[hibernate-issues] [Hibernate-JIRA] Created: (HHH-4924) Unnecessary "left outer join". Probably this "left outer join" can be eliminated. OneToOne when optional=true and LAZY

[Adam Wozniak (JIRA)]

Unnecessary "left outer join". Probably this "left outer join" can be eliminated. OneToOne when optional=true and LAZY
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                 Key: HHH-4924
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-4924
             Project: Hibernate Core
          Issue Type: Improvement
          Components: core
    Affects Versions: 3.3.1
         Environment: n/a
            Reporter: Adam Wozniak


Hi

Relation between Person and Office is: 1 to {0 or 1}

There a 3 classes (sources attached):
* PersonPk
* Person
* Office

SCENARIO
--------
	final Office office = em.find(Office.class, new PersonPk("adam", "woz"));
	System.out.println(office.getPerson().getZodiac());

I second line the following SQL is generated:
select
        person0_.first_name as first1_22_1_,
        person0_.last_name as last2_22_1_,
        person0_.zodiac as zodiac22_1_,
        office1_.first_name as first1_23_0_,
        office1_.last_name as last2_23_0_,
        office1_.address as address23_0_ 
    from
        PERSON person0_ 
    left outer join
        OFFICE office1_ 
            on person0_.first_name=office1_.first_name 
            and person0_.last_name=office1_.last_name 
    where
        person0_.first_name=? 
        and person0_.last_name=?

But we already know all columns for OFFICE so there is need to loaded them once again. In other words this SQL can be reduced to such SQL:

select
        person0_.first_name as first1_22_1_,
        person0_.last_name as last2_22_1_,
        person0_.zodiac as zodiac22_1_,
    from
        PERSON person0_ 
    where
        person0_.first_name=? 
        and person0_.last_name=?

Kind regards,
Adam Woźniak / Poland

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