721 lines
22 KiB
Markdown
721 lines
22 KiB
Markdown
# Elasticsearch::Model
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The `elasticsearch-model` library builds on top of the
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the [`elasticsearch`](https://github.com/elasticsearch/elasticsearch-ruby) library.
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It aims to simplify integration of Ruby classes ("models"), commonly found
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e.g. in [Ruby on Rails](http://rubyonrails.org) applications, with the
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[Elasticsearch](http://www.elasticsearch.org) search and analytics engine.
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The library is compatible with Ruby 1.9.3 and higher.
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## Installation
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Install the package from [Rubygems](https://rubygems.org):
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gem install elasticsearch-model
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To use an unreleased version, either add it to your `Gemfile` for [Bundler](http://bundler.io):
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gem 'elasticsearch-model', git: 'git://github.com/elasticsearch/elasticsearch-rails.git'
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or install it from a source code checkout:
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git clone https://github.com/elasticsearch/elasticsearch-rails.git
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cd elasticsearch-rails/elasticsearch-model
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bundle install
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rake install
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## Usage
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Let's suppose you have an `Article` model:
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```ruby
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require 'active_record'
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ActiveRecord::Base.establish_connection( adapter: 'sqlite3', database: ":memory:" )
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ActiveRecord::Schema.define(version: 1) { create_table(:articles) { |t| t.string :title } }
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class Article < ActiveRecord::Base; end
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Article.create title: 'Quick brown fox'
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Article.create title: 'Fast black dogs'
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Article.create title: 'Swift green frogs'
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```
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### Setup
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To add the Elasticsearch integration for this model, require `elasticsearch/model`
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and include the main module in your class:
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```ruby
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require 'elasticsearch/model'
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class Article < ActiveRecord::Base
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include Elasticsearch::Model
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end
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```
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This will extend the model with functionality related to Elasticsearch.
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#### Feature Extraction Pattern
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Instead of including the `Elasticsearch::Model` module directly in your model,
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you can include it in a "concern" or "trait" module, which is quite common pattern in Rails applications,
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using e.g. `ActiveSupport::Concern` as the instrumentation:
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```ruby
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# In: app/models/concerns/searchable.rb
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#
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module Searchable
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extend ActiveSupport::Concern
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included do
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include Elasticsearch::Model
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mapping do
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# ...
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end
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def self.search(query)
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# ...
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end
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end
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end
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# In: app/models/article.rb
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#
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class Article
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include Searchable
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end
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```
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#### The `__elasticsearch__` Proxy
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The `Elasticsearch::Model` module contains a big amount of class and instance methods to provide
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all its functionality. To prevent polluting your model namespace, this functionality is primarily
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available via the `__elasticsearch__` class and instance level proxy methods;
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see the `Elasticsearch::Model::Proxy` class documentation for technical information.
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The module will include important methods, such as `search`, into the class or module only
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when they haven't been defined already. Following two calls are thus functionally equivalent:
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```ruby
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Article.__elasticsearch__.search 'fox'
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Article.search 'fox'
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```
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See the `Elasticsearch::Model` module documentation for technical information.
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### The Elasticsearch client
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The module will set up a [client](https://github.com/elasticsearch/elasticsearch-ruby/tree/master/elasticsearch),
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connected to `localhost:9200`, by default. You can access and use it as any other `Elasticsearch::Client`:
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```ruby
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Article.__elasticsearch__.client.cluster.health
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# => { "cluster_name"=>"elasticsearch", "status"=>"yellow", ... }
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```
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To use a client with different configuration, just set up a client for the model:
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```ruby
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Article.__elasticsearch__.client = Elasticsearch::Client.new host: 'api.server.org'
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```
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Or configure the client for all models:
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```ruby
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Elasticsearch::Model.client = Elasticsearch::Client.new log: true
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```
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You might want to do this during your application bootstrap process, e.g. in a Rails initializer.
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Please refer to the
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[`elasticsearch-transport`](https://github.com/elasticsearch/elasticsearch-ruby/tree/master/elasticsearch-transport)
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library documentation for all the configuration options, and to the
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[`elasticsearch-api`](http://rubydoc.info/gems/elasticsearch-api) library documentation
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for information about the Ruby client API.
