Remove ci_running_builds FK to projects

We already have ci_running_builds FK to ci_builds, and also an LFK from
ci_running_builds to projects.

Changelog: other

db/post_migrate/20220112015940_remove_projects_ci_running_builds_fk.rb

+# frozen_string_literal: true
+
+class RemoveProjectsCiRunningBuildsFk < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  def up
+    with_lock_retries do
+      execute('LOCK projects, ci_running_builds IN ACCESS EXCLUSIVE MODE')
+
+      remove_foreign_key_if_exists(:ci_running_builds, :projects, name: "fk_rails_dc1d0801e8")
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key(:ci_running_builds, :projects, name: "fk_rails_dc1d0801e8", column: :project_id, target_column: :id, on_delete: "cascade")
+  end
+end

db/schema_migrations/20220112015940

+e4417c3367115d6adba023e18657d8aecd476b8d1c4227c73e06f97d05af07ad
\ No newline at end of file

db/structure.sql

@@ -31338,9 +31338,6 @@ ALTER TABLE ONLY issues_prometheus_alert_events
 ALTER TABLE ONLY board_user_preferences
     ADD CONSTRAINT fk_rails_dbebdaa8fe FOREIGN KEY (board_id) REFERENCES boards(id) ON DELETE CASCADE;
 
-ALTER TABLE ONLY ci_running_builds
-    ADD CONSTRAINT fk_rails_dc1d0801e8 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY vulnerability_occurrence_pipelines
     ADD CONSTRAINT fk_rails_dc3ae04693 FOREIGN KEY (occurrence_id) REFERENCES vulnerability_occurrences(id) ON DELETE CASCADE;
 

lib/gitlab/database/gitlab_loose_foreign_keys.yml

@@ -57,6 +57,10 @@ ci_runner_namespaces:
   - table: namespaces
     column: namespace_id
     on_delete: async_delete
+ci_running_builds:
+  - table: projects
+    column: project_id
+    on_delete: async_delete
 ci_namespace_mirrors:
   - table: namespaces
     column: namespace_id

spec/models/ci/running_build_spec.rb

@@ -49,4 +49,9 @@ RSpec.describe Ci::RunningBuild do
       end
     end
   end
+
+  it_behaves_like 'cleanup by a loose foreign key' do
+    let!(:parent) { create(:project) }
+    let!(:model) { create(:ci_running_build, project: parent) }
+  end
 end