title: mongo - how to query a nested json
body: <p>I am a complete mongo newbie. I am using mongo hub for mac. I need to query the for following json -</p>
  
  <pre><code>{ "_id" : ObjectId( "abcd" ),
  "className" : "com.myUser",
  "reg" : 12345,
  "test" : [ 
  { "className" : "com.abc",
    "testid" : "pqrs" } ] }
  </code></pre>
  
  <p>and find records where testid is pqrs. How would I go about doing that?</p>