ruby-ulid

Overview

ulid/spec defines some useful features.
In particular, it has uniqueness, randomness, extractable timestamps, and sortability.
This gem aims to provide the generator, optional monotonicity, parser, and other manipulations around ULID.
RBS definitions are also included.

---

Universally Unique Lexicographically Sortable Identifier

UUID can be suboptimal for many uses-cases because:

• It isn't the most character efficient way of encoding 128 bits of randomness
• UUID v1/v2 is impractical in many environments, as it requires access to a unique, stable MAC address
• UUID v3/v5 requires a unique seed and produces randomly distributed IDs, which can cause fragmentation in many data structures
• UUID v4 provides no other information than randomness which can cause fragmentation in many data structures

Instead, herein is proposed ULID:

• 128-bit compatibility with UUID
• 1.21e+24 unique ULIDs per millisecond
• Lexicographically sortable!
• Canonically encoded as a 26 character string, as opposed to the 36 character UUID
• Uses Crockford's base32 for better efficiency and readability (5 bits per character)
• Case insensitive
• No special characters (URL safe)
• Monotonic sort order (correctly detects and handles the same millisecond)

Usage

Install

Tested only in the last 2 Rubies. So you need Ruby 3.3 or higher.

Add this line to your Gemfile.

gem('ruby-ulid', '~> 0.9.0')

And load it.

require 'ulid'

NOTE: This README contains information about the development version.
If you would like to see released version's one. Look at the ref.

In Nix, you can skip the installation steps for both ruby and ruby-ulid to try.

> nix run github:kachick/ruby-ulid#ruby -- -e 'p ULID.generate'
ULID(2024-03-03 18:37:06.152 UTC: 01HR2SNY789ZZ027EDJEHAGQ62)

> nix run github:kachick/ruby-ulid#irb
irb(main):001:0> ULID.parse('01H66XG2A9WWYRCYGPA62T4AZA')
=> ULID(2023-07-25 16:18:12.937 UTC: 01H66XG2A9WWYRCYGPA62T4AZA)

Generator and Parser

ULID.generate returns ULID instance. It is not just a string.

ulid = ULID.generate #=> ULID(2021-04-27 17:27:22.826 UTC: 01F4A5Y1YAQCYAYCTC7GRMJ9AA)

ULID.parse returns ULID instance from exists encoded ULIDs.

ulid = ULID.parse('01F4A5Y1YAQCYAYCTC7GRMJ9AA') #=> ULID(2021-04-27 17:27:22.826 UTC: 01F4A5Y1YAQCYAYCTC7GRMJ9AA)

It has inspector methods.

ulid.to_time #=> 2021-04-27 17:27:22.826 UTC
ulid.milliseconds #=> 1619544442826
ulid.encode #=> "01F4A5Y1YAQCYAYCTC7GRMJ9AA"
ulid.to_s #=> "01F4A5Y1YAQCYAYCTC7GRMJ9AA"
ulid.timestamp #=> "01F4A5Y1YA"
ulid.randomness #=> "QCYAYCTC7GRMJ9AA"
ulid.to_i #=> 1957909092946624190749577070267409738
ulid.octets #=> [1, 121, 20, 95, 7, 202, 187, 60, 175, 51, 76, 60, 49, 73, 37, 74]

ULID.generate can take fixed Time instance. ULID.at is the shorthand.

time = Time.at(946684800).utc #=> 2000-01-01 00:00:00 UTC
ULID.generate(moment: time) #=> ULID(2000-01-01 00:00:00.000 UTC: 00VHNCZB00N018DCPJA4H9379P)
ULID.generate(moment: time) #=> ULID(2000-01-01 00:00:00.000 UTC: 00VHNCZB006WQT3JTMN0T14EBP)
ULID.at(time) #=> ULID(2000-01-01 00:00:00.000 UTC: 00VHNCZB002W5BGWWKN76N22H6)

Also ULID.encode and ULID.decode_time can be used to get primitive values for most usecases.

