[hibernate-issues] [Hibernate-JIRA] Created: (HHH-2739) 'illegal attempt to dereference collection' when referencing a single-valued association in an implicit join

[Martin Kouba (JIRA)]

'illegal attempt to dereference collection' when referencing a single-valued association in an implicit join
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                 Key: HHH-2739
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2739
             Project: Hibernate3
          Issue Type: Bug
    Affects Versions: 3.2.4.sp1, 3.2.4, 3.2.3
         Environment: I have found that behaviour in version 3.2.4.sp1 and 3.2.3 (I didn't test 3.2.4 pre sp1)
Database: ORACLE 10g
            Reporter: Martin Kouba


After upgrading to the latest Hibernate version I got this error.

I try to use a statement like this
from cat c where c.mate.id = 13

the expected resulting SQL should be something like
SELECT * FROM CAT C WHERE C.MATE_ID = 13

which is much more performant than making a join
from cat c join c.mate m where m.id = 13

which would result in something like that
SELECT * FROM CAT C INNER JOIN MATE M ON C.MATE_ID = M.ID WHERE M.ID = 13

This works as expected in 3.1.3, 3.2.0 and 3.2.2

It doesn't work with version 3.2.3 and with 3.2.4.sp1.

As test case you can take the example from the documentation chapter 5.1.16

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="eg">

        <class name="Cat" table="CATS">
                <id name="id" column="uid" type="long">
                        <generator class="hilo"/>
                </id>
                <property name="birthdate" type="date"/>
                <property name="color" not-null="true"/>
                <property name="sex" not-null="true"/>
                <property name="weight"/>
                <many-to-one name="mate"/>
                <set name="kittens">
                        <key column="MOTHER"/>
                        <one-to-many class="Cat"/>
                </set>
                <joined-subclass name="DomesticCat" table="DOMESTIC_CATS">
                    <key column="CAT"/>
                    <property name="name" type="string"/>
                </joined-subclass>
        </class>

        <class name="eg.Dog">
                <!-- mapping for Dog could go here -->
        </class>

</hibernate-mapping>


c = new Cat();
c.setMate(new Cat());
c.persist();
int id = c.getId();

List results = session.createQuery("from Cat as c where c.mate.id = 16).list();


according to manual section 14.5 this should work
http://www.hibernate.org/hib_docs/v3/reference/en/html_single/#queryhql-identifier-property


Ok, I hope this is clear enough and the test case is clear enough as well.
This is a major stopper for an upgrade. I have reported that on June 11th
http://opensource.atlassian.com/projects/hibernate/browse/HHH-2667

But it seems that others used the same case to report a similar issue regarding automatic joins.
According to Christian Bauer automatic joins are no longer supported, closed the case and told me to reopen it again.

So to all others please do not add comments to this case if it is not about it. And to the Hibernate developers: Greate work you are doing but please I think the issue was clear when I reported it the first time. It is quite easy to reproduce and occurs quite often in a medium size project.

Gratitude
Martin

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