title: SOLR df and qf explanation
body: <p>I cannot find an adequeate explanation of how these query params interact</p>
  
  <p>I am getting suprising (to me) results that if I specify </p>
  
  <pre><code>qf=title^20 description^10
  </code></pre>
  
  <p>then I get no results
  however if I then add</p>
  
  <pre><code>df=description
  </code></pre>
  
  <p>I do get results</p>
  
  <p>df is set to text in solrconfig.xml - which will change - but my question is this - does the df setting somehow override the qf setting?  this seems odd</p>