Group stage in aggregation is being skipped

So, this is my query, being performed using the legacy driver for node.

  files.aggregate([ {
    $match : {
      filename : {
        $in : name
      }
    }
  }, {
    $group : {
      _id : '$onDisk',
      ids : {
        $push : '$_id'
      }
    }

And my issue is, if the amount of documents matched exceeds a little over 500 , the group stage is completely skipped and I get an array of matched documents that contain just the _id. I do not get an error about maximum size for bson exceeded, the aggregation simply returns me what it has before the group stage. I can’t tell if this issue is on the driver or mongo itself. The mongod version is 6 and legacy driver is 5.0.0, with the mongodb driver being 5.9.2.

I don’t know if it’s relevant, but ‘onDisk’ can be null, and it was when it failed, I can’t tell if it failed with large amounts an non-null values for onDisk.

I don’t know if this is relevant, but this aggregation is performed immediately after another aggregation on the same collection.

 files.aggregate([ {
    $match : {
      'metadata.type' : 'captcha',
      'metadata.expiration' : {
        $lte : new Date()
      }
    }
  }, {
    $group : {
      _id : 0,
      files : {
        $push : '$filename'
      }
    }

That points for an issue on the database itself. What is your mongod version?

It was solved if you are using their SAAS. For everyone else it boils down to “yeah, we have a botched update out there lmao”.

It’s been a month and 6.0.17 is still out there. Just updated a vm I had around and it went to the broken version.