[hibernate-issues] [Hibernate-JIRA] Created: (HHH-5719) Applying projection to criteria with restricted subcriterias generates wrong SQL

[Victor Cherkassky (JIRA)]

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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