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### Importing the data
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The first thing you'll want to do is importing your data into the index:
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```ruby
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Article.import
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# => 0
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```
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It's possible to import only records from a specific `scope` or `query`, transform the batch with the `transform`
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and `preprocess` options, or re-create the index by deleting it and creating it with correct mapping with the `force` option -- look for examples in the method documentation.
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No errors were reported during importing, so... let's search the index!
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### Searching
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For starters, we can try the "simple" type of search:
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```ruby
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response = Article.search 'fox dogs'
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response.took
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# => 3
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response.results.total
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# => 2
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response.results.first._score
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# => 0.02250402
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response.results.first._source.title
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# => "Quick brown fox"
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```
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#### Search results
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The returned `response` object is a rich wrapper around the JSON returned from Elasticsearch,
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providing access to response metadata and the actual results ("hits").
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Each "hit" is wrapped in the `Result` class, and provides method access
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to its properties via [`Hashie::Mash`](http://github.com/intridea/hashie).
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The `results` object supports the `Enumerable` interface:
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```ruby
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response.results.map { |r| r._source.title }
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# => ["Quick brown fox", "Fast black dogs"]
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response.results.select { |r| r.title =~ /^Q/ }
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# => [#<Elasticsearch::Model::Response::Result:0x007 ... "_source"=>{"title"=>"Quick brown fox"}}>]
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```
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In fact, the `response` object will delegate `Enumerable` methods to `results`:
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```ruby
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response.any? { |r| r.title =~ /fox|dog/ }
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# => true
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```
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To use `Array`'s methods (including any _ActiveSupport_ extensions), just call `to_a` on the object:
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```ruby
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response.to_a.last.title
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# "Fast black dogs"
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```
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#### Search results as database records
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Instead of returning documents from Elasticsearch, the `records` method will return a collection
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of model instances, fetched from the primary database, ordered by score:
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```ruby
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response.records.to_a
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# Article Load (0.3ms) SELECT "articles".* FROM "articles" WHERE "articles"."id" IN (1, 2)
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# => [#<Article id: 1, title: "Quick brown fox">, #<Article id: 2, title: "Fast black dogs">]
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```
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The returned object is the genuine collection of model instances returned by your database,
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i.e. `ActiveRecord::Relation` for ActiveRecord, or `Mongoid::Criteria` in case of MongoDB.
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This allows you to chain other methods on top of search results, as you would normally do:
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```ruby
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response.records.where(title: 'Quick brown fox').to_a
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# Article Load (0.2ms) SELECT "articles".* FROM "articles" WHERE "articles"."id" IN (1, 2) AND "articles"."title" = 'Quick brown fox'
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# => [#<Article id: 1, title: "Quick brown fox">]
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response.records.records.class
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# => ActiveRecord::Relation::ActiveRecord_Relation_Article
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```
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The ordering of the records by score will be preserved, unless you explicitly specify a different
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order in your model query language:
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```ruby
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response.records.order(:title).to_a
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# Article Load (0.2ms) SELECT "articles".* FROM "articles" WHERE "articles"."id" IN (1, 2) ORDER BY "articles".title ASC
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# => [#<Article id: 2, title: "Fast black dogs">, #<Article id: 1, title: "Quick brown fox">]
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```
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The `records` method returns the real instances of your model, which is useful when you want to access your
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model methods -- at the expense of slowing down your application, of course.
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In most cases, working with `results` coming from Elasticsearch is sufficient, and much faster. See the
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[`elasticsearch-rails`](https://github.com/elasticsearch/elasticsearch-rails/tree/master/elasticsearch-rails)
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library for more information about compatibility with the Ruby on Rails framework.
