Rails 3.使用原始SQL或Arel编写ActiveRecord查询

Question

I am looking through a legacy codebase and I see something like this:

def all_story_links
    StoryLink.complete.where("
      (storyable_type = 'Recipe' AND storyable_id = ?)
      OR
      (storyable_type = 'RecipeStep' AND storyable_id IN (?))
      OR
      (storyable_type = 'RecipeIngredient' AND storyable_id IN (?)
      )", id, recipe_step_ids, recipe_ingredient_ids)
  end

What is that called inside the where method? What is it? Is it AREL? Does this exist because there is no ActiveRecord convenience methods that resolves to this? is it SQL or Arel? Got any good resources to learn AREL quickly?

Answer 1

What's inside the where method is mostly plain old SQL, with the added feature of Rails doing substitutions wherever it sees the question marks ("?"). Rails substitutes for the question marks, the values given to the where method after the query itself: id, recipe_step_ids.... .

It is not AREL.

The plain old SQL was probably used in this case because the ANDs and ORs would have been difficult or impossible to implement using the ActiveRecord API.