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

Query selectors

The following is a list of all supported methods that are supported on any Mongoid class. The following table states the attributes of the query selectors, their usage, and description:


Book.all(reviews: ['good', 'excellent'])

This finds all the documents where the field (typically an array) matches all the values in the array. So, this means that reviews is an array inside the Book document, and it must contain at least two values good and excellent.

In case reviews is an embedded document, we can also write this like the following code:

Book.all("reviews.content" => ['good', 'excellent'])


Author.exists(books_count: true)

This finds all the documents in which the field exists.

:gt/:gte/:lt/:lte 1)

Author.lte(books_count: 10)

This finds all the documents in which count is greater than (:gt) or greater than or equal to (:gte) and lesser than (:lt) and lesser than or equal to (:lte).


:nin ['Gautam', 'Charles...