uuid-ossp: Unique Identifiers

The uuid-ossp extension can be used to generate a UUID.

Overview

A UUID is a "Universally Unique Identifier" and it is, for practical purposes, unique. This makes them particularly well suited as Primary Keys. It is occasionally referred to as a GUID, which stands for "Globally Unique Identifier".

Enable the extension

Note: Currently uuid-ossp extension is enabled by default and cannot be disabled.

-- Example: enable the "uuid-ossp" extension
create extension "uuid-ossp" with schema extensions;

-- Example: disable the "uuid-ossp" extension
drop extension if exists "uuid-ossp";

The uuid type

Once the extension is enabled, you now have access to a uuid type.

uuid_generate_v1()

Creates a UUID value based on the combination of computer’s MAC address, current timestamp, and a random value.

uuid_generate_v4()

Creates UUID values based solely on random numbers. You can also use Postgres's built-in gen_random_uuid() function to generate a UUIDv4.

Examples

Within a query

select uuid_generate_v4();

As a primary key

Automatically create a unique, random ID in a table:

create table contacts (
  id uuid default uuid_generate_v4(),
  first_name text,
  last_name text,
  primary key (id)
);

Resources

• Choosing a Postgres Primary Key
• The Basics Of Postgres UUID Data Type