class DatabaseBackendFactory

class DatabaseBackendFactory implements CacheFactoryInterface {
    
    /**
     * The database connection.
     *
     * @var \Drupal\Core\Database\Connection
     */
    protected $connection;
    
    /**
     * The cache tags checksum provider.
     *
     * @var \Drupal\Core\Cache\CacheTagsChecksumInterface
     */
    protected $checksumProvider;
    
    /**
     * The site settings.
     *
     * @var \Drupal\Core\Site\Settings
     */
    protected $settings;
    
    /**
     * Constructs the DatabaseBackendFactory object.
     *
     * @param \Drupal\Core\Database\Connection $connection
     *   Database connection
     * @param \Drupal\Core\Cache\CacheTagsChecksumInterface $checksum_provider
     *   The cache tags checksum provider.
     * @param \Drupal\Core\Site\Settings $settings
     *   (optional) The site settings.
     *
     * @throws \BadMethodCallException
     */
    public function __construct(Connection $connection, CacheTagsChecksumInterface $checksum_provider, Settings $settings = NULL) {
        $this->connection = $connection;
        $this->checksumProvider = $checksum_provider;
        $this->settings = $settings ?: Settings::getInstance();
    }
    
    /**
     * Gets DatabaseBackend for the specified cache bin.
     *
     * @param $bin
     *   The cache bin for which the object is created.
     *
     * @return \Drupal\Core\Cache\DatabaseBackend
     *   The cache backend object for the specified cache bin.
     */
    public function get($bin) {
        $max_rows = $this->getMaxRowsForBin($bin);
        return new DatabaseBackend($this->connection, $this->checksumProvider, $bin, $max_rows);
    }
    
    /**
     * Gets the max rows for the specified cache bin.
     *
     * @param string $bin
     *   The cache bin for which the object is created.
     *
     * @return int
     *   The maximum number of rows for the given bin. Defaults to
     *   DatabaseBackend::DEFAULT_MAX_ROWS.
     */
    protected function getMaxRowsForBin($bin) {
        $max_rows_settings = $this->settings
            ->get('database_cache_max_rows');
        // First, look for a cache bin specific setting.
        if (isset($max_rows_settings['bins'][$bin])) {
            $max_rows = $max_rows_settings['bins'][$bin];
        }
        elseif (isset($max_rows_settings['default'])) {
            $max_rows = $max_rows_settings['default'];
        }
        else {
            // Fall back to the default max rows if nothing else is configured.
            $max_rows = DatabaseBackend::DEFAULT_MAX_ROWS;
        }
        return $max_rows;
    }

}