title: Getting only the first item for an array property in mongodb
body: <p>Given the following layout in a collection...</p>
  
  <pre><code>{
    vehicle_id: 1
    ,// bunch of properties I don't want
    ,vehicle: {
      mfg_year: 1928
      ,mfg_make: "Ford"
      ,mfg_model: "Model A"
      ,mfg_trim: "T-Bucket"
      ,// bunch of properties I don't want
      ,images: [
        {url:'...',...}
        ,...
      ]
    }
  }</code></pre>
  
  <p>How would I return a result with only the above fields, and only the first result under images?  I don't mind if the results are in one flattened object, with only the images being a nested object.</p>
  
  <p>I've looked into the Aggregation Framework, which doesn't seem to match what I am looking for.  I know I could do a map/reduce on the results set, or do a group on the listing_id, am just hoping to have a simpler query structure without needing to resort to group, or reduce.</p>
  
  <p>If this isn't possible currently via the aggregation framework, a working group or map-reduce would be an acceptable answer.</p>
  
  <hr>
  
  <p>EDIT: There are about 50+ properties that I don't want in the final result.. with the $slice directive, it seems I can't just specify the fields I want.</p>