mongodb

What is mongodb?

The mongodb npm package is the official Node.js driver for MongoDB. It provides a high-level API to connect to and interact with MongoDB databases. With this package, developers can perform CRUD operations, manage database connections, and work with MongoDB features like transactions, indexes, and aggregation.

What are mongodb's main functionalities?

Connecting to a MongoDB database

This code sample demonstrates how to connect to a MongoDB database using the MongoClient object provided by the mongodb package.

const { MongoClient } = require('mongodb');
const url = 'mongodb://localhost:27017';
const client = new MongoClient(url);
async function connect() {
  try {
    await client.connect();
    console.log('Connected to MongoDB');
  } catch (e) {
    console.error(e);
  }
}
connect();

CRUD Operations

This code sample shows how to perform CRUD (Create, Read, Update, Delete) operations on a MongoDB collection using the mongodb package.

const { MongoClient } = require('mongodb');
const url = 'mongodb://localhost:27017';
const client = new MongoClient(url);
const dbName = 'myDatabase';
async function crudOperations() {
  try {
    await client.connect();
    const db = client.db(dbName);
    const collection = db.collection('documents');

    // Create a document
    await collection.insertOne({ a: 1 });

    // Read documents
    const docs = await collection.find({}).toArray();

    // Update a document
    await collection.updateOne({ a: 1 }, { $set: { b: 1 } });

    // Delete a document
    await collection.deleteOne({ b: 1 });
  } catch (e) {
    console.error(e);
  } finally {
    await client.close();
  }
}
crudOperations();

Index Management

This code sample illustrates how to manage indexes in a MongoDB collection, including creating an index and listing all indexes.

const { MongoClient } = require('mongodb');
const url = 'mongodb://localhost:27017';
const client = new MongoClient(url);
const dbName = 'myDatabase';
async function manageIndexes() {
  try {
    await client.connect();
    const db = client.db(dbName);
    const collection = db.collection('documents');

    // Create an index
    await collection.createIndex({ a: 1 });

    // List indexes
    const indexes = await collection.indexes();
    console.log(indexes);
  } catch (e) {
    console.error(e);
  } finally {
    await client.close();
  }
}
manageIndexes();

Aggregation

This code sample demonstrates how to use the aggregation framework provided by MongoDB to process data and compute aggregated results.

const { MongoClient } = require('mongodb');
const url = 'mongodb://localhost:27017';
const client = new MongoClient(url);
const dbName = 'myDatabase';
async function aggregateData() {
  try {
    await client.connect();
    const db = client.db(dbName);
    const collection = db.collection('documents');

    // Perform an aggregation query
    const aggregation = await collection.aggregate([
      { $match: { a: 1 } },
      { $group: { _id: '$b', total: { $sum: 1 } } }
    ]).toArray();
    console.log(aggregation);
  } catch (e) {
    console.error(e);
  } finally {
    await client.close();
  }
}
aggregateData();

Other packages similar to mongodb

mongoose

Mongoose is an Object Data Modeling (ODM) library for MongoDB and Node.js. It manages relationships between data, provides schema validation, and is used to translate between objects in code and the representation of those objects in MongoDB. Mongoose offers a more structured approach to data handling with predefined schemas compared to the flexibility of the mongodb package.

couchbase

Couchbase is the official Node.js client library for the Couchbase database. While Couchbase is a different NoSQL database system with its own set of features and capabilities, the couchbase npm package offers similar functionalities in terms of CRUD operations, connection management, and querying as the mongodb package does for MongoDB.

redis

Redis is an in-memory data structure store, used as a database, cache, and message broker. The npm package for Redis provides Node.js bindings to the Redis server. It is similar to mongodb in that it allows for data storage and retrieval, but it operates in-memory and is typically used for different use cases such as caching.

README

Install

To install the most recent release from npm, run:

npm install mongodb

To install from the latest from the repository, run::

npm install path/to/node-mongodb-native

Community

Check out the google group node-mongodb-native for questions/answers from users of the driver.

Introduction

This is a node.js driver for MongoDB. It's a port (or close to a port) of the libary for ruby at http://github.com/mongodb/mongo-ruby-driver/.