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When you want to access both the database `records` and search `results`, use the `each_with_hit`
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(or `map_with_hit`) iterator:
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```ruby
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response.records.each_with_hit { |record, hit| puts "* #{record.title}: #{hit._score}" }
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# * Quick brown fox: 0.02250402
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# * Fast black dogs: 0.02250402
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```
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#### Searching multiple models
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It is possible to search across multiple models with the module method:
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```ruby
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Elasticsearch::Model.search('fox', [Article, Comment]).results.to_a.map(&:to_hash)
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# => [
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# {"_index"=>"articles", "_type"=>"article", "_id"=>"1", "_score"=>0.35136628, "_source"=>...},
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# {"_index"=>"comments", "_type"=>"comment", "_id"=>"1", "_score"=>0.35136628, "_source"=>...}
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# ]
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Elasticsearch::Model.search('fox', [Article, Comment]).records.to_a
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# Article Load (0.3ms) SELECT "articles".* FROM "articles" WHERE "articles"."id" IN (1)
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# Comment Load (0.2ms) SELECT "comments".* FROM "comments" WHERE "comments"."id" IN (1,5)
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# => [#<Article id: 1, title: "Quick brown fox">, #<Comment id: 1, body: "Fox News">, ...]
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```
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By default, all models which include the `Elasticsearch::Model` module are searched.
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NOTE: It is _not_ possible to chain other methods on top of the `records` object, since it
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is a heterogenous collection, with models potentially backed by different databases.
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#### Pagination
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You can implement pagination with the `from` and `size` search parameters. However, search results
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can be automatically paginated with the [`kaminari`](http://rubygems.org/gems/kaminari) or
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[`will_paginate`](https://github.com/mislav/will_paginate) gems.
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(The pagination gems must be added before the Elasticsearch gems in your Gemfile,
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or loaded first in your application.)
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If Kaminari or WillPaginate is loaded, use the familiar paging methods:
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```ruby
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response.page(2).results
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response.page(2).records
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```
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In a Rails controller, use the the `params[:page]` parameter to paginate through results:
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```ruby
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@articles = Article.search(params[:q]).page(params[:page]).records
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@articles.current_page
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# => 2
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@articles.next_page
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# => 3
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```
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To initialize and include the Kaminari pagination support manually:
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```ruby
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Kaminari::Hooks.init
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Elasticsearch::Model::Response::Response.__send__ :include, Elasticsearch::Model::Response::Pagination::Kaminari
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```
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#### The Elasticsearch DSL
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In most situation, you'll want to pass the search definition
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in the Elasticsearch [domain-specific language](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl.html) to the client:
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```ruby
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response = Article.search query: { match: { title: "Fox Dogs" } },
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highlight: { fields: { title: {} } }
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response.results.first.highlight.title
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# ["Quick brown <em>fox</em>"]
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```
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You can pass any object which implements a `to_hash` method, or you can use your favourite JSON builder
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to build the search definition as a JSON string:
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```ruby
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require 'jbuilder'
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query = Jbuilder.encode do |json|
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json.query do
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json.match do
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json.title do
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json.query "fox dogs"
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end
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end
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end
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end
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response = Article.search query
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response.results.first.title
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# => "Quick brown fox"
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```
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### Index Configuration
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For proper search engine function, it's often necessary to configure the index properly.
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The `Elasticsearch::Model` integration provides class methods to set up index settings and mappings.
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```ruby
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class Article
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settings index: { number_of_shards: 1 } do
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mappings dynamic: 'false' do
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indexes :title, analyzer: 'english', index_options: 'offsets'
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end
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end
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end
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Article.mappings.to_hash
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# => {
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# :article => {
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# :dynamic => "false",
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# :properties => {
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# :title => {
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# :type => "string",
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# :analyzer => "english",
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# :index_options => "offsets"
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# }
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# }
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# }
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# }
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Article.settings.to_hash
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# { :index => { :number_of_shards => 1 } }
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```
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You can use the defined settings and mappings to create an index with desired configuration:
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```ruby
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Article.__elasticsearch__.client.indices.delete index: Article.index_name rescue nil
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Article.__elasticsearch__.client.indices.create \
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index: Article.index_name,
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body: { settings: Article.settings.to_hash, mappings: Article.mappings.to_hash }
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```
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There's a shortcut available for this common operation (convenient e.g. in tests):
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```ruby
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Article.__elasticsearch__.create_index! force: true
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Article.__elasticsearch__.refresh_index!
