title: How to query RavenDb index and perform changes on the result
body: <p>I'm experimenting a bit with RavenDb. </p>
  
  <p>I have grouping indexes (Map/Reduce and Live Projection). </p>
  
  <p>I want to take the result from those indexes and update the documents from which the result is projected from. </p>
  
  <p>This is part of an execution pipeline where Raven serves as a queue. The grouping is crucial. And when one of the grouped documents has been processed I want to mark it as processed.</p>
  
  <p>How would I do this?</p>