Sort Items fast with mysql and postgres queries on acts_as_list position column

sort_items_extension.rb

module SortItemsExtension
  def sort_items(ids)
    unless ids.is_a?(Array)
      raise ArgumentError, "ids isn't an array"
    end

    ids.map!(&:to_i)
    old_ids = proxy_association.ids_reader
    ids = ids - (ids - old_ids)

    if old_ids.size != ids.size
      raise ArgumentError, "Not all the ids were passed to sort! method"
    end

    scope = proxy_association.reflection.klass.where(id: ids)

    if ActiveRecord::ConnectionAdapters::Mysql2Adapter
      scope.update_all(['position = FIND_IN_SET(id, ?)', ids.join(',')])
    elsif ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
      scope.update_all(["position = STRPOS(?, ','||id||',')", ",#{ids.join(',')},"], id: ids)
    end
  end
end

usage.rb

  has_many :photos, -> { extending(SortItemsExtension).order(:position) }, dependent: :destroy