Book Image

Learning Mongoid

By : Gautam Rege
Book Image

Learning Mongoid

By: Gautam Rege

Overview of this book

Mongoid helps you to leverage the power of schema-less and efficient document-based design, dynamic queries, and atomic modifier operations. Mongoid eases the work of Ruby developers while they are working on complex frameworks. Starting with why and how you should use Mongoid, this book covers the various components of Mongoid. It then delves deeper into the detail of queries and relations, and you will learn some tips and tricks on improving performance. With this book, you will be able to build robust and large-scale web applications with Mongoid and Rails. Starting with the basics, this book introduces you to components such as moped and origin, and how information is managed, learn about the various datatypes, embedded documents, arrays, and hashes. You will learn how a document is stored and manipulated with callbacks, validations, and even atomic updates. This book will then show you the querying mechanism in detail, right from simple to complex queries, and even explains eager loading, lazy evaluation, and chaining of queries. Finally, this book will explain the importance of performance tuning and how to use the right indexes. It also explains MapReduce and the Aggregation Framework.
Table of Contents (14 chapters)
Learning Mongoid
About the Author
About the Reviewers


Indexing ensures faster reads. However, indexes have a hit on writes, that is, creation and updating of documents. There are various types of indexes supported by MongoDB. We have already seen these various types of indexes earlier.


Indexes are not automatically created. When we specify the index in our model, we need to run the rake db:mongoid:create_indexes command to create them. To get a list of database tasks that Mongoid supports, issue the rake –T db:mongoid command.

The following table gives a quick summary of the various options that are available for index creation:





index({name: 1})
index({name: 1}, {name: 'n' })
index({"address.location" => 1})

This is the typical index that gets created. The index name gets saved as a concatenation of the field names unless the :name option is provided. Also, notice that indexes can be ordered in ascending or descending order using 1 and -1, respectively.