Swap FK ci_refs to projects for LFK

Swaps FK for ci_refs.project_id to projects

Changelog: changed

db/post_migrate/20220124214131_remove_projects_ci_refs_project_id_fk.rb

+# frozen_string_literal: true
+
+class RemoveProjectsCiRefsProjectIdFk < 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_refs, :projects, name: "fk_rails_4249db8cc3")
+
+    with_lock_retries do
+      execute('LOCK projects, ci_refs IN ACCESS EXCLUSIVE MODE') if transaction_open?
+
+      remove_foreign_key_if_exists(:ci_refs, :projects, name: "fk_rails_4249db8cc3")
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key(:ci_refs, :projects, name: "fk_rails_4249db8cc3", column: :project_id, target_column: :id, on_delete: :cascade)
+  end
+end

db/schema_migrations/20220124214131

+af60c6df0fb178a4820ea8cb40b402178da7fb4b6ebeabb8739dc45b96225f89
\ No newline at end of file

db/structure.sql

@@ -30422,9 +30422,6 @@ ALTER TABLE ONLY geo_node_namespace_links
 ALTER TABLE ONLY epic_issues
     ADD CONSTRAINT fk_rails_4209981af6 FOREIGN KEY (issue_id) REFERENCES issues(id) ON DELETE CASCADE;
 
-ALTER TABLE ONLY ci_refs
-    ADD CONSTRAINT fk_rails_4249db8cc3 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY ci_resources
     ADD CONSTRAINT fk_rails_430336af2d FOREIGN KEY (resource_group_id) REFERENCES ci_resource_groups(id) ON DELETE CASCADE;
 

lib/gitlab/database/gitlab_loose_foreign_keys.yml

@@ -138,6 +138,10 @@ merge_trains:
   - table: ci_pipelines
     column: pipeline_id
     on_delete: async_nullify
+ci_refs:
+  - table: projects
+    column: project_id
+    on_delete: async_delete
 ci_group_variables:
   - table: namespaces
     column: group_id

spec/lib/gitlab/database/no_cross_db_foreign_keys_spec.rb

@@ -28,7 +28,6 @@ RSpec.describe 'cross-database foreign keys' do
       ci_pipelines.merge_request_id
       ci_pipelines.project_id
       ci_project_monthly_usages.project_id
-      ci_refs.project_id
       ci_resource_groups.project_id
       ci_runner_namespaces.namespace_id
       ci_runner_projects.project_id

spec/models/ci/ref_spec.rb

@@ -231,4 +231,11 @@ RSpec.describe Ci::Ref do
       it_behaves_like 'no-op'
     end
   end
+
+  context 'loose foreign key on ci_refs.project_id' do
+    it_behaves_like 'cleanup by a loose foreign key' do
+      let!(:parent) { create(:project) }
+      let!(:model) { create(:ci_ref, project: parent) }
+    end
+  end
 end