How to filter array in subdocument with MongoDB?

MongoDBDatabaseBig Data Analytics

You can use aggregate and unwind the array list before applying match. To understand the above concept, let us create a collection with documents. The query to create a collection with document is as follows:

> db.filterArray.insertOne( { "L": [{ "N":1 }, { "N":2 } , { "N":3 }, { "N":4 }, { "N":5 } ]});

The following is visible after running the above query:

{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c6d63f2734e98fc0a434aeb")
}

Display document from a collection with the help of find() method. The query is as follows:

> db.filterArray.find().pretty();

The following is the output:

{
   "_id" : ObjectId("5c6d63f2734e98fc0a434aeb"),
   "L" : [
      {
         "N" : 1
      },
      {
         "N" : 2
      },
      {
         "N" : 3
      },
      {
         "N" : 4
      },
      {
         "N" : 5
      }
   ]
}

Here is the query to filter array in subdocument with MongoDB. We have used $gt to get the fields greater than 3:

> db.filterArray.aggregate({ $match:{_id:ObjectId("5c6d63f2734e98fc0a434aeb")}}, {
$unwind:'$L'}, {$match:{'L.N':{$gt:3}}},
{$group:{_id:'$_id',subDocument:{$push:'$L.N'}}}).pretty();

The following is the output:

{
   "_id" : ObjectId("5c6d63f2734e98fc0a434aeb"),
   "subDocument" : [
      4,
      5
   ]
}
raja
Published on 18-Mar-2019 11:28:42
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