0
好的,所以我有这个Concern
其中包含一个方法top
用于检索记录顺序的次数由某人已经聆听他们(如果该记录是一首歌曲,直接或通过歌曲,如果它是别的东西,如流派或艺术家)。如果是平局,则按其他网站上的受欢迎程度排序记录。如何将此SQL转换为ActiveRecord查询?
以下代码几乎完美地工作。它以正确的顺序返回一个对象数组。我的主要问题是我得到一个数组而不是一个关系。因此,来电者不能再添加诸如Song.top.limit 3
或Genre.top.offset(10).limit(5)
之类的内容。
这里是我的方法:
def top(options = {})
tname = self.name.tableize
inner_select = self.select("#{tname}.*,COUNT(DISTINCT(listens.id)) AS listens_count")
inner_select = inner_select.joins(:songs) unless self.name == 'Song'
inner_select = inner_select.joins("LEFT JOIN listens ON listens.song_id = songs.id")
inner_select = inner_select.where("listens.user_id = ?", options[:for].id) if options[:for].is_a? User
inner_select = inner_select.group("#{tname}.id").to_sql
# this is the part that needs fixin'
find_by_sql("
SELECT
#{tname}.*,
#{tname}.listens_count,
SUM(sources.popularity) AS popularity_count
FROM (#{inner_select}) AS #{tname}
LEFT JOIN sources ON
sources.resource_id = #{tname}.id
AND
sources.resource_type = '#{self.name}
GROUP BY #{tname}.id
ORDER BY listens_count DESC, popularity_count DESC
")
end
下面是生成,按要求SQL查询。这是Song.top
:
SELECT
songs.*,
songs.listens_count,
SUM(sources.popularity) AS popularity_count
FROM (SELECT songs.*,COUNT(DISTINCT(listens.id)) AS listens_count FROM "songs" LEFT JOIN listens ON listens.song_id = songs.id GROUP BY songs.id) AS songs
LEFT JOIN sources ON
sources.resource_id = songs.id
AND
sources.resource_type = 'Song'
GROUP BY songs.id
ORDER BY listens_count DESC, popularity_count DESC
这是Artist.top
:
SELECT
artists.*,
artists.listens_count,
SUM(sources.popularity) AS popularity_count
FROM (SELECT artists.*,COUNT(DISTINCT(listens.id)) AS listens_count FROM "artists" INNER JOIN "artists_songs" ON "artists_songs"."artist_id" = "artists"."id" INNER JOIN "songs" ON "songs"."id" = "artists_songs"."song_id" LEFT JOIN listens ON listens.song_id = songs.id GROUP BY artists.id) AS artists
LEFT JOIN sources ON
sources.resource_id = artists.id
AND
sources.resource_type = 'Artist'
GROUP BY artists.id
ORDER BY listens_count DESC, popularity_count DESC
它可能是有点容易(从日志,或使用'to_sql') – IS04 2014-08-27 20:28:08