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```
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By default, index name and document type will be inferred from your class name,
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you can set it explicitely, however:
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```ruby
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class Article
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index_name "articles-#{Rails.env}"
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document_type "post"
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end
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```
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### Updating the Documents in the Index
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Usually, we need to update the Elasticsearch index when records in the database are created, updated or deleted;
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use the `index_document`, `update_document` and `delete_document` methods, respectively:
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```ruby
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Article.first.__elasticsearch__.index_document
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# => {"ok"=>true, ... "_version"=>2}
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```
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#### Automatic Callbacks
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You can automatically update the index whenever the record changes, by including
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the `Elasticsearch::Model::Callbacks` module in your model:
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```ruby
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class Article
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include Elasticsearch::Model
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include Elasticsearch::Model::Callbacks
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end
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Article.first.update_attribute :title, 'Updated!'
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Article.search('*').map { |r| r.title }
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# => ["Updated!", "Lime green frogs", "Fast black dogs"]
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```
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The automatic callback on record update keeps track of changes in your model
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(via [`ActiveModel::Dirty`](http://api.rubyonrails.org/classes/ActiveModel/Dirty.html)-compliant implementation),
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and performs a _partial update_ when this support is available.
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The automatic callbacks are implemented in database adapters coming with `Elasticsearch::Model`. You can easily
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implement your own adapter: please see the relevant chapter below.
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#### Custom Callbacks
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In case you would need more control of the indexing process, you can implement these callbacks yourself,
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by hooking into `after_create`, `after_save`, `after_update` or `after_destroy` operations:
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```ruby
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class Article
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include Elasticsearch::Model
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after_save { logger.debug ["Updating document... ", index_document ].join }
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after_destroy { logger.debug ["Deleting document... ", delete_document].join }
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end
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```
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For ActiveRecord-based models, use the `after_commit` callback to protect
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your data against inconsistencies caused by transaction rollbacks:
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```ruby
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class Article < ActiveRecord::Base
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include Elasticsearch::Model
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after_commit on: [:create] do
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__elasticsearch__.index_document if self.published?
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end
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after_commit on: [:update] do
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__elasticsearch__.update_document if self.published?
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end
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after_commit on: [:destroy] do
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__elasticsearch__.delete_document if self.published?
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end
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end
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```
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#### Asynchronous Callbacks
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Of course, you're still performing an HTTP request during your database transaction, which is not optimal
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for large-scale applications. A better option would be to process the index operations in background,
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with a tool like [_Resque_](https://github.com/resque/resque) or [_Sidekiq_](https://github.com/mperham/sidekiq):
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```ruby
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class Article
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include Elasticsearch::Model
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after_save { Indexer.perform_async(:index, self.id) }
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after_destroy { Indexer.perform_async(:delete, self.id) }
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end
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```
