Ross,
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Ross Ferris
> Sent: Friday, 1 July 2005 10:51
> To: [email protected]
> Subject: RE: [U2] - Determining time sequence
>
> My only issue with using UUID's is the fact that they weren't DESIGNED
> for time sequencing, and you could run foul of the implementation.
>
> I just ran a quick test, fired off 4 phantoms and another screen based
> process to get 5,000 sequential ID's - they all finished in under a
> second, so 25,000+tps seems AOK ... if the item IS in contention, it
> will be in cache, so in practice I don't think this should be an
issue.
The scenario where it does become an issue is where you have
transactions
that run for a long (relatively) time. This means that although you
have
the capacity to increment the counter quickly, you can't actually do it
because the update lock on the incrementing counter has to be held for
the
entire length of the transaction.
I don't actually see how having the counter automagically maintained by
the DBMS would help. For example, suppose that
Transaction "A" starts and gets counter "654321123"
Transaction "B" starts and gets counter "654321124"
Transaction "C" starts and gets counter "654321125"
Transaction "D" starts and gets counter "654321126"
Now suppose that transaction "B" fails ...
Surely transactions "C" & "D" have to be rolled back because
they
now have the 'wrong' counter value?
I don't see this as being any advance over the UV mechanism, except that
it's less coding at the application level.
Regards
Mike
>
> Phil was originally concerned about this being a bottleneck - my
> (limited) testing leads me to believe this will not be the
> case .... The good news is that he now has multiple alternatives to
trial.
>
> Ross Ferris
> Stamina Software
> Visage - an Evolution in Software Development
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