[hibernate-dev] Eager fetch and duplicates of collection elements

[Gunnar Morling]

Filed bug https://hibernate.atlassian.net/browse/HHH-10519; Reproducer
is at https://github.com/gunnarmorling/hibernate-test-case-templates/commit/3c5507755f83039fe40eac7daaa9f1060d97e426.

--Gunnar


2016-02-11 15:13 GMT+01:00 Steve Ebersole <steve at hibernate.org>:
> We can make that change in SQM,  but its not an option to change that
> before.
>
> But Gunnar your load use case would be a bug if true
>
>
> On Thu, Feb 11, 2016, 7:55 AM Vlad Mihalcea <mihalcea.vlad at gmail.com> wrote:
>>
>> Hi,
>>
>> True. I also wondered why don't we use the DISTINCT as the default
>> mechanism.
>> While the underlying SQL would return a result-set according to the total
>> number of joined relations, we are building the entity tree hierarchy and
>> I don's see why a user would be interested in getting duplicate root
>> entity
>> objetc references.
>>
>> If I want to fetch the parent entity along with all its children, then I'd
>> rather expect to see distinct parent objects than an object reference for
>> each child entity.
>>
>> Vlad
>>
>> On Thu, Feb 11, 2016 at 3:48 PM, Gunnar Morling <gunnar at hibernate.org>
>> wrote:
>>
>> > Hi,
>> >
>> > I understand that $subject is a known source of confusion for people
>> > when working with HQL/criteria queries and not applying something like
>> > DistinctRootEntityResultTransformer.
>> >
>> > I am seeing the same behaviour though when getting a root entity by id
>> > and join-fetching two (nested) collections. That's my model:
>> >
>> >     @Entity
>> >     public class Parent {
>> >
>> >         @Id @GeneratedValue
>> >         private Long id;
>> >
>> >         @OneToMany(cascade = CascadeType.ALL, fetch=FetchType.EAGER)
>> >         @JoinColumn(name = "parent_id")
>> >         private List<Child> children = new ArrayList<>();
>> >     }
>> >
>> >     @Entity
>> >     public class Child {
>> >
>> >         @Id @GeneratedValue
>> >         private Long id;
>> >
>> >         @ElementCollection(fetch=FetchType.EAGER)
>> >         @JoinTable(name = "Child_Properties")
>> >         @MapKeyColumn(name = "key")
>> >         @Column(name = "value")
>> >         private Map<String, String> properties = new HashMap<>();
>> >     }
>> >
>> > I am persisting a parent with one Child which has three "properties"
>> > entries. Loading the Parent by id yields three elements in the
>> > "children" list:
>> >
>> >     Parent loaded = session.get( Parent.class, 123 );
>> >     assert 1 == loaded.getConfigurations().size(); // <!-- Fails, it
>> > contains the same Child three times
>> >
>> > I don't think that's expected?
>> >
>> > I can file an issue, but first wanted to make sure I am not missing
>> > anything obvious.
>> >
>> > Thanks,
>> >
>> > --Gunnar
>> > _______________________________________________
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>> > hibernate-dev at lists.jboss.org
>> > https://lists.jboss.org/mailman/listinfo/hibernate-dev
>> >
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