title: Mongoose multi update
body: <p>I want to update multiple docs with different values.</p>
  
  <p>My Database looks something like this.</p>
  
  <pre><code>[
      {
          "_id": 1,
          "value": 50
      },
      {
          "_id": 2,
          "value": 100
      }
  ]
  </code></pre>
  
  <p>This Query return an error because i'm passing an array instead of an object in the $set.</p>
  
  <pre><code>    Model.update({_id: {$in: ids}}, {$set: ids.value}, {multi: true};
  </code></pre>
  
  <p>I want my database to look like this</p>
  
  <pre><code>[
          {
              "_id": 1,
              "value": 4
          },
          {
              "_id": 2,
              "value": 27
          }
      ]
  </code></pre>