| From: | Scott Ribe <scott_ribe(at)elevated-dev(dot)com> |
|---|---|
| To: | Bill Moran <wmoran(at)potentialtech(dot)com> |
| Cc: | Radosław Smogura <rsmogura(at)softperience(dot)eu>, PostgreSQL general <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: UUID column as pimrary key? |
| Date: | 2011-01-05 16:18:37 |
| Message-ID: | A6A6ABF5-71F7-4941-9D0B-D1CEE5C8ED0D@elevated-dev.com |
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| Lists: | pgsql-general |
On Jan 5, 2011, at 8:55 AM, Bill Moran wrote:
> That statement demonstrates a lack of investigation and/or consideration
> of the circumstances.
No, it doesn't.
> However, if there are 5000 devices generating 100 UUIDs per hour, and you'll
> be keeping those records for 10+ years, the chances of collisions near
> the end of that 10 year span get high enough to actually make developers
> nervous.
No, they don't. At the end of your hypothetical 10-year period, you will have used about 43,000,000,000 UUIDs, or about 1/100,000,000,000,000,000,000,000,000th of the UUID space (assuming random UUIDs). Leaving you with a chance of a single collision of about 1/18,000,000,000,000,000.
Assuming of course good entropy. If the generation of random numbers is bad, then UUIDs are not so useful ;-)
--
Scott Ribe
scott_ribe(at)elevated-dev(dot)com
http://www.elevated-dev.com/
(303) 722-0567 voice
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