ULID.encode returns normalized String without ULID object creation.
It can take same arguments as ULID.generate.

ULID.encode #=> "01G86M42Q6SJ9XQM2ZRM6JRDSF"
ULID.encode(moment: Time.at(946684800).utc) #=> "00VHNCZB00SYG7RCEXZC9DA4E1"

ULID.decode_time returns Time. It can take in keyarg as same as Time.at.

ULID.decode_time('00VHNCZB00SYG7RCEXZC9DA4E1') #=> 2000-01-01 00:00:00 UTC
ULID.decode_time('00VHNCZB00SYG7RCEXZC9DA4E1', in: '+09:00') #=> 2000-01-01 09:00:00 +0900

This project does not prioritize on the speed. However it actually works faster than others! ⚡

Snapshot on v0.8.0 with Ruby 3.2.1 is below

• Generator is 1.9x faster than - ulid gem - v1.4.0
• Generator is 2.0x faster than - ulid-ruby gem - v1.0.2
• Parser is 3.1x faster than - ulid-ruby gem - v1.0.2

You can see further detail at Benchmark.

Sortable by timestamp

ULIDs are sortable when they are generated in different timestamp with milliseconds precision.

ulids = 1000.times.map do
  sleep(0.001)
  ULID.generate
end
ulids.uniq(&:to_time).size #=> 1000
ulids.sort == ulids #=> true

The basic generator prefers randomness, the results in the same milliseconds are not sortable.

ulids = 10000.times.map do
  ULID.generate
end
ulids.uniq(&:to_time).size #=> 35 (the size is not fixed, might be changed in environment)
ulids.sort == ulids #=> false

How to keep Sortable even if in same timestamp

If you prefer sortability, you can use MonotonicGenerator instead.
It is referred to as Monotonicity in the spec.
(Although it starts with a new random value when the timestamp is changed)

monotonic_generator = ULID::MonotonicGenerator.new
ulids = 10000.times.map do
  monotonic_generator.generate
end
sample_ulids_by_the_time = ulids.uniq(&:to_time)
sample_ulids_by_the_time.size #=> 32 (the size is not fixed, might be changed in environment)

# In same milliseconds creation, it just increments the end of randomness part
ulids.take(3) #=>
# [ULID(2021-05-02 15:23:48.917 UTC: 01F4PTVCSN9ZPFKYTY2DDJVRK4),
#  ULID(2021-05-02 15:23:48.917 UTC: 01F4PTVCSN9ZPFKYTY2DDJVRK5),
#  ULID(2021-05-02 15:23:48.917 UTC: 01F4PTVCSN9ZPFKYTY2DDJVRK6)]

# When the milliseconds is updated, it starts with new randomness
sample_ulids_by_the_time.take(3) #=>
# [ULID(2021-05-02 15:23:48.917 UTC: 01F4PTVCSN9ZPFKYTY2DDJVRK4),
#  ULID(2021-05-02 15:23:48.918 UTC: 01F4PTVCSPF2KXG4ABT7CK3204),
#  ULID(2021-05-02 15:23:48.919 UTC: 01F4PTVCSQF1GERBPCQV6TCX2K)]

ulids.sort == ulids #=> true

Same instance of ULID::MonotonicGenerator does not generate duplicated ULIDs even in multi threads environment. It is implemented with Monitor.

