Consider this:

{

  $group: {

    _id: "$SomeField",

    items:

  }

}

The aggregation above allows to return all ids grouped but what if you are only interested in the first 10 ids?

It would be nice if $push would allow a limit so that only a certain number is returned.

I often have to write queries to return oldest 10 records grouped by some criteria and it is almost impossible to do in mongodb at the moment.