title: Solr4 currently only looks at the default "df" field, how can we search multiple fields?
body: <p>In Solr 4, I see that we've configured the default field "df" in the <code>/select</code> request handler:</p>
  
  <pre><code>  &lt;requestHandler name="/select" class="solr.SearchHandler"&gt;
      &lt;!-- default values for query parameters can be specified, these
           will be overridden by parameters in the request
        --&gt;
       &lt;lst name="defaults"&gt;
         &lt;str name="echoParams"&gt;explicit&lt;/str&gt;
         &lt;int name="rows"&gt;10&lt;/int&gt;
         &lt;str name="df"&gt;id&lt;/str&gt;
  </code></pre>
  
  <p>But <code>id</code> is our unique document field, so all queries are defaulting to "id:my_query", which always returns 0 results.</p>
  
  <p>How do I define which fields should be queried by default?</p>
  
  <p>This is an upgrade from v3 to v4 and this part of it seems to have been broken along the way.</p>