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Mongoose Query: compare two values ​​in one document

How can I query a Mongo collection using Mongoose to find all documents that have a specific relationship between two of their own properties?

For example, how can I query collections charactersto find all those characters whose value is currentHitPointsless than their value maximumHitPoints? Or all those projectswho have currentPledgedMoneyfewer of them pledgeGoal?

I tried to do something like this:

mongoose.model('Character')
    .find({
        player: _currentPlayer
    })
    .where('status.currentHitpoints').lt('status.maximumHitpoints')
    .exec(callback)

but I get errors as the argument ltshould be Number. The same thing happens if I use $.status.maximumHitpoints(I was hoping that Mongoose would be able to resolve it, as when performing assembly operations).

Is this something that can be done in a query? I would expect so, but I can’t figure out how to do this. Otherwise, I can filter the entire collection using underscore, but I suspect that this will have a negative impact on performance.

PS: I also tried using similar approaches with a findboneless call .

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2 answers

Thanks to Aniket's suggestion in the comments on the question, I found that the same thing can be done with Mongoose using the following syntax:

mongoose.model('Character')
    .find({
        player: _currentPlayer
    })
    .$where('this.status.currentHitpoints < this.status.maximumHitpoints')
    .exec(callback)

Note that the method is $whereused instead of the method where.

: Derick , Mongoose, , , . Mongoose Schema, - :

var CharacterSchema = new mongoose.Schema({
    // ...
    status: {
        hitpoints: Number,
        maxHitpoints: Number,
        isInFullHealth: {type: Boolean, default: false}
    }
})
.plugin(function(schema, options) {
     schema.pre('save', function(next) {
         this.status.isInFullHealth = (this.status.hitPoints >= this.status.maxHitpoints);

         next();
     })
 })
+5

MongoDB 3.6 :

db.monthlyBudget.find( { $expr: { $gt: [ "$spent" , "$budget" ] } } )

https://docs.mongodb.com/manual/reference/operator/query/expr/

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