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db.collection.insertOne()

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  • Definition
  • Behaviors
  • Examples

Definition

db.collection.insertOne()

Important

mongosh Method

This page documents a mongosh method. This is not the documentation for database commands or language-specific drivers, such as Node.js.

For the database command, see the insert command.

For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.

For the legacy mongo shell documentation, refer to the documentation for the corresponding MongoDB Server release:

Inserts a single document into a collection.

The insertOne() method has the following syntax:

db.collection.insertOne(
   <document>,
   {
      writeConcern: <document>
   }
)
Parameter
Type
Description
document
document
A document to insert into the collection.
writeConcern
document

Optional. 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 as true if the operation ran with write concern or false 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

See also:

Create Collections and Indexes In a Transaction

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:

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db.collection.insert()