ActiveRecord not retrieving all models - ruby-on-rails

Question

I have 2 models, Car and Person. Each person can have many cars. I have loaded some data through from seed.rb but when I try Car.find_by(owner_id: 1) in the console, I see just one car. When I am expecting 2 cars because I assigned 2 cars to one particular Person. Why am I just seeing one car?
car.rb (model)
class Car < ActiveRecord::Base
belongs_to :owner, class_name: "Person", foreign_key: "owner_id"
has_many :place_rents
validates :owner, presence: true
validates :registration_number, presence: true
validates :model, presence: true
end
person.rb
class Person < ActiveRecord::Base
has_many :cars, foreign_key: "owner_id"
has_many :parkings, foreign_key: "owner_id"
validates :first_name, presence: true
end
seed.rb
people = Person.create([{first_name: "Emmanuel", last_name: "Hayford"}, {first_name: "Steve", last_name: "Jobs"},
{first_name: "James", last_name: "Bond"}, {first_name: "Michael", last_name: "Jordan"}])
addresses = Address.create([{street: "Limanowskiego", city: "Kraków", zip_code: "98-734"}, {street: "Zeromskiego",
city: "Wrocław", zip_code: "45-622"}, {street: "Chopin", city: "Gdańsk", zip_code: "98-734"},
{street: "Putin", city: "Opole", zip_code: "90-938"}])
cars = Car.create([{owner: Person.first, model: "BMW", registration_number: "UJ8483"}, {owner: Person.second, model: "Lambo", registration_number: "JH4857"},
{owner: Person.second, model: "Jaguar", registration_number: "DW3455"}, { owner: Person.second, model: "Ferrari", registration_number: "KP8734"},
{owner: Person.first,model: "Bugatti Veyron", registration_number: "ZK9837"}])
parkings = Parking.create([{kind: "indoor", hour_price: 45.50, day_price: 200, places: 5, owner: Person.first, address_id: Address.first},
{kind: "outdoor", hour_price: 20.50, day_price: 150.00, places: 10, owner: Person.second, address_id: Address.second},
{kind: "street", hour_price: 270.50, day_price: 89.45, places: 7, owner: Person.second, address_id: Address.second},
{kind: "private", hour_price: 40.50, day_price: 30.45, places: 2, owner: Person.find(2), address_id: Address.find(2)},])
place_rents = PlaceRent.create([{parking: Parking.first, car: Car.first, start_date: Time.now, end_date: Time.now + 3.days, price: 30}])
2.1.4 :023 > Car.all
Car Load (0.5ms) SELECT "cars".* FROM "cars"
=> #<ActiveRecord::Relation [#<Car id: 1, registration_number: "UJ8483", model: "BMW", owner_id: 1, created_at: "2014-11-10 00:10:26", updated_at: "2014-11-10 00:10:26">, #<Car id: 2, registration_number: "JH4857", model: "Lambo", owner_id: 2, created_at: "2014-11-10 00:10:26", updated_at: "2014-11-10 00:10:26">, #<Car id: 3, registration_number: "DW3455", model: "Jaguar", owner_id: 2, created_at: "2014-11-10 00:10:26", updated_at: "2014-11-10 00:10:26">, #<Car id: 4, registration_number: "KP8734", model: "Ferrari", owner_id: 2, created_at: "2014-11-10 00:10:26", updated_at: "2014-11-10 00:10:26">, #<Car id: 5, registration_number: "ZK9837", model: "Bugatti Veyron", owner_id: 1, created_at: "2014-11-10 00:10:26", updated_at: "2014-11-10 00:10:26">]>
2.1.4 :024 > Car.find_by(owner_id: 1)
Car Load (0.6ms) SELECT "cars".* FROM "cars" WHERE "cars"."owner_id" = 1 LIMIT 1
=> #<Car id: 1, registration_number: "UJ8483", model: "BMW", owner_id: 1, created_at: "2014-11-10 00:10:26", updated_at: "2014-11-10 00:10:26">
2.1.4 :025 >

Answer 1

You misunderstand how find_by works:
find_by(*args)
Finds the first record matching the specified conditions.
find_by only gets one record from the database, hence the LIMIT 1 in the SQL it generates. If you want to find several things, then use where:
Car.where(owner_id: 1)
or, since you have the associations set up, use Person#cars:
person = Person.find(1)
cars = person.cars

Answer 2

Car.find_by_owner_id(1) is the same as Car.where(owner_id: 1).first so basically it returns one record rather than an array of record. Car.where(owner_id: 1) will get you your two records.