Filtering IDs with Time

ULID can be element of the Range. If they were generated with monotonic generator, ID based filtering is easy and reliable.

include_end = ulid1..ulid2
exclude_end = ulid1...ulid2

ulids.grep(one_of_the_above)
ulids.grep_v(one_of_the_above)

When want to filter ULIDs with Time, we should consider to handle the precision.
So this gem provides ULID.range to generate reasonable Range[ULID] from Range[Time]

# Both of below, The begin of `Range[ULID]` will be the minimum in the floored milliseconds of the time1
include_end = ULID.range(time1..time2) #=> The end of `Range[ULID]` will be the maximum in the floored milliseconds of the time2
exclude_end = ULID.range(time1...time2) #=> The end of `Range[ULID]` will be the minimum in the floored milliseconds of the time2

# Below patterns are acceptable
pinpointing = ULID.range(time1..time1) #=> This will match only for all IDs in `time1`
until_the_end = ULID.range(..time1) #=> This will match only for all IDs upto `time1`
until_the_ulid_limit = ULID.range(time1..) # This will match only for all IDs from `time1` to max value of the ULID limit

# So you can use the generated range objects as below
ulids.grep(one_of_the_above)
ulids.grep_v(one_of_the_above)
#=> I hope the results should be actually you want!

If you want to manually handle the Time objects, ULID.floor returns new Time with truncating excess precisions in ULID spec.

time = Time.at(946684800, Rational('123456.789')).utc #=> 2000-01-01 00:00:00.123456789 UTC
ULID.floor(time) #=> 2000-01-01 00:00:00.123 UTC

Tools

Scanner for string (e.g. JSON)

For rough operations, ULID.scan might be useful.

json = <<'JSON'
{
  "id": "01F4GNAV5ZR6FJQ5SFQC7WDSY3",
  "author": {
    "id": "01F4GNBXW1AM2KWW52PVT3ZY9X",
    "name": "kachick"
  },
  "title": "My awesome blog post",
  "comments": [
    {
      "id": "01F4GNCNC3CH0BCRZBPPDEKBKS",
      "commenter": {
        "id": "01F4GNBXW1AM2KWW52PVT3ZY9X",
        "name": "kachick"
      }
    },
    {
      "id": "01F4GNCXAMXQ1SGBH5XCR6ZH0M",
      "commenter": {
        "id": "01F4GND4RYYSKNAADHQ9BNXAWJ",
        "name": "pankona"
      }
    }
  ]
}
JSON

ULID.scan(json).to_a
#=>
# [ULID(2021-04-30 05:51:57.119 UTC: 01F4GNAV5ZR6FJQ5SFQC7WDSY3),
#  ULID(2021-04-30 05:52:32.641 UTC: 01F4GNBXW1AM2KWW52PVT3ZY9X),
#  ULID(2021-04-30 05:52:56.707 UTC: 01F4GNCNC3CH0BCRZBPPDEKBKS),
#  ULID(2021-04-30 05:52:32.641 UTC: 01F4GNBXW1AM2KWW52PVT3ZY9X),
#  ULID(2021-04-30 05:53:04.852 UTC: 01F4GNCXAMXQ1SGBH5XCR6ZH0M),
#  ULID(2021-04-30 05:53:12.478 UTC: 01F4GND4RYYSKNAADHQ9BNXAWJ)]

Get boundary ULIDs

ULID.min and ULID.max return termination values for ULID spec.

It can take Time instance as an optional argument. Then returns min/max ID that has limit of randomness part in the time.

ULID.min #=> ULID(1970-01-01 00:00:00.000 UTC: 00000000000000000000000000)
ULID.max #=> ULID(10889-08-02 05:31:50.655 UTC: 7ZZZZZZZZZZZZZZZZZZZZZZZZZ)

time = Time.at(946684800, Rational('123456.789')).utc #=> 2000-01-01 00:00:00.123456789 UTC
ULID.min(time) #=> ULID(2000-01-01 00:00:00.123 UTC: 00VHNCZB3V0000000000000000)
ULID.max(time) #=> ULID(2000-01-01 00:00:00.123 UTC: 00VHNCZB3VZZZZZZZZZZZZZZZZ)

As an element in Enumerable and Range

ULID#next and ULID#succ returns next(successor) ULID.
Especially ULID#succ makes it possible Range[ULID]#each.

NOTE: However basically Range[ULID]#each should not be used. Incrementing 128 bits IDs are not reasonable operation in most cases.

