Re: primary key and existing unique fields

On Wed, Oct 27, 2004 at 00:10:27 +0200,
  Dawid Kuroczko <qnex42@gmail.com> wrote:
> 3. If you'll need things like "last 50 keys", you can SELECT * FROM
> foo ORDER BY yourserialkey DESC LIMIT 50;

You really shouldn't be doing that if you are using sequences to generate
the key. Sequences are just guarenteed to return unique values, not to
return them in order. Because groups of sequences can be allocated to
a backend at once depending on a setting settable by a client, you can
get assignments out of order. Also for overlapping transactions what
the application means by the last 50 entries may not match what you
get when you get the 50 highest serial values.