mastodon/app/models/concerns/paginable.rb

module Paginable
  extend ActiveSupport::Concern

  included do
    scope :paginate_by_max_id, -> (limit, max_id = nil, since_id = nil) {
      query = order(arel_table[:id].desc).limit(limit)
      query = query.where(arel_table[:id].lt(max_id)) unless max_id.blank?
      query = query.where(arel_table[:id].gt(since_id)) unless since_id.blank?
      query
    }
  end
end