This post should get you started to use Sphinx on your Rails application. I only try to cover some of core topics of Sphinx that is Indexing and Searching.

Sphinx

Sphinx is an open source full text search server, designed from the ground up with performance, relevance (aka search quality), and integration simplicity in mind. It's written in C++ and works on Linux (RedHat, Ubuntu, etc), Windows, MacOS, Solaris, FreeBSD, and a few other systems.

Sphinx lets you either batch index and search data stored in an SQL database, NoSQL storage, or just files quickly and easily — or index and search data on the fly, working with Sphinx pretty much as with a database server.

Sphinx can directly access and index data stored in MySQL (all storage engines are supported), PostgreSQL, Oracle, Microsoft SQL Server, SQLite, Drizzle, and anything else that supports ODBC.

Thingking Sphinx

A Ruby connector between Sphinx and ActiveRecord

The Rails application

Let say I have a simple blog application and I would like to add search functionality to it.

Install Sphinx

Download the code from Sphinx website. The standard set of commands should install it with MySQL support.

1. Extract the downloaded file

   tar xvfz sphinx-2.0.3-release.tar.gz

2. Do the usual make steps

   ./configure
   make
   sudo make install

Install Thinking Sphinx

Add the following to your Gemfile

gem 'thinking-sphinx'

then run bundle install.

Indexing

The first thing you want to do after having thingking-sphinx is installed is to set up the indexes for your model.

class Post < ActiveRecord::Base
  define_index do
    indexes title, :sortable => true
    indexes content

    has created_at, updated_at
  end
end

Now some sort explaination. Why do we define indexes? Sphinx daemon talk to a collection of indexes. Each index tracks a set of documents and each document is made up of fields and attributes. From the snippet above, title and content are fields. They are used as the content of your search queries. After the fields, there are attributes. Attributes are used for sorting, filtering and grouping your search results.

Now let's run the rake task to get Sphinx process the data

rake ts:index

You will see a message like below

...
collected 3 docs ...
...

The number after 'collected' indicate rows count in the table, in our example, "posts". A row is defined as a document.

You don't need to re-index if you adding new data into the table unless you have made structural changes (like adding or removing fields). If you need to re-index, it can be done through a single rake task

rake ts:rebuild

Searching

Before you can search using Post model, you need to let the Sphinx daemon running.

rake ts:start

If everything is good to go, you will see a messagce much like this

Started successfully (pid 8379).

Now let's add a simple search form to the post index page.

<%= form_tag posts_path, :method => :get do %>
  <%= label_tag 'query', 'Search' %>
  <%= text_field_tag 'query' %>
  <%= submit_tag 'Go' %>
  <% end %>

Then in your controller index method use Post.search

@posts = params[:query].blank? ? Post.all : Post.search(params[:query])

Now go the blog application and try the new search form.

Summary

Sphinx enable you to setup a search engine for your application. It is faster then just store the searchable content in plain database table

The Thinking Sphinx gems make it easier to integrate Sphinx with existing Rails application. You can have a complex search logic without having to write any complex SQL queries.

There are plenty more Sphinx features to explore. Once you have done with the basic stuff, I urge you to try more advance topics.