Even if it is a hair slower, UUIDs (or similar schemes) are advantageous for reasons beyond being able to merge tables.<p>Another big advantage is being able to use the UUID as a key, without worrying about exploits from guessing serial numbers:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Predictable_serial_number_attack" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Predictable_serial_number_atta...</a>