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Write Data to MongoDB

Insert Documents

On this page

  • Overview
  • Sample Data
  • The _id Field
  • Insert One Document
  • Insert Multiple Documents
  • Modify Insert Behavior
  • Example
  • Additional Information
  • API Documentation

Overview

In this guide, you can learn how to use the C++ driver to add documents to a MongoDB collection by performing insert operations.

An insert operation inserts one or more documents into a MongoDB collection. You can perform an insert operation by using the insert_one() method to insert a single document or the insert_many() method to insert one or more documents.

Sample Data

The examples in this guide use the sample_restaurants.restaurants collection from the Atlas sample datasets. To access this collection from your C++ application, instantiate a client that connects to an Atlas cluster and assign the following values to your db and collection variables:

auto db = client["sample_restaurants"];
auto collection = db["restaurants"];

To learn how to create a free MongoDB Atlas cluster and load the sample datasets, see the Get Started with Atlas guide.

The _id Field

In a MongoDB collection, each document must contain an _id field with a unique field value.

MongoDB allows you to manage this field in two ways:

  • You can set this field for each document yourself, ensuring each _id field value is unique.

  • You can let the driver automatically generate unique ObjectId values for each document _id.

Unless you can guarantee uniqueness, we recommend letting the driver automatically generate _id values.

Note

Duplicate _id values violate unique index constraints, which causes the driver to return a mongocxx::bulk_write_exception error.

To learn more about the _id field, see the Unique Indexes guide in the MongoDB Server manual.

To learn more about document structure and rules, see the Documents guide in the MongoDB Server manual.

Insert One Document

To add a single document to a MongoDB collection, call the insert_one() method and pass the document you want to add.

The following example inserts a document into the restaurants collection:

auto result = collection.insert_one(make_document(kvp("name", "Mongo's Burgers")));

Insert Multiple Documents

To add multiple documents to a MongoDB collection, call the insert_many() method and pass a vector that stores the documents you want to add.

The following example inserts two documents into the restaurants collection:

std::vector<bsoncxx::document::value> restaurants;
restaurants.push_back(make_document(kvp("name", "Mongo's Burgers")));
restaurants.push_back(make_document(kvp("name", "Mongo's Pizza")));
auto result = collection.insert_many(restaurants);

Modify Insert Behavior

You can modify the behavior of the insert_one() and insert_many() methods by passing an instance of the mongocxx::options::insert class as an optional parameter. The following table describes the fields you can set in a mongocxx::options::insert instance:

Field
Description
bypass_document_validation
If set to true, allows the write to opt out of document-level validation.
Defaults to false.
Type: bool
write_concern
Sets the write concern for the operation.
Defaults to the write concern of the namespace.
Type: mongocxx::write_concern
ordered
If set to true, the operation stops inserting documents when one insert fails. If false, the operation continues to insert the remaining documents when one insert fails.
Defaults to true.
Type: bool
comment
A comment to attach to the operation. For more information, see the insert command fields guide in the MongoDB Server manual.
Type: bsoncxx::types::bson_value::view_or_value

Example

The following code uses the insert_many() method to insert three new documents into a collection. Because the bypass_document_validation field is set to true in a mongocxx::options::insert instance, this insert operation bypasses document-level validation:

std::vector<bsoncxx::document::value> docs;
docs.push_back(make_document(kvp("name", "Mongo's Burgers")));
docs.push_back(make_document(kvp("name", "Mongo's Pizza")));
docs.push_back(make_document(kvp("name", "Mongo's Tacos")));
mongocxx::options::insert opts;
opts.bypass_document_validation(true);
auto result = collection.insert_many(docs, opts);

Additional Information

For runnable code examples of inserting documents with the C++ driver, see Write Data to MongoDB.

API Documentation

To learn more about any of the methods or types discussed in this guide, see the following API documentation:

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