PostgreSQL UUID V7 function

pg-uuid-v7.sql

create extension if not exists pgcrypto;

create or replace function uuid_generate_v7()
returns uuid
as $$
declare
  ver_rand_var bytea = e'\\000\\000\\000';
  unix_time_ms bytea;
  rand_bytes   bytea;
begin
  unix_time_ms = substring(int8send(floor(extract(epoch from clock_timestamp()) * 1000)::bigint) from 3);
  rand_bytes = gen_random_bytes(3);

  ver_rand_var = set_byte(ver_rand_var, 0, (b'0111'||get_byte(rand_bytes, 0)::bit(4))::bit(8)::int);
  ver_rand_var = set_byte(ver_rand_var, 1, get_byte(rand_bytes, 1));
  ver_rand_var = set_byte(ver_rand_var, 2, (b'10'||get_byte(rand_bytes, 2)::bit(6))::bit(8)::int);

  return substring((unix_time_ms || ver_rand_var || gen_random_bytes(7))::text from 3)::uuid;
end
$$
language plpgsql
volatile;