ULID.parse('01BX5ZZKBKZZZZZZZZZZZZZZZY').next.to_s #=> "01BX5ZZKBKZZZZZZZZZZZZZZZZ"
ULID.parse('01BX5ZZKBKZZZZZZZZZZZZZZZZ').next.to_s #=> "01BX5ZZKBM0000000000000000"
ULID.parse('7ZZZZZZZZZZZZZZZZZZZZZZZZZ').next #=> nil

ULID#pred returns predecessor ULID.

ULID.parse('01BX5ZZKBK0000000000000001').pred.to_s #=> "01BX5ZZKBK0000000000000000"
ULID.parse('01BX5ZZKBK0000000000000000').pred.to_s #=> "01BX5ZZKBJZZZZZZZZZZZZZZZZ"
ULID.parse('00000000000000000000000000').pred #=> nil

ULID#+ is also provided to realize Range#step since ruby-3.4.0 spec changes.

# This code works only in ruby-3.4.0dev or later
(ULID.min...).step(42).take(3)
# =>
[ULID(1970-01-01 00:00:00.000 UTC: 00000000000000000000000000),
 ULID(1970-01-01 00:00:00.000 UTC: 0000000000000000000000001A),
 ULID(1970-01-01 00:00:00.000 UTC: 0000000000000000000000002M)]

Test helpers

ULID.sample returns random ULIDs.

Basically ignores generating time.

ULID.sample #=> ULID(2545-07-26 06:51:20.085 UTC: 0GGKQ45GMNMZR6N8A8GFG0ZXST)
ULID.sample #=> ULID(5098-07-26 21:31:06.946 UTC: 2SSBNGGYA272J7BMDCG4Z6EEM5)
ULID.sample(0) #=> []
ULID.sample(1) #=> [ULID(2241-04-16 03:31:18.440 UTC: 07S52YWZ98AZ8T565MD9VRYMQH)]
ULID.sample(3)
#=>
#[ULID(5701-04-29 12:41:19.647 UTC: 3B2YH2DV0ZYDDATGTYSKMM1CMT),
# ULID(2816-08-01 01:21:46.612 UTC: 0R9GT6RZKMK3RG02Q2HAFVKEY2),
# ULID(10408-10-05 17:06:27.848 UTC: 7J6CPTEEC86Y24EQ4F1Y93YYN0)]

You can specify a range object for the timestamp restriction, see also ULID.range.

ulid1 = ULID.parse('01F4A5Y1YAQCYAYCTC7GRMJ9AA') #=> ULID(2021-04-27 17:27:22.826 UTC: 01F4A5Y1YAQCYAYCTC7GRMJ9AA)
ulid2 = ULID.parse('01F4PTVCSN9ZPFKYTY2DDJVRK4') #=> ULID(2021-05-02 15:23:48.917 UTC: 01F4PTVCSN9ZPFKYTY2DDJVRK4)
ulids = ULID.sample(3, period: ulid1..ulid2)
#=>
#[ULID(2021-05-02 06:57:19.954 UTC: 01F4NXW02JNB8H0J0TK48JD39X),
# ULID(2021-05-02 07:06:07.458 UTC: 01F4NYC372GVP7NS0YAYQGT4VZ),
# ULID(2021-05-01 06:16:35.791 UTC: 01F4K94P6F6P68K0H64WRDSFKW)]
ULID.sample(3, period: ulid1.to_time..ulid2.to_time)
#=>
# [ULID(2021-04-29 06:44:41.513 UTC: 01F4E5YPD9XQ3MYXWK8ZJKY8SW),
#  ULID(2021-05-01 00:35:06.629 UTC: 01F4JNKD85SVK1EAEYSJGF53A2),
#  ULID(2021-05-02 12:45:28.408 UTC: 01F4PHSEYRG9BWBEWMRW1XE6WW)]

Variants of format

I'm afraid so, we should consider Current ULID spec has orthographical variants of the format possibilities.

