title: Rearranging data on changing clustered index in a huge table
body: <p>As described <a href="https://stackoverflow.com/questions/2266142/what-does-this-sentence-mean-clustered-indexes-are-stored-physically-on-the-tab?rq=1">here</a> clustered index in database affects how data is physically allocated on the disk.</p>
  
  <p>Does it mean that if I have a huge database table and will decide that I want to change PRIMARY KEY it will lead to rearranging physical data? </p>
  
  <p>How much free space will I need for this operation (if needed)? </p>
  
  <p>Lets say my db file contain a single table and has size of 100 GB.</p>