Postgres uuid_generate_v7 function

create_uuid_generate_v7.sql

CREATE OR REPLACE FUNCTION uuid_generate_v7() RETURNS uuid AS $$
  DECLARE
    unix_ts_ms bytea;
    uuid_bytes bytea;
  BEGIN
    unix_ts_ms = substring(int8send((extract(epoch from clock_timestamp()) * 1000)::bigint) from 3);
    uuid_bytes = uuid_send(gen_random_uuid());
    uuid_bytes = overlay(uuid_bytes placing unix_ts_ms from 1 for 6);
    uuid_bytes = set_bit(set_bit(uuid_bytes, 53, 1), 52, 1);
    RETURN encode(uuid_bytes, 'hex')::uuid;
  END
  $$ LANGUAGE plpgsql VOLATILE;