This is a snippet of code that I've ben using in a custom repository implementation, pretty similar to `persistence` from @karmi : https://github.com/elasticsearch/elasticsearch-rails/blob/persistence/elasticsearch-persistence/README.md

find_each.rb

    def find_each(options = {}, &block)
      search_options = {}
      search_options[:index] = options.fetch(:index) { default_index(options) }
      search_options[:body] = options.fetch(:body) {
        { query: { match_all: {} } }
      }
      search_options[:scroll] = options.fetch(:scroll) { "5m" }
      search_options[:search_type] = "scan"

      if options.key?(:_source)
        search_options[:_source] = options[:_source]
      end

      response = client.search(search_options)
      scroll_id = response.fetch("_scroll_id")

      loop do
        response = client.scroll({
          scroll: '1m',
          scroll_id: scroll_id
        })
        scroll_id = response.fetch("_scroll_id")
        hits = response.fetch("hits").fetch("hits")

        if hits.count > 0
          hits.each { |e| yield(e) }
        else
          break
        end
      end

    end

It might not be the perfect implementation, but it works for me.