MongoDB New CRUD API

The new mongodb shell includes new CRUD API! In addition to the old insert, update, and remove, the shell now supports insertMany, replaceOne, and a variety of other new methods.

> // the old insert API
> db.test.insert({_id: 1})
WriteResult({ "nInserted" : 1 })
> db.test.insert([{_id: 2}, {_id: 3}, {_id: 4}])
BulkWriteResult({
    "writeErrors" : [ ],
    "writeConcernErrors" : [ ],
    "nInserted" : 3,
    "nUpserted" : 0,
    "nMatched" : 0,
    "nModified" : 0,
    "nRemoved" : 0,
    "upserted" : [ ]
})

The new API better distinguishes single- and bulk-insert, and returns more useful results:

> // the new CRUD API
> db.test2.insertOne({_id: 1})
{
    "acknowledged" : true,
    "insertedId" : 1
}
> db.test2.insertMany([{_id: 2}, {_id: 3}, {_id: 4}])
{ 
    "acknowledged" : true,
    "insertedIds" : [ 2, 3, 4 ]
}

> // the old update API
> db.test.update(
... {_id: 1},
... {$set: {x: 1}},
... true              /* upsert */,
... false             /* multi */
)
WriteResult({
    "nMatched" : 0,
    "nUpserted" : 1,
    "nModified" : 0,
    "_id" : 1
})

> // the new update API
> db.test2.updateOne(
... {_id: 1},
... {$set: {x: 1}},
... {upsert: true}
)
{
    "acknowledged" : true,
    "matchedCount" : 0,
    "modifiedCount" : 0,
    "upsertedId" : 1
}

> // the old replace API
> db.test.update(
... {_id: 1},
... {set: {x: 1}}  // OOPS!!
)
WriteResult({
    "nMatched" : 1,
    "nUpserted" : 0,
    "nModified" : 1
})
> // document was replaced
> db.test.findOne()
{ "_id" : 1, "set" : { "x" : 1 } }

> // the old delete API
> db.test.remove({})  // remove EVERYTHING!!

> // the new delete API
> db.test2.deleteOne({})
{ "acknowledged" : true, "deletedCount" : 1 }
> db.test2.deleteMany({})
{ "acknowledged" : true, "deletedCount" : 3 }

Read more on 

https://www.mongodb.com/blog/post/consistent-crud-api-next-generation-mongodb-drivers