How safe is it to use UUID to uniquely identify something (I'm using it for files uploaded to the server)? As I understand it, it is based off random numbers. However, it seems to me that given enough time, it would eventually repeat it self, just by pure chance. Is there a better system or a pattern of some type to alleviate this issue?
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Quoting from Wikipedia:
Thus, anyone can create a UUID and use it to identify something with reasonable confidence that the identifier will never be unintentionally used by anyone for anything else
It goes on to explain in pretty good detail on how safe it actually is. So to answer your question: Yes, it's safe enough.
Dave Vogt
2009-07-20 18:10:51
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If by "given enough time" you mean 100 years and you're creating them at a rate of a billion a second, then yes, you have a 50% chance of having a collision after 100 years.
rein
2009-07-20 18:14:13
But only after using up 256 exabytes of storage for those IDs.
Bob Aman
2009-09-10 07:04:11
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For what you are using it for, it should be relatively safe. Some Linux distributions have had problems with duplicate UUIDs for filesystems.
fpmurphy
2009-07-20 18:15:37
If you have any references; This is the first time I've heard of a UUID conflict in the real world.
T Pops
2009-07-22 20:55:21
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UUID schemes generally use not only a pseudo-random element, but also the current system time, and some sort of often-unique hardware ID if available, such as a network MAC address.
The whole point of using UUID is that you trust it to do a better job of providing a unique ID than you yourself would be able to do. This is the same rationale behind using a 3rd party cryptography library rather than rolling your own. Doing it yourself may be more fun, but it's typically less responsible to do so.
Parappa
2009-07-20 18:53:46
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Been doing it for years. Never run into a problem.
I usually set up my DB's to have one table that contains all the keys and the modified dates and such. Haven't run into a problem of duplicate keys ever.
The only drawback that it has is when you are writing some queries to find some information quickly you are doing a lot of copying and pasting of the keys. You don't have the short easy to remember ids anymore.
Posthuma
2009-07-20 18:58:05
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I don't know if this matters to you, but keep in mind that GUIDs are globally unique, but substrings of GUIDs aren't.
Grant Wagner
2009-07-20 22:18:54