Case insensitive

I can understand it might be considered in actual use-case. So ULID.parse accepts upcase and downcase.
However it is a controversial point, discussing in ulid/spec#3.

Uses Crockford's base32 for better efficiency and readability (5 bits per character)

The original Crockford's base32 maps I, L to 1, O to 0.
And accepts freestyle inserting Hyphens (-).
To consider this patterns or not is different in each implementations.

I have suggested to clarify subset of Crockford's base32 in ulid/spec#57.

This gem provides some methods to handle the nasty possibilities.

ULID.normalize, ULID.normalized?, ULID.valid_as_variant_format? and ULID.parse_variant_format

ULID.normalize('01g70y0y7g-z1xwdarexergsddd') #=> "01G70Y0Y7GZ1XWDAREXERGSDDD"
ULID.normalized?('01g70y0y7g-z1xwdarexergsddd') #=> false
ULID.normalized?('01G70Y0Y7GZ1XWDAREXERGSDDD') #=> true
ULID.valid_as_variant_format?('01g70y0y7g-z1xwdarexergsddd') #=> true
ULID.parse_variant_format('01G70Y0Y7G-ZLXWDIREXERGSDoD') #=> ULID(2022-07-03 02:25:22.672 UTC: 01G70Y0Y7GZ1XWD1REXERGSD0D)

UUID

Both ULID and UUID are 128-bit IDs. But with different specs. Especially UUID has some versions probably UUIDv4.

All UUIDv4s can be converted to ULID, but this will not have the correct "timestamp".
Most ULIDs cannot be converted to UUIDv4 while maintaining reversibility, because UUIDv4 requires version and variants in the fields.

See also ulid/spec#64 for further detail.

For now, this gem provides 4 methods for UUIDs.

• Reversibility is preferred: ULID.from_uuidish, ULID.to_uuidish
• Prefer UUIDv4 specification: ULID.from_uuidv4, ULID.to_uuidv4

# All UUIDv4 IDs can be reversible even if converted to ULID
uuid = SecureRandom.uuid
ULID.from_uuidish(uuid) == ULID.from_uuidv4(uuid) #=> true
ULID.from_uuidish(uuid).to_uuidish == ULID.from_uuidv4(uuid).to_uuidv4 #=> true

# But most ULIDs cannot be converted to UUIDv4 
ulid = ULID.parse('01F4A5Y1YAQCYAYCTC7GRMJ9AA')
ulid.to_uuidv4 #=> ULID::IrreversibleUUIDError
# So 2 ways to get substitute strings that might satisfy the use case
ulid.to_uuidv4(force: true) #=> "0179145f-07ca-4b3c-af33-4c3c3149254a" this cannot be reverse to source ULID
ulid == ULID.from_uuidv4(ulid.to_uuidv4(force: true)) #=> false
ulid.to_uuidish #=> "0179145f-07ca-bb3c-af33-4c3c3149254a" does not satisfy UUIDv4 spec
ulid == ULID.from_uuidish(ulid.to_uuidish) #=> true

# Seeing boundary IDs makes it easier to understand
ULID.min.to_uuidish #=> "00000000-0000-0000-0000-000000000000"
ULID.min.to_uuidv4(force: true) #=> "00000000-0000-4000-8000-000000000000"
ULID.max.to_uuidish #=> "ffffffff-ffff-ffff-ffff-ffffffffffff"
ULID.max.to_uuidv4(force: true) #=> "ffffffff-ffff-4fff-bfff-ffffffffffff"

UUIDv6, UUIDv7, UUIDv8 are other candidates for sortable and randomness ID.
Latest ruby/securerandom merged the UUIDv7 generator.
See tracker for further detail.

Migration from other gems

See wiki page for gem migration.

RBS

• Try at examples/rbs_sandbox.
• See the overview in our wiki page for RBS

References

• Repository
• API documents
• ulid/spec