Optimize Queries with Indexes

Overview

On this page, you can see copyable code examples that demonstrate how to use the C++ driver to work with common types of indexes.

To use an example from this page, copy the code example into the sample application or your own application. Be sure to replace all placeholders in the code examples, such as <connection string>, with the relevant values for your MongoDB deployment.

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#include <iostream>
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#include <bsoncxx/builder/basic/document.hpp>
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#include <bsoncxx/json.hpp>
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#include <mongocxx/client.hpp>
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#include <mongocxx/exception/exception.hpp>
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#include <mongocxx/instance.hpp>
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#include <mongocxx/uri.hpp>
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using bsoncxx::builder::basic::kvp;
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using bsoncxx::builder::basic::make_document;
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int main() {
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    try {
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        mongocxx::instance instance;
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        mongocxx::uri uri("<connection string>");
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        mongocxx::client client(uri);
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        auto database = client["<database name>"];
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        auto collection = database["<collection name>"];
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        // Start example code here
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        // End example code here
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    } catch (const mongocxx::exception& e) {
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        std::cout << "An exception occurred: " << e.what() << "\n";
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        return EXIT_FAILURE;
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    }
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    return EXIT_SUCCESS;
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}

Single-Field Index

The following code shows how to create an ascending single-field index:

auto index_specification = make_document(kvp("<fieldName>", 1));
auto result = collection.create_index(index_specification.view());
std::cout << "Index created: " << bsoncxx::to_json(result) << std::endl;

Index created: { "name" : "fieldName_1" }

To learn more about single-field indexes, see the Single Field Indexes guide.

Compound Index

The following code shows how to create a descending compound index:

auto index_specification = make_document(kvp("<fieldName1>", -1), kvp("<fieldName2>", -1));
auto result = collection.create_index(index_specification.view());
std::cout << "Index created: " << bsoncxx::to_json(result) << std::endl;

Index created: { "name" : "fieldName1_-1_fieldName2_-1" }

To learn more about compound indexes, see the Compound Indexes guide.

Remove an Index

The following code shows how to remove an index:

collection.indexes().drop_one("<indexName>");
std::cout << "Index dropped." << std::endl;

Index dropped.

To learn more about removing indexes, see the Remove an Index section of the Work With Indexes guide.

Remove All Indexes

The following code shows how to remove all indexes in a collection:

collection.indexes().drop_all();
std::cout << "All indexes removed." << std::endl;

All indexes removed.

To learn more about removing indexes, see the Remove an Index section of the Work With Indexes guide.

Atlas Search Index Management

The following sections contain code examples that describe how to manage Atlas Search indexes. To learn more about Atlas Search indexes, see the Atlas Search Indexes guide.

// Create an index model with your index name and definition
auto siv = collection.search_indexes();
auto name = "<searchIndexName>";
auto definition = make_document(kvp("mappings", make_document(kvp("dynamic", true))));
auto model = mongocxx::search_index_model(name, definition.view());
// Create the search index
auto result = siv.create_one(model);
std::cout << "New index name: " << result << std::endl;

New index name: searchIndexName

auto siv = collection.search_indexes();
auto result = siv.list(); 
for (const auto &idx : result) {
    std::cout << bsoncxx::to_json(idx) << std::endl;
}

auto siv = collection.search_indexes();
auto update_fields = make_document(kvp("<fieldName>", make_document(kvp("type", "<fieldType>"))));
auto update_definition = make_document(kvp("mappings", make_document(kvp("dynamic", false), kvp("fields", update_fields))));
siv.update_one("<searchIndexName>", update_definition.view());

auto siv = collection.search_indexes();
siv.drop_one("<searchIndexName>");