Swap FK ci_stages to projects for LFK

Swaps FK for ci_stages.project_id to projects

Changelog: changed

db/post_migrate/20220121214752_remove_projects_ci_stages_project_id_fk.rb

+# frozen_string_literal: true
+
+class RemoveProjectsCiStagesProjectIdFk < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  def up
+    return if Gitlab.com? # unsafe migration, skip on GitLab.com due to https://gitlab.com/groups/gitlab-org/-/epics/7249#note_819625526
+    return unless foreign_key_exists?(:ci_stages, :projects, name: "fk_2360681d1d")
+
+    with_lock_retries do
+      execute('LOCK projects, ci_stages IN ACCESS EXCLUSIVE MODE') if transaction_open?
+
+      remove_foreign_key_if_exists(:ci_stages, :projects, name: "fk_2360681d1d")
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key(:ci_stages, :projects, name: "fk_2360681d1d", column: :project_id, target_column: :id, on_delete: :cascade)
+  end
+end

db/schema_migrations/20220121214752

+c56983a489b56eb6b4a5cd5ae6947a322fd58b8e96bcdee1e38634d99727c432
\ No newline at end of file

db/structure.sql

@@ -29261,9 +29261,6 @@ ALTER TABLE ONLY users_star_projects
 ALTER TABLE ONLY alert_management_alerts
     ADD CONSTRAINT fk_2358b75436 FOREIGN KEY (issue_id) REFERENCES issues(id) ON DELETE SET NULL;
 
-ALTER TABLE ONLY ci_stages
-    ADD CONSTRAINT fk_2360681d1d FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY import_failures
     ADD CONSTRAINT fk_24b824da43 FOREIGN KEY (group_id) REFERENCES namespaces(id) ON DELETE CASCADE;
 

lib/gitlab/database/gitlab_loose_foreign_keys.yml

@@ -191,6 +191,10 @@ ci_sources_pipelines:
   - table: projects
     column: project_id
     on_delete: async_delete
+ci_stages:
+  - table: projects
+    column: project_id
+    on_delete: async_delete
 ci_triggers:
   - table: users
     column: owner_id

spec/models/ci/stage_spec.rb

@@ -362,4 +362,11 @@ RSpec.describe Ci::Stage, :models do
   end
 
   it_behaves_like 'manual playable stage', :ci_stage_entity
+
+  context 'loose foreign key on ci_stages.project_id' do
+    it_behaves_like 'cleanup by a loose foreign key' do
+      let!(:parent) { create(:project) }
+      let!(:model) { create(:ci_stage_entity, project: parent) }
+    end
+  end
 end