title: MySQL Error when dropping index (errno 150)
body: <p>I've got problem with dropping foreign key index, I always get the same error </p>
  
  <pre><code> ALTER TABLE `comments` DROP INDEX `id_user`  
  </code></pre>
  
  <p>which outputs</p>
  
  <pre><code> 1025 - Error on rename of './postuj_cz1/#sql-d834_a0c704' 
   to './postuj_cz1/comments' (errno: 150) 
  </code></pre>
  
  <p>The <code>id_user</code> on the other table is simple primary key index.</p>
  
  <p>I'm using MySQL version 5.0.85</p>