Re: [Modeling-users] Re: Implementing inheritance through vertical mapping

[Federico H. <fh...@vi...>]

On Thu, 2003-09-25 at 19:18, Sebastien Bigaret wrote:
> Not at all! For postgresql e.g., we use dedicated sequences, one for
> each inheritance tree;

Trying to recall why we didn't go for this approach, I vagely remember
that we discarded it in search of database independence... (the
exploration of PostgreSQL's inheritance is just meant as a temporary
hack, DBMS independence is important to us). But we might reconsider
this.

> Well, since the siblings get different ids, resolving FKs "simply" means
> deep-fetching the inheritance tree to find the related row.

I checked the code... and it looks suspiciously simple. You're hiding
something from me! :-) I guess there's some cool magic hidden in there,
my guess is that objectsForSourceGlobalID has some clever tricks up its
sleeve. It's late now, I'll look into it tomorrow. Right now, my
sleep-deprived brain can't imagine any other ways of doing it than
trying all tables in sequence until you find one that has the record
you're looking for, or keeping a table that tracks what table got
assigned which key, all of which doesn't sound more efficient than
joins...

But things may look clearer tomorrow. Sleep is a marvelous thing, when
you can get some :-)

>     Will this allow a second look at horizontal mapping ? ;)

You seem to be advocating it very much... Any particular reason? We've
been doing the vertical mapping thing with databases that are
representative of our target, running on slow machines, and the DB never
was the bottleneck.

	Fede