db.collection.insert()

Write Concern

The insert() method uses the insert command, which uses the default write concern. To specify a different write concern, include the write concern in the options parameter.

Create Collection

If the collection does not exist, then the insert() method will create the collection.

_id Field

If the document does not specify an _id field, then MongoDB will add the _id field and assign a unique ObjectId() for the document before inserting. Most drivers create an ObjectId and insert the _id field, but the mongod will create and populate the _id if the driver or application does not.

If the document contains an _id field, the _id value must be unique within the collection to avoid duplicate key error.

Transactions

db.collection.insert() can be used inside multi-document transactions.

Insert a Document without Specifying an _id Field

In the following example, the document passed to the insert() method does not contain the _id field:

db.products.insert( { item: "card", qty: 15 } )

During the insert, mongod will create the _id field and assign it a unique ObjectId() value, as verified by the inserted document:

{ "_id" : ObjectId("5063114bd386d8fadbd6b004"), "item" : "card", "qty" : 15 }

The ObjectId values are specific to the machine and time when the operation is run. As such, your values may differ from those in the example.

Insert a Document Specifying an _id Field

In the following example, the document passed to the insert() method includes the _id field. The value of _id must be unique within the collection to avoid duplicate key error.

db.products.insert( { _id: 10, item: "box", qty: 20 } )

The operation inserts the following document in the products collection:

{ "_id" : 10, "item" : "box", "qty" : 20 }

Insert Multiple Documents

The following example performs a bulk insert of three documents by passing an array of documents to the insert() method. By default, MongoDB performs an ordered insert. With ordered inserts, if an error occurs during an insert of one of the documents, MongoDB returns on error without processing the remaining documents in the array.

The documents in the array do not need to have the same fields. For instance, the first document in the array has an _id field and a type field. Because the second and third documents do not contain an _id field, mongod will create the _id field for the second and third documents during the insert:

db.products.insert(
   [
     { _id: 11, item: "pencil", qty: 50, type: "no.2" },
     { item: "pen", qty: 20 },
     { item: "eraser", qty: 25 }
   ]
)

The operation inserted the following three documents:

{ "_id" : 11, "item" : "pencil", "qty" : 50, "type" : "no.2" }
{ "_id" : ObjectId("51e0373c6f35bd826f47e9a0"), "item" : "pen", "qty" : 20 }
{ "_id" : ObjectId("51e0373c6f35bd826f47e9a1"), "item" : "eraser", "qty" : 25 }

Perform an Unordered Insert

The following example performs an unordered insert of three documents. With unordered inserts, if an error occurs during an insert of one of the documents, MongoDB continues to insert the remaining documents in the array.

db.products.insert(
   [
     { _id: 20, item: "lamp", qty: 50, type: "desk" },
     { _id: 21, item: "lamp", qty: 20, type: "floor" },
     { _id: 22, item: "bulk", qty: 100 }
   ],
   { ordered: false }
)

Override Default Write Concern

The following operation to a replica set specifies a write concern of w: 2 with a wtimeout of 5000 milliseconds. This operation either returns after the write propagates to both the primary and one secondary, or times out after 5 seconds.

db.products.insert(
    { item: "envelopes", qty : 100, type: "Clasp" },
    { writeConcern: { w: 2, wtimeout: 5000 } }
)

Successful Results

The insert() returns a WriteResult() object that contains the status of the operation. Upon success, the WriteResult() object contains information on the number of documents inserted:

WriteResult({ "nInserted" : 1 })

Write Concern Errors

If the insert() method encounters write concern errors, the results include the WriteResult.writeConcernError field:

WriteResult({
  "nInserted" : 1,
  "writeConcernError"({
     "code" : 64,
     "errmsg" : "waiting for replication timed out",
     "errInfo" : {
       "wtimeout" : true,
       "writeConcern" : {    // Added in MongoDB 4.4
         "w" : "majority",
         "wtimeout" : 100,
         "provenance" : "getLastErrorDefaults"
       }
     }
})

Errors Unrelated to Write Concern

If the insert() method encounters a non-write concern error, the results include the WriteResult.writeError field:

WriteResult({
   "nInserted" : 0,
   "writeError" : {
      "code" : 11000,
      "errmsg" : "insertDocument :: caused by :: 11000 E11000 duplicate key error index: test.foo.$_id_  dup key: { : 1.0 }"
   }
})