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Comment by zackbloom | Hacker News Reader

I appreciate where you're coming from, but as it says in the article, UUIDs are really unnecessarily long for no good reason. The traditional hex encoding is also much longer than it needs to be.

In any case, the article exists to help you decide how long you need to make your ids for you to be comfortable. If you decide you aren't comfortable with a 1 in a million chance, the math is there for you to figure out what does work for you.

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> UUIDs are really unnecessarily long for no good reason.

Their purpose is to be universally unique, presumably indefinitely. The practical choice is to align on a power of 2.

When UUIDs were invented, they were based on a MAC address plus a timestamp. MAC addresses are 48 bits, leaving 16 bits. Of these, between 1 and 3 are used up giving the variant code and another four bits are used giving the version code.

If they'd used 64 bits, there'd be between 8 and 11 bits left for a unique timestamp. Which is OK, but not a very strong guarantee for a "unique" scheme.

As it happens the length has made it possible to create multiple versions of UUIDs that are generated in different ways. UUID has been successful at separating the concerns of the structure of the ID from how it is generated. Most alternative schemes are effectively implementation-defined.

This is all true, and I'm not here to say the original implementers did anything wrong. As you say though, UUIDs are a general solution, which means they're not going to be optimal for every problem.

No, but I think most people overoptimise on the shiny stuff ("oooooh, I saved some bits!") over the important stuff (nasty surprises, several years from now).

Yeah, but sometimes "saving some bits" is really important. It's also really inconvenient to work with UUIDS, like in writing SQL queries etc. The solution these guys came up with obviously works for them.

> It's also really inconvenient to work with UUIDS, like in writing SQL queries etc.

http://www.postgresql.org/docs/8.3/static/datatype-uuid.html makes it look pretty easy…

Precisely the argument from Dilbert's Y2K episode: http://www.tv.com/shows/dilbert/y2k-12015/

How are these eager.io IDs any easier to work with in SQL queries etc.?

UUIDs are optimal for every problem, in that they are unique and fairly fast to generate. There can be no better solution than that, except maybe to save a few bits. And we're only talking about 16 bytes here; not much to complain about. They're cheap at the price.

Yeah its hard to get folks to come into the modern age of computering. FOr some reason there's tremendous resistance to abandoning the old crusty buggy solutions (indexes and handles that collide and need remapping) and using stuff that just works (identifying everything immutable with a uuid). Folks say 'its too many bits' and 'it takes too long'. Then they proceed to write megabytes worth of patchy code to try and save 64 bits worth of identifier.

As for database efficiency, that's a problem. But its a problem with the database - certainly no comfort for the user. But databases could do better, and I think they will one day come to handle uuids with less grief to the developer.

They already do. Postgres and SQL Server have UUID types.

Yeah, exactly. Building weakness into one's protocol because of an unhealthy attachment to saving a few bits and an even more unhealthy attachment to MySQL just seems foolish.

If you work with large amounts of data it hugely matters. 16 bytes times 1 billion records ends up being way more than 16GB of data, indexes, foreign keys, hot backup, etc. to manage and query.

Even that is a small amount of memory. I have that much RAM on my computer. See, its an obsolete conversation, yet folks raised in an ecology of scarcity can't get past it.

It depends on what you are optimizing for. If you need to store your entire database in physical memory, then the difference between 16GB and 128MB is significant.

UUIDs are 128-bits...

> If they'd used 64 bits

Actually I think that is the biggest problem with the article. It gives you no way to asses which probability is good enough.

I think thats a business decision, not a technical one. You have to decide what odds you are willing to accept, based on how many records you anticipate, how hard it will be to increase the length if that estimation is wrong, and how bad it would be if there was a collision.

In any case though, there are certainly many bad things which could happen to your company which are more likely than 1 in a million.

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