Learn ElasticSearch with Ruby

ElasticSearch (ES) is a popular search and analytics engine. I’ve been using it in most of my Ruby on Rails projects. Usually in a project we will started of by building an ActiveRecord model and establish the ES index mapping before we could start running the search.

In this post, I’ll start with basic and minimal code as possible to get us started with ES.

Pre-requisite

Install elasticsearch gem.

Initialize ES Client

client = Elasticsearch::Client.new

We’ll be using above client instance throughout our example.

Create ES Index Mapping

setting = {
  properties: {
    name: {
      type: :text
    },
    birth_date: {
      type: :date
    }
  }
}

client.create(index: :foo, type: :doc, body: {})

client.indices.put_mapping(index: :foo, type: :doc, body: mapping)
client.create(index: :foo, type: :doc, body: setting)

This creates new index named foo with following properties:

1. name field as text data type.
2. birth_date field as date data type.

Index Document(s)

adam = {
  name: 'Adam Hakeem',
  birth_date: '2006-12-08'
}

alif = {
  name: 'Alif Hussain',
  birth_date: '2009-04-28'
}

ammar = {
  name: 'Ammar Hamzah',
  birth_date: '2016-07-03'
}

client.index(id: 1, index: :foo, type: :doc, body: adam)
client.index(id: 2, index: :foo, type: :doc, body: alif)
client.index(id: 3, index: :foo, type: :doc, body: ammar)

Search away

Now you could start searching your data in ES index.

Below search by name with partial keyword am*.

body = {
  query: {
    query_string: {
      query: 'am*'
    }
  }
}

client.search(index: :foo, body: body)

#Output:
{
  "took"=>13,
  "timed_out"=>false,
  "_shards"=>{"total"=>5, "successful"=>5, "skipped"=>0, "failed"=>0},
  "hits"=> {
    "total"=>1,
    "max_score"=>0.2876821,
    "hits"=>[
      {"_index"=>"foo", "_type"=>"doc", "_id"=>"3", "_score"=>0.2876821, "_source"=>{"name"=>"Ammar Hamzah", "birth_date"=>"2016-07-03"}}
    ]
  }
}

Below search by date range.

body = {
  query: {
    range: {
      birth_date: {
        gte: '2009-01-01'
      }
    }
  }
}

client.search(index: :foo, body: body)

#Output:
{
  "took"=>2,
  "timed_out"=>false,
  "_shards"=>{"total"=>5, "successful"=>5, "skipped"=>0, "failed"=>0},
  "hits"=> {
    "total"=>2,
    "max_score"=>1.0,
    "hits"=> [
      {"_index"=>"foo", "_type"=>"doc", "_id"=>"2", "_score"=>1.0, "_source"=>{"name"=>"Alif Hussain", "birth_date"=>"2009-04-28"}},
      {"_index"=>"foo", "_type"=>"doc", "_id"=>"3", "_score"=>1.0, "_source"=>{"name"=>"Ammar Hamzah", "birth_date"=>"2016-07-03"}}
    ]
  }
}

Cleanup After Yourself

If you are done playing around with your index, you might want to remove your dummy data. You can run below to delete our particular dummy index.

client.indices.delete(index: :foo)

Conclusions

Hopefully this will give you a good start on how to learn ElasticSearch with Ruby.