Re: BUG #1139: Auto-increment and Rollback

On Mon, Apr 19, 2004 at 20:16:15 -0300,
  PostgreSQL Bugs List <pgsql-bugs@postgresql.org> wrote:
>
> The following bug has been logged online:
>
> Bug reference:      1139
> Logged by:          Emil Tarazi
>
> Email address:      emil@cmu.edu
>
> PostgreSQL version: 7.4
>
> Operating system:   Linux
>
> Description:        Auto-increment and Rollback
>
> Details:
>
> If a query is called within a BEGIN-COMMIT/ROLLBACK block that
> auto-increments some field, a ROLLBACK will not decrement that field.

Assuming you are refering to sequences, that's the way it is supposed
to work.
You really should only be using sequences to get unique values.
Within a single session expecting the values to be monotonically
increasing is also valid. Other than that you shouldn't be making
any assumptions about the relation between returned values.