UpdateBackend.php

<?php

namespace Drupal\Core\Update;

use Drupal\Core\Cache\CacheBackendInterface;
use Drupal\Core\Cache\NullBackend;

/**
 * Defines a cache backend for use during Drupal database updates.
 *
 * Passes on deletes to another backend while extending the NullBackend to avoid
 * using anything cached prior to running updates.
 */
class UpdateBackend extends NullBackend {
    
    /**
     * The regular runtime cache backend.
     *
     * @var \Drupal\Core\Cache\CacheBackendInterface
     */
    protected $backend;
    
    /**
     * UpdateBackend constructor.
     *
     * @param \Drupal\Core\Cache\CacheBackendInterface $backend
     *   The regular runtime cache backend.
     */
    public function __construct(CacheBackendInterface $backend) {
        $this->backend = $backend;
    }
    
    /**
     * {@inheritdoc}
     */
    public function delete($cid) {
        $this->backend
            ->delete($cid);
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteMultiple(array $cids) {
        $this->backend
            ->deleteMultiple($cids);
    }
    
    /**
     * {@inheritdoc}
     */
    public function deleteAll() {
        $this->backend
            ->deleteAll();
    }

}