MongoDB: db.collection.save() method
db.collection.save
The db.collection.save() method is used to updates an existing document or inserts a new document, depending on its document parameter.
Syntax:
db.collection.save()
Parameters:
Name | Description | Required / Optional |
Type |
---|---|---|---|
document | A document to save to the collection. | Required | document |
writeConcern | A document expressing the write concern. Omit to use the default write concern. | Optional | document |
Returns:
A WriteResult object that contains the status of the operation.
Example: Save a New Document without Specifying an_idField
In the following example,save()method performs an insert since the document passed to the method does not contain the_idfield:
db.invoice.save( { inv_no: "I00001", inv_date: "10/10/2012", ord_qty:200 } );
Output:
> db.invoice.save( { inv_no: "I00001", inv_date: "10/10/2012", ord_qty:200 } ); WriteResult({ "nInserted" : 1 })
During the insert, the shell will create the _id field with a unique ObjectId value, as verified by the inserted document:
> db.invoice.find();
{ "_id" : ObjectId("5677ddc7fad7da08e362a3b8"), "inv_no" : "I00001", "inv_date" : "10/10/2012", "ord_qty" : 200 }
Example>: Save a New Document Specifying an_idField
In the following example,save()performs an update withupsert :truesince the document contains an_idfield:
db.invoice.save( { _id: 1001,inv_no: "I00001", inv_date: "10/10/2012", ord_qty:200 } );
Output:
> db.invoice.save( { _id: 1001,inv_no: "I00001", inv_date: "10/10/2012", ord_qty:200 } ); WriteResult({ "nMatched" : 0, "nUpserted" : 1, "nModified" : 0, "_id" : 1001 })
The operation results in the following new document in the invoice collection.
> db.invoice.find();
{ "_id" : 1001, "inv_no" : "I00001", "inv_date" : "10/10/2012", "ord_qty" : 200 }
Example: Replace an Existing Document
Theproductscollection contains the following document:
{ "_id" : 1001, "inv_no" : "I00001", "inv_date" : "10/10/2012", "ord_qty" : 200 }
The save() method performs an update with upsert:true since the document contains an _id field:
db.invoice.save( { _id: 1001,inv_no: "I00015", inv_date: "15/10/2012", ord_qty:500 } );
Output:
> db.invoice.save( { _id: 1001,inv_no: "I00015", inv_date: "15/10/2012", ord_qty:500 } ); WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
Because the _id field holds a value that exists in the collection, the operation performs an update to replace the document and results in the following document:
> db.invoice.find();
{ "_id" : 1001, "inv_no" : "I00015", "inv_date" : "15/10/2012", "ord_qty" : 500 }
Retrieve the restaurants data from here
Behavior
Safe Writes
The save() method uses either the insert or the update command, which use the default write concern. To specify a different write concern, include the write concern in the options parameter.
Insert
If the document does not contain an _id field, then the save() method calls the insert() method. During the operation, the mongo shell will create an ObjectId and assign it to the _id field.
NOTE: Most MongoDB driver clients will include the _id field and generate an ObjectId before sending the insert operation to MongoDB; however, if the client sends a document without an _id field, the mongod will add the _id field and generate the ObjectId.
Update
If the document contains an _id field, then the save() method is equivalent to an update with the upsert option set to true and the query predicate on the _id field.
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