Adding advanced search functionality to your Rails app with Elasticsearch

Elasticsearch is an external service that offers powerful searching features. You can build a simple search feature for your Rails App using standard SQL queries. However when it comes to advanced features such as working with AND, OR statements and ranked results it is better to rely on a industrial strength external solution. Search is often at the core of any CRUD Rails App.

Set-up

Set up Elasticsearch locally

Install Java and Elasticsearch via Brew

  $ brew update
  $ brew install Caskroom/cask/java
  $ brew install elasticsearch

To run Elasticsearch simply type $ elasticsearch in your Terminal.

By default Elasticsearch runs on localhost:9200. You can test it with $ curl -X GET http://localhost:9200/

Set up Elasticsearch with your Rails App in development and test environments

Install the following gems from this Elasticsearch Rails resource:

  gem 'elasticsearch-model'
  gem 'elasticsearch-rails'

Run $ bundle install
Go into rails console and create the index

$ rails console
Post.__elasticsearch__.create_index!
Post.__elasticsearch__.import

Set up Elasticsearch in production

If you use CircleCI for continuous deployment add elasticsearch to your circle.yml file.

  machine:
    ruby:
      version: 2.1.6
    services:
      - elasticsearch
  deployment:
    ...

On Heroku you can use the SearchBox add-on. Install it with

$ heroku addons:create searchbox

If you have an extra app for staging remember to install it there as well ($ heroku addons:create searchbox --app staging-app-name)

On your Heroku environment you also have to create the index

$ heroku run rails console
Post.__elasticsearch__.create_index!
Post.__elasticsearch__.import

Create an initializer in your Rails app config/initializers/elasticsearch.rb

  Elasticsearch::Model.client =
    if Rails.env.staging? || Rails.env.production?
      Elasticsearch::Client.new url: ENV['SEARCHBOX_URL']
    elsif Rails.env.development?
      Elasticsearch::Client.new log: true
    else
      Elasticsearch::Client.new
    end

If you use RSpec add the following in your RSpec.configure block

  config.before(:each, elasticsearch: true) do
    Video.__elasticsearch__.create_index! force: true
  end

You will also have to tag all your Elasticsearch related specs with :elasticsearch

  describe ".search", :elasticsearch do
    let(:refresh_index) do
      Post.import
      Post.__elasticsearch__.refresh_index!
    end
    # ...

Use

Index the model you want to search in rails console

  Post.__elasticsearch__.create_index!
  Post.__elasticsearch__.import

Include the Elastic libraries in your model

  # app/models/post.rb

  class Post < ActiveRecord::Base
    include Elasticsearch::Model
    include Elasticsearch::Model::Callbacks

    index_name ["app_name", Rails.env].join("_")
    # ...

Add a search method to the same model and parse the search as json for Elasticsearch. All objects in Elasticsearch are in json.

  # app/models/post.rb
  # ... 

  def self.search(query)
    search_definition = {
      query: {
        multi_match: {
          query: query, 
          fields: ["title", "description"],
          operator: "and"
        }
      }
    }
    __elasticsearch__.search(search_definition)
  end

  def as_indexed_json(options={})
    as_json(only: [:title, :description])
  end

Add a search method to your controller

  # app/controllers/posts_controller.rb
  # ...

  def advanced_search
    if params[:query]
      @posts = Post.search(params[:query]).records.to_a
    else
      @posts = []
    end
  end

In the view your search form can perform a simple get request

  # app/views/posts/advanced_search.html.haml

  %section.advanced_search.container
    %form.form-horizontal
    = form_tag advanced_search_posts_path, class: "form-horizontal", method: :get do
      %header
        %h1 Advanced Search
      .form-group
        .col-sm-6
          = search_field_tag :query, params[:query], placeholder: "Search posts by title, description", class: "form-control"
      .form-group
        .col-sm-6
          = button_tag(type: "submit", class: "btn btn-primary") do
            %span.glyphicon.glyphicon-search
            Search

Don't forget to add a route for the search action

  # routes.rb
  # ... 

  resources :posts, only: [:show, :index] do
    collection do
      get :advanced_search, to: 'videos#advanced_search'
    end
    resources :comments, only: [:create]
  end

  # ...

The example above only scratches the surface of what you can do with Elasticsearch. To learn more check out the documentation.