A simple example of inserting a document.

var client = new Db('test', new Server("127.0.0.1", 27017, {})),
    test = function (err, collection) {
      collection.insert({a:2}, function(err, docs) {

        collection.count(function(err, count) {
          test.assertEquals(1, count);
        });

        // Locate all the entries using find
        collection.find().toArray(function(err, results) {
          test.assertEquals(1, results.length);
          test.assertTrue(results.a === 2);

          // Let's close the db
          client.close();
        });
      });
    };

client.open(function(err, p_client) {
  client.collection('test_insert', test);
});

Data types

To store and retrieve the non-JSON MongoDb primitives (ObjectID, Long, Binary, Timestamp, DBRef, Code), you have to use one of the types from the bson_serializer.

In particular, every document has a unique _id which can be almost any type, and by default a 12-byte ObjectID is created. ObjectIDs can be represented as 24-digit hexadecimal strings, but you must convert the string back into an ObjectID before you can use it in the database. For example:

var idString = '4e4e1638c85e808431000003';
collection.findOne({_id: new client.bson_serializer.ObjectId(idString)}, console.log)  // ok
collection.findOne({_id: idString}, console.log)  // wrong! callback gets undefined

Here are the constructors the non-Javascript BSON primitive types:

var client = new Db(...);
new client.bson_serializer.Long(numberString)
new client.bson_serializer.ObjectID(hexString)
new client.bson_serializer.Timestamp()  // the actual unique number is generated on insert.
new client.bson_serializer.DBRef(collectionName, id, dbName)
new client.bson_serializer.Binary(buffer)  // takes a string or Buffer
new client.bson_serializer.Code(code, [context])

The C/C++ bson parser/serializer

From V0.8.0 to V0.9.6.9, the Javascript bson parser was slower than an optional C/C++ bson parser. As of V0.9.6.9+, due to performance improvements in the Javascript parser, the C/C++ perser is deprecated and is not installed by default anymore.

If you are running a version of this library has the C/C++ parser compiled, to enable the driver to use the C/C++ bson parser pass it the option native_parser:true like below

// using Deprecated native_parser:
var client = new Db('integration_tests_20',
                    new Server("127.0.0.1", 27017),
                    {native_parser:true});

Since objects created using the C/C++ bson parser are incompatible with a client configured to use the Javascript bson parser and vice versa, you should call constructors using client.bson_serializer as described above (don't use mongodb.BSONNative and mongodb.BSONPure directly).

GitHub information

The source code is available at http://github.com/christkv/node-mongodb-native. You can either clone the repository or download a tarball of the latest release.

Once you have the source you can test the driver by running

$ make test

in the main directory. You will need to have a mongo instance running on localhost for the integration tests to pass.

Examples

For examples look in the examples/ directory. You can execute the examples using node.

$ cd examples
$ node queries.js

GridStore

The GridStore class allows for storage of binary files in mongoDB using the mongoDB defined files and chunks collection definition.

For more information have a look at Gridstore

Replicasets

For more information about how to connect to a replicaset have a look at Replicasets

Notes

The current version does not support connection pooling, but it will be implemented soon.

Primary Key Factories

Defining your own primary key factory allows you to generate your own series of id's (this could f.ex be to use something like ISBN numbers). The generated the id needs to be a 12 byte long "string".

Simple example below

// Custom factory (need to provide a 12 byte array);
CustomPKFactory = function() {}
CustomPKFactory.prototype = new Object();
CustomPKFactory.createPk = function() {
  return new ObjectID("aaaaaaaaaaaa");
}

var p_client = new Db('integration_tests_20', new Server("127.0.0.1", 27017, {}), {'pk':CustomPKFactory});
p_client.open(function(err, p_client) {
  p_client.dropDatabase(function(err, done) {
    p_client.createCollection('test_custom_key', function(err, collection) {
      collection.insert({'a':1}, function(err, docs) {
        collection.find({'_id':new ObjectID("aaaaaaaaaaaa")}, function(err, cursor) {
          cursor.toArray(function(err, items) {
            test.assertEquals(1, items.length);

