Make sure we delete on cascade for insights

db/schema.rb

@@ -3605,8 +3605,8 @@ ActiveRecord::Schema.define(version: 20190506135400) do
   add_foreign_key "identities", "saml_providers", name: "fk_aade90f0fc", on_delete: :cascade
   add_foreign_key "import_export_uploads", "projects", on_delete: :cascade
   add_foreign_key "index_statuses", "projects", name: "fk_74b2492545", on_delete: :cascade
-  add_foreign_key "insights", "namespaces"
-  add_foreign_key "insights", "projects"
+  add_foreign_key "insights", "namespaces", on_delete: :cascade
+  add_foreign_key "insights", "projects", on_delete: :cascade
   add_foreign_key "internal_ids", "namespaces", name: "fk_162941d509", on_delete: :cascade
   add_foreign_key "internal_ids", "projects", on_delete: :cascade
   add_foreign_key "issue_assignees", "issues", name: "fk_b7d881734a", on_delete: :cascade

ee/db/migrate/20190415172035_update_insights_foreign_keys.rb

+# frozen_string_literal: true
+
+# rubocop: disable Migration/AddConcurrentForeignKey
+
+class UpdateInsightsForeignKeys < ActiveRecord::Migration[5.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def up
+    remove_foreign_key_if_exists(:insights, column: :project_id)
+    add_foreign_key(:insights, :projects, column: :project_id, on_delete: :cascade)
+
+    remove_foreign_key_if_exists(:insights, column: :namespace_id)
+    add_foreign_key(:insights, :namespaces, column: :namespace_id, on_delete: :cascade)
+  end
+
+  def down
+    remove_foreign_key_if_exists(:insights, column: :namespace_id)
+    add_foreign_key(:insights, :namespaces, column: :namespace_id)
+
+    remove_foreign_key_if_exists(:insights, column: :project_id)
+    add_foreign_key(:insights, :projects, column: :project_id)
+  end
+end

lib/gitlab/database/migration_helpers.rb

@@ -905,6 +905,12 @@ module Gitlab
         end
       end
 
+      def remove_foreign_key_if_exists(*args)
+        if foreign_key_exists?(args)
+          remove_foreign_key(args)
+        end
+      end
+
       def remove_foreign_key_without_error(*args)
         remove_foreign_key(*args)
       rescue ArgumentError