title: MySQL Query Times out - Need to speed it up
body: <p>I whipped up a query here that does something particular with retrieving results that do not match the join (as suggested by this SO question).</p>
  
  <pre><code>SELECT cf.f_id
  FROM comments_following AS cf
  INNER JOIN comments AS c ON cf.c_id = c.id
  WHERE NOT EXISTS (
      SELECT 1 FROM follows WHERE f_id = cf.f_id
  )
  </code></pre>
  
  <p>Any ideas on how to speed this up? There are anywhere from 30k-200k rows it's looking through and appears to be using indexes, but the query times out.</p>
  
  <p>EXPLAIN/DESCRIBE Info:</p>
  
  <pre><code>1   PRIMARY c   ALL PRIMARY NULL    NULL    NULL    39119   
  1   PRIMARY cf  ref c_id, c_id_2    c_id    8   ...c.id 11  Using where; Using index
  2   DEPENDENT SUBQUERY  following   index   NULL    PRIMARY 8   NULL    35612   Using where; Using index
  </code></pre>