title: Use 'on duplicate key update' when saving record in CakePHP
body: <p>My model has 2 unique indexes. The primary key, and an alphanumeric id.</p>
  
  <p>I only have the alphanumeric id when updating said record, so I need to add an "on duplicate key update" statement to the save function, but how do I do that?</p>
  
  <p>And I do not want to query for the primary key first, as that would make the import process incredibly long and slow.</p>