RE: [eclipselink-users] Why is getResultList() grouped by Class even whe

[t3_chris <c.reiter@xxxxxxx>]

Hi Christopher!

Thank you a lot for your very detailled Explanation of how things
are working when using Inheritance.

I'll try the QueryHints on Monday!

Thank you!

best regards,
  christian



Christopher Delahunt wrote:
> 
> Hello Christian,
> 
> If you set the logging to fine to see the SQL EclipseLink generates, you
> would see that when querying on the root of an inheritance hierarchy it
> will
> issue the query first to get all the subclass types.  EclipseLink will
> then
> use these results to determine which subclasses to issue queries on.  So
> for
> instance, you'll see:
>   Select type from root_table order by blah
>   Select * from subclass1 order by blah
>   Select * from subclass2 order by blah
> Etc.  The results returned from each query are concatenated and returned,
> which is why you will see them ordered by subclass.
> 
> EclipseLink has a shouldOuterJoinSubclasses flag that can force these
> queries to be done using an outerjoin instead.  This flag can be set on
> the
> ObjectLevelReadQuery, on the descriptor's inheritance policy, or as a
> query
> hint through the eclipselink.inheritance.outer-join hint.  This flag is
> false by default unless you are using a cursor or are filtering results
> using firstrows or maxresults.
> 
> Hope this helps,
> 
> Chris
> 
> -----Original Message-----
> From: eclipselink-users-bounces@xxxxxxxxxxx
> [mailto:eclipselink-users-bounces@xxxxxxxxxxx] On Behalf Of t3_chris
> Sent: Thursday, December 11, 2008 4:43 AM
> To: eclipselink-users@xxxxxxxxxxx
> Subject: Re: [eclipselink-users] Why is getResultList() grouped by Class
> even when ORDER BY is used?
> 
> 
> Hi!
> 
> If someone is seeking a solution to a similar problem, the following might
> help:
> 
> I've now mapped a completely new class named
> VendingmachineComponentNumberingHelper to the same table in the DB, but
> this
> new class VendingmachineComponentNumberingHelper doesn't have any
> relationship to the original Class-Hierarchy VendingmachineComponent. It
> also doesn't have any setters and i do only use it for getting the next
> inventoryId. Here's an example of that class:
> 
> @Entity
> @Table(name = "vendingmachinecomponent")
> public class VendingmachineComponentNumberingHelper implements
> Serializable
> {
>     private static final long serialVersionUID = 1L;
>     
>     @Id @GeneratedValue(strategy=GenerationType.IDENTITY)
>     @Column(name = "vendingmachinecomponent_rowid", nullable = false)
>     private Integer rowid;
>         
>     @Column(name = "vendingmachinecomponent_inventoryid")
>     private Integer inventoryId;
>     
> 
>     public VendingmachineComponentNumberingHelper() {
>        
>     }
> 
>     public VendingmachineComponentNumberingHelper(Integer
> vendingmachinecomponentRowid) {
>         this();
>         this.rowid = vendingmachinecomponentRowid;
>     }
> 
>     public Integer getInventoryId() {
>         return inventoryId;
>     }
> 
>     public Integer getRowid() {
>         return rowid;
>     }
> }
> 
> With that new class without any inheritance the ordering works as
> expected.
> A somewhat dirty solution, but it works.
> 
> If anyone of you has got a better solution, please post!
> 
> Best regards,
>   christian
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> ORDER-BY-is-used--tp20937838p20952358.html
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