UUID generator (UUID-OSSP)

Version 4 — random (recommended)

uuid_generate_v4() → uuid

SELECT uuid_generate_v4();

Output:

         uuid_generate_v4
--------------------------------------
 170d0eb6-520a-4f93-a1b3-89458fffb54c
(1 row)

Use a version 4 UUID as the default primary key in a table:

CREATE TABLE contacts (
  id         uuid DEFAULT uuid_generate_v4() PRIMARY KEY,
  first_name text,
  last_name  text
);

Version 5 — deterministic with SHA-1

uuid_generate_v5(namespace uuid, name text) → uuid

The namespace parameter must be one of the constants returned by the uuid_ns_*() functions (see UUID namespace constants). The name parameter is an identifier within that namespace.

The same namespace and name always produce the same UUID. No plaintext can be derived from the output.

SELECT uuid_generate_v5(uuid_ns_url(), 'example.com');

Output:

         uuid_generate_v5
--------------------------------------
 a5cf6e8e-4cfa-5f31-a804-6de6d1245e26
(1 row)

Version 3 — deterministic with MD5

uuid_generate_v3(namespace uuid, name text) → uuid

Works the same way as v5, but uses MD5 instead of SHA-1. Use v5 when possible.

SELECT uuid_generate_v3(uuid_ns_url(), 'example.com');

Output:

         uuid_generate_v3
--------------------------------------
 a0473a67-27a1-3c05-a2d1-5c134639347f
(1 row)

Version 1 — timestamp-based

uuid_generate_v1() → uuid

SELECT uuid_generate_v1();

Output:

         uuid_generate_v1
--------------------------------------
 a6808efc-13c8-11ed-ad4f-00163e010e52
(1 row)

Version 1 UUIDs embed the real MAC address of the database server and the exact generation timestamp. This makes the generating machine identifiable and the UUID partially predictable. Use uuid_generate_v1mc() instead if you need time-ordering without exposing the real MAC address.

uuid_generate_v1mc() → uuid

SELECT uuid_generate_v1mc();

This function uses a random multicast MAC address instead of the real MAC address, preserving time-ordering while avoiding machine identification.