Sand Fox (Posts about uuid)

Generating UUIDv7 in PostgreSQL 18

2025-10-02T00:37:00+03:00

Another post just turned from a useful algorithm to madskillz. Since PostgreSQL 18 the method is just:

select uuidv7();

Generating UUIDv7 in PostgreSQL

2025-10-02T00:43:00+03:00

But what about Postgres? We can do it too. Hopefully generators for new UUID versions will be added to uuid-ossp but it is not yet the case.

The easiest way for now is to use pgcrypto, so let's start with that:

create extension pgcrypto;

Now port the solution from the MySQL post:

select
    lpad(to_hex((extract(epoch from now()) * 1000)::bigint), '12', '0') ||
    '7' || -- version
    substr(encode(gen_random_bytes(2), 'hex'), 2) ||
    to_hex((floor(random() * 4) + 8)::int) || -- variant bits
    substr(encode(gen_random_bytes(8), 'hex'), 2)
    as uuid;

Like with MariaDB, Postgres doesn't care about dashes on insertion, so this value can be directly applied to a field with the uuid type.

And again, to make it a formatted value, use a type cast:

select
    (lpad(to_hex((extract(epoch from now()) * 1000)::bigint), '12', '0') ||
    '7' ||
    substr(encode(gen_random_bytes(2), 'hex'), 2) ||
    to_hex((floor(random() * 4) + 8)::int) ||
    substr(encode(gen_random_bytes(8), 'hex'), 2))::uuid
    as uuid;

And to have a bytea value, use decode:

select
    decode(
        lpad(to_hex((extract(epoch from now()) * 1000)::bigint), '12', '0') ||
        '7' ||
        substr(encode(gen_random_bytes(2), 'hex'), 2) ||
        to_hex((floor(random() * 4) + 8)::int) ||
        substr(encode(gen_random_bytes(8), 'hex'), 2),
        'hex'
    ) as uuid;

Generating UUIDv7 in MySQL and MariaDB

2024-01-20T07:06:00+02:00

A quick way to generate UUIDv7 in MySQL 8 and MariaDB 11:

select
    concat(
        -- Use NOW(3) to get milliseconds
        lpad(hex(unix_timestamp(now(3)) * 1000), 12, '0'),
        '7', -- version
        substr(hex(random_bytes(2)), 2),
        hex(floor(rand() * 4 + 8)), -- variant bits
        substr(hex(random_bytes(8)), 2)
   ) as uuid;

This will generate a hex string that can be inserted into MariaDB's UUID type as is, dashes will be added automatically.

If you need it as a binary value, wrap with unhex:

select
    unhex(concat(
        lpad(hex(unix_timestamp(now(3)) * 1000), 12, '0'),
        '7',
        substr(hex(random_bytes(2)), 2),
        hex(floor(rand() * 4 + 8)),
        substr(hex(random_bytes(8)), 2)
    )) as uuid;

If you specifically need a valid RFC 4122 string representation, use a bin formatter function (MySQL) or a type cast (MariaDB):

-- MySQL
select
    bin_to_uuid(unhex(concat(
        lpad(hex(unix_timestamp(now(3)) * 1000), 12, '0'),
        '7',
        substr(hex(random_bytes(2)), 2),
        hex(floor(rand() * 4 + 8)),
        substr(hex(random_bytes(8)), 2)
    ))) as uuid;

-- MariaDB
select
    cast((concat(
        lpad(hex(unix_timestamp(now(3)) * 1000), 12, '0'),
        '7',
        substr(hex(random_bytes(2)), 2),
        hex(floor(rand() * 4 + 8)),
        substr(hex(random_bytes(8)), 2)
    )) as uuid) as uuid;

UPD: Postgres can do it too!

UUID Library (and ULID to UUID migration)

2023-07-14T05:48:00+03:00

I created a UUID and ULID library with Doctrine support. Well, who didn't :D

The main scenario for myself was a possible migration for a project from ULIDs to UUIDs since UUIDs got a little bit of support in MySQL 8.

Example code:

<?php

use Arokettu\Uuid\UuidParser;

// Just a random ULID
$ulid = UuidParser::fromBase32('01H44RDYXJPFCF895N3BBXCZRC');
var_dump($ulid->isUuidV7Compatible()); // false
// UnexpectedValueException: This ULID cannot be converted to UUID v7 losslessly
// $uuid = $ulid->toUuidV7();
$uuid = $ulid->toUuidV7(lossy: true);
// note digit 13 becoming '7' and digit 17 moving into [89ab] range
var_dump($uuid->toString());    // 01890986-fbb2-73d8-b424-b51ad7d67f0c
var_dump($ulid->toRfc4122());   // 01890986-fbb2-b3d8-f424-b51ad7d67f0c
var_dump($uuid->toBase32());    // 01H44RDYXJEFCB895N3BBXCZRC
var_dump($ulid->toString());    // 01H44RDYXJPFCF895N3BBXCZRC