            // Let's close the db
            p_client.close();
          });
        });
      });
    });
  });
});

Strict mode

Each database has an optional strict mode. If it is set then asking for a collection that does not exist will return an Error object in the callback. Similarly if you attempt to create a collection that already exists. Strict is provided for convenience.

var error_client = new Db('integration_tests_', new Server("127.0.0.1", 27017, {auto_reconnect: false}), {strict:true});    
  test.assertEquals(true, error_client.strict);
  
  error_client.open(function(err, error_client) {
  error_client.collection('does-not-exist', function(err, collection) {
    test.assertTrue(err instanceof Error);
    test.assertEquals("Collection does-not-exist does not exist. Currently in strict mode.", err.message);
  });

  error_client.createCollection('test_strict_access_collection', function(err, collection) {
    error_client.collection('test_strict_access_collection', function(err, collection) {
      test.assertTrue(collection instanceof Collection);
      // Let's close the db
      error_client.close();
    });
  });
});

Documentation

If this document doesn't answer your questions, see the source of Collection or Cursor, or the documentation at MongoDB for query and update formats.

Find

The find method is actually a factory method to create Cursor objects. A Cursor lazily uses the connection the first time you call nextObject, each, or toArray.

The basic operation on a cursor is the nextObject method that fetches the next matching document from the database. The convenience methods each and toArray call nextObject until the cursor is exhausted.

Signatures:

var cursor = collection.find(query, [fields], options);
cursor.sort(fields).limit(n).skip(m).

cursor.nextObject(function(err, doc) {});
cursor.each(function(err, doc) {});
cursor.toArray(function(err, docs) {});

cursor.rewind()  // reset the cursor to its initial state.

Useful chainable methods of cursor. These can optionally be options of find instead of method calls:

• .limit(n).skip(m) to control paging.
• .sort(fields) Order by the given fields. There are several equivalent syntaxes:
  • .sort({field1: -1, field2: 1}) descending by field1, then ascending by field2.
  • .sort([['field1', 'desc'], ['field2', 'asc']]) same as above
  • .sort([['field1', 'desc'], 'field2']) same as above
  • .sort('field1') ascending by field1

Other options of find:

• fields the fields to fetch (to avoid transferring the entire document)
• tailable if true, makes the cursor tailable.
• batchSize The number of the subset of results to request the database to return for every request. This should initially be greater than 1 otherwise the database will automatically close the cursor. The batch size can be set to 1 with batchSize(n, function(err){}) after performing the initial query to the database.
• hint See Optimization: hint.
• explain turns this into an explain query. You can also call explain() on any cursor to fetch the explanation.
• snapshot prevents documents that are updated while the query is active from being returned multiple times. See more details about query snapshots.
• timeout if false, asks MongoDb not to time out this cursor after an inactivity period.

For information on how to create queries, see the MongoDB section on querying.

var mongodb = require('mongodb');
var server = new mongodb.Server("127.0.0.1", 27017, {});
new mongodb.Db('test', server, {}).open(function (error, client) {
  if (error) throw error;
  var collection = new mongodb.Collection(client, 'test_collection');
  collection.find({}, {limit:10}).toArray(function(err, docs) {
    console.dir(docs);
  });
});

Insert

Signature:

collection.insert(docs, options, [callback]);

where docs can be a single document or an array of documents.

Useful options:

• safe:true Should always set if you have a callback.

See also: MongoDB docs for insert.

var mongodb = require('mongodb');
var server = new mongodb.Server("127.0.0.1", 27017, {});
new mongodb.Db('test', server, {}).open(function (error, client) {
  if (error) throw error;
  var collection = new mongodb.Collection(client, 'test_collection');
  collection.insert({hello: 'world'}, {safe:true},
                    function(err, objects) {
    if (err) console.warn(err.message);
    if (err && err.message.indexOf('E11000 ') !== -1) {
      // this _id was already inserted in the database
    }
  });
});

Note that there's no reason to pass a callback to the insert or update commands unless you use the safe:true option. If you don't specify safe:true, then your callback will be called immediately.

