Support for MongoDB's sample() method?

help
1

I’d like to show random users on the home-page of my app, together with an end-less scrolling mechanism. Before Meteor was on MongoDB 3.2, I used some pretty weird code to do this, but with MongoDB 3.2, there is a sample() method:

https://docs.mongodb.com/manual/reference/operator/aggregation/sample/

Now I am wondering how I could use this in combination with Meteor’s MongoDB wrappers? The API only supports skip and limit, but not sample. Is there a way to workaround this limitation by accessing the underlying Mongo collection code? I only need this on server-side, inside a Meteor method.

2

Exactly that. However, this is an aggregation pipeline stage, so it’s a little more complex than a straight collection query.

Meteor.methods({
  async getRandomDocs(n) {
    // return array of n random docs
    return await someCollection.rawCollection().aggregate([ { $sample: { size: n} } ]).toArray();
  },
});

I just hacked that in here, so it’s untested!

2 Likes
3

Hey, thanks a lot for your fast reply. Highly appreciated, as always!

Wonder if that also works in combination with a cursor, i.e. skip and limit? This would help implementing endless scrolling with delayed loading. I’ll try it.

BTW: Didn’t know yet that you can use async/await in this context. Pretty cool.