title: md5 hash for urls in unique Index
body: <p>I was asked this before with slight different with current question. but did not got the answer I was looking into.</p>
  
  <p>My question is do I need to <strong>store</strong> <code>md5($url)</code> in unique index in MySQL?? I have seen this in some code actually I don't remember..this is a large database with more than 5 million urls and the indexing is done by calling urls.</p>
  
  <p>Any ideas?</p>