[hibernate-issues] [Hibernate-JIRA] Created: (HHH-5291) Hibernate generates several join clauses for same table

[Igor Nikolaev (JIRA)]

Hibernate generates several join clauses for same table
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                 Key: HHH-5291
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-5291
             Project: Hibernate Core
          Issue Type: Bug
          Components: core
    Affects Versions: 3.5.2
         Environment: Hibernate 3.5.2
            Reporter: Igor Nikolaev


Suppose you've got a mapping:

    <class name="Class" table="TABLE1" dynamic-update="true">
        <id name="id" type="int">
            <column name="ID" />
            <generator class="assigned" />
        </id>
        
        <discriminator column="CLASS_TYPE"/>

	<property name="property1" type="string" column="PROPERTY1" update="false" insert="false"/>
        
	<join table="TABLE2" optional="true">
		<key column="ID" not-null="false"/>
		<property name="property2" column="PROPERTY2"/>
	</join>
		
	<subclass name="Subclass" discriminator-value="SUBCLASS">
		<join table="TABLE2">
			<key column="swift_id"/>
			<property name="property3" column="PROPERTY3"/>
		</join>
	</subclass>
    </class>

As you can notice, we join the same table in subclass. 
Expected result is that Hibernat generates a query like this one: 
    select
        this_.ID,
        this_.PROPERTY1,
        this_1_.PROPERTY2,
        this_1_.PROPERTY3
    from
        TABLE1 this_ 
    left inner join
        TABLE2 this_1_ 
            on this_.ID=this_1_.ID 

Instead, Hibernate joins TABLE2 twice and generates the following query:

    select
        this_.ID,
        this_.PROPERTY1,
        this_1_.PROPERTY2,
        this_2_.PROPERTY3
    from
        TABLE1 this_ 
    left inner join
        TABLE2 this_1_ 
            on this_.ID=this_1_.ID 
    left outer join
        TABLE2 this_2_ 
            on this_.ID=this_2_.ID 


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