[RAILS] Added a the file with Rake tasks for importing the model(s)

Add this e.g. into the `lib/tasks/elasticsearch.rake` file in your Rails application:

    require 'elasticsearch/rails/tasks/import'

Run this command inside your application folder to display usage instructions:

    bundle exec rake -D elasticsearch

Author: karmi

elasticsearch-rails/lib/elasticsearch/rails/tasks/import.rb

@@ -0,0 +1,103 @@
+# A collection of Rake tasks to facilitate importing data from yout models into Elasticsearch.
+#
+# Add this e.g. into the `lib/tasks/elasticsearch.rake` file in your Rails application:
+#
+#     require 'elasticsearch/rails/tasks/import'
+#
+# To import the records from your `Article` model, run:
+#
+#     $ bundle exec rake environment elasticsearch:import:model CLASS='MyModel'
+#
+# Run this command to display usage instructions:
+#
+#     $ bundle exec rake -D elasticsearch
+#
+STDOUT.sync = true
+STDERR.sync = true
+
+begin; require 'ansi/progressbar' rescue LoadError; end
+
+namespace :elasticsearch do
+
+  task :import => 'import:model'
+
+  namespace :import do
+    desc <<-DESC.gsub(/    /, '')
+      Import data from your model (pass name as CLASS environment variable).
+
+        $ rake environment elasticsearch:import:model CLASS='MyModel'
+
+      Force rebuilding the index (delete and create):
+        $ rake environment elasticsearch:import:model CLASS='Article' FORCE=y
+
+      Customize the batch size:
+        $ rake environment elasticsearch:import:model CLASS='Article' BATCH=100
+
+      Set target index name:
+        $ rake environment elasticsearch:import:model CLASS='Article' INDEX='articles-new'
+    DESC
+    task :model do
+      if ENV['CLASS'].to_s == ''
+        puts '='*90, 'USAGE', '='*90, import_model_desc, ""
+        exit(1)
+      end
+
+      klass  = eval(ENV['CLASS'].to_s)
+      total  = klass.count rescue nil
+      pbar   = ANSI::Progressbar.new(klass.to_s, total) rescue nil
+
+      unless ENV['DEBUG']
+        begin
+          klass.__elasticsearch__.client.transport.logger.level = Logger::WARN
+        rescue NoMethodError; end
+        begin
+          klass.__elasticsearch__.client.transport.tracer.level = Logger::WARN
+        rescue NoMethodError; end
+      end
+
+      klass.import force:      ENV.fetch('FORCE', false),
+                   batch_size: ENV.fetch('BATCH', 1000).to_i,
+                   index:      ENV.fetch('INDEX', nil),
+                   type:       ENV.fetch('TYPE',  nil) do |response|
+        pbar.inc response['items'].size if pbar
+        STDERR.flush
+      end
+      pbar.finish if pbar
+
+      puts '[IMPORT] Done'
+    end
+
+    desc <<-DESC.gsub(/    /, '')
+      Import all indices from `app/models` (or use DIR environment variable).
+
+        $ rake environment elasticsearch:import:all DIR=app/models
+    DESC
+    task :all do
+      dir    = ENV['DIR'].to_s != '' ? ENV['DIR'] : Rails.root.join("app/models")
+
+      puts "[IMPORT] Loading models from: #{dir}"
+      Dir.glob(File.join("#{dir}/**/*.rb")).each do |path|
+        model_filename = path[/#{Regexp.escape(dir.to_s)}\/([^\.]+).rb/, 1]
+
+        next if model_filename.match(/^concerns\//i) # Skip concerns/ folder
+
+        begin
+          klass = model_filename.camelize.constantize
+        rescue NameError
+          require(path) ? retry : raise(RuntimeError, "Cannot load class '#{klass}'")
+        end
+
+        # Skip if the class doesn't have Elasticsearch integration
+        next unless klass.respond_to?(:__elasticsearch__)
+
+        puts "[IMPORT] Processing model: #{klass}..."
+
+        ENV['CLASS'] = klass.to_s
+        Rake::Task["elasticsearch:import:model"].invoke
+        puts
+      end
+    end
+
+  end
+
+end