How can I find a document based on value in a nested array with integer keys?

Question

My find query looks like the following:

bson.M{"_id": oId, "items": bson.M{"$elemMatch": bson.M{"id": theId, "active": true}}} (where theId is the object id from a method)

What I'm trying to do is to select a document with the matching id and where active is set to true

{ 
    "_id" : ObjectId("5ca0e44acb216df65405dc5f"), 
    "items" : {
        "0" : {
            "id" : ObjectId("5c9fbb25e86deef65491c321"), 
            "active" : true
        }, 
        "1" : {
            "id" : ObjectId("5c9fbb57cb216df65405dc5c"), 
            "active" : false
        }, 
        "2" : {
            "id" : ObjectId("5c9fbb65cb216df65405dc5d"), 
            "active" : false
        }
    }, 
}

But no matter how I do it, it never finds any documents. How can this be done?

Edit: Added my Go code.

func CountRows(find interface{}) int {
    session := database.GetMongoSession()
    defer session.Close()

    c := session.DB(config.Settings.Database.Name).C("list")

    count, err := c.Find(find).Count()
    if err != nil {
        log.Fatal(err)
    }

    return count
}

func IsActive(oId bson.ObjectId, theId bson.ObjectId) bool {
    if CountRows(bson.M{"_id": oId, "items": bson.M{"$elemMatch": bson.M{"id": theId , "active": true}}}) > 0 {
        return true
    }

    return false
}

It always returns false because it can't find any documents.

Please post what you've tried (Go code). Aim for a minimal reproducible example. — icza
– icza, Commented Apr 9, 2019 at 20:00

Jonas Tuemand Møller · Accepted Answer · 2019-04-09 20:57:56Z

1

If you own the database I would suggest restructuring your data to look like this:

{ 
    "_id" : ObjectId("5ca0e44acb216df65405dc5f"), 
    "items" : [
        {
            "id" : ObjectId("5c9fbb25e86deef65491c321"), 
            "active" : true
        }, 
        {
            "id" : ObjectId("5c9fbb57cb216df65405dc5c"), 
            "active" : false
        }, 
        {
            "id" : ObjectId("5c9fbb65cb216df65405dc5d"), 
            "active" : false
        }
    ]
}

Then you can use the MongoDB's own documentation: Query an Array of Embedded Documents methods.

answered Apr 9, 2019 at 20:57

Jonas Tuemand Møller

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