没有重复的“喜欢” function 的有效方法？

Question

I am making a "Like" function (facebook or instagram kind of), but not sure what is the right way to do it.

I could think of 2 ways.... (User cannot like same article twice)

A. "User" data has an array of "Article" IDs...

 // simplified user schema MongoDB const UserSchema ={ id:ObjectID, username:String, likes:[{type:ObjectID,ref:"Article"}] } // simplified article schema const AriticleSchema = { id:ObjectID, title:String, content:String, likes:Number, }

B. "Article" data has an array of "User" IDs...

 // simplified user schema MongoDB const UserSchema ={ id:ObjectID, username:String, } // simplified article schema const AriticleSchema = { id:ObjectID, title:String, content:String, likes:[{type:ObjectID,ref:"User"}], }

I tried both ways and they all worked fine when I only have few users and few articles.

but What if I have thousands of "User"s and thousands of "Article"s? I am worrying that everytime I request "User" data or "Article" data(let's say several at a time), I also have to bring arrays of thousands? I think there must be better way to do this...

Do you know how people or companies do this? I want to know the concept of how "Like" function works.

Thank you.

** Adding some details **

I want "User" can login for reading articles, and press "like button" to like it. Article "like" will go up by 1 every time unique user likes it (no duplicate). Somebody who already liked the " article" they can "unlike" it or "user" will see they already liked the "article", which means we gotta know that "user" like this "article" or not. Other people dosen't need to know.

Answer 1

I'll extrapolate on a solution by going through the requirements you elaborated step by step.

User can login

This will require some system for authorization. You could perhaps use another Mongo table dedicated to this sort of thing - at the minimum it should link some authorization token to a user id.

const AuthSchema = {
  user_id: ObjectID,
  auth_token: string,
}

The way you get this auth token is through various means - really depends on how you auth your users, eg phone auth or username/password. All that's a bit beyond the scope of this answer.

Article "like" will go up by 1 every time unique user likes it (no duplicate). Somebody who already liked the " article" can "unlike" it or "user" will see they already liked the "article"

A Redis Set would model this quite well. Every time a user likes an article, add their user_id into a Redis Set for that article. The key for such set could look like this:

article:${article_id}:likes

Get the number of people who liked the article by taking the size of its set (full of unique user_ids). Whenever someone unlikes an article, remove their user_id from the set.

Further reading:

• Redis Sets and other Redis datatypes
• Redis sadd command .