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From David Boxenhorn <da...@lookin2.com>
Subject Re: UUIDs whose alphanumeric order is the same as their chronological order
Date Tue, 22 Jun 2010 16:12:09 GMT
A little bit of time fuzziness on the order of a few milliseconds is fine
with me. This is user-generated data, so it only has to be time-ordered at
the level that a user can perceive.

I have no worries about my solution working - I'm sure it will work. I just
wonder if TimeUUIDType isn't superior for some reason that I don't know
about. (TimeUUIDType seems so bad in so many ways that I wonder why anyone
uses it. There must be some reason!)

On Tue, Jun 22, 2010 at 7:04 PM, Tatu Saloranta <tsaloranta@gmail.com>wrote:

> On Tue, Jun 22, 2010 at 5:58 AM, David Boxenhorn <david@lookin2.com>
> wrote:
> > I want to use UUIDs whose alphanumeric order is the same as their
> > chronological order. So I'm generating Version 4 UUIDs (
> ...
> > Is there anything wrong with this idea?
>
> If you want to keep it completely ordered, it's probably not enough to
> rely on System.currentTimeMillis(). It seems likely that it would
> sometimes be called twice for same clock value?  This is easy to solve
> locally (just use an additional counter, that's what UUID packages do
> to get to 100 nanosecond resolution); and it might not matter in
> concurrent case (intra-node ordering is arbitrary but close enough).
> The other theoretical problem is reduction in random value space, but
> 75 bits of randomness may be well is enough.
>
> -+ Tatu +-
>

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