After showing and demonstrating code for demographic queries, the book looks ahead:

Now let’s apply the same approach to our product ratings query.

However, the product ratings query uses a constructor, not a reducer:

def with_user_ratings(user) do
  base()
  |> preload_user_ratings(user)
end

Compare that with the demographic query reducer on page 177:

def for_user(query \\ base(), user) do
  query
  |> where([d], d.user_id == ^user.id)
end

Other examples later in the book also use the reducer design:

page 242:

• def with_average_ratings(query \\ base()) do

page 257:

• def join_users(query \\ base()) do
• def join_demographics(query \\ base()) do
• def filter_by_age_group(query \\ base(), filter) do

page 266:

• def with_zero_ratings(query \\ base()) do

I suggest that the book consistently use the reducer design or explain why the constructor design is preferred for the product ratings query.