Move Timestamp Generation into its own Method

db/migrate/20231003000823494_add_foreign_key_to_spree_orders_spree_users_created_by_id.rb

@@ -0,0 +1,15 @@
+# Orphaned records can be found before running this migration with the following SQL:
+
+# SELECT COUNT(*)
+# FROM spree_orders
+# LEFT JOIN spree_users
+#   ON spree_orders.created_by_id = spree_users.id
+# WHERE spree_users.id IS NULL
+#   AND spree_orders.created_by_id IS NOT NULL
+
+
+class AddForeignKeyToSpreeOrdersSpreeUsersCreatedById < ActiveRecord::Migration[6.0]
+  def change
+    add_foreign_key :spree_orders, :spree_users, column: :created_by_id
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 20231002000137116) do
+ActiveRecord::Schema[7.0].define(version: 20231003000823494) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pg_stat_statements"
   enable_extension "plpgsql"
@@ -1157,6 +1157,7 @@ ActiveRecord::Schema[7.0].define(version: 20231002000137116) do
   add_foreign_key "spree_orders", "order_cycles", name: "spree_orders_order_cycle_id_fk"
   add_foreign_key "spree_orders", "spree_addresses", column: "bill_address_id", name: "spree_orders_bill_address_id_fk"
   add_foreign_key "spree_orders", "spree_addresses", column: "ship_address_id", name: "spree_orders_ship_address_id_fk"
+  add_foreign_key "spree_orders", "spree_users", column: "created_by_id"
   add_foreign_key "spree_orders", "spree_users", column: "user_id", name: "spree_orders_user_id_fk"
   add_foreign_key "spree_payments", "spree_orders", column: "order_id", name: "spree_payments_order_id_fk"
   add_foreign_key "spree_payments", "spree_payment_methods", column: "payment_method_id", name: "spree_payments_payment_method_id_fk"

spec/models/database_spec.rb

@@ -104,11 +104,7 @@ RSpec.describe "Database" do
     migration_name = "add_foreign_key_to_#{model_class.table_name}_" \
                      "#{foreign_key_table_name}_#{foreign_key_column}"
     migration_class_name = migration_name.camelize
-    millisecond_timestamp = Time.now.utc.strftime('%Y%m%d%H%M%S%L')
-    if millisecond_timestamp == @last_timestamp
-      millisecond_timestamp.to_i += 1
-    end
-    @last_timestamp = millisecond_timestamp
+    millisecond_timestamp = generate_timestamp
     migration_file_name = "db/migrate/#{millisecond_timestamp}_" \
                           "#{migration_name}.rb"
     orphaned_records_query = generate_orphaned_records_query(model_class, foreign_key_table_name,
@@ -144,4 +140,20 @@ RSpec.describe "Database" do
       #   AND #{model_class.table_name}.#{foreign_key_column} IS NOT NULL
     SQL
   end
+
+  # Generates a unique timestamp.
+  #
+  # We may create multiple migrations within the same second, maybe even millisecond.
+  # So we add precision to milliseconds and increment on conflict.
+  def generate_timestamp
+    @last_creation_time ||= Time.new.utc(0)
+
+    creation_time = Time.now.utc
+    if creation_time <= @last_creation_time
+      creation_time += 0.001.seconds
+    end
+    @last_creation_time = creation_time
+
+    creation_time.utc.strftime('%Y%m%d%H%M%S%L')
+  end
 end