Is there a way to get all distinct values for a field in Mongo Compass?

Question

I would like to be able to get all the distinct values for a field or nested field in MongoDB Compass.

Answer 1

Here's a way that I've been using in Compass.

If you go into Compass to the collection you want and go to the aggregation tab, you can unwind and group as such:

Select $unwind and then fill in the field you want, prefixed with $. I usually ignore null and empty arrays if the field is an array.

{
  path: '$displayFirstName',
  preserveNullAndEmptyArrays: false
}

Then use a $group stage to group the values and add them to a set:

{
  _id: null,
  uniqueFirstNames: {
    $addToSet: '$displayFirstName'
  }
}

The unique list of values will be displayed on the right of the $group stage.

If the value is nested and you want to flatten the results, just add more $unwind stages per level before the final $group stage. For example, if you had user.addresses which is an array of objects and you wanted to get all the possible address types of all your users as a flattened list you could do this.

$unwind

{
  path: '$addresses',
  preserveNullAndEmptyArrays: false
}

2nd $unwind

{
  path: '$addresses.type',
  preserveNullAndEmptyArrays: false
}

$group

{
  _id: null,
  uniqueAddressTypes: {
    $addToSet: '$addresses.type'
  }
}