title: MongoDB Indexing and Projection
body: <p>I have a few questions about MongoDB:</p>
  
  <p>(1) Does indexing help with projection?</p>
  
  <p>(2) I have assigned a collection a number of indexes and tried to run a find with sort, and then use <code>explain</code>, it shows <code>BtreeCursor</code> index on the sorted field. </p>
  
  <p>Could it be that the other indexes have helped in the query part and <code>explain</code> just didn't show it because it shows only the last index that helped the find? </p>
  
  <p>Or <code>explain</code> should show all indexes that assisted in querying, sorting, etc?</p>
  
  <p>Thanks.</p>