title: How to not list all fields one by one in project when aggregating?
body: <p>I am using Mongo 3.2.14</p>
  
  <p>I have a mongo collection that looks like this:</p>
  
  <pre><code>{
  '_id':...
  'field1':...
  'field2':...
  'field3':...
  etc...
  }
  </code></pre>
  
  <p>I want to aggregate this way:</p>
  
  <pre><code>db.collection.aggregate{
                          '$match':{},
                          '$project':{
                                      'field1':1,
                                      'field2':1,
                                      'field3':1,
                                      etc...(all fields)
                                      }
                          }
  </code></pre>
  
  <p>Is there a way to include all fields in the project without listing each field one by one ? (I have around 30 fields, and growing...)</p>
  
  <p>I have found info on this here:</p>
  
  <p><a href="https://stackoverflow.com/questions/20497499/mongodb-project-retain-previous-pipeline-fields/24557029#24557029">MongoDB $project: Retain previous pipeline fields</a></p>
  
  <p><a href="https://stackoverflow.com/questions/19431773/include-all-existing-fields-and-add-new-fields-to-document">Include all existing fields and add new fields to document</a></p>
  
  <p><a href="https://stackoverflow.com/questions/43782945/how-to-not-write-every-field-one-by-one-in-project">how to not write every field one by one in project</a></p>
  
  <p>However, I'm using mongo 3.2.14 and I don't need to create a new field, so, I think I cannot use $addFields. But, if I could, can someone show me how to use it?</p>