Simple task: given that an article has many comments, be able to display in a long list of articles how many comments each article has. I'm trying to work out how to preload this data with Arel.
The "Complex Aggregations" section of the README file seems to discuss that type of situation, but it doesn't exactly offer sample code, nor does it offer a way to do it in two queries instead of one joined query, which is worse for performance.
Given the following:
class Article
has_many :comments
end
class Comment
belongs_to :article
end
How can I preload for an article set how many comments each has?