Book Image

Learn MongoDB 4.x

By : Doug Bierer
Book Image

Learn MongoDB 4.x

By: Doug Bierer

Overview of this book

When it comes to managing a high volume of unstructured and non-relational datasets, MongoDB is the defacto database management system (DBMS) for DBAs and data architects. This updated book includes the latest release and covers every feature in MongoDB 4.x, while helping you get hands-on with building a MongoDB database app. You’ll get to grips with MongoDB 4.x concepts such as indexes, database design, data modeling, authentication, and aggregation. As you progress, you’ll cover tasks such as performing routine operations when developing a dynamic database-driven website. Using examples, you’ll learn how to work with queries and regular database operations. The book will not only guide you through design and implementation, but also help you monitor operations to achieve optimal performance and secure your MongoDB database systems. You’ll also be introduced to advanced techniques such as aggregation, map-reduce, complex queries, and generating ad hoc financial reports on the fly. Later, the book shows you how to work with multiple collections as well as embedded arrays and documents, before finally exploring key topics such as replication, sharding, and security using practical examples. By the end of this book, you’ll be well-versed with MongoDB 4.x and be able to perform development and administrative tasks associated with this NoSQL database.
Table of Contents (22 chapters)
Section 1: Essentials
Section 2: Building a Database-Driven Web Application
Section 3: Digging Deeper
Section 4: Replication, Sharding, and Security in a Financial Environment
Working with Complex Documents Across Collections

Using ObjectId as a unique key

In the case of MongoDB, the equivalent of an RDBMS primary key would be the autogenerated ObjectId. You can reference this value via the alias _id. Unlike RDBMS sequences or auto-increment fields, however, the MongoDB _id field includes both sequential as well as random elements. It consists of 12 bytes broken down as follows:

  • A 4-byte value representing the number of seconds since midnight on January 1, 1970 (Unix epoch)
  • A 5-byte random value
  • A 3-byte counter (seeded by a random value)

The _id field could potentially be used when conducting cross-collection operations (see the discussion on DBRefs earlier in this chapter). There is a method, ObjectId.valueOf(), that returns a hexadecimal string of 24 characters. However, within your application code, or when performing an operation using the aggregation framework, as this field is actually an object (for example, ObjectId), you would need to perform further conversions before being able to use...