印象派宝石代码/impressionist/blob/master/lib/impressionist/is_impressionable.rb#L15-L20rel =nofollow> association ，并在 impressionist_coun您可以创建自己的范围，如下所示：

 范围：order_by_starting_at， - > （start_date）{
 impressions_table = Impression.quoted_table_name 

 query = if start_date.present？ 
＃{impressions_table} .created_at> ='＃{start_date}'AND
 else 
'
 end 

 query + = ＃{impressions_table} .created_at< ='＃{Time.now}'

 order（％Q {
 COALESCE（（
 SELECT 
 COUNT（＃ {impressions_table} .impressionable_id）
 FROM 
＃{impressions_table} 
 JOIN 
＃{Post.quoted_table_name} AS popular_posts 
 ON 
 popular_posts.id =＃ {impressions_table} .impressionable_id 
 AND 
＃{impressions_table} .impressionable_id ='＃{self.to_s}'
 WHERE 
＃{query} 
），0） DESC 
}）
} 

范围：view_counts_for_first， - > （number）{
 order_by_starting_at.limit（number）
} 
 

现在你可以：

  Post.order_by_starting_at（1.week.ago）.limit（10）
 Post.order_by_starting_at.limit （10）
 

编辑：

然而，结果证明这个效果更好 -

  Post.joins（：impressions）.where（impressions.created_at   

I have Post model and It's impressionable using Impressionist gem I want to show top 10 most visited Post in last month.

Here is the way I came up with:

Post.all.sort_by{|post| post.view_count_last_month}.first 10

and view_count_last_monthmethod is in Post model:

def view_count_last_week
    impressionist_count(:start_date => 1.week.ago)
end

But I think it's not good for performance because It loads all the Posts and then sort them by view_count_last_month method.

What is the best way to do that?

Thanks

By looking at the Impressionist gem code for association and in impressionist_count, you can actually create your own scope like this:

  scope :order_by_starting_at, -> (start_date){ 
    impressions_table = Impression.quoted_table_name

    query = if start_date.present?
      "#{impressions_table}.created_at >= '#{start_date}' AND "
    else
      ''
    end

    query += "#{impressions_table}.created_at <= '#{Time.now}'"

    order(%Q{
            COALESCE((
              SELECT
                COUNT(#{impressions_table}.impressionable_id)
              FROM
                #{impressions_table}
              JOIN
                #{Post.quoted_table_name} AS popular_posts
              ON
                popular_posts.id = #{impressions_table}.impressionable_id
              AND
                #{impressions_table}.impressionable_id = '#{self.to_s}'
              WHERE
                #{query}
             ), 0) DESC
          })
    }

  scope :view_counts_for_first,-> (number){  
    order_by_starting_at.limit(number) 
    }

now you can:

Post.order_by_starting_at(1.week.ago).limit(10)
Post.order_by_starting_at.limit(10)

EDIT:

However, it turned out that this worked even better -

Post.joins(:impressions).where("impressions.created_at<='#{Time.now}' and impressions.created_at >= '#{start_time}'").group("impressions.impressionable_id").order("count(impression‌​s.id) DESC")