Difference between save and insert in MongoDB 2016-06-13 22:47
Insert data into MongoDB is very easy. In this page I will tell you the difference between save method and insert method in MongoDB. If you don't know how to insert data into MongoDB you can see this blog(Insert data in MongoDB). To put it simply, save method will call insert or update method. It is depends on the data you saved contain the _id or not. If the data you saved contain the _id save method will call update method. If not it will call insert method. Examples are here.
> db.user.save({name:"Henry"})
WriteResult({ "nInserted" : 1 })
> db.user.findOne()
{ "_id" : ObjectId("575f6ec5f045569ea421c495"), "name" : "Henry" }
MongoDB will generate _id for every document if it do not have one. If you save this document again(without _id) MongoDB will save it as a new document.
> db.user.find({})
{ "_id" : ObjectId("575f6ec5f045569ea421c495"), "name" : "Henry" }
{ "_id" : ObjectId("575f6fa3f045569ea421c496"), "name" : "Henry" }
If you save the document with _id and this id exist in MongoDB save method will call update method to update this document.
> db.user.save({"_id":ObjectId("575f6ec5f045569ea421c495"),name:"new Henry"})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.user.find({})
{ "_id" : ObjectId("575f6ec5f045569ea421c495"), "name" : "new Henry" }
{ "_id" : ObjectId("575f6fa3f045569ea421c496"), "name" : "Henry" }