I have a typical forum style app. There is a Topics model which has_many Posts.
我有一个典型的论坛风格的应用。有一个主题模型，有很多帖子。
What I want to do using Rails 2.3.x is query the topics table and sort by the most recent post in that topic.
我想使用Rails 2.3做什么。x是查询主题表并根据该主题中最近的文章进行排序。
@topics = Topic.paginate :page => params[:page], :per_page => 25,
:include => :posts, :order => 'HELP'
I'm sure this is a simple one but no joy with Google. Thanks.
我确信这是一个简单的，但没有快乐的谷歌。谢谢。
1 个解决方案
#1
1
Sorting on a joined column is probably a bad idea and will take an enormous amount of time to run in many situations. What would be better is to twiddle a special date field on the Topic model when a new Post is created:
对已连接的列进行排序可能不是一个好主意，并且在许多情况下需要大量的时间来运行。最好是在创建新帖子时，在主题模型上创建一个特殊的日期字段:
class Post < ActiveRecord::Base
after_create :update_topic_activity_at
protected
def update_topic_activity_at
Topic.update_all({ :activity_at => Time.now }, { :id => self.topic_id})
end
end
Then you can easily sort on the activity_at column as required.
然后您可以根据需要在activity_at列上轻松排序。
When adding this column you can always populate the initial activity_at with the highest posting time if you have existing data to migrate.
在添加此列时，如果要迁移现有数据，则可以始终使用最高的发布时间填充初始的activity_at。
#1
1
Sorting on a joined column is probably a bad idea and will take an enormous amount of time to run in many situations. What would be better is to twiddle a special date field on the Topic model when a new Post is created:
对已连接的列进行排序可能不是一个好主意，并且在许多情况下需要大量的时间来运行。最好是在创建新帖子时，在主题模型上创建一个特殊的日期字段:
class Post < ActiveRecord::Base
after_create :update_topic_activity_at
protected
def update_topic_activity_at
Topic.update_all({ :activity_at => Time.now }, { :id => self.topic_id})
end
end
Then you can easily sort on the activity_at column as required.
然后您可以根据需要在activity_at列上轻松排序。
When adding this column you can always populate the initial activity_at with the highest posting time if you have existing data to migrate.
在添加此列时，如果要迁移现有数据，则可以始终使用最高的发布时间填充初始的activity_at。