title: ALTER TABLE takes forever even for a very little table
body: <p>I am working with a DB on Heroku.
  I tried to add another column without default.
  the table has only 3 rows and 5 columns, but the statement still takes forever to finish.</p>
  
  <p>I'm very new to SQL stuff. Is there anything I could do to fix it? A quicker option will be welcome too.</p>