在需要计数器的轨道中修复N+1查询

我对优化查询很陌生,我有一个n+1查询,它似乎需要一个计数器,但我不确定如何继续:

...
SQL (0.5ms)  SELECT COUNT(*) AS count_id FROM (SELECT 1 FROM `photos` WHERE (`photos`.attachable_id = 4864 AND `photos`.attachable_type = 'Recipe')) AS subquery
SQL (2.1ms)  SELECT COUNT(*) AS count_id FROM (SELECT 1 FROM `votes` WHERE (`votes`.voteable_id = 4864 AND `votes`.voteable_type = 'Recipe') AND (`votes`.`vote` = 1)) AS subquery
SQL (2.0ms)  SELECT COUNT(*) AS count_id FROM (SELECT 1 FROM `votes` WHERE (`votes`.voteable_id = 4864 AND `votes`.voteable_type = 'Recipe') AND (`votes`.`vote` = 0)) AS subquery
SQL (0.3ms)  SELECT COUNT(*) AS count_id FROM (SELECT 1 FROM `photos` WHERE (`photos`.attachable_id = 4865 AND `photos`.attachable_type = 'Recipe')) AS subquery
SQL (2.6ms)  SELECT COUNT(*) AS count_id FROM (SELECT 1 FROM `votes` WHERE (`votes`.voteable_id = 4865 AND `votes`.voteable_type = 'Recipe') AND (`votes`.`vote` = 1)) AS subquery
SQL (2.4ms)  SELECT COUNT(*) AS count_id FROM (SELECT 1 FROM `votes` WHERE (`votes`.voteable_id = 4865 AND `votes`.voteable_type = 'Recipe') AND (`votes`.`vote` = 0)) AS subquery
...

所以我有两个奇怪的问题。我有这种多态性 vote 模型,我需要总结一下,基本上,如果有人投了反对票,它的价值是 0 上 投票 列和A 1 如果用户投了赞成票。不过,它似乎创建了这个疯狂的查询。

我怎样才能补救?

我认为造成这种情况的原因从我的观点中的这种方法开始:

<%= recipe.votes.tally %>

这就是我计算选票的方式:

class Vote < ActiveRecord::Base

  scope :up, where(:vote => true)
  scope :down, where(:vote => false)

  def self.tally
    self.up.count - self.down.count
  end

end

但是因为我要为每个对象做很多次,它必须做这个逻辑,我们最终得到一个疯狂的n+1。