Get min and max value in single query in mongodb

Question

Considering the following Documents in "Words":

[{
  _id: 1,
  usages: 2,
  word: "Name"
}, {
  _id: 2,
  usages: 1,
  word: "Street"
}, {
  _id: 3,
  usages: 1,
  word: "House"
}, {
  _id: 4,
  usages: 3,
  word: "Table"
}, {
  _id: 5,
  usages: 3,
  word: "Bread"
}, {
  _id: 6,
  usages: 4,
  word: "Door"
}]

How can i get all the records where the number of usages is the lowest or highest? Lowest should return id 2 and 3(and their word), highest should return id 6 with its word.

I need to aggregate this data into a random amount of lowest/highest records (50 to be exact) so it needs to be an aggregate.

It should be a single lookup, so the min/max cannot be found using another query with $max or $min.

The MongoDB version is 3.4.7, Mongoose version 5.0.0-rc1. Mongoose solution not requred since I can use a raw query. (It is preferred however!)

Example:

Words.aggregate([ 
  { 
    $match: { _
      usages: { WHAT_SHOULD_I_HAVE_HERE }
    }
  }, { 
    $sample: { 
      size: 50 
    } 
  }
])

Thanks!

Answer 1

Given the following collection MyCollection data:

{ "_id" : ObjectId("ob1"), "value" : 17 }
{ "_id" : ObjectId("ob2"), "value" : 99 }
{ "_id" : ObjectId("ob3"), "value" : 35 }
{ "_id" : ObjectId("ob4"), "value" : 46 }
{ "_id" : ObjectId("ob5"), "value" : 12 }

You can perform the following query:

db.MyCollection.aggregate([
   { "$group": {
      "_id": null,
      "max_val": { "$max": "$value" },
      "min_val": { "$min": "$value" }
   }}
]);

And get:

{ "_id" : null, "max_val" : 99, "min_val" : 12 }