We have an old system that generated some UUIDs. We have more records that need UUID but can't use the old system to generate them, so we will need to generate them elsewhere. This immediately struck me as not a good idea and have been searching for an answer but haven't found this exact question. There would be no check to make sure the UUID wasn't generated already in the old system. The UUID would just get populated for records that don't have one. Safe?
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I suggest you that you read this: https://stackoverflow.com/questions/1155008/how-unique-is-uuid – Yuri Melo Apr 22 '21 at 22:37
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Thanks, Yuri. This doesn't exactly answer my question, though. – Jennifer Greenwood Apr 23 '21 at 18:50
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@JenniferGreenwood It kind of does, unless there's a compelling reason why it *doesn't*. – Dave Newton Jun 02 '21 at 04:07
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If you use UUID V1, all values generated are guaranteed to be unique. However, most folks avoid V1 because it leaks data about the system that generated it (specially, the MAC address) and the exact time, neither of which is ideal in many contexts.
Most folks use UUID V4, which is statistically unique. While it is theoretically possible for the same value to be generated twice, the odds of it ever actually happening before the heat death of the universe is approximately zero, which is good enough for any practical purpose.
UUID V3/V5 are used for when you want predictable values, which doesn’t sound like a good fit for your needs.
StephenS
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