MongoDB - Find Difference Between Two Collections

I have two collections:

User

var UserSchema = new mongoose.Schema({      likes: [{ type: mongoose.Schema.Types.ObjectId, ref: 'Products' }],      dislikes: [{ type: mongoose.Schema.Types.ObjectId, ref: 'Products' }],  })  

Product

var ProductSchema = new mongoose.Schema({    title: {      type: String,      required: true,    },  })  

I would like to return all of the products that is not in the User.likes or User.dislikes. Here is how I am currently doing it:

const user = await User.findById(req.user.id, 'likes dislikes');  let seenProducts = [];    user.likes.forEach(p => {      seenProducts.push(new mongoose.Types.ObjectId(p));  })    user.dislikes.forEach(p=> {      seenProducts.push(new mongoose.Types.ObjectId(p));  })    Product.aggregate([      {          $match: { _id: { $nin: seenProducts } },      }  ])  

It works, but I would like to switch over to using the aggregration pipeline framework to do this if possible. It does not seem like it is easy to compare two collections... I have been trying this for a while with no luck. $setUnion and $setDifference look promising, but I can't find a way to set the union of the likes & dislikes of the user, and then the difference of that with all products.

https://stackoverflow.com/questions/67363069/mongodb-find-difference-between-two-collections May 03, 2021 at 11:07AM