Re: Meta integrity

Yes, its not a task for _relation_ dbms.
I am database developer, I like rdbms, but now I think that I should start
to use LDAP for these kind of tasks.
What people can say?

Jul 25, 08:22 -0700, Josh Berkus wrote:

> Renato,
>
> > ...will only guarantee that each attribute points to an existent
> > object
> > but it will not care about the object's class. Question is: how could
> > I
> > also enforce this kind of "meta integrity"? The following table
> > definition came to my mind, but its an illegal construction:
> >
> > CREATE TABLE specific_attribute (
> >        id        INTEGER NOT NULL,
> >        value     TEXT    NOT NULL,
> >        object_id INTEGER NOT NULL,
> >        PRIMARY KEY (id),
> >        FOREIGN KEY (object_id, 'X') REFERENCES object (id, class_id)
> > );
>
> This is a fairly common problem that has no solution using REFERENCES,
> either in Postgres or in SQL 99.  You basically have two choices:
>
> 1. The rigorous -- write your own Triggers and Constraints to enforce
> this kind of integrity, including INSERT, UPDATE, and DELETE triggers on
> the various tables.  Between postgresql.org and Roberto Mello's sight,
> there's quite a bit of material on triggers.
>
> 2. The simple -- write functions to perform inserts, updates and deletes
> on these tables.  Put the relation into those functions, and make users
> use those functions instead of direct SQL command access.
>
> I took the second approach to solve a similar problem, because I had
> quite a number of other business rules I needed to apply, and adding the
> special relationship rule was only one more.
>
> -Josh
>
>
>
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my best regards,
----------------
Grigoriy G. Vovk