How to use elasticsearch for searching step by step

1. Add the elasticsearch and elasticsearch-model gems: Add these to your Gemfile:

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

   Then run:

   sh
   bundle install
   

Step 3: Configure Elasticsearch in Rails

1. Create an Elasticsearch Configuration File: Create a file named config/elasticsearch.yml with the following content:

   yaml
   development:
     url: http://localhost:9200
   
   test:
     url: http://localhost:9200
   
   production:
     url: <your-production-elasticsearch-url>
   

2. Create an Initializer: Create an initializer file config/initializers/elasticsearch.rb:

   ruby
   Elasticsearch::Model.client = Elasticsearch::Client.new host: ENV['ELASTICSEARCH_URL'] || 'localhost:9200'
   

Step 4: Integrate Elasticsearch with Your Models

1. Include Elasticsearch in Your Model: Let's say you have a Post model. Include Elasticsearch and its necessary modules:

   ruby
   class Post < ApplicationRecord
     include Elasticsearch::Model
     include Elasticsearch::Model::Callbacks
   end
   

2. Customize Your Elasticsearch Index: You can customize how your model is indexed. Add an index definition to your model:

   ruby
   class Post < ApplicationRecord
     include Elasticsearch::Model
     include Elasticsearch::Model::Callbacks
   
     settings do
       mappings dynamic: false do
         indexes :title, type: :text, analyzer: 'english'
         indexes :content, type: :text, analyzer: 'english'
       end
     end
   end
   

3. Index Existing Records: After setting up your model, you need to index your existing records:

   ruby:
   
   Post.import # for importing all records to Elasticsearch
   

Step 5: Implement Search Functionality

1. Add a Search Method in Your Model:

   ruby:
   
   class Post < ApplicationRecord
     include Elasticsearch::Model
     include Elasticsearch::Model::Callbacks
   
     settings do
       mappings dynamic: false do
         indexes :title, type: :text, analyzer: 'english'
         indexes :content, type: :text, analyzer: 'english'
       end
     end
   
     def self.search(query)
       __elasticsearch__.search(
         {
           query: {
             multi_match: {
               query: query,
               fields: ['title^10', 'content']
             }
           }
         }
       )
     end
   end
   

2. Create a Controller Action for Search: In your controller, add a search action:

   ruby;
   
   class PostsController < ApplicationController
     def search
       @posts = Post.search(params[:query]).records
     end
   end
   

3. Add a Route for Search: In your config/routes.rb:

   ruby:
   
   get 'search', to: 'posts#search'
   

4. Create a View for Search: Create a search view app/views/posts/search.html.erb:

   <h1>Search Results</h1>
   <%= form_with url: search_path, method: :get do %>
     <%= text_field_tag :query, params[:query] %>
     <%= submit_tag 'Search' %>
   <% end %>
   
   <% @posts.each do |post| %>
     <div>
       <h2><%= post.title %></h2>
       <p><%= post.content %></p>
     </div>
   <% end %>

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

after used this code i am getting this errors Elastic::Transport::Transport::Errors::NotFound in Posts#search Showing /home/bittern/Desktop/rinku/projects/simple_dummy/app/views/posts/search.html.erb where line #7 raised:

[404] {"error":{"root_cause":[{"type":"index_not_found_exception","reason":"no such index [posts]","resource.type":"index_or_alias","resource.id":"posts","index_uuid":"na","index":"posts"}],"type":"index_not_found_exception","reason":"no such index [posts]","resource.type":"index_or_alias","resource.id":"posts","index_uuid":"na","index":"posts"},"status":404}

Elastic::Transport::Transport::Errors::NotFound: no such index [posts], indicates that the Elasticsearch index for your Post

Steps to Resolve the Error

1. Create the Index: Use the import method to create the index and populate it with your existing records. Run the following command in your Rails console:

   ruby
   Run: Post.import(force: true)
   

   This command will create the posts index in Elasticsearch and add all existing Post records to the index.
   
   Ager Ye wala step chal rha hai to Second wala nhi chalana (2. Ensure Elasticsearch is Running)

2. Ensure Elasticsearch is Running: Make sure that your Elasticsearch service is running. You can check the status of Elasticsearch with the following command:

   sh
   Run: sudo systemctl status elasticsearch
   

   If it is not running, start it with:

   sh
   sudo systemctl start elasticsearch
   

3. Check Elasticsearch Connection: Verify that your Rails application can connect to Elasticsearch. You can do this by testing a simple query in the Rails console:

   ruby
   Post.__elasticsearch__.client.cluster.health
   

   This should return the health status of your Elasticsearch cluster.

4. you can use the following steps:

   1. Delete the Existing Index: You can delete the existing index using the Rails console:

      ruby
      
      Run: Post.__elasticsearch__.client.indices.delete index: Post.index_name
      

   2. Recreate and Populate the Index: After deleting the index, recreate and populate it with:

      ruby:
      
      Run: Post.__elasticsearch__.create_index!(force: true)
      Run: Post.import