How to select where sum of fields is greater than a value in MongoDB

Question

Using MongoDB, How would I write this regular SQL statement?

SELECT * FROM table WHERE (field1+field2+field3) > 1

I've been messing with $group, $project, $add, etc. I feel like I'm dancing all around the solution but can't figure it out.

Answer 1

The easiest way to do this is by using $where (I am not telling that it is not possible to do this with aggregation)

db.table.find({$where: function() {
   return this.field1 + this.field2 + this.field3 > 1
   // most probably you have to handle additional cases if some of the fields do not exist.
}}

The pros of it is that it is easy and intuitive, whereas cons:

requires that the database processes the JavaScript expression or function for each document in the collection.

If you need to perform this kind of searches often, I would go ahead and create a new field which will have a sum of 3 fields stored in it and put an index on it. The downside is that you have to increase your app logic.