Ensure foreign keys on Clusters Applications

Closes #43802

changelogs/unreleased/43802-ensure-foreign-keys-on-clusters-applications.yml

+---
+title: Ensure foreign keys on clusters applications
+merge_request: 17488
+author:
+type: other

db/migrate/20180302152117_ensure_foreign_keys_on_clusters_applications.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class EnsureForeignKeysOnClustersApplications < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    unless foreign_keys_for(:clusters_applications_ingress, :cluster_id).any?
+      add_concurrent_foreign_key :clusters_applications_ingress, :clusters,
+        column: :cluster_id,
+        on_delete: :cascade
+    end
+
+    unless foreign_keys_for(:clusters_applications_prometheus, :cluster_id).any?
+      add_concurrent_foreign_key :clusters_applications_prometheus, :clusters,
+        column: :cluster_id,
+        on_delete: :cascade
+    end
+  end
+
+  def down
+    if foreign_keys_for(:clusters_applications_ingress, :cluster_id).any?
+      remove_foreign_key :clusters_applications_ingress, column: :cluster_id
+    end
+
+    if foreign_keys_for(:clusters_applications_prometheus, :cluster_id).any?
+      remove_foreign_key :clusters_applications_prometheus, column: :cluster_id
+    end
+  end
+end

db/schema.rb

@@ -2028,6 +2028,8 @@ ActiveRecord::Schema.define(version: 20180307012445) do
   add_foreign_key "cluster_providers_gcp", "clusters", on_delete: :cascade
   add_foreign_key "clusters", "users", on_delete: :nullify
   add_foreign_key "clusters_applications_helm", "clusters", on_delete: :cascade
+  add_foreign_key "clusters_applications_ingress", "clusters", on_delete: :cascade
+  add_foreign_key "clusters_applications_prometheus", "clusters", on_delete: :cascade
   add_foreign_key "clusters_applications_runners", "ci_runners", column: "runner_id", name: "fk_02de2ded36", on_delete: :nullify
   add_foreign_key "clusters_applications_runners", "clusters", on_delete: :cascade
   add_foreign_key "container_repositories", "projects"