Are UUIDs generated in hexadecimal order?

[Matthijs Burke]

Hi there,

I have a question. I use the Java UUID generator to generate IDs for executions and store the UUIDs to my DB. I am not entirely sure how the generator behaves and therefore I want to ask if the generated UUIDs are always generated in hexadecimal order, or can there be discrepancies? What is the exact behavior? Can anyone help me with this?

Thanks and best regards,

Mat

[Tatu Saloranta]

A reasonable explanation of UUID generation can be found from Wikipedia:

http://en.wikipedia.org/wiki/Universally_unique_identifier

and it explains the methods JUG uses. Resulting UUIDs are not unfortunately in hexadecimal order; although bit of slicing and dicing of UUIDs generaed using Time+Location - based variants can be used to provide monotonically increasing (~= alphabetic) ordering. UUID specification indicates order of fields in hex-representation in case you want to do such shuffling. I am planning to do something similar for one of my projects, to get creation-time index.

Random-/Hash-based variants will not produce anything ordered in any way.

Hope this helps,

-+ Tatu +-

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