MongoDB: How to get N decimals precision in a query

Question

Given the following documents in a MongoDB collection...

{ \"_id\": 1, \"amount\": { \"value\": 1.123456789999, \"rate\": 1.2 }}
{ \"_id\": 2, \"amount\": { \"va         


        

Answer 1

You can do this with the $where operator.

db.collection.find({ "$where": function() { 
    return Math.round(this.amount.value * 100)/ 100 === 1.12; 
    }
})

---

EDIT (after this comment)

In this case you should use the aggregation framework especially the $redact operator and this is much faster than the solution using $where

db.collection.aggregate([
    { "$redact": { 
        "$cond": [
            { "$eq": [
                { "$subtract": [ 
                    "$amount.value", 
                    { "$mod": [ "$amount.value",  0.01 ] }
                ]}, 
                0.03
            ]}, 
            "$$KEEP", 
            "$$PRUNE"
        ]
     }}
])