MongoDB extend Embedded Documents
<p>I have a mongo document as follows:</p>

<pre><code>{
  _id: ... ,
  field_1: ...,
  field_2: ...,
  changes:{
    "1474607149339":"a7hhs",
    "1474607149463":"98nhs",
    "1474607149657":"cxskk9",
    "1474607149880":"csdda3",
    "1474607151575":"bfddrd",
    "1474607153389":"54fbbb",
  }
}
</code></pre>

<p>The big numbers in the <code>changes</code> are timestamp values. (this is to track history of certain fields in my application). 
I'm sending this changes as small chunks containing few similar entries 
eg: </p>

<pre><code>{
        "1474607159708":"zcdgv",
        "1474607159932":"4h7kk",
        "1474607165362":"nbmnn"
}
</code></pre>

<p>how can I extend the <code>changes</code> field in the mongo document to include new changes in a single query (large number of changes need to be recoreded)?  </p>