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An example implementation of the `Indexer` worker class could look like this:
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```ruby
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class Indexer
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include Sidekiq::Worker
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sidekiq_options queue: 'elasticsearch', retry: false
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Logger = Sidekiq.logger.level == Logger::DEBUG ? Sidekiq.logger : nil
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Client = Elasticsearch::Client.new host: 'localhost:9200', logger: Logger
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def perform(operation, record_id)
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logger.debug [operation, "ID: #{record_id}"]
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case operation.to_s
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when /index/
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record = Article.find(record_id)
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Client.index index: 'articles', type: 'article', id: record.id, body: record.as_indexed_json
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when /delete/
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Client.delete index: 'articles', type: 'article', id: record_id
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else raise ArgumentError, "Unknown operation '#{operation}'"
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end
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end
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end
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```
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Start the _Sidekiq_ workers with `bundle exec sidekiq --queue elasticsearch --verbose` and
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update a model:
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```ruby
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Article.first.update_attribute :title, 'Updated'
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```
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You'll see the job being processed in the console where you started the _Sidekiq_ worker:
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```
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Indexer JID-eb7e2daf389a1e5e83697128 DEBUG: ["index", "ID: 7"]
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Indexer JID-eb7e2daf389a1e5e83697128 INFO: PUT http://localhost:9200/articles/article/1 [status:200, request:0.004s, query:n/a]
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Indexer JID-eb7e2daf389a1e5e83697128 DEBUG: > {"id":1,"title":"Updated", ...}
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Indexer JID-eb7e2daf389a1e5e83697128 DEBUG: < {"ok":true,"_index":"articles","_type":"article","_id":"1","_version":6}
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Indexer JID-eb7e2daf389a1e5e83697128 INFO: done: 0.006 sec
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```
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### Model Serialization
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By default, the model instance will be serialized to JSON using the `as_indexed_json` method,
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which is defined automatically by the `Elasticsearch::Model::Serializing` module:
|
|
|
|
```ruby
|
|
Article.first.__elasticsearch__.as_indexed_json
|
|
# => {"id"=>1, "title"=>"Quick brown fox"}
|
|
```
|
|
|
|
If you want to customize the serialization, just implement the `as_indexed_json` method yourself,
|
|
for instance with the [`as_json`](http://api.rubyonrails.org/classes/ActiveModel/Serializers/JSON.html#method-i-as_json) method:
|
|
|
|
```ruby
|
|
class Article
|
|
include Elasticsearch::Model
|
|
|
|
def as_indexed_json(options={})
|
|
as_json(only: 'title')
|
|
end
|
|
end
|
|
|
|
Article.first.as_indexed_json
|
|
# => {"title"=>"Quick brown fox"}
|
|
```
|
|
|
|
The re-defined method will be used in the indexing methods, such as `index_document`.
|
|
|
|
Please note that in Rails 3, you need to either set `include_root_in_json: false`, or prevent adding
|
|
the "root" in the JSON representation with other means.
|
|
|
|
#### Relationships and Associations
|
|
|
|
When you have a more complicated structure/schema, you need to customize the `as_indexed_json` method -
|
|
or perform the indexing separately, on your own.
|
|
For example, let's have an `Article` model, which _has_many_ `Comment`s,
|
|
`Author`s and `Categories`. We might want to define the serialization like this:
|
|
|
|
```ruby
|
|
def as_indexed_json(options={})
|
|
self.as_json(
|
|
include: { categories: { only: :title},
|
|
authors: { methods: [:full_name], only: [:full_name] },
|
|
comments: { only: :text }
|
|
})
|
|
end
|
|
|
|
Article.first.as_indexed_json
|
|
# => { "id" => 1,
|
|
# "title" => "First Article",
|
|
# "created_at" => 2013-12-03 13:39:02 UTC,
|
|
# "updated_at" => 2013-12-03 13:39:02 UTC,
|
|
# "categories" => [ { "title" => "One" } ],
|
|
# "authors" => [ { "full_name" => "John Smith" } ],
|
|
# "comments" => [ { "text" => "First comment" } ] }
|
|
```
|
|
|
|
Of course, when you want to use the automatic indexing callbacks, you need to hook into the appropriate
|
|
_ActiveRecord_ callbacks -- please see the full example in `examples/activerecord_associations.rb`.
|
|
|
|
### Other ActiveModel Frameworks
|
|
|
|
The `Elasticsearch::Model` module is fully compatible with any ActiveModel-compatible model, such as _Mongoid_:
|
|
|
|
```ruby
|
|
require 'mongoid'
|
|
|
|
Mongoid.connect_to 'articles'
|
|
|
|
class Article
|
|
include Mongoid::Document
|
|
|
|
field :id, type: String
|
|
field :title, type: String
|
|
|
|
attr_accessible :id, :title, :published_at
|
|
|
|
include Elasticsearch::Model
|
|
|
|
def as_indexed_json(options={})
|
|
as_json(except: [:id, :_id])
|
|
end
|
|
end
|
|
|
|
Article.create id: '1', title: 'Quick brown fox'
|
|
Article.import
|
|
|
|
response = Article.search 'fox';
|
|
response.records.to_a
|
|
# MOPED: 127.0.0.1:27017 QUERY database=articles collection=articles selector={"_id"=>{"$in"=>["1"]}} ...
|
|
# => [#<Article _id: 1, id: nil, title: "Quick brown fox", published_at: nil>]
|
|
```
|
|
|
|
Full examples for CouchBase, DataMapper, Mongoid, Ohm and Riak models can be found in the `examples` folder.
