Generating CUID2 with PostgreSQL

cuid2.sql

CREATE OR REPLACE FUNCTION generate_cuid2(target_length INT DEFAULT 24)
    RETURNS TEXT AS $$
DECLARE
    timestamp_part TEXT;  -- Encoded timestamp in base36
    random_part TEXT;     -- Random string for uniqueness
    random_length INT;    -- Length of the random part
    characters TEXT := 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'; -- Alphanumeric characters
    result TEXT;          -- Final result to return
BEGIN
    -- Validate input length
    IF target_length < 8 THEN
        RAISE EXCEPTION 'Target length must be at least 8 characters';
    END IF;

    -- Generate the time-based prefix (always 8 characters)
    timestamp_part := LPAD(TO_HEX(EXTRACT(EPOCH FROM clock_timestamp())::BIGINT), 8, '0');

    -- Calculate the length of the random part
    random_length := target_length - LENGTH(timestamp_part);

    -- Generate the random part
    random_part := (
        SELECT STRING_AGG(SUBSTRING(characters, FLOOR(1 + RANDOM() * 62)::INT, 1), '')
        FROM generate_series(1, random_length)
    );

    -- Combine timestamp and random parts
    result := LEFT(timestamp_part || random_part, target_length);

    RETURN result;
END;
$$ LANGUAGE plpgsql;

example.sql

select gen_cuid2() cuid, clock_timestamp()-statement_timestamp() time_taken;

CREATE TABLE users (
    user_id CHAR(24) PRIMARY KEY DEFAULT generate_cuid2(), -- Generate a 24-character cuid2
    username TEXT NOT NULL UNIQUE,                         -- Username must be unique
    email TEXT NOT NULL UNIQUE,                            -- Email must be unique
    password_hash TEXT NOT NULL,                           -- Securely store password hashes
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,        -- Automatically set creation time
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP         -- Automatically set update time
);

CREATE TABLE longer_users (
    user_id CHAR(32) PRIMARY KEY DEFAULT generate_cuid2(32), -- Generate a 32-character cuid2
    username TEXT NOT NULL UNIQUE,                           -- Username must be unique
    email TEXT NOT NULL UNIQUE,                              -- Email must be unique
    password_hash TEXT NOT NULL,                             -- Securely store password hashes
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,          -- Automatically set creation time
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP           -- Automatically set update time
);