CODEWITHSUNDEEP
node.jsmongodbaggregation-framework
Comfort Eagle
Comfort Eagle

Reputation: 2462

MongoDB: How to resolve DBRef on client-side?

I'm new to mongodb, so sorry if this questions is dumb: I've pulled a document with the following structure:

{
"_id" : ObjectId("575df70512a1aa0adbc2b496"),
"name" : "something",
"content" : {
    "product" : {
        "$ref" : "products",
        "$id" : ObjectId("575ded1012a1aa0adbc2b394"),
        "$db" : "mdb"
    },
    "client" : {
        "$ref" : "clients",
        "$id" : ObjectId("575ded1012a1aa0adbc2b567"),
        "$db" : "mdb"
    }
}

where I'm referring to documents in the products and clients collection. I've read that it is possible to resolve these DBRefs on client-side (https://stackoverflow.com/a/4067227/1114975).

How do I do this? I'd like to avoid querying these objects and embedding them into the document. Thank you

Upvotes: 1

Views: 1668

Answers (2)

irokhes
irokhes

Reputation: 1703

I would consider use Mongoose which helps you with this and other issues. In this case you can use something like: 

Collection.find({}).populate('products').populate('clients')
          .exec(function(err, books) {...});

Mongoose populate

Upvotes: 1

chridam
chridam

Reputation: 103365

You can resolve this with the $lookup operator. Consider the following aggregation pipeline:

// Execute aggregate, notice the pipeline is expressed as an Array
collection.aggregate([
    {
        "$lookup": {
            "from": "product",
            "localField": "content.product.$id",
            "foreignField": "_id",
            "as": "products"
        }
    },
    {
        "$lookup": {
            "from": "clients",
            "localField": "content.client.$id",
            "foreignField": "_id",
            "as": "clients"
        }
    },
  ], function(err, result) {
    console.log(result);
});

Upvotes: 3

Related Questions