This might be a design decision, and I'd like to understand it before
perceiving it as a bug. Here is my script:
require 'sequel'
require 'logger'
DB = Sequel.sqlite
DB.loggers = [Logger.new(STDOUT)]
Sequel::Model.db.extension(:pagination)
DB.create_table? :cars do
primary_key :id
end
DB.create_table? :wheels do
foreign_key :car_id, :cars
column :number, Integer
end
class Car < Sequel::Model
one_to_many :wheels
end
class Wheel < Sequel::Model
many_to_one :car
end
puts "database is set..."
3.times do
car = Car.create
car.add_wheel number: 1
car.add_wheel number: 2
car.add_wheel number: 3
car.add_wheel number: 4
end
puts "eaching:"
Car.eager(:wheels).map(&:wheels)
puts "with .all: "
Car.eager(:wheels).all.map(&:wheels)
puts "with .pagination: "
Car.eager(:wheels).paginate(1, 4).all.map(&:wheels)
DB.drop_table :wheels, :cars
if you look at the db logs, you see that associations are only eager load
by explicit call to .all . I don't understand why, because if I explicit
pass to a dataset that it has to eager load an association to its models, I
expect them to be eager loaded as soon as I start iterating on them. If I
don't call .all, it effectively breaks the eager chainability.
You might have good reasons for not introducing it, but think about this
use case: I want to paginate the collection. I usually render the list of
elements in html and add the pagination buttons in the end. If I keep the
paginated collection in a variable, I have access to the pagination
extension methods, like total_pages, and kaminari/will_paginate work out of
the box, but iterating on the collection breaks eager call. If I paginate
then call all, I have the collection page eager loaded into an array with
the association eager loaded, but the object doesn't contain the pagination
extensions, thereby crashing will_paginate/kaminari integration.
My workaround is to keep 2 instances in memory (the eager loaded and the
pagination plugin extended), which while working, doesn't seem very
convenient.
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