simple voting system with MongoDB

Question

quick question I have a list of articals in mongodb and I want users to be able to upvote or down vote the artical.

My first way would be in the artical collection t

Answer 1

When you would do it that way, you wouldn't track which user has already voted, so users can vote multiple times. That's surely not in your interest.

For that reason I would add an array "votes" to each article which includes an object for each vote which uniquely identifies the user who made it:

votes: [ 
        { voter:"name or ID or IP address or some other unique identifier for the person who voted",
          vote:-1 },
        { voter:"someone else",
          vote:1 },
        { voter:"and someone entirely different",
          vote:-1 }
    ]

When you create an unique index over the article ID and votes.voter, you have already ensured that nobody can vote twice for an article.

When you use a value of "-1" for downvote and "1" for upvote you can calculate the total score of an article by using the $sum aggregate function (It would also easily allow you to introduce weighted votes later, when you feel like it).