Re: [eclipselink-users] To query an entity with filters on a OneToMany a

[david.haccoun@xxxxxxx]

Tom,

Thank you for your response.

"o get a subset of the addresses, you should query for just addresses."
You propose exactly the solution that i want to avoid : too many requests
to retrieve data related between objects.

"i.e. If you use that instance of Person later,
how do you know what query was used to retrieve it and what parts of the
addresses collection are properly populated"
I don't agree. A service is called in a precise context. If I retrieve one
person with some of his addresses, it's because the client of my
entiyService has this need. So, it would know what parts of the addresses
collection are properly populated.

For information, with Hibernate, this kind of fetch queries works well.

The JPA specification says nothing to this subject ?

David HACCOUN
CNAV - DSI - DED
Unité Droit et Service
01 55 45 60 45
david.haccoun@xxxxxxx


                                                                       
             Tom Ware                                                  
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                                       Re: [eclipselink-users] To query an
                                       entity with filters on a OneToMany
             06/12/2011 19:12          attribute gives a weird result  
                                                                       
                                                                       
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In an Object-Relational world, retrieving a Person and only some of it's
addresses does not really make sense.  If that kind of thing is allowed,
you
cannot trust the instance of Person you have found to represent the Person
as it
is represented in the database.  (i.e. If you use that instance of Person
later,
how do you know what query was used to retrieve it and what parts of the
addresses collection are properly populated)

To get a subset of the addresses, you should query for just addresses.

select a From Person p join p.addresses a where......

-Tom

On 06/12/2011 12:36 PM, david.haccoun@xxxxxxx wrote:
> Hello,
>
> I use  EclipseLink for 9 months and so far no problem. Since I have the
> need to query an entity with a OneToMany attribute, it's all the
contrary.
> It gives me a strange result.
> I have simplified my entities until the maximum but the problem remains.
>
> I will explain my need which is ultra simple :  I have two entities :
> Person which has a bidirectional relation with Address.
> Person has potentially several Addresses but an Address belongs to one
and
> only Person.
>
> In Classes, it gives that :
>
> @Entity
> public class Person implements Serializable {
>
>      @Id
>      private Long id;
>
>      @OneToMany(mappedBy = "person", fetch = FetchType.LAZY)
>      private Set<Address>  addresses;
>
> // Getter and setter
> ...
>
> }
>
>
> @Entity
> public class Address implements Serializable {
>
>       @Id
>      private String idAddress;
>
>      @ManyToOne(fetch = FetchType.LAZY)
>      @JoinColumn(name = "idPerson", referencedColumnName = "idPerson")
>      private Person person;
>
> // Getter and setter
> ...
> }
>
> I want to query personne with their adresses. All that with some
conditions
> on personne and adresse.
> My simplified query  "select pers FROM Person pers join pers.addresses
> address
>                       where pers.matricule=:matricule  and
> address.date=:dateContract"
>
> When i execute it, i retrieve the right person but with all addresses
> linked (with foreign key) with this person. Even the addresses which
don't
> match with the dateContract condition.
>
> It seems that it's a problem related to the use of filtering on a
oneToMany
> attribute in my query. The problem is solved if i do several requests but
> it will give low performances as I have several requests like this.
> I have tried with the oneToMany in eager initialization and with a
> fetch-join query hint but i have got the same result.
>
> Thank you for having read me :)
>
> PS : I have written the code manually, so a little typo is not impossible
>
> David
>
>
> _______________________________________________
> eclipselink-users mailing list
> eclipselink-users@xxxxxxxxxxx
> https://dev.eclipse.org/mailman/listinfo/eclipselink-users
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