6:03 a.m.
Applying projection to criteria with restricted subcriterias generates wrong SQL
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Key: HHH-5719
URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-5719
Project: Hibernate Core
Issue Type: Bug
Components: query-criteria
Affects Versions: 3.2.0.ga
Environment: Hibernate 3.2.0 GA
Reporter: Victor Cherkassky
Priority: Minor
Detailed issue description and solution is here
http://facingtech.blogspot.com/2010_09_01_archive.html
I will describe only the technical aspect of the issue here.
Considuer the following model.
There is an entity {{User}}, which is in relation with {{Workplace}}. While {{Workplace}}
has an {{Activity}} (the purpose of this workplace). Each {{Activity}} has a collection of
{{Description}} entities ({{Description}} entities are just the same {{Activity}}
description translated into several languages, thus having locale property).
Result of the query should look like this:
||User.name||Workplace.name||Activity.code||Description.text||
|John|Main office|R|Research|
|Polly|Main office|R|Research|
|Craig|Main office|R|Research|
Here is the criteria for getting that result:
{code}
Criteria criteria = session.createCriteria(User.class);
criteria.createAlias("workplace.activity.descriptions",
"descriptionsAlias", Criteria.INNER_JOIN);
criteria.add(Restrictions.eq("descriptionsAlias.locale", "en_US"));
criteria.list();
{code}
It works just fine. Produces the table shown above and generates SQL like this:
{code}
select
this_.id as id18_3_,
this_.name as name18_3_,
this_.workplaceId as workplac3_18_3_,
workplace3_.id as id111_0_,
workplace3_.activityId as activityId111_0_,
workplace3_.name as name111_0_,
activity4_.id as id114_1_,
activity4_.code as code114_1_,
descriptio1_.id as id24_2_,
descriptio1_.locale as locale24_2_,
descriptio1_.text as text24_2_
from
user this_
left outer join
workplace workplace3_
on this_.workplaceId=workplace3_.id
left outer join
activity activity4_
on workplace3_.activityId=activity4_.id
inner join
description descriptio1_
on activity4_.id=descriptio1_.activityId
where
descriptio1_.locale=?
{code}
While if you want paging, you should make a rowcount projection first, so your query will
look like this:
{code}
Criteria criteria = this.sessionFactory.getCurrentSession().createCriteria(User.class);}}
criteria.createAlias("workplace.activity.descriptions",
"descriptionsAlias", criteria.INNER_JOIN);
criteria.add(Restrictions.eq("descriptionsAlias.locale", "en_US"));
criteria.setProjection(Projections.rowCount());
Integer rowCount = (Integer) criteria.uniqueResult();
{code}
And you expect Hibernate to produce this SQL:
{code}
select
count(*) as y0_
from
user this_
left outer join
workplace workplace3_
on this_.workplaceId=workplace3_.id
left outer join
activity activity4_
on workplace3_.activityId=activity4_.id
inner join
description descriptio1_
on activity4_.id=descriptio1_.activityId
where
descriptio1_.locale=?
{code}
But the SQL produced is this:
{code}
select
count(*) as y0_
from
user this_
where
descriptio1_.locale=?
{code}
I suppose that this is a bug, because you expect one behavior, while you get another. I
don't think, that this is a big deal, but when you experience such an issue, it is
time consuming to get it fixed.
Here is a workaround (or fix) of the issue. You should always assign aliases to all
associated "links" of the "entities chain" of the path to an entity
you want to restrict if you use projections. In other words, if you have anything in where
clause and you are using projections, you should assign aliases to all associations
between root entity and the entity, fields of which are used in where clause.
This criteria
{code}
Criteria criteria = this.sessionFactory.getCurrentSession().createCriteria(User.class);
criteria.createAlias("workplace", "workplaceAlias");
criteria.createAlias("workplaceAlias.activity", "activityAlias");
criteria.createAlias("activityAlias.descriptions",
"descriptionsAlias", Criteria.INNER_JOIN);
criteria.add(Restrictions.eq("descriptionsAlias.locale", "en_US"));
criteria.setProjection(Projections.rowCount());
Integer rowCount = (Integer) criteria.uniqueResult();
{code}
Produces the right result
{code}
select
count(*) as y0_
from
user this_
inner join
workplace workplacea1_
on this_.workplaceId=workplacea1_.id
inner join
activity activityal2_
on workplacea1_.activityId=activityal2_.id
inner join
description descriptio3_
on activityal2_.id=descriptio3_.activityId
where
descriptio3_.locale=?
{code}
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