On 5/3/07, Jeff Davis <pgsql@xxxxxxxxxxx> wrote:
On Thu, 2007-05-03 at 08:58 -0700, Matthew Hixson wrote:
> I'm investigating the usage of a UUID primary key generator using
> Hibernate and Postgres. The reason for using a UUID is that we will
> have an application hosted at different sites in different
> databases. We will need to aggregate the data back into a single
> database from time to time and we want to avoid PK collisions.
> Is there a significant performance difference between using int
> primary keys and string primary keys in Postgres?
If the only thing you need to do is avoid primary key collisions, why
not just store an extra int that represents the "site ID" and have a
primary key on (the_key, site_id)?
That way you're *sure* no collisions happen. A UUID has a lot of bits,
but if the random generator is flawed a collision can still happen.
Also, why not simply use sequences?
You can declare sequence to START WITH 1 and INCREMENT BY 10,
and on the other site START WITH 2 INCREMENT BY 10.
There is no chance these will collide (unless human intervenes ;)),
and you can safely add 8 more similar servers, each with similar
sequence.
Regards,
Dawid