Update; update and insert (upsert)

The update operation will update the first document that matches your query (or all documents that match if you use multi:true). If safe:true, upsert is not set, and no documents match, your callback will be given an error.

See the MongoDB docs for the modifier ($inc, $set, $push, etc.) formats.

Signature:

collection.update(criteria, objNew, options, [callback]);

Useful options:

• safe:true Should always set if you have a callback.
• multi:true If set, all matching documents are updated, not just the first.
• upsert:true Atomically inserts the document if no documents matched.

Example for update:

var mongodb = require('mongodb');
var server = new mongodb.Server("127.0.0.1", 27017, {});
new mongodb.Db('test', server, {}).open(function (error, client) {
  if (error) throw error;
  var collection = new mongodb.Collection(client, 'test_collection');
  collection.update({hi: 'here'}, {$set: {hi: 'there'}}, {safe:true},
                    function(err) {
    if (err) console.warn(err.message);
    else console.log('successfully updated');
  });
});

Find and modify

findAndModify is like update, but it also gives the updated document to your callback. But there are a few key differences between findAndModify and update:

1. The signatures differ.
2. You can only findAndModify a single item, not multiple items.
3. The callback does not get an error when the item doesn't exist, just an undefined object.

Signature:

collection.findAndModify(query, sort, update, options, callback)

The sort parameter is used to specify which object to operate on, if more than one document matches. It takes the same format as the cursor sort (see Connection.find above).

See the MongoDB docs for findAndModify for more details.

Useful options:

• remove:true set to a true to remove the object before returning
• new:true set to true if you want to return the modified object rather than the original. Ignored for remove.
• upsert:true Atomically inserts the document if no documents matched.

Example for findAndModify:

var mongodb = require('mongodb');
var server = new mongodb.Server("127.0.0.1", 27017, {});
new mongodb.Db('test', server, {}).open(function (error, client) {
  if (error) throw error;
  var collection = new mongodb.Collection(client, 'test_collection');
  collection.findAndModify({hello: 'world'}, [['_id','asc']], {$set: {hi: 'there'}}, {},
                    function(err, object) {
    if (err) console.warn(err.message);
    else console.dir(object);  // undefined if no matching object exists.
  });
});

Save

The save method is a shorthand for upsert if the document contains an _id, or an insert if there is no _id.

Sponsors

Just as Felix Geisendörfer I'm also working on the driver for my own startup and this driver is a big project that also benefits other companies who are using MongoDB.

If your company could benefit from a even better-engineered node.js mongodb driver I would appreciate any type of sponsorship you may be able to provide. All the sponsors will get a lifetime display in this readme, priority support and help on problems and votes on the roadmap decisions for the driver. If you are interested contact me on [e-mail] for details.

And I'm very thankful for code contributions. If you are interested in working on features please contact me so we can discuss API design and testing.

Release Notes

See HISTORY

Credits

1. 10gen
2. Google Closure Library
3. Jonas Raoni Soares Silva

Contributors

Aaron Heckmann, Christoph Pojer, Pau Ramon Revilla, Nathan White, Emmerman, Seth LaForge, Boris Filipov, Stefan Schärmeli, Tedde Lundgren, renctan, Sergey Ukustov, Ciaran Jessup, kuno, srimonti, Erik Abele, Pratik Daga, Slobodan Utvic, Kristina Chodorow, Yonathan Randolph, Brian Noguchi, Sam Epstein, James Harrison Fisher, Vladimir Dronnikov, Ben Hockey, Henrik Johansson, Simon Weare, Alex Gorbatchev, Shimon Doodkin, Kyle Mueller, Eran Hammer-Lahav, Marcin Ciszak, François de Metz, Vinay Pulim, nstielau, Adam Wiggins, entrinzikyl, Jeremy Selier, Ian Millington, Public Keating, andrewjstone, Christopher Stott, Corey Jewett, brettkiefer, Rob Holland, Senmiao Liu, heroic, gitfy

License

Copyright 2009 - 2010 Christian Amor Kvalheim.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.