Re: How to create "auto-increment" field WITHOUT a sequence object?

Hey Alban,

2011/7/3 Alban Hertroys <dalroi(at)solfertje(dot)student(dot)utwente(dot)nl>

> On 3 Jul 2011, at 16:10, Dmitriy Igrishin wrote:
>
> > "you MUST lock on insert to get gapless sequences"
> > Not me :-). The OP must do it. So, what problem here? Deadlocks?
> > Again, if deadlocks are so dangerous, why the LOCK command exists?
>
> It's not deadlocks, it's concurrent updates that are the trouble. If you
> don't lock, you run the risk for two records being assigned the same number
> concurrently.
>
Thanks for clarify, but I know why resources must be locked when
they are used concurrently :-). See my previous post about SELECT FOR UPDATE
...
and I don't see the problem with it. As well as with the LOCK command.

> With a unique constraint added into the mix (and there should be one) that
> means that one of the transactions will fail the unique constraint check on
> commit.
>
> It's possible to catch that in the client and redo the transaction with a
> new ID, but if that's not acceptable (for example because it matters which
> transaction got the ID first) then you need to lock records.
>
Sure.

>
> Alban Hertroys
>
> --
> If you can't see the forest for the trees,
> cut the trees and you'll see there is no forest.
>
>
> !DSPAM:1257,4e109f6512095013212184!
>
>
>

--
// Dmitriy.