title: Possibility of duplicate Mongo ObjectId's being generated in two different collections?
body: <p>Is it possible for the same exact Mongo ObjectId to be generated for a document in two different collections?  I realize that it's definitely very unlikely, but is it possible?  </p>
  
  <p>Without getting too specific, the reason I ask is that with an application that I'm working on we show public profiles of elected officials who we hope to convert into full fledged users of our site.  We have separate collections for users and the elected officials who aren't currently members of our site.  There are various other documents containing various pieces of data about the elected officials that all map back to the person using their elected official ObjectId.</p>
  
  <p>After creating the account we still highlight the data that's associated to the elected official but they now also are a part of the users collection with a corresponding users ObjectId to map their profile to interactions with our application.</p>
  
  <p>We had begun converting our application from MySql to Mongo a few months ago and while we're in transition we store the legacy MySql id for both of these data types and we're also starting to now store the elected official Mongo ObjectId in the users document to map back to the elected official data.</p>
  
  <p>I was pondering just specifying the new user ObjectId as the previous elected official ObjectId to make things simpler but wanted to make sure that it wasn't possible to have a collision with any existing user ObjectId.</p>
  
  <p>Thanks for your insight.</p>
  
  <p>Edit:  Shortly after posting this question, I realized that my proposed solution wasn't a very good idea.  It would be better to just keep the current schema that we have in place and just link to the elected official '_id' in the users document.</p>