How to count $lookup data

Working with Data
1

I have two collections, users and versions. Here is a sample of the version collection

{
    "_id": {
        "$oid": "6013838305cbb735a07481be"
    },
    "schemaVersion": "1.0.0",
    "releaseType": "Stable",
    "version": "0.6.2",
    "createdAt": "2021-01-14T21:34:39.838Z",
    "updatedAt": {
        "$date": "2021-09-14T02:59:57.605Z"
    },
    "availability": "discontinue",
    "default": false
}

Here is a record from the users that references the version collection.

{
    "_id": {
        "$oid": "6068b22556a8375b842af8e4"
    },
    "server": {
        "licenseValid": true,
        "allowedStart": true,
        "restorePoint": {
            "$date": "2022-09-29T19:33:16.889Z"
        },
        "licenseKey": "DEMO ACCOUNT",
        "releaseVersion": {
            "$oid": "6013838305cbb735a07481be"
        }
    },
   
}

I am trying to create an aggregation that the end result looks like:

{
 version: "0.6.2",
 count: 1
}

I want to query all the versions and then count how many users are using that version. I have tried all kinds of permutations and just can’t seem to get it. In the old mysql days… this was pretty easy. Any help would be greatly appreciated.

2

Did you try anything?

From the text, it seems you will need:

  • $lookup stage
  • $group using as id the version, while summing up one on each match

This wont get just one but all the versions.

I think it will benefit you to try and share it. Use https://mongoplayground.net if you like.

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