Question

I am running Ruby on Rails 3.1. I am querying the database in order to retrieve article objects that have not category relationship with a user and I am trying to improve the following code:

article_relationship_ids =
  User.article_category_relationships
  .uniq_by{|article_category_relationship| article_category_relationship.article_id}
  .map(&:article_id)

user.articles.where("articles.id NOT IN (?)", article_relationship_ids)

How can I improve the above code?

P.S.: Is my “retrieving approach” “logically” correct to make what I would like?

Answer 1

This should fetch your ids without further processing on the ruby side:

article_relationship_ids =
  User.article_category_relationships.select(:article_id).uniq