title: Correct indexing when using OR operator
body: <p>I have a query like this:</p>
  
  <pre><code>SELECT fields FROM table
  WHERE field1='something' OR field2='something' 
  OR field3='something' OR field4='something'
  </code></pre>
  
  <p>What would be the correct way to index such a table for this query?</p>
  
  <p>A query like this takes a entire second to run! I have 1 index with all 4 of those fields in it, so I'd think mysql would do something like this:</p>
  
  <p>Go through each row in the index thinking this:
  Is field1 something? How about field2? field3? field4? Ok, nope, go to the next row.</p>