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

Monitoring query performance

MongoDB provides a lot of tools for monitoring performance of the database. By default, it is configured to log only slow queries—those that consume more than 100 ms in database operations. It's very important to monitor these logs.

If you see any query commands taking a long time, in most cases it means that the fields need to be indexed as follows:

[conn23] query sodibee_development.authors query: { $query: { ... } ntoreturn:10 ntoskip:0 nscanned:17158 scanAndOrder:1 keyUpdates:0 numYields: 1 locks(micros) r:272157 nreturned:10 reslen:20221 169m

This query log has some interesting information as shown in the following table:




This is the client connection.


This is the command that was fired. It can be insert, update, and so on.


This is the database and the collection on which this query was fired.

{ $query: { ... }

This is the actual query that was fired.


This is 1000 unless...