CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-3.2associationshas-manymodel-associations
Jody Heavener
Jody Heavener

Reputation: 2864

Find and destroy dependent records

Over a period of time my Rails app has had various rewrites, and in some cases incorrect model associations.

Currently my User model has_many :posts and its destroy method correctly removes all dependent Posts, but at times when things were improperly written this did not happen. I'm now left with a handful of Post records that cause errors all over because their User does not exist.

What would be the most efficient way to manually filter through all Post records, check if its User actually exists, and if not destroy that Post?

I'm imagining something like:

Post.all.select{ |post| post.user.nil? }.destroy

But that seems incredibly inefficient for thousands of records. I'd love to know the best way to do this. Thank you!

Upvotes: 0

Views: 1139

Answers (3)

Deepak Mahakale
Deepak Mahakale

Reputation: 23661

Delete the orphan posts using

  • If you want to destroy the dependent associations with Post and run the callbacks

    Post.where("user_id NOT IN (?)", User.pluck(:id)).destroy_all

  • If you just want to delete the posts 

    Post.where("user_id NOT IN (?)", User.pluck(:id)).delete_all

Here is one good post about finding and deleting orphan records

Upvotes: 0

daryn
daryn

Reputation: 926

Fastest way would probably be to do it directory in the db console, but if you've got other dependent relationships and activerecord callbacks that you need to get fired, you could do something like:

Post.where("id in (select p.id from posts p left outer join users u on p.user_id = u.id where u.id is null)").destroy_all

Upvotes: 0

usha
usha

Reputation: 29349

any reason why you cannot do it directly on the database?

delete from posts where user_id not in (select id from users);

Upvotes: 1

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