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From Joseph Schmidt <joseph_schmid...@yahoo.com>
Subject Re: "Can't get primary key from temporary id" :(
Date Tue, 21 Apr 2009 16:44:38 GMT
> Hm. You're defining a relationship; I've always mapped relationships aas 
> relationships, and let Cayenne deal with the id specifics.  Note that 
> cayenne won't force the creation foreign key (although you should create 
> one, if your db supports it).
> 
> You say you have "too many tables like that"... what order of magnitude 
> are you talking about?
~ 3/4 of the tables present in the scheme.

> I think the upfront work of mapping relationships as relationships will 
> be worth it to you, long term.
I do use ObjRelationships as they're discovered by the Cayenne Modeler at
the reverse engineering step.
Some tables however have "soft" relations to other tables(unfortunately 
with many tables). These "soft" relations are not modeled in the DB as 
FKs because it would mean to connect almost every table  with too many 
other, and would just pollute the model (about efficiency not to mention).
So what is required constantly by the business logic and the 
application, has FKs (and accordingly Cayenne ObjRelatinships discovede 
by CM), and the rest (for audit, or what external tools need, or very 
seldom cases) is using only by value - no FK constraint.

> In terms of committing it all in the "same transaction", if you're using 
> myisam in mysql, it doesn't support true transactions, anyway.
Yes, I'm aware :). I'm using MySQL only with InnoDB or other DBs that 
have "true" transactions :). The code in the parent was was just a quick 
example I got in reply to my message forward that this "would be a DB 
issue".

> Anyway, if you /really/ want to deal with all of the nastiness of id's, 
> then I would think about using SQLTemplate.
> You can script that using velocity directives and variables, so then you 
> may just wind up executing a query chain of SQLTemplates, where the 
> first template inserts into t_1 and the second template in the chain 
> inserts into t_2 per your requirements.  If you really want low-level 
> jdbc-like functionality, SQLTemplate is the key.
I don't :). I just need the IDs :). Most webapplications and REST like
architectures need them anyway.
I like the fact that I can simply save the entity T1 with Cayenne API. 
If I need to do SQL for it too, than I have no justification in front of 
the team to introduce Cayenne in the project in first place :(.

thanks,
Joseph.


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