Re: Relationship between 2 models
Re: Relationship between 2 models
- Subject: Re: Relationship between 2 models
- From: Art Isbell <email@hidden>
- Date: Tue, 7 Oct 2003 12:22:24 -1000
On Tuesday, October 7, 2003, at 11:21 AM, Arturo Pirez wrote:
On Tuesday, October 7, 2003, at 04:46 PM, Art Isbell wrote:
Avoid anything that would create an SQL join between tables in each
DB. E.g., no flattened attributes or relationships across models, no
fetch specs that involve attributes from both models, etc. You'll
need to do the joins locally in your app. Otherwise, it's doable.
I thought one of the features was letting you do pseudo-joins like the
above? What happens when you
do cross-model relationship?
You can model a relationship across eomodels even if the eomodels
model different DB's. You can fetch objects from the source entity
which will create relationship faults. When these faults fire, objects
from the destination entity will be fetched. This should work fine
even if the source and destination entities model tables in different
DB's. But I don't think you can prefetch a cross-eomodel relationship
because that involves a join across tables in different DB's. Someone
correct me if I'm wrong.
You can't do anything in your eomodel that would generate SQL that
joins tables in different DB's like flattening an attribute across a
cross-eomodel relationship or flattening a cross-eomodel relationship.
And you can't define a fetch spec in an eomodel or write one in code
that involves attributes in different entities that model tables in
different DB's or key paths that include a cross-eomodel relationship.
It's unfortunate that one must be aware of these limitations, but I'm
not sure that EOF could detect this and do the right thing
automatically in all cases.
Aloha,
Art
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