title: Are ids in mysql guaranteed not to be repeated, even if rows are deleted?
body: <p>Of course if I put enough rows eventually there will be a repeat. But let's assume I choose a big enough id field.</p>
  
  <p>I want to know if I can assume that the id uniquely identifies the row over time. And if the client sends me an id I want to be able to determine what row it refers or if the row was deleted (or if it is a fake id, but in that case I will not care telling, wrongly, that the row was deleted).</p>
  
  <p>Please refer also to the following: if I restart the database, or backup and restore - will it be continue creating ids where it left - or may be it will decide to "fill in the holes"</p>