get recursive position

position_title.rb

def position_titles
  columns = %w"id parent_item_id title position"
  columns_joined = columns.join(",")
  sql = <<-SQL.squish
    WITH RECURSIVE agenda_item_tree(#{columns_joined}, level)
      AS (
        SELECT #{columns_joined}, 0
        FROM agenda_items
        WHERE id = #{id}
        UNION
          SELECT #{columns.map { |col| 'agenda_items_2.' + col }.join(',')}, ct.level + 1
          FROM agenda_items agenda_items_2, agenda_item_tree ct
          WHERE agenda_items_2.id = ct.parent_item_id
    ) SELECT *
      FROM agenda_item_tree
  SQL
  AgendaItem.find_by_sql(sql).map { |agenda_item| [agenda_item.title, agenda_item.position] }.reverse
end