title: Order of columns in a primary key, performance
body: <p>I have a small question for performance reasons.</p>
  
  <p>I'm working with symfony and doctrine. I always used annotations in my entities and decided recently to switch to yml files.</p>
  
  <p>So I exported externally all my entities and generated the yml files. </p>
  
  <p>I compared the yml files with the database. There was a diff file generated which drops the primary key on certain tables and then adds them, simply in a different order. These primary keys have multiple columns.</p>
  
  <p>It seems that this happens only when one of the columns is a foreign key.</p>
  
  <p>The question is whether I can execute the change to my database and switch the order of the key columns, or whether it will affect my performance?</p>