Here's the only issue I could find:
From a quick reading apparently the decision was made from the old problem of User 0 (Anonymous) not being inserted at times.
Jamie Holly http://www.intoxination.net http://www.hollyit.net
On 11/30/2012 8:42 AM, Earnie Boyd wrote:
On Fri, Nov 30, 2012 at 8:32 AM, Jamie Holly wrote:
This isn't the case in D7. UID is assigned by a SELECT MAX(uid) FROM {users}. Check user.module line 571.
Unless the whole users table is locked then this is guaranteed to fail under heavy use. Some poor user is going to get a DB error of duplicate key. The chances may be small but there is a chance it will happen. Do you know the issue # that caused this to happen?