title: Create an index on a huge MySQL production table without table locking
body: <p>I need to create an index on a ~5M rows MySQL table. It is a production table, and I fear a complete block of everything if I run a CREATE INDEX statement... </p>
  
  <p>Is there a way to create that index without blocking inserts and selects?</p>
  
  <p>Just wondering I have not to stop, create index and restart my system!</p>