[英]How to reduce number of identical queries when retrieving records in model
I have started using query-analyzer and it's warning me about identical queries. 我已经开始使用查询分析器 ,它警告我有关相同的查询。
For context, I am loading 25 "posts" on the page, and the current user can "star" a post: 对于上下文,我在页面上加载了25个“帖子”,当前用户可以“加注星标”一个帖子:
0.018s 25 identical queries
SELECT SQL_NO_CACHE N AS one FROM 'stars' WHERE 'stars'.'post_id' = N AND 'stars'.'user_id' = N LIMIT N
0.018s 25个相同的查询在
SELECT SQL_NO_CACHE N AS one FROM 'stars' WHERE 'stars'.'post_id' = N AND 'stars'.'user_id' = N LIMIT N
This is the method in the User model: 这是用户模型中的方法:
def has_starred_post?(post)
return false if post.nil?
Star.where(post_id: post.id, user_id: self.id).exists?
end
How can I satisfy this warning by reducing the number of queries? 如何通过减少查询数量来满足此警告?
Update: 更新:
Per Taryn East's tip, I updated the User
model method to: 根据Taryn East的技巧,我将
User
模型方法更新为:
def has_starred_post?(post)
return false if post.nil?
self.stars.where(post_id: post.id).exists?
# OR post.stars.where(:user_id => self.id).exists?
end
Although this allows me to associate/cache the stars belonging to the User, I still have to use where
to check if any of those stars belong to the post. 尽管这使我可以关联/缓存属于该用户的星标,但是我仍然必须使用
where
来检查where
任何星标是否属于该帖子。 Right? 对?
You can reduce this kind of duplicate query by using associations - which are automatically cached by Rails. 您可以通过使用关联来减少这种重复查询-关联会由Rails自动缓存。
class Post
has_many :stars
class User
def has_starred_post?(post)
return false if post.nil?
post.stars.exists?
end
Or re-organise so it makes sense to your actual object model... 或重新组织,以使其对您的实际对象模型有意义。
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