title: What happens if you kill a long-running alter query?
body: <p>What happens if you kill a long-running alter query? Will the alter query simply revert? How long could that take (as a proportion of the time it has already been running)?</p>
  
  <p>What if that query is being replicated onto another server? Will killing the process on the other server revert the original server's alter query?</p>
  
  <p>We're running mysql</p>