Remove foreign key project_pages_metadata.ci_job_artifacts

We plan to remove the column entirely. We want to remove the
foreign key now, however, because it is blocking other work for
decomposing the CI database.

Changelog: other

db/migrate/20211217050753_remove_artifacts_archive_id_foreign_key_from_project_pages_metadata.rb

+# frozen_string_literal: true
+
+class RemoveArtifactsArchiveIdForeignKeyFromProjectPagesMetadata < Gitlab::Database::Migration[1.0]
+  CONSTRAINT_NAME = 'fk_69366a119e'
+
+  disable_ddl_transaction!
+
+  def up
+    with_lock_retries do
+      execute('lock table ci_job_artifacts, project_pages_metadata in access exclusive mode')
+
+      remove_foreign_key :project_pages_metadata, to_table: :ci_job_artifacts, column: :artifacts_archive_id, on_delete: :nullify, name: CONSTRAINT_NAME
+    end
+  end
+
+  def down
+    add_concurrent_foreign_key :project_pages_metadata, :ci_job_artifacts, column: :artifacts_archive_id, on_delete: :nullify, name: CONSTRAINT_NAME
+  end
+end

db/schema_migrations/20211217050753

+fe5cbf928d45d506132078678cf70264f01190cfe581628a5038d77f68a52961
\ No newline at end of file

db/structure.sql

@@ -29264,9 +29264,6 @@ ALTER TABLE ONLY merge_requests
 ALTER TABLE ONLY ci_builds
     ADD CONSTRAINT fk_6661f4f0e8 FOREIGN KEY (resource_group_id) REFERENCES ci_resource_groups(id) ON DELETE SET NULL;
 
-ALTER TABLE ONLY project_pages_metadata
-    ADD CONSTRAINT fk_69366a119e FOREIGN KEY (artifacts_archive_id) REFERENCES ci_job_artifacts(id) ON DELETE SET NULL;
-
 ALTER TABLE ONLY application_settings
     ADD CONSTRAINT fk_693b8795e4 FOREIGN KEY (push_rule_id) REFERENCES push_rules(id) ON DELETE SET NULL;
 

spec/models/project_pages_metadatum_spec.rb

@@ -18,4 +18,15 @@ RSpec.describe ProjectPagesMetadatum do
       expect(described_class.only_on_legacy_storage).to eq([legacy_storage_project.pages_metadatum])
     end
   end
+
+  it_behaves_like 'cleanup by a loose foreign key' do
+    let!(:model) do
+      artifacts_archive = create(:ci_job_artifact, :legacy_archive)
+      metadatum = artifacts_archive.project.pages_metadatum
+      metadatum.artifacts_archive = artifacts_archive
+      metadatum
+    end
+
+    let!(:parent) { model.artifacts_archive }
+  end
 end

spec/support/shared_examples/loose_foreign_keys/have_loose_foreign_key.rb

@@ -55,7 +55,8 @@ RSpec.shared_examples 'cleanup by a loose foreign key' do
   end
 
   def find_model
-    model.class.find_by(id: model.id)
+    primary_key = model.class.primary_key.to_sym
+    model.class.find_by(primary_key => model.public_send(primary_key))
   end
 
   it 'deletes the model' do