UUID
ulid
| UUID | ulid | |
|---|---|---|
| 9 | 4 | |
| 12,338 | 644 | |
| - | - | |
| 7.8 | 0.0 | |
| 5 days ago | about 1 year ago | |
| PHP | Python | |
| MIT License | Apache License 2.0 |
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UUID
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Weekly help thread
I'd recommend using either Ramsey/uuid or generating a random number using random_bytes(32) then compressing it. 32 bits of randomness should be sufficient for most programs.
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eli5 With billions and billions of people over time, how can fingerprints be unique to each person. With the small amount of space, wouldn’t they eventually have to repeat the pattern?
Of course, theoretical math and applied math often work out differently. Here's a thread with a guy claiming his team's software is running into "Several hundred [UUID] collisions per day"
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weird php results microtime/hrtime
Or just use a library.
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UUIDs are a wonderful invention
I'll leave this here https://github.com/ramsey/uuid/issues/80
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What are types of bugs that only show up after thousands or millions of times of the code being run.
Not really in the realm of “thousands” of runs, but UUID collisions are possible and have been observed multiple times after only 1 million generations due to unknown reasons.
- Generating unique key code using PHP
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Sortable Collision-Free UUIDs
There's also the risk of bad randomness sources and/or bugs.
One popular UUID library got a bug report stating: "We are generating about 1M UUID4 a day, and we are getting several hundred collisions a day". And so they were; turned out to be a bug/weird interaction between the OpenSSL library they were using for randomness and forking. (Details here, although it was all fixed years ago of course: https://github.com/ramsey/uuid/issues/80)
On paper, you should never, ever, ever see a collision when generating a mere million v4 UUIDs a day, much less hundreds of collisions. But that doesn't mean it can't happen!
This is also an interesting bit of analysis; comes from a company that processed a lot of UUIDs generated in browsers, checked, and discovered about 5 collisions per million UUIDs. Again, not what you'd naively expect! (Turned out to be mostly driven by misbehaving crawlers.) https://medium.com/teads-engineering/generating-uuids-at-sca...
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Things You Should Do Now
just make sure you have everything configured correctly on your system if using UUIDs:
https://github.com/ramsey/uuid/issues/80
In the types of systems that need UUIDs there is probably no easy way to check for collisions. The prospect of mystery data corruption with no ability to trace it down frightens the hell out of me.
The only reason that issue was reported is because someone was actually doing the collision checking. That's not going to be the norm in UUID systems. Think about it.
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A UUID can have so many combinations that UUIDs are effectively unique. But it's possible to generate the same one twice, however small the chance. Is it best practice to take this chance into account, checking to be sure you haven't used it?
In theory the risk of collision is so small it can be written off, but implementations can have bugs.
ulid
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Plan B for UUIDs: double AES-128
I really like ULID for this problem (e.g: https://github.com/ahawker/ulid)
- same number of bytes as UUID
- start with a date, so has great locality. Plus you get extra information in the uid that you can extract.
- can be created from an existing date or uuid, and exported to a uuid, so there is a migration path
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New UUID Formats from IETF
As the author of a popular ULID implementation in python[1], the spec has no stewardship anymore. The specification repo[2] has plenty of open issues and no real guidance or communication beyond language implementation authors discussing corner cases. The monotonic functionality is ambiguous (at best) and is implemented differently per-languages [3].
Functionality, UUIDv7 might be the _same_ but the hope would be for a more rigid specification for interoperability.
[1]: https://github.com/ahawker/ulid
[2]: https://github.com/ulid/spec
[3]: https://github.com/ulid/spec/issues/11
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Sortable Collision-Free UUIDs
Looks similar to ULID[0] (I am the author of a popular python implementation[1]).
It appears to have a similar constraint that two ID's generated within the same timestamp (ms, ns) have no strong guarantee of ordering. That might not be a deal breaker depending on your use case but something to consider.
* https://github.com/ulid/spec
* https://github.com/ahawker/ulid
- Usando ULIDs para criar ordem em dados não ordenados
What are some alternatives?
cuid - Collision-resistant ids optimized for horizontal scaling and performance.
ksuid - K-Sortable Globally Unique IDs
php-ulid - A PHP port of alizain/ulid with some minor improvements.
python-ulid - ULID implementation for Python
ksuid - Java implementation of K-Sortable Globally Unique IDs
uuid - Generate RFC-compliant UUIDs in JavaScript
Slugify - Converts a string to a slug. Includes integrations for Symfony, Silex, Laravel, Zend Framework 2, Twig, Nette and Latte.
EXREX - Irregular methods on regular expressions
Device Detector - The Universal Device Detection library will parse any User Agent and detect the browser, operating system, device used (desktop, tablet, mobile, tv, cars, console, etc.), brand and model.
xeger - Library to generate random strings from regular expressions.
Mobile-Detect - Mobile_Detect is a lightweight PHP class for detecting mobile devices (including tablets). It uses the User-Agent string combined with specific HTTP headers to detect the mobile environment.
essential-generators - Dead Simple Document Generation