Re: [eclipselink-users] Conditional LEFT JOIN in JPQL

[Tom Ware <tom.ware@xxxxxxxxxx>]

Hi Vidas,

  You may want to look at our Dynamic JPA feature.  Here's a link to an example:

http://wiki.eclipse.org/EclipseLink/Examples/JPA/Dynamic

  The feature is quite new and evolving quickly, so please post any issues you 
have to this forum.

-Tom

Vidas Timukas wrote:
> Hi, Frank,
>
> Thanks for advice, but:
>
> 2010/5/7 Frank Schwarz <fs5@xxxxxxx <mailto:fs5@xxxxxxx>>
>
>
>     The additional fields can also be mapped by a
>     java.util.Map-structure, i.e.
>
>     public class Country {
>     ...
>      @ElementCollection
>      @CollectionTable(name="ExtCharFields",
>     joinColumns=@JoinColumn(name="country_id"))
>      @MapKeyColumn(name="fieldName")
>      @Column(name="fieldValue")
>      private Map<String, String> extChatFields;
>     ...
>     }
>
>
> Yep, that's true, and my first version was in this direction, but, in my 
> real application:
>
> 1) Tables extCharFields, extIntFields, extDateFields... can hold 
> additional data also from other tables.
>
> 2) There is a big performance issue, because with collections, 
> additional records are retrieved in separate calls to DB per every 
> parent row, and in my solution I can get all required data with single SQL.
>  
>
>      With this mapping, you would even have transparent "write access" to
>     ExtCharFields.
>
>
> I also did this in my component :-)
>
>
> --
> Sincerely,
> Vidas
>
>
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