Bulk Write Operations

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Overview

Sample Data
Create a Bulk Write Instance
Define the Write Operations
Insert Operations
Update Operations
Replace Operations
Delete Operations
Run the Bulk Operation
Customize Bulk Write Operations
Return Value
Additional Information
API Documentation

Overview

In this guide, you can learn how to perform multiple write operations in a single database call by using bulk write operations.

Consider a scenario in which you want to insert a document into a collection, update multiple other documents, then delete a document. If you use individual methods, each operation requires its own database call. Instead, you can use a bulk operation to reduce the number of calls to the database.

Sample Data

The examples in this guide use the restaurants collection in the sample_restaurants database from the Atlas sample datasets. To access this collection from your C++ application, instantiate a mongocxx::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.

Create a Bulk Write Instance

Before running a bulk write operation, call the create_bulk_write() method on a collection. This method returns an instance of the mongocxx::bulk_write class that you can use to store instructions about which types of bulk writes to perform.

The following example calls the create_bulk_write() method on the restaurants collection:

auto bulk = collection.create_bulk_write();

You can then append write models to your mongocxx::bulk_write instance to define the bulk operation. For more information, see the following Define the Write Operations section.

Define the Write Operations

For each write operation you want to perform, create an instance of one of the following model classes:

mongocxx::model::insert_one
mongocxx::model::update_one
mongocxx::model::update_many
mongocxx::model::replace_one
mongocxx::model::delete_one
mongocxx::model::delete_many

Then, append each write model to the mongocxx::bulk_write instance returned by the create_bulk_write() method.

The following sections show how to create and use instances of the preceding write model classes.

Insert Operations

To perform an insert operation, create an instance of the mongocxx::model::insert_one class and specify the document you want to insert. Then, append the model instance to an instance of the mongocxx::bulk_write class.

The following example creates an instance of mongocxx::model::insert_one and appends it to a mongocxx::bulk_write instance called bulk:

auto insert_doc = make_document(kvp("name", "Mongo's Deli"),
                                kvp("cuisine", "Sandwiches"),
                                kvp("borough", "Manhattan"),
                                kvp("restaurant_id", "1234"));
mongocxx::model::insert_one insert_op{insert_doc.view()};
bulk.append(insert_op);

To insert multiple documents, create an instance of mongocxx::model::insert_one for each document.

Update Operations

To update a document, create an instance of mongocxx::model::update_one. This model instructs the driver to update the first document that matches your query filter. Then, append the model instance to an instance of the mongocxx::bulk_write class.

Pass the following arguments to the mongocxx::model::update_one model:

Query filter document, which specifies the criteria used to match documents in your collection.
Update document, which specifies the kind of update to perform. For more information about update operations, see the Field Update Operators guide in the MongoDB Server manual.

The following example creates an instance of mongocxx::model::update_one and appends it to a mongocxx::bulk_write instance called bulk:

auto filter_doc = make_document(kvp("name", "Mongo's Deli"));
auto update_doc = make_document(kvp("$set", make_document(kvp("cuisine", "Sandwiches and Salads"))));
mongocxx::model::update_one update_op{filter_doc.view(), update_doc.view()};
bulk.append(update_op);

To update multiple documents, create an instance of mongocxx::model::update_many and pass in the same arguments. This model instructs the driver to update all documents that match your query filter.

The following example creates an instance of mongocxx::model::update_many and appends it to bulk:

auto filter_doc = make_document(kvp("name", "Mongo's Deli"));
auto update_doc = make_document(kvp("$set", make_document(kvp("cuisine", "Sandwiches and Salads"))));
mongocxx::model::update_many update_op{filter_doc.view(), update_doc.view()};
bulk.append(update_op);

Replace Operations

A replace operation removes all fields and values of a specified document and replaces them with new ones. To perform a replace operation, create an instance of the mongocxx::model::replace_one class and pass it a query filter and the fields and values you want to store in the matching document. Then, append the model instance to an instance of the mongocxx::bulk_write class.

The following example creates an instance of mongocxx::model::replace_one and appends it to a mongocxx::bulk_write instance called bulk:

auto filter_doc = make_document(kvp("restaurant_id", "1234"));
auto replace_doc = make_document(kvp("name", "Mongo's Deli"),
                                kvp("cuisine", "Sandwiches and Salads"),
                                kvp("borough", "Brooklyn"),
                                kvp("restaurant_id", "5678"));
mongocxx::model::replace_one replace_op{filter_doc.view(), replace_doc.view()};
bulk.append(replace_op);

To replace multiple documents, you must create a new instance of mongocxx::model::replace_one for each document.

Delete Operations

To delete a document, create an instance of the mongocxx::model::delete_one class and pass in a query filter specifying the document you want to delete. This model instructs the driver to delete only the first document that matches your query filter. Then, append the model instance to an instance of the mongocxx::bulk_write class.

