Remove foreign key ci_daily_build_group_report_results.group_id

The loose foreign key was already added for this in
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/77636 . We've
already determined in
https://gitlab.com/gitlab-org/gitlab/-/issues/348269 it is safe to
change this foreign key to a loose foreign key.

Changelog: other

db/post_migrate/20220106231518_remove_foreign_key_ci_daily_build_group_report_results_group_id.rb

+# frozen_string_literal: true
+
+class RemoveForeignKeyCiDailyBuildGroupReportResultsGroupId < Gitlab::Database::Migration[1.0]
+  disable_ddl_transaction!
+
+  CONSTRAINT_NAME = 'fk_fd1858fefd'
+
+  def up
+    with_lock_retries do
+      remove_foreign_key_if_exists(:ci_daily_build_group_report_results, :namespaces, name: CONSTRAINT_NAME)
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key :ci_daily_build_group_report_results, :namespaces, column: :group_id, on_delete: :cascade, name: CONSTRAINT_NAME
+  end
+end

db/schema_migrations/20220106231518

+aafb52337688e8b57712872f6f7e8e67da132406b244df5e11a736b01e23354f
\ No newline at end of file

db/structure.sql

@@ -29884,9 +29884,6 @@ ALTER TABLE ONLY system_note_metadata
 ALTER TABLE ONLY vulnerability_remediations
     ADD CONSTRAINT fk_fc61a535a0 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;
 
-ALTER TABLE ONLY ci_daily_build_group_report_results
-    ADD CONSTRAINT fk_fd1858fefd FOREIGN KEY (group_id) REFERENCES namespaces(id) ON DELETE CASCADE;
-
 ALTER TABLE ONLY merge_requests
     ADD CONSTRAINT fk_fd82eae0b9 FOREIGN KEY (head_pipeline_id) REFERENCES ci_pipelines(id) ON DELETE SET NULL;
 

spec/models/ci/daily_build_group_report_result_spec.rb

@@ -164,4 +164,10 @@ RSpec.describe Ci::DailyBuildGroupReportResult do
       end
     end
   end
+
+  it_behaves_like 'cleanup by a loose foreign key' do
+    let!(:model) { create(:ci_daily_build_group_report_result) }
+
+    let!(:parent) { model.group }
+  end
 end