title: Mongodb aggregate error
body: <p>this is the command and the error generate:</p>
  
  <pre><code>db.tweets.aggregate(
      {$project:{'entities.hashtags.text':1}},
      {$unwind:'$entities.hashtags'},
      {$group:{_id:'$entities.hashtags.text'}})
  
  {
      "errmsg" : "exception: aggregation result exceeds maximum document size (16MB)",
      "code" : 16389,
      "ok" : 0
  }
  </code></pre>
  
  <p>i would want to do a follow query:</p>
  
  <p>group by entities.hashtags.text and count the number of document that contains that hashtags for every hashtags taht exist.</p>
  
  <p>this is a part of document:</p>
  
  <p>...</p>
  
  <p>entities: 
      {</p>
  
  <pre><code>   media: [
  
           ...
  
      ],
  
      urls: [],
  
      hashtags: [
  
          {
  
              text: "makeuploos",
  
              indices: [
  
                  54,
  
                  65
  
              ]
  
          },
  
          {
  
              text: "onbewerkt",
  
              indices: [
  
                  66,
  
                  76
  
              ]
  
          },
  
          {
  
              text: "hoer",
  
              indices: [
  
                  77,
  
                  82
  
              ]
  
          }
  
      ],
  </code></pre>
  
  <p>...</p>
  
  <p>how can i do this??</p>