How to improve querying field in MongoDB?

To improve querying field in MongoDB, you need to use index. Let us create a collection with documents

> db.improveQueryDemo.insertOne(
... {
...    "PlayerDetails":[
...       {"PlayerName": "John", "PlayerGameScore": 5690},
...       {"PlayerName": "Carol", "PlayerGameScore": 2690},
...    ]
... }
... );
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5c9dbaf875e2eeda1d5c3670")
}

Following is the query to display all documents from a collection with the help of find() method

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

This will produce the following output

{
   "_id" : ObjectId("5c9dbaf875e2eeda1d5c3670"),
   "PlayerDetails" : [
      {
         "PlayerName" : "John",
         "PlayerGameScore" : 5690
      },
      {
         "PlayerName" : "Carol",
         "PlayerGameScore" : 2690
      }
   ]
}

Now you need to create an index on the field to improve querying. Following is the query

> db.improveQueryDemo.ensureIndex({"PlayerDetails.PlayerName":1});

This will produce the following output

{
   "createdCollectionAutomatically" : false,
   "numIndexesBefore" : 1,
   "numIndexesAfter" : 2,
   "ok" : 1
}

Now you can search by the exact match. Following is the query

> db.improveQueryDemo.find({"PlayerDetails.PlayerName":"Carol"}).pretty();

This will produce the following output

{
   "_id" : ObjectId("5c9dbaf875e2eeda1d5c3670"),
   "PlayerDetails" : [
      {
         "PlayerName" : "John",
         "PlayerGameScore" : 5690
      },
      {
         "PlayerName" : "Carol",
         "PlayerGameScore" : 2690
      }
   ]
}