Question

我有以下模式:

User
Playlist
SongLike
Song
...

当我询问其所有歌曲的演唱者时,我收到了一系列的歌曲。找到用户“喜欢”的这些歌曲中哪些是最有效的方法? 类似情况储存在SongLike模式中:

class SongLike < ActiveRecord::Base
  belongs_to :user
  belongs_to :song, :counter_cache => "likes_count"
end

......这是歌曲模式:

class Song < ActiveRecord::Base
  has_and_belongs_to_many :playlists
  has_many :featured_songs
  has_many :song_likes
  has_many :users, :through => :song_likes
  ...
end

Answer 1

• 利用你的歌曲——类似于歌曲,以记忆,而不是多次质疑:

# user.rb
def songs_liked_from(subset)
  like_ids = self.song_likes.where(:song_id => subset.map(&:id)).select(:song_id).map(&:song_id)
  subset.select{|s| liked_ids.include?(s.id) }
end

Answer 2

You could put an index on user_id and song_id being looked up together and maybe make it unique if that works for your system.

  def songs_user_liked
    user_liked_songs = []
    songs.each do |song|
      song_like = SongLike.find_by_user_id_and_song_id(#,song)
      if song_like.song_like_count > 0
        user_liked_songs << song
      end
    end
    user_liked_songs
  end

友情链接