Framework our quick hack to avoid the extra queries from Kaminari

pager.rb

class Pager
  attr_reader :arel, :page, :per_page

  def initialize(arel, options={})
    @arel = arel
    @page = Integer(options[:page]) rescue 1
    @per_page = Integer(options[:per_page]) rescue arel.klass.default_per_page
  end

  def paged_results
    offset = (page - 1) * per_page
    table_name = arel.klass.table_name

    results = arel.
      select("COUNT(#{table_name}.id) OVER () AS non_paged_count, #{table_name}.*").
      offset(offset).
      limit(per_page).all

    total_count = non_paged_count_from(results)
    Kaminari.paginate_array(results, :total_count => total_count).page(page).per(per_page)
  end

  def non_paged_count_from(results)
    results.empty? ? 0 : results.first.non_paged_count
  end
end