Add foreign keys to lfs_objects_projects

It's added without a validation until the data is cleaned up

app/models/lfs_object.rb

@@ -7,7 +7,7 @@ class LfsObject < ApplicationRecord
   include ObjectStorage::BackgroundMove
   include FileStoreMounter
 
-  has_many :lfs_objects_projects, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :lfs_objects_projects
   has_many :projects, -> { distinct }, through: :lfs_objects_projects
 
   scope :with_files_stored_locally, -> { where(file_store: LfsObjectUploader::Store::LOCAL) }

app/models/project.rb

@@ -286,7 +286,7 @@ class Project < ApplicationRecord
   has_many :users_star_projects
   has_many :starrers, through: :users_star_projects, source: :user
   has_many :releases
-  has_many :lfs_objects_projects, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+  has_many :lfs_objects_projects
   has_many :lfs_objects, -> { distinct }, through: :lfs_objects_projects
   has_many :lfs_file_locks
   has_many :project_group_links

db/migrate/20210511165250_add_foreign_key_to_lfs_objects_projects.rb

+# frozen_string_literal: true
+
+class AddForeignKeyToLfsObjectsProjects < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_foreign_key :lfs_objects_projects, :lfs_objects, column: :lfs_object_id, on_delete: :restrict, validate: false
+    add_concurrent_foreign_key :lfs_objects_projects, :projects, column: :project_id, on_delete: :cascade, validate: false
+  end
+
+  def down
+    with_lock_retries do
+      remove_foreign_key :lfs_objects_projects, column: :lfs_object_id
+      remove_foreign_key :lfs_objects_projects, column: :project_id
+    end
+  end
+end

db/schema_migrations/20210511165250

+8f746d7eb604ae31a5941840d6a078eae2e4fa59b7185bf8cc0db9c55b463c33
\ No newline at end of file

db/structure.sql

@@ -25401,6 +25401,9 @@ ALTER TABLE ONLY notes
 ALTER TABLE ONLY members
     ADD CONSTRAINT fk_2e88fb7ce9 FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE;
 
+ALTER TABLE ONLY lfs_objects_projects
+    ADD CONSTRAINT fk_2eb33f7a78 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE NOT VALID;
+
 ALTER TABLE ONLY lists
     ADD CONSTRAINT fk_30f2a831f4 FOREIGN KEY (iteration_id) REFERENCES sprints(id) ON DELETE CASCADE;
 
@@ -25713,6 +25716,9 @@ ALTER TABLE ONLY bulk_import_entities
 ALTER TABLE ONLY users
     ADD CONSTRAINT fk_a4b8fefe3e FOREIGN KEY (managing_group_id) REFERENCES namespaces(id) ON DELETE SET NULL;
 
+ALTER TABLE ONLY lfs_objects_projects
+    ADD CONSTRAINT fk_a56e02279c FOREIGN KEY (lfs_object_id) REFERENCES lfs_objects(id) ON DELETE RESTRICT NOT VALID;
+
 ALTER TABLE ONLY dast_profiles_pipelines
     ADD CONSTRAINT fk_a60cad829d FOREIGN KEY (ci_pipeline_id) REFERENCES ci_pipelines(id) ON DELETE CASCADE;
 

spec/models/lfs_object_spec.rb

@@ -178,4 +178,17 @@ RSpec.describe LfsObject do
       expect(described_class.calculate_oid(path)).to eq expected
     end
   end
+
+  context 'when an lfs object is associated with a project' do
+    let!(:lfs_object) { create(:lfs_object) }
+    let!(:lfs_object_project) { create(:lfs_objects_project, lfs_object: lfs_object) }
+
+    it 'cannot be deleted' do
+      expect { lfs_object.destroy! }.to raise_error(ActiveRecord::InvalidForeignKey)
+
+      lfs_object_project.destroy!
+
+      expect { lfs_object.destroy! }.not_to raise_error
+    end
+  end
 end

spec/models/project_spec.rb

@@ -6452,6 +6452,10 @@ RSpec.describe Project, factory_default: :keep do
           expect(subject).to eq([lfs_object.oid])
         end
       end
+
+      it 'lfs_objects_projects associations are deleted along with project' do
+        expect { project.delete }.to change(LfsObjectsProject, :count).by(-2)
+      end
     end
 
     context 'when project has no associated LFS objects' do