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Re^3: Generate a unique ID

by admiral_grinder (Pilgrim)
on Nov 15, 2010 at 20:19 UTC ( #871569=note: print w/ replies, xml ) Need Help??

in reply to Re^2: Generate a unique ID
in thread Generate a unique ID

I would say that your chances of collision is very, very, very small, even on Windows.

I wrote a benchmark once (using Benchmark) that used GUID and UUID (from UUID, not Data::UUID) to generate session keys for me. I ran it through 100k iterations on my windows box and it generated fast (1.1 seconds) and produced 0 collisions. I even had a variant that would cut the result to make the string 16 characters (substr(0, 16)) to save storage space. 0 Collisions in 1.1 seconds.

I just cut it further to 8 characters and it still produced no collisions.

Sure installing UUID is a pain on windows, and the code for using it is ugly, but I don't see a reason not to use it.

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Re^4: Generate a unique ID
by BrowserUk (Pope) on Nov 15, 2010 at 20:41 UTC

    Thanks. I hadn't seen UUID. But I don't see installing it is possible on windows?

    As for your testing, if you generate them sequentially, there is probably little danger of collision, but what happens if two (or more) concurrent processes or threads call it at the same time?

    My program is threaded and different threads will be generating their own spill files concurrently so this is a significant possibility. And most "UUID" simulate the "clock sequence" value of the spec. which is meant to be initialised once per system/NIC card change using per process globals derived from the same time source as they use for the time component, rendering its purpose negated.

    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.

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