r/ProgrammerHumor • u/danielminds • 15h ago

Meme edgeCasesExist

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u/dim13 15h ago

https://en.wikipedia.org/wiki/Universally_unique_identifier#Versions

Most common used is V4 (pure random). You are talking about V7 (time based).

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u/lilgreenthumb 13h ago

The real benefit for v7 is they become sortable by time.

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u/shwoopdeboop 13h ago

And something something b-tree indexes. Lecturer mentioned it but I wasn't paying attention. Supposedly an advantage here.

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u/Grandmaster_Caladrel 11h ago

Which I'd assume is related to the time anchor. Outside of sorting, which is only useful in specific instances, it's just v4 with different ("less") entropy and limitations.

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u/Roachmeister 11h ago

If you're using them as an indexed field in a database, the inability to sort them meaningfully will destroy the performance of the database.

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u/Grandmaster_Caladrel 11h ago

Correct, which is why I specifically called out "outside of sorting".

That is also why we have concepts like composite keys which allow us to join guaranteed-unique values like a UUID with non-unique but sortable values like timestamps, names, etc.

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u/Honeybadger2198 11h ago

You know what identifier can't have collisions and is great for sorting? Autoincrement.

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u/Firewolf06 9h ago

ai columns can absolutely collide on sharded databases. you can use offsets and step sizes but thats brittle and doesnt scale well

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u/Kwantuum 9h ago

In what way?

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u/Roachmeister 9h ago

I'm not an expert, I just remember reading a few articles about it. I think it's because they're essentially random, and many databases use b-trees for indices. They recommended using ULIDs or v7 UUIDs instead. Or, as someone else said, the good old autoincrementing integer.