title: mongoimport query for upsert the fields
body: <p>I have record like this</p>
  
  <pre><code>{ "name" : "durga prasad", "company" : "big datamatica", "size" : 50, "role" : "CEO" }
  </code></pre>
  
  <p>I need to update like this</p>
  
  <pre><code>{ "name" : "durga prasad", "company" : "google", "size" : 50, "role" : "CEO" }
  </code></pre>
  
  <p>when i use import</p>
  
  <pre><code>mongoimport -d durga -c prasad --upsert --upsertFields name,company,size,role sample.json
  </code></pre>
  
  <p>I able to get </p>
  
  <pre><code>{ "name" : "durga prasad", "company" : "big datamatica", "size" : 50, "role" : "CEO" }
  { "name" : "durga prasad", "company" : "google", "size" : 50, "role" : "CEO" }
  </code></pre>
  
  <p>I am getting both the records I need updated record only
  If the field not exists it should add to the existing record</p>