title: Single-word searches in Solr are not accurate
body: <p>I am developing an application to search a product on an e-Commence site. We have about 5,000,000 products that we put into Solr index with all the regular fields: title, description and etc. And while multiple-word search phrases work very well (for example "summer sandals" or "golf shirt"). Single word searches are not so good.  </p>
  
  <p>For example when I search for "guitar" Solr returns a bunch of product that mention guitar. Somehow, however guitar music CDs, guides on how to play guitars and guitar shaped key chains are ranked higher than actual guitar. The first actual guitar appears on 120th place or so.
  From user prospective, I am thinking, if I enter "gutar" I am looking for actual guitar. If I needed guide on how to play guitar I would search "guitar play guide", which by the way works perfectly.      </p>
  
  <p>Same problem if you search "shoes". It brings back bunch of music CDs. Apparently there are a lot of such that have word shoes either in title or description. </p>
  
  <p>One observation I made is that these "irrelevant" products in search results have very short titles and descriptions. That I guess raises significance of every single word in there. If you have a title of music CD "French Shoes", and not much else to go by, Solr is tricked. So am thinking is there a way to assign higher ranks to documents with longer text? I would have to operate with the notion of a field length not sure if it is an easy tweak in Solr.</p>
  
  <p>Any other suggestions?</p>