The following example creates an instance of mongocxx::model::delete_one and appends it to a mongocxx::bulk_write instance called bulk:

auto filter_doc = make_document(kvp("restaurant_id", "5678"));
mongocxx::model::delete_one delete_op{filter_doc.view()};
bulk.append(delete_op);

To delete multiple documents, create an instance of the mongocxx::model::delete_many class and pass in a query filter specifying the document you want to delete. This model instructs the driver to delete all documents that match your query filter.

The following example creates an instance of mongocxx::model::delete_many and appends it to bulk:

auto filter_doc = make_document(kvp("borough", "Manhattan"));
mongocxx::model::delete_many delete_op{filter_doc.view()};
bulk.append(delete_op);

Run the Bulk Operation

To run a bulk operation, call the execute() method on an instance of the mongocxx::bulk_write class that contains your write models. By default, the execute() method runs the operations in the order they're appended to the mongocxx::bulk_write instance.

The following example performs the insert, update, replace, and delete operations specified in the preceding sections of this guide by appending each corresponding write model to an instance of mongocxx::bulk_write and calling the execute() method. Then, it prints the number of modified documents:

auto bulk = collection.create_bulk_write();
// Specifies documents to insert, update, replace, or delete
auto insert_doc = make_document(kvp("name", "Mongo's Deli"),
                                kvp("cuisine", "Sandwiches"),
                                kvp("borough", "Manhattan"),
                                kvp("restaurant_id", "1234"));
auto update_filter = make_document(kvp("name", "Mongo's Deli"));
auto update_doc = make_document(kvp("$set", make_document(kvp("cuisine", "Sandwiches and Salads"))));
auto replace_filter = make_document(kvp("restaurant_id", "1234"));
auto replace_doc = make_document(kvp("name", "Mongo's Deli"),
                                kvp("cuisine", "Sandwiches and Salads"),
                                kvp("borough", "Brooklyn"),
                                kvp("restaurant_id", "5678"));
auto delete_filter = make_document(kvp("borough", "Manhattan"));
// Creates write models for each write operation using the preceding documents
mongocxx::model::insert_one insert_op{insert_doc.view()};
mongocxx::model::update_many update_op{update_filter.view(), update_doc.view()};
mongocxx::model::replace_one replace_op{replace_filter.view(), replace_doc.view()};
mongocxx::model::delete_many delete_op{delete_filter.view()};
// Appends each write model to the bulk operation
bulk.append(insert_op);
bulk.append(update_op);
bulk.append(replace_op);
bulk.append(delete_op);
// Runs the bulk operation
auto result = bulk.execute();
std::cout << "Modified documents: " << result->modified_count() << std::endl;

Modified documents: 2

If any of the write operations fail, the C++ driver raises a mongocxx::bulk_write_exception and does not perform any further operations.

Tip

To learn more about the modified_count() function, see the Return Value section of this guide.

Customize Bulk Write Operations

You can modify the behavior of the create_bulk_write() method by passing an instance of the mongocxx::options::bulk_write class as a parameter. The following table describes the fields you can set in a mongocxx::options::bulk_write instance:

Field	Description
`ordered`	If `true`, the driver performs the write operations in the order provided. If an error occurs, the remaining operations are not attempted. If `false`, the driver performs the operations in an arbitrary order and attempts to perform all operations. Defaults to `true`.
`bypass_document_validation`	Specifies whether the operation bypasses document-level validation. For more information, see Schema Validation in the MongoDB Server manual. Defaults to `false`.
`write_concern`	Specifies the write concern for the bulk operation. For more information, see Write Concern in the MongoDB Server manual.
`comment`	Attaches a comment to the operation. For more information, see the delete command fields guide in the MongoDB Server manual.
`let`	Specifies a document with a list of values to improve operation readability. Values must be constant or closed expressions that don't reference document fields. For more information, see the let statement in the MongoDB Server manual.

The following example calls the create_bulk_write() method from the Create a Bulk Write Instance example on this page, but sets the ordered field of a mongocxx::options::bulk_write instance to false:

mongocxx::options::bulk_write opts;
opts.ordered(false);
auto bulk = collection.create_bulk_write(opts);

If any of the write operations in an unordered bulk write fail, the C++ driver reports the errors only after attempting all operations.

Note

Unordered bulk operations do not guarantee order of execution. The order can differ from the way you list them to optimize the runtime.

Return Value

The execute() method returns an instance of the mongocxx::result::bulk_write class. The mongocxx::result::bulk_write class contains the following member functions:

Function	Description
`deleted_count()`	Returns the number of documents deleted, if any.
`inserted_count()`	Returns the number of documents inserted, if any.
`matched_count()`	Returns the number of documents matched for an update, if applicable.
`modified_count()`	Returns the number of documents modified, if any.
`upserted_count()`	Returns the number of documents upserted, if any.
`upserted_ids()`	Returns a map of the operation's index to the `_id` of the upserted documents, if applicable.

Additional Information

To learn how to perform individual write operations, see the following guides:

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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