Merge branch 'jprovazn-project_fk' into 'master'

Nullify project_namespace_id reference

See merge request gitlab-org/gitlab!78046

db/post_migrate/20220112090556_remove_cascade_delete_from_project_namespace_foreign_key.rb

+# frozen_string_literal: true
+
+class RemoveCascadeDeleteFromProjectNamespaceForeignKey < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  TARGET_COLUMN = :project_namespace_id
+
+  def up
+    with_lock_retries do
+      remove_foreign_key_if_exists(:projects, column: TARGET_COLUMN)
+    end
+
+    add_concurrent_foreign_key(:projects, :namespaces, column: TARGET_COLUMN, on_delete: :nullify)
+  end
+
+  def down
+    with_lock_retries do
+      remove_foreign_key_if_exists(:projects, column: TARGET_COLUMN)
+    end
+
+    add_concurrent_foreign_key(:projects, :namespaces, column: TARGET_COLUMN, on_delete: :cascade)
+  end
+end

db/schema_migrations/20220112090556

+e78e11a47017c67130fe88fa538578553b7015c18cf222b5e7fb7f503254dc6d
\ No newline at end of file

db/structure.sql

@@ -29346,7 +29346,7 @@ ALTER TABLE ONLY protected_branch_push_access_levels
     ADD CONSTRAINT fk_7111b68cdb FOREIGN KEY (group_id) REFERENCES namespaces(id) ON DELETE CASCADE;
 
 ALTER TABLE ONLY projects
-    ADD CONSTRAINT fk_71625606ac FOREIGN KEY (project_namespace_id) REFERENCES namespaces(id) ON DELETE CASCADE;
+    ADD CONSTRAINT fk_71625606ac FOREIGN KEY (project_namespace_id) REFERENCES namespaces(id) ON DELETE SET NULL;
 
 ALTER TABLE ONLY integrations
     ADD CONSTRAINT fk_71cce407f9 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;

spec/models/namespaces/project_namespace_spec.rb

@@ -17,11 +17,11 @@ RSpec.describe Namespaces::ProjectNamespace, type: :model do
     let_it_be(:project) { create(:project) }
     let_it_be(:project_namespace) { project.project_namespace }
 
-    it 'also deletes the associated project' do
+    it 'keeps the associated project' do
       project_namespace.delete
 
       expect { project_namespace.reload }.to raise_error(ActiveRecord::RecordNotFound)
-      expect { project.reload }.to raise_error(ActiveRecord::RecordNotFound)
+      expect(project.reload.project_namespace).to be_nil
     end
   end
 end