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From Jean-Baptiste BRIAUD -- Novlog <j-b.bri...@novlog.com>
Subject Re: Fetch plan question
Date Mon, 07 Dec 2009 20:48:21 GMT

On Dec 7, 2009, at 18:57 , Michael Vorburger wrote:

> Jean-Baptiste,
Hi Michael,
> 
> I realized that in our own in-house "framework to simply to the max the
> use of fetchPlan" (just like yours... and ours?) we must be doing the
> same
we may share some ideas or some directions ...

> , so I refereshed my memories by looking back at that code for you
Thanks !

> (written over a year ago) and suddenly remembered that indeed there is a
> little "trick", you have to:
> 
>   fp.removeFetchGroup(FetchGroup.NAME_DEFAULT);
> 
It was that, a big big thanks.
I'm still wondering why the API do not provide a removeAllGroups and removeALLFields, so even
without knowing the name of any groups or fields, the fetch plan would be 100% empty.

I thought that it was already done by that code :
        final FetchPlan fetchPlan = entityManager.getFetchPlan();
        fetchPlan.clearFetchGroups();
        fetchPlan.clearFields();

Now, thanks to you, I'm doing the following :
        final FetchPlan fetchPlan = entityManager.getFetchPlan();
        fetchPlan.clearFetchGroups();
        fetchPlan.clearFields();
        fetchPlan.removeFetchGroup(FetchGroup.NAME_DEFAULT);

> Because (quote from doc) "any field that is eagerly loaded according to
> the JPA metadata rules into the built-in default fetch group. As its
> name implies, the default fetch group is active by default. You may also
> define your own..."
> 
In fact, you right, I read that but I still thought I didn't have fetchGroup forgetting the
default one.

> Does this help?  If yes, why don't you create a little Defect suggest
> that the documentation be slightly slightly improved to take this
> crystal clear?  Once you know it I guess the phrase above is clear, but
> if you don't, it's probably not clear enough?
Exactly that !

>  A few lines of example & explanation may have helped you?
Yes definitively, I would have notices the extra fetchPlan.removeFetchGroup(FetchGroup.NAME_DEFAULT);
> 
> 
>> Magazine mag = em.find(Magazine.class, magId);
>> Will it work also with a query and not only with the find(id) method ?
>> Something like that : em.createQuery("SELECT blablabla ..."); ??
> 
> Yes yes of course.  Make sure you also read & understand the
> http://openjpa.apache.org/builds/1.2.1/apache-openjpa-1.2.1/docs/manual/
> ref_guide_perfpack_eager.html stuff though.
> 
OK, this was like others recents question a way to confirm what I try to do is correct. When
something goes wrong, I always suspect my own understanding first.

> Ciao.
> 
Thanks a lot, I could spent days without finding that default fetchgroup thing.


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