Rails - Aug 2005 - Deal with foreign key constraints in app and/or db?

That Postgres vs MySQL thread made me decide to get to know my DB
(Postgres) a lot better.  One of the things that I don''t use in any of
my apps, but I''m sure is a good idea, is foreign key constraints.  In
all of my models that belong_to something else, I have a custom
validate method which makes sure that the parent exists before saving.
 If it doesn''t, I add an error.

That seems like a nice safeguard, but not the right way of doing it. 
To actually maintain referential integrity, you''d have foreign key
constraints in the DB.  So it''s no big deal to use fks AND do some
validation in the model.  But then we violated DRY...and in reality
there''s no reason why Rails shouldn''t be able to parse foreign
key
violations from the DB.  Maybe there is, maybe there isn''t, I
don''t
know.

So really what I''d like to know is the best way to deal with business
logic where you need to maintain referential integrity.  Put it in the
DB and add another layer in your rails app?  Or is there some way for
the rails app to infer it from the DB?

FWIW, this has probably been discussed numerous times...but I think
the gmane search is broken or something.  No results even came up when
I searched for ''ruby'' on the list.  Of course we
don''t talk about Ruby
a whole lot here...

Pat

Quoting Pat Maddox
<pergesu-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:
> So really what I''d like to know is the best way to deal with
business
> logic where you need to maintain referential integrity.  Put it in the
> DB and add another layer in your rails app?  Or is there some way for
> the rails app to infer it from the DB?
The right way to do it is definitely to put foreign key constraints in
the database. And it would be great if rails could inspect the
database and generate the has_many or other attributes for the
resulting classes. Problem with that is that you will end up writing
custom code for each database that pulls out this information. That
is, assuming that each database has an easy (I''m not talking about
parsing the table you get from MySQL''s ''describe
table'') way to query
table structure/relationship information from each supported database.

-- 
Cynthia Kiser