| Re: Is spl_object_hash unique in the SQL sense? Can it be used as a unique SQL db column? [message #178389 is a reply to message #178386] |
Tue, 12 June 2012 19:26   |
Peter H. Coffin
Messages: 245
Registered: September 2010
Karma:
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Senior Member |
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On Tue, 12 Jun 2012 11:47:04 -0700 (PDT), kurtk(at)pobox(dot)com wrote:
>> No, hashes can never guaranteed to be unique.
>
> I opted to use
>
> md5(uniqid());
>
> to create a unique key.
Still not guaranteed to be unique. You've even got a defined 13-hexdigit
space thing what you're hashing. Which means as soon as you've got more
than 4,503,599,627,370,495 entries, you are GUARANTEED a collision. That
seems like a lot, but you're down to a one in a billion shot at a
collision when you've got a few million entries. And everybody knows,
that one in a billion changes turn up nine times in ten.
--
48. I will treat any beast which I control through magic or technology
with respect and kindness. Thus if the control is ever broken, it
will not immediately come after me for revenge.
--Peter Anspach's list of things to do as an Evil Overlord
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