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

Document distribution within shards

For greater efficiency, the MongoDB sharded cluster balancer (the sharding mechanism) doesn't operate at the document level. Rather, documents are grouped into chunks. Which documents are placed into a given chunk is determined by the shard key range. Mongo shell helper methods exist that let you view the size of individual shards and manually move one or more chunks from one shard to another. This process is known as chunk migration (covered in the next chapter, Chapter 16, Sharded Cluster Management and Development).

Here is a diagram that illustrates the shard key's distributional role:

The overall diagram represents a sharded cluster. In this diagram, we're assuming the shard key is a field named X. Within each shard is a distribution of two chunks. Within each chunk is a group of documents. The key space for X ranges from its smallest value, labeled X:minKey,to its largest, labelled X:maxKey. The...