function DrupalDatabaseCache::garbageCollection

Garbage collection for get() and getMultiple().

Parameters

$bin: The bin being requested.

File

includes/cache.inc, line 383

Class

DrupalDatabaseCache

Defines a default cache implementation.

Code

protected function garbageCollection() {
    $cache_lifetime = variable_get('cache_lifetime', 0);
    // Clean-up the per-user cache expiration session data, so that the session
    // handler can properly clean-up the session data for anonymous users.
    if (isset($_SESSION['cache_expiration'])) {
        $expire = REQUEST_TIME - $cache_lifetime;
        foreach ($_SESSION['cache_expiration'] as $bin => $timestamp) {
            if ($timestamp < $expire) {
                unset($_SESSION['cache_expiration'][$bin]);
            }
        }
        if (!$_SESSION['cache_expiration']) {
            unset($_SESSION['cache_expiration']);
        }
    }
    // Garbage collection of temporary items is only necessary when enforcing
    // a minimum cache lifetime.
    if (!$cache_lifetime) {
        return;
    }
    // When cache lifetime is in force, avoid running garbage collection too
    // often since this will remove temporary cache items indiscriminately.
    $cache_flush = variable_get('cache_flush_' . $this->bin, 0);
    if ($cache_flush && $cache_flush + $cache_lifetime <= REQUEST_TIME) {
        // Reset the variable immediately to prevent a meltdown in heavy load situations.
        variable_set('cache_flush_' . $this->bin, 0);
        // Time to flush old cache data
        db_delete($this->bin)
            ->condition('expire', CACHE_PERMANENT, '<>')
            ->condition('expire', $cache_flush, '<=')
            ->execute();
    }
}