title: Finding who shared a link publicly and finding who reshared a given link
body: <p>Two questions regarding tracking shared links:</p>
  
  <ol>
  <li><p>I have a URL and I want to get a list of <strong>public</strong> shares for that URL. I found this was answered a couple of times here on stackoverflow claiming it's impossible, but I don't understand why this is not allowed. If I can query public posts for given search keywords, like: <a href="https://graph.facebook.com/search?q=watermelon&amp;type=post" rel="nofollow">https://graph.facebook.com/search?q=watermelon&amp;type=post</a>, then why can't I use URLs as my search query? Or is there a way to do this that I just missed somehow?</p></li>
  <li><p>Let's say I have a link_id for a shared URL in the "link" FQL table. How can I find reshares of that link? (As possible in the Facebook website.)</p></li>
  </ol>
  
  <p>As an attempt to find middle ground between the above 2 problems, I tried to perform this FQL query:</p>
  
  <pre><code>SELECT link_id, owner, title FROM link WHERE url="&lt;url&gt;" AND (
      owner = me() OR owner IN (SELECT uid2 FROM friend WHERE uid1 = me())
  )
  </code></pre>
  
  <p>But this failed, with error:</p>
  
  <pre><code>&lt;error_response xmlns="http://api.facebook.com/1.0/"&gt;
      &lt;error_code&gt;1&lt;/error_code&gt;
      &lt;error_msg&gt;An unknown error occurred&lt;/error_msg&gt;
  &lt;/error_response&gt;
  </code></pre>