In a concurrent system, you cannot guarantee "no gaps", even with your
semaphore (which is a bad idea, verging on evil).

The best you can aim for is that events that are known to cause gaps are
logged. this will take a bit of math, but is not actually too bad.

I hope this helps.

On Tue, 2006-03-14 at 13:17 +0100, Sándor Tamás (HostWare Kft.) wrote:
> <<You should not even think of such an idea. You could never tell
> from
> *this* transaction, whether *that* transaction had reduced the
> generator. It doesn't matter if there are gaps. Once a unique number
> is generated, it should never be recycled.
> >>
>
> I have a question: How can I get straight numbers without gaps safely?
> I
> thought about a table, where I can store the actual value, and a field
> which
> can be set if anybody gets the value, and increments by one. Then
> unsets
> that field. When somebody tries to get a value, it first checks if
> that
> 'semaphore' is set.
> Of course I have to do this only when somebody posts and commits the
> data
> with that value. (like in trigger, or something).
>
> How's that idea? Or is there a better one?
>
> Any advice welcome.
>
> Thanks,
> SanTa
>
>
>
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