result

select b1_.id as id1_, b1_.name as name1_
from
A a0_inner join B b1_ on a0_.b_id=b1_.id
cross join B b2_ <----------- unneeded join
where
a0_.b_id=b2_.id <----------- unneeded join
and b2_.name='entity_B'


Hibernate 3.2.4

It generate the SQL as expected (note that the HQL has a.b.id in projection)


- HQL

- select a.b from A a where a.b.name = 'entity_B'

- SQL result

select
b1_.id as id0_,
b1_.name as name0_
from
A a0_
inner join
B b1_
on a0_.b_id=b1_.id
where
b1_.name='entity_B'




Its look like the problem is happening with the join, locate after the where, which is causing the colateral effect on the sql generator.

It is not a critical bug it may impact in performance. Hope you fix this in next releases to make hibernate better than it is already is.


Thanks in advance