You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: 20230704074124_replace_old_fk_p_ci_runner_machine_builds_to_builds.rb
    path of file: ./repos/gitlabhq/db/post_migrate
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

class ReplaceOldFkPCiRunnerMachineBuildsToBuilds < Gitlab::Database::Migration[2.1]
  include Gitlab::Database::PartitioningMigrationHelpers
  include Gitlab::Database::MigrationHelpers::WraparoundAutovacuum

  disable_ddl_transaction!

  def up
    return unless should_run?
    return if new_foreign_key_exists?

    with_lock_retries do
      remove_foreign_key
    
  def down
    return unless should_run?
    return unless new_foreign_key_exists?

    add_concurrent_partitioned_foreign_key :p_ci_runner_machine_builds, :ci_builds,
      name: :temp_fk_bb490f12fe_p,
      column: [:partition_id, :build_id],
      target_column: [:partition_id, :id],
      on_update: :cascade,
      on_delete: :cascade,
      validate: true,
      reverse_lock_order: true

    switch_constraint_names :p_ci_runner_machine_builds, :fk_bb490f12fe_p, :temp_fk_bb490f12fe_p

    Gitlab::Database::PostgresPartitionedTable.each_partition(:p_ci_runner_machine_builds) do |partition|
      switch_constraint_names partition.identifier, :fk_bb490f12fe_p, :temp_fk_bb490f12fe_p
    end
  end