My mongodb aggregation query is taking too much time. How can I enhance the performance?

Question

I'm joining two collection using aggregation and using "output" to generate a new collection with the joined data, but it's taking too much time(never ends). How can I enhance the performance? The collection A has 260k documents and collection B has 17.2m.

I have already tested the same script with different data sets and it works fine. At first glance, issue seems to be related with the size of collections.

db.colection_A.aggregate([
    {
        $match : { property_X: "X" }
    },
    {   "$lookup":
        {
            from: "collection_B",
            localField: "property_A",
            foreignField: "property_B",
            as: "joined_data"
        }
    },
    {   $unwind:
        {
            path: "$joined_data",
            preserveNullAndEmptyArrays: false
        }
    },
    {   $project: 
        {   
            "_id": 0,
            "joined_data": 1
         } 
    },
    {   $replaceRoot: 
            { newRoot: "$joined_data" } 
    },
    //{ $limit : 1 }
    { $out: "new_collection"}
    ]);

Expected result is creation of the collection "new_collection" containing data filtered in the "match" and "lookup" conditions.

Answer 1

The aggregation query was working fine, the problem was related with indexing in Mongo. After creation of the index, the query performed much better. Index was created with:

db.collection_B.createIndex( { property_B: 1 } );