The best way to delete a collection on a specified condition

[Serguei Cambour]

I wonder what is the best way to delete all the records of the association on a specified condition.

For example, you have User model that has many Post(s). How would keep all the recent User's Posts and delete all the last Posts when a Users have more than 25 ?

There is a solution like that:

def self.delete_old_posts
    old_posts = []
    users = includes(:post)
    users.each do |user|
      old_posts =+ user.posts.offset(25) unless user.posts.empty?
    end


    old_posts.delete_all
end

Any other ideas ? Thank you.

[Colin Law]

You need to order the posts otherwise there is no guarantee which ones
will be deleted. I don't think you need includes(:post). Also you
don't need the unless. Are you sure you want delete_all? That will
not call callbacks. In fact I am not sure you can use delete_all in
this situation.

Colin

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[Serguei Cambour]

Thank you Colin.

Yes, I know about callbacks, I don't care about it in this case. I just want to clean posts and keep not more than the last 25 ones. Thank you for the tip regarding the ordering, I'll take care about that.

[Serguei Cambour]

Just one editing, - I had to use a plural form with includes as follows:

users = includes(:posts)

to have eager loading of posts association for every User.

On Saturday, 6 August 2016 19:10:01 UTC+2, Serguei Cambour wrote: