title: how can I reset broken _ids
body: <p>I have imported my database entries from a csv file into mongodb and in the process of doing so the imported entries's '_id's aren't in the typical randomised format. e.g instead of looking like </p>
  
  <pre><code>"_id": "R6AnePqKecNNe7dkr"
  </code></pre>
  
  <p>they look like </p>
  
  <pre><code>"_id": 28
  </code></pre>
  
  <p>For some reason this means that when I try to refer to the database entry with an _id of 28 it can't find it. I thought it might be an issue in that they _id is not a string because they're not in quotes but I've tried to convert them to strings and that doesn't make a difference. I've tried making a function that randomly generates a new _id but it can't find the old _id to put the new _id into. </p>
  
  <p>Is there any way to do a bulk "generate new _ids for everything in this collection"? I'm having trouble finding anything equivalent</p>