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db.collection.insertOne()
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Definition
db.collection.insertOne()
Important
mongosh Method
This is a
mongosh
method. This is not the documentation forNode.js
or other programming language specific driver methods.In most cases,
mongosh
methods work the same way as the legacymongo
shell methods. However, some legacy methods are unavailable inmongosh
.For the legacy
mongo
shell documentation, refer to the documentation for the corresponding MongoDB Server release:For MongoDB API drivers, refer to the language specific MongoDB driver documentation.
Inserts a single document into a collection.
The
insertOne()
method has the following syntax:db.collection.insertOne( <document>, { writeConcern: <document> } ) ParameterTypeDescriptiondocument
documentA document to insert into the collection.writeConcern
documentOptional. A document expressing the write concern. Omit to use the default write concern.
Do not explicitly set the write concern for the operation if run in a transaction. To use write concern with transactions, see Transactions and Write Concern.
Returns: A document containing: A boolean
acknowledged
astrue
if the operation ran with write concern orfalse
if write concern was disabled.A field
insertedId
with the_id
value of the inserted document.
Behaviors
Collection Creation
If the collection does not exist, then the
insertOne()
method creates the collection.
_id
Field
If the document does not specify an _id field, then mongod
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.
Explainability
insertOne()
is not compatible with
db.collection.explain()
.
Error Handling
On error, db.collection.insertOne()
throws either a writeError
or writeConcernError
exception.
Transactions
db.collection.insertOne()
can be used inside multi-document transactions.
Important
In most cases, multi-document transaction incurs a greater performance cost over single document writes, and the availability of multi-document transactions should not be a replacement for effective schema design. For many scenarios, the denormalized data model (embedded documents and arrays) will continue to be optimal for your data and use cases. That is, for many scenarios, modeling your data appropriately will minimize the need for multi-document transactions.
For additional transactions usage considerations (such as runtime limit and oplog size limit), see also Production Considerations.
Collection Creation in Transactions
Starting in MongoDB 4.4, you can create collections and indexes inside a multi-document transaction if the transaction is not a cross-shard write transaction.
Specifically, in MongoDB 4.4 and greater, if you specify an insert on a non-existing collection in a transaction, the collection is implicitly created.
In MongoDB 4.4 and earlier, the operation must be run on an existing collection.
Tip
Write Concerns and Transactions
Do not explicitly set the write concern for the operation if run in a transaction. To use write concern with transactions, see Transactions and Write Concern.
Examples
Insert a Document without Specifying an _id
Field
In the following example, the document passed to the
insertOne()
method does not contain the _id
field:
try { db.products.insertOne( { item: "card", qty: 15 } ); } catch (e) { print (e); };
The operation returns the following document:
{ "acknowledged" : true, "insertedId" : ObjectId("56fc40f9d735c28df206d078") }
Because the documents did not include _id
,
mongod
creates and adds the _id
field and
assigns it a unique ObjectId()
value.
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
insertOne()
method includes the _id
field.
The value of _id
must be unique within the collection to avoid
duplicate key error.
try { db.products.insertOne( { _id: 10, item: "box", qty: 20 } ); } catch (e) { print (e); }
The operation returns the following:
{ "acknowledged" : true, "insertedId" : 10 }
Inserting an duplicate value for any key that is part of a unique index, such as _id
, throws an exception. The following attempts to insert
a document with a _id
value that already exists:
try { db.products.insertOne( { _id: 10, "item" : "packing peanuts", "qty" : 200 } ); } catch (e) { print (e); }
Since _id: 10
already exists, the following exception is thrown:
WriteError({ "index" : 0, "code" : 11000, "errmsg" : "E11000 duplicate key error collection: inventory.products index: _id_ dup key: { : 10.0 }", "op" : { "_id" : 10, "item" : "packing peanuts", "qty" : 200 } })
Increase Write Concern
Given a three member replica set, the following operation specifies a
w
of majority
, wtimeout
of 100
:
try { db.products.insertOne( { "item": "envelopes", "qty": 100, type: "Self-Sealing" }, { writeConcern: { w : "majority", wtimeout : 100 } } ); } catch (e) { print (e); }
If the acknowledgement takes longer than the wtimeout
limit, the following
exception is thrown:
WriteConcernError({ "code" : 64, "errmsg" : "waiting for replication timed out", "errInfo" : { "wtimeout" : true, "writeConcern" : { // Added in MongoDB 4.4 "w" : "majority", "wtimeout" : 100, "provenance" : "getLastErrorDefaults" } } })
Tip
See also:
To insert multiple documents, see
db.collection.insertMany()