|
|
|
|
### Adapters
|
|
|
|
To support various "OxM" (object-relational- or object-document-mapper) implementations and frameworks,
|
|
the `Elasticsearch::Model` integration supports an "adapter" concept.
|
|
|
|
An adapter provides implementations for common behaviour, such as fetching records from the database,
|
|
hooking into model callbacks for automatic index updates, or efficient bulk loading from the database.
|
|
The integration comes with adapters for _ActiveRecord_ and _Mongoid_ out of the box.
|
|
|
|
Writing an adapter for your favourite framework is straightforward -- let's see
|
|
a simplified adapter for [_DataMapper_](http://datamapper.org):
|
|
|
|
```ruby
|
|
module DataMapperAdapter
|
|
|
|
# Implement the interface for fetching records
|
|
#
|
|
module Records
|
|
def records
|
|
klass.all(id: @ids)
|
|
end
|
|
|
|
# ...
|
|
end
|
|
end
|
|
|
|
# Register the adapter
|
|
#
|
|
Elasticsearch::Model::Adapter.register(
|
|
DataMapperAdapter,
|
|
lambda { |klass| defined?(::DataMapper::Resource) and klass.ancestors.include?(::DataMapper::Resource) }
|
|
)
|
|
```
|
|
|
|
Require the adapter and include `Elasticsearch::Model` in the class:
|
|
|
|
```ruby
|
|
require 'datamapper_adapter'
|
|
|
|
class Article
|
|
include DataMapper::Resource
|
|
include Elasticsearch::Model
|
|
|
|
property :id, Serial
|
|
property :title, String
|
|
end
|
|
```
|
|
|
|
When accessing the `records` method of the response, for example,
|
|
the implementation from our adapter will be used now:
|
|
|
|
```ruby
|
|
response = Article.search 'foo'
|
|
|
|
response.records.to_a
|
|
# ~ (0.000057) SELECT "id", "title", "published_at" FROM "articles" WHERE "id" IN (3, 1) ORDER BY "id"
|
|
# => [#<Article @id=1 @title="Foo" @published_at=nil>, #<Article @id=3 @title="Foo Foo" @published_at=nil>]
|
|
|
|
response.records.records.class
|
|
# => DataMapper::Collection
|
|
```
|
|
|
|
More examples can be found in the `examples` folder. Please see the `Elasticsearch::Model::Adapter`
|
|
module and its submodules for technical information.
|
|
|
|
## Development and Community
|
|
|
|
For local development, clone the repository and run `bundle install`. See `rake -T` for a list of
|
|
available Rake tasks for running tests, generating documentation, starting a testing cluster, etc.
|
|
|
|
Bug fixes and features must be covered by unit tests.
|
|
|
|
Github's pull requests and issues are used to communicate, send bug reports and code contributions.
|
|
|
|
To run all tests against a test Elasticsearch cluster, use a command like this:
|
|
|
|
```bash
|
|
curl -# https://download.elasticsearch.org/elasticsearch/elasticsearch/elasticsearch-1.0.0.RC1.tar.gz | tar xz -C tmp/
|
|
SERVER=start TEST_CLUSTER_COMMAND=$PWD/tmp/elasticsearch-1.0.0.RC1/bin/elasticsearch bundle exec rake test:all
|
|
```
|
|
|
|
## License
|
|
|
|
This software is licensed under the Apache 2 license, quoted below.
|
|
|
|
Copyright (c) 2014 Elasticsearch <http://www.elasticsearch.org>
|
|
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
|
you may not use this file except in compliance with the License.
|
|
You may obtain a copy of the License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
See the License for the specific language governing permissions and
|
|
limitations under the License.
|