The Daily WTF

There are many ways to mess up doing unique identifiers. It’s a hard problem, and that’s why we’ve sorta agreed on a few distinct ways to do it. First, we can just autonumber. Easy, but it doesn’t always scale that well, especially in distributed systems. Second, we can use something like UUIDs: mix a few bits of real data in with a big pile of random data, and you can create a unique ID. Finally, there are some hashing-related options, where the data itself generates its ID.

Tiffanie was digging into some weird crashes in a database application, and discovered that their MODULES table couldn’t decide which was correct, and opted for two: MODULE_ID, an autonumbered field, and MODULE_UUID, which one would assume, held a UUID. There were also the requsite MODULE_NAME and similar fields. A quick scan of the table looked like:

MODULE_ID MODULE_NAME MODULE_UUID MODULE_DESC 0 Defects 8461aa9b-ba38-4201-a717-cee257b73af0

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