title: Postgres doesn't use index with "ORDER BY"
body: <ul>
  <li>I have a very large table.</li>
  <li>I have an index on columns col1.</li>
  <li>I would like to get the data ordered by col1.</li>
  <li>From the query plan I can say it doesn't use the index.</li>
  <li>When I add "LIMIT", it starts to use the index</li>
  <li>For large value for "LIMIT", it stops using the index.</li>
  </ul>
  
  <p>Any clue?</p>
  
  <p>P.S. I would like to get the data clustered by values of col1 (not necessarily sorted), any suggestions other than "ORDER BY".</p>
  
  <p>THANKS !!</p>