Eager loading: The right way to do things

Question

I am running Ruby on Rails 3.1. I read the following articles and documentations about eager loading and I would like to find a right way to do things:

Answer 1

After my eager loading, is it possible / correct to make something like @article.comments = my_eager_loaded_comments so to "pass"/"associate"/"interpolate" comments to articles?

Yes, it is possible. I do this regularly.

Note that my solution still retrieves ALL the associated objects from the DB. I don't think there is any solution to retrieving just the filtered association objects if your condition is dynamic. My solution focuses on the filtering of the retrieved association objects.

I am assuming the requirement is to get a list of articles and in each article, eager load the comments of only one particular user.

In the Article model:

def self.get_articles_with_comments_of_user( article_ids, user_id )
  articles = Article.where( id: article_ids ).includes( :comments )

  articles.each do |article|
    filtered_comments = article.comments.select { |comment| comment.user_id == user_id }
    article.association("comments").target = filtered_comments
  end

  articles
end

In the collection of articles returned by the above method, the comments association will have only the comments of that particular user.

I hope this is what you are asking for.