How to add a random number in slug that already exists in MongoDB?

Question

Currently a document looks like this:

{
  "_id": {
    "$oid": "630f3c32c1a580642a9ff4a0"
  },
  "title": "This is a title",
  "slug": "this-is-a-title",
  "Post": "this is a post"
}

But I want it like this:

{
  "_id": {
    "$oid": "630f3c32c1a580642a9ff4a0"
  },
  "title": "This is a title",
  "slug": "this-is-a-title-548631",
  "Post": "this is a post"
}

How can I add a 6 digit random number at the end of slug in all documents?

Answer 1

You can use $rand to generate a random number, combined with some other operators you can force the 6 digits constraint, like so:

db.collection.updateMany({},
[
  {
    $set: {
      slug: {
        $concat: [
          "$slug",
          "-",
          {
            $toString: {
              $round: {
                $add: [
                  {
                    $multiply: [
                      {
                        $rand: {}
                      },
                      899999
                    ]
                  },
                  100000
                ]
              }
            }
          }
        ]
      }
    }
  }
])

Mongo Playground

(this will gives results in the range of 100,000 to 999,999), if you want to allow 0 prefixes, like 000123 then you can still use the same approach and pad with zeros based on the number length.