Loose foreign key definition experiment

This change adds loose foreign key definition and triggers to the
following tables:

- chat_names -> ci_pipeline_chat_data
- ci_runners -> clusters_applications_runners

Changelog: added

app/models/chat_name.rb

 # frozen_string_literal: true
 
 class ChatName < ApplicationRecord
+  include LooseForeignKey
+
   LAST_USED_AT_INTERVAL = 1.hour
 
   belongs_to :integration, foreign_key: :service_id
@@ -14,6 +16,8 @@ class ChatName < ApplicationRecord
   validates :user_id, uniqueness: { scope: [:service_id] }
   validates :chat_id, uniqueness: { scope: [:service_id, :team_id] }
 
+  loose_foreign_key :ci_pipeline_chat_data, :chat_name_id, on_delete: :async_delete
+
   # Updates the "last_used_timestamp" but only if it wasn't already updated
   # recently.
   #

app/models/ci/runner.rb

@@ -12,6 +12,7 @@ module Ci
     include Gitlab::Utils::StrongMemoize
     include TaggableQueries
     include Presentable
+    include LooseForeignKey
 
     add_authentication_token_field :token, encrypted: :optional
 
@@ -167,6 +168,8 @@ module Ci
 
     validates :config, json_schema: { filename: 'ci_runner_config' }
 
+    loose_foreign_key :clusters_applications_runners, :runner_id, on_delete: :async_nullify
+
     # Searches for runners matching the given query.
     #
     # This method uses ILIKE on PostgreSQL for the description field and performs a full match on tokens.

db/post_migrate/20211027064021_track_deletions_in_ci_runners.rb

+# frozen_string_literal: true
+
+class TrackDeletionsInCiRunners < Gitlab::Database::Migration[1.0]
+  include Gitlab::Database::MigrationHelpers::LooseForeignKeyHelpers
+
+  enable_lock_retries!
+
+  def up
+    track_record_deletions(:ci_runners)
+  end
+
+  def down
+    untrack_record_deletions(:ci_runners)
+  end
+end

db/post_migrate/20211027064156_track_deletions_in_chat_names.rb

+# frozen_string_literal: true
+
+class TrackDeletionsInChatNames < Gitlab::Database::Migration[1.0]
+  include Gitlab::Database::MigrationHelpers::LooseForeignKeyHelpers
+
+  enable_lock_retries!
+
+  def up
+    track_record_deletions(:chat_names)
+  end
+
+  def down
+    untrack_record_deletions(:chat_names)
+  end
+end

db/schema_migrations/20211027064021

+f1b218eaddb9bcc5e4d854a6b43fc5e122b38dc989225327a1c4a899f41e5ac6
\ No newline at end of file

db/schema_migrations/20211027064156

+3d7b72684102836d7a7efcab7590b3d14bc63eb3e1bfbc7a95fb5eb5c6a906af
\ No newline at end of file

db/structure.sql

@@ -27550,6 +27550,10 @@ ALTER INDEX product_analytics_events_experimental_pkey ATTACH PARTITION gitlab_p
 
 ALTER INDEX product_analytics_events_experimental_pkey ATTACH PARTITION gitlab_partitions_static.product_analytics_events_experimental_63_pkey;
 
+CREATE TRIGGER chat_names_loose_fk_trigger AFTER DELETE ON chat_names REFERENCING OLD TABLE AS old_table FOR EACH STATEMENT EXECUTE FUNCTION insert_into_loose_foreign_keys_deleted_records();
+
+CREATE TRIGGER ci_runners_loose_fk_trigger AFTER DELETE ON ci_runners REFERENCING OLD TABLE AS old_table FOR EACH STATEMENT EXECUTE FUNCTION insert_into_loose_foreign_keys_deleted_records();
+
 CREATE TRIGGER trigger_91dc388a5fe6 BEFORE INSERT OR UPDATE ON dep_ci_build_trace_sections FOR EACH ROW EXECUTE FUNCTION trigger_91dc388a5fe6();
 
 CREATE TRIGGER trigger_delete_project_namespace_on_project_delete AFTER DELETE ON projects FOR EACH ROW WHEN ((old.project_namespace_id IS NOT NULL)) EXECUTE FUNCTION delete_associated_project_namespace();

spec/models/chat_name_spec.rb

@@ -43,4 +43,12 @@ RSpec.describe ChatName do
       expect(subject.last_used_at).to eq(time)
     end
   end
+
+  it_behaves_like 'it has loose foreign keys' do
+    let(:factory_name) { :chat_name }
+
+    before do
+      Ci::PipelineChatData # ensure that the referenced model is loaded
+    end
+  end
 end

spec/models/ci/runner_spec.rb

@@ -5,6 +5,14 @@ require 'spec_helper'
 RSpec.describe Ci::Runner do
   it_behaves_like 'having unique enum values'
 
+  it_behaves_like 'it has loose foreign keys' do
+    let(:factory_name) { :ci_runner }
+
+    before do
+      Clusters::Applications::Runner # ensure that the referenced model is loaded
+    end
+  end
+
   describe 'groups association' do
     # Due to other assoctions such as projects this whole spec is allowed to
     # generate cross-database queries. So we have this temporary spec to

spec/support/shared_examples/loose_foreign_keys/have_loose_foreign_key.rb

+# frozen_string_literal: true
+
+RSpec.shared_examples 'it has loose foreign keys' do
+  let(:factory_name) { nil }
+  let(:table_name) { described_class.table_name }
+  let(:connection) { described_class.connection }
+
+  it 'includes the LooseForeignKey module' do
+    expect(described_class.ancestors).to include(LooseForeignKey)
+  end
+
+  it 'responds to #loose_foreign_key_definitions' do
+    expect(described_class).to respond_to(:loose_foreign_key_definitions)
+  end
+
+  it 'has at least one loose foreign key definition' do
+    expect(described_class.loose_foreign_key_definitions.size).to be > 0
+  end
+
+  it 'has the deletion trigger present' do
+    sql = <<-SQL
+    SELECT trigger_name
+    FROM information_schema.triggers
+    WHERE event_object_table = '#{table_name}'
+    SQL
+
+    triggers = connection.execute(sql)
+
+    expected_trigger_name = "#{table_name}_loose_fk_trigger"
+    expect(triggers.pluck('trigger_name')).to include(expected_trigger_name)
+  end
+
+  it 'records record deletions' do
+    model = create(factory_name) # rubocop: disable Rails/SaveBang
+    model.destroy!
+
+    deleted_record = LooseForeignKeys::DeletedRecord.find_by(fully_qualified_table_name: "#{connection.current_schema}.#{table_name}", primary_key_value: model.id)
+
+    expect(deleted_record).not_to be_nil
+  end
+
+  it 'cleans up record deletions' do
+    model = create(factory_name) # rubocop: disable Rails/SaveBang
+
+    expect { model.destroy! }.to change { LooseForeignKeys::DeletedRecord.count }.by(1)
+
+    LooseForeignKeys::ProcessDeletedRecordsService.new(connection: connection).execute
+
+    expect(LooseForeignKeys::DeletedRecord.status_pending.count).to be(0)
+    expect(LooseForeignKeys::DeletedRecord.status_processed.count).to be(1)
+  end
+end