ruby-on-rails - Rails : Eager loading as_json includes

Question

  render :json => {
    "playlist" => playlist_description,
    "songs" => @playlist.songs.as_json(:include => {:playlist_songs => {:only => [:id, :position]}})
  }

上面的代码导致对数据库的1 + N个查询，每个查询将为每首歌曲加载playlist_songs。
播放列表已预加载到@playlist中。

这太慢了，我该如何优化？

Answer 1

我的猜测:您现在不急于加载playlist_songs。您目前正在等待as_json调用(此后所有歌曲均已加载)，然后代码必须遍历每首歌曲并随后获取playlist_songs。

我的猜测(这完全未经测试，可能包含错误)

@playlist.songs.all(:include => :playlist_songs).as_json(:include => {:playlist_songs => {:only => [:id, :position]}})

AFAICT，这应该首先渴望加载所有歌曲和playlist_songs ...，然后呈现为json。