Move different elements to another array in MongoDB?

Use forEach and check for the different elements and use save() along with some condition. Let us create a collection with documents −

> db.demo646.insertOne( ...    { ... ...       "Information": [ ...          { id: 100, Name:"Chris" }, ...          { id: 100, Name:"Chris" }, ...          { id: 101, Name:"David" }, ...          { id: 100, Name:"Chris" } ...       ], ...       "different": [] ...    } ... ) {    "acknowledged" : true,    "insertedId" : ObjectId("5e9c82ec6c954c74be91e6ed") }

Display all documents from a collection with the help of find() method −

> db.demo646.find().pretty();

This will produce the following output −

{    "_id" : ObjectId("5e9c82ec6c954c74be91e6ed"),    "Information" : [       {          "id" : 100,          "Name" : "Chris"       },       {          "id" : 100,          "Name" : "Chris"       },       {          "id" : 101,          "Name" : "David"       },       {          "id" : 100,          "Name" : "Chris"       }    ],    "different" : [ ] }

Following is the query to move elements to another array −

> db.demo646.find({}).forEach(function(d) { ...    d.different = d.Information.filter(function(v) { return v.id == 101 }) ...    d.Information = d.Information.filter(function(v) { return v.id != 101 }) ...    db.demo646.save(d) ...    } ... )

Display all documents from a collection with the help of find() method −

> db.demo646.find().pretty();

This will produce the following output −

{    "_id" : ObjectId("5e9c82ec6c954c74be91e6ed"),    "Information" : [       {          "id" : 100,          "Name" : "Chris"       },       {          "id" : 100,          "Name" : "Chris"       },       {          "id" : 100,          "Name" : "Chris"       }    ],    "different" : [       {          "id" : 101,          "Name" : "David"       }    ] }