Recursive import with has_many association that has a custom primary_key fails

[difernandez]

Problem

The failure comes from the associated object trying to find the main record through the id column instead of the configured primary_key. For example, if we have:

class Book < ApplicationRecord
  validates :identifier, presence: true, uniqueness: true
  has_many :reviews, dependent: :destroy
end

# == Schema Information
#
# Table name: books
#
#  id         :bigint(8)        not null, primary key
#  identifier :bigint(8)        not null
#  created_at :datetime         not null
#  updated_at :datetime         not null
#
# Indexes
#
#  index_books_on_identifier  (identifier) UNIQUE
#

class Review < ApplicationRecord
  belongs_to :book, primary_key: :identifier
end

# == Schema Information
#
# Table name: reviews
#
#  id         :bigint(8)        not null, primary key
#  book_id    :bigint(8)        not null
#  created_at :datetime         not null
#  updated_at :datetime         not null
#
# Indexes
#
#  index_reviews_on_book_id  (book_id) UNIQUE
#
# Foreign Keys
#
#  fk_rails_...  (book_id => books.identifier) ON DELETE => cascade
#

And then we do the following:

book = Book.new(identifier: 123456789)
book.reviews.new
Book.import!([book], recursive: true)

It results in a foreign key error, where it tries to insert the book.id in the review.book_id column instead of using book.identifier

  Book Create Many (2.6ms)  INSERT INTO "books" ("id","identifier","created_at","updated_at") VALUES (nextval('public.books_id_seq'),123456789,'2025-07-15 16:53:50.766835','2025-07-15 16:53:50.766835') RETURNING "id"
  Review Create Many (1.3ms)  INSERT INTO "reviews" ("id","book_id","created_at","updated_at") VALUES (nextval('public.reviews_id_seq'),3,'2025-07-15 16:53:50.771991','2025-07-15 16:53:50.771991') RETURNING "id"
ActiveRecord::InvalidForeignKey: PG::ForeignKeyViolation: ERROR:  insert or update on table "reviews" violates foreign key constraint "fk_rails_924a0b30ca"
DETAIL:  Key (book_id)=(3) is not present in table "books".

from /Users/my.user/.rbenv/versions/3.1.4/lib/ruby/gems/3.1.0/gems/activerecord-6.1.6/lib/active_record/connection_adapters/postgresql_adapter.rb:672:in `exec_params'
Caused by PG::ForeignKeyViolation: ERROR:  insert or update on table "reviews" violates foreign key constraint "fk_rails_924a0b30ca"
DETAIL:  Key (book_id)=(3) is not present in table "books".

Possible origin and solution

I think the problem originates in this line:

def find_associated_objects_for_import(associated_objects_by_class, model)
	#...
	child.public_send("#{column}=", Array(model.id)[index])
	#...
end

Specifically, the use of model.id directly. I could be wrong, but I think replacing that with model.send(association_reflection.inverse_of.association_primary_key) would fix the issue. At least I did quick test overriding the method and it seems to work.