Re: Invoice number

On Thu, Dec 21, 2000 at 05:50:43PM +0000, Oliver Elphick wrote:
> Mike Castle wrote:
>   >On Thu, Dec 21, 2000 at 11:10:00AM +0100, Kaare Rasmussen wrote:
>   >> - Sequences are not rollback'able.
>   >
>   >Did you mean SERIAL instead of sequence here?
>   >
>   >If so, why is no rollbackable an issue?  All you should need is unique
>   >numbers.  Not necessarily exactly sequential numbers.
> 
> For invoice numbers, it matters.
> 
> Numbers missing from such a sequence are likely to provoke questions from
> auditors and taxmen; why borrow trouble?

What do you do on the following scenario:

Client 1 is placing an order, gets invoice #1.
Client 2 is simultaneously placing an order, and gets invoice #2.

Client 1 changes mind and cancels order.  Invoice #1 is not used.  Invoice
#2 is.

Client 3 comes along.  Do they use invoice #1, out of order, or invoice #3?

I suppose of the assignment of the invoice number is set up in such a way
as it is the very last action performed just before the commit, you should
be able to ensure that indeed the situation of having to deal with a
rollback would never occur (outside of a system crash between assignment of
invoice and commit, and that could be explained to auditors).

[What happens in a paper world if a cup of coffee is spilt on some
invoices, and these precious items are thrown in the trash?]

mrc
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