title: How long should it take to build an index using ALTER TABLE in MySQL?
body: <p>This might be a bit like asking how long a length of string is, but the stats are:</p>
  
  <ul>
  <li>Intel dual core 4GB RAM</li>
  <li>Table with 8million rows, ~ 20 columns, mostly varchars with an auto_increment primary id</li>
  <li>Query is: ALTER TABLE my_table ADD INDEX <code>my_index</code> (my_column);</li>
  <li>my_column is varchar(200)</li>
  <li>Storage is MyISAM</li>
  </ul>
  
  <p>Order of magnitude, should it be 1 minute, 10 minutes, 100 minutes?</p>
  
  <p>Thanks</p>
  
  <p><b>Edit:</b> OK it took 2 hours 37 minutes, compared to 0 hours 33 mins on a lesser spec machine, with essentially identical set ups. I've no idea why it took so much longer. The only possibility is that the prod machine HD is 85% full, with 100GB free. Should be enough, but i guess it depends on how that free space is distributed.</p>