lets say I have post Model and schema contains UserId , Title, Desc and likes array which takes userId's as ref
when I make a query I get a virtual property like this to find out num of like of a post would have
schema.virtual("numLikes").get(function () {
return this.likes.length;
});
But the problem is when I run the findById() Method I dont want to get likes from database because likes array would contain large list of users
const post = await Post.findById(postId).select("-likes -shares");
so how do I get Likes count without fetching likes array ?
I believe this can be done using aggregation, by using the $size operators in a projection:
const aggregate = Post.aggregate([
{ $match: {_id: postId}},
{ $project: {
numberOfLikes: { $size: "$likes" }
}
}
]);
https://docs.mongodb.com/manual/reference/operator/aggregation/size/ https://mongoosejs.com/docs/api/aggregate.html#aggregate_Aggregate-project