pgulid's Introduction

Universally Unique Lexicographically Sortable Identifier

A PostgreSQL (pgcrypto) implementation of alizain/ulid based on OK Log's Go port.

Background

A GUID/UUID can be suboptimal for many use-cases because:

It isn't the most character efficient way of encoding 128 bits
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

A ULID however:

Is compatible with UUID/GUID's
1.21e+24 unique ULIDs per millisecond (1,208,925,819,614,629,174,706,176 to be exact)
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

SELECT generate_ulid(); -- Output: 01D45VGTV648329YZFE7HYVGWC

Specification

Below is the current specification of ULID as implemented in this repository.

Components

Timestamp

48 bits
UNIX-time in milliseconds
Won't run out of space till the year 10895 AD

Entropy

80 bits

String Representation

 01AN4Z07BY      79KA1307SR9X4MV3
|----------|    |----------------|
 Timestamp           Entropy
  10 chars           16 chars
   48bits             80bits
   base32             base32

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