function DrupalDatabaseCache::clear

Implements DrupalCacheInterface::clear().

Overrides DrupalCacheInterface::clear

File

includes/cache.inc, line 487

Class

DrupalDatabaseCache

Defines a default cache implementation.

Code

function clear($cid = NULL, $wildcard = FALSE) {
    global $user;
    if (empty($cid)) {
        if (variable_get('cache_lifetime', 0)) {
            // We store the time in the current user's session. We then simulate
            // that the cache was flushed for this user by not returning cached
            // data that was cached before the timestamp.
            $_SESSION['cache_expiration'][$this->bin] = REQUEST_TIME;
            $cache_flush = variable_get('cache_flush_' . $this->bin, 0);
            if ($cache_flush == 0) {
                // This is the first request to clear the cache, start a timer.
                variable_set('cache_flush_' . $this->bin, REQUEST_TIME);
            }
            elseif (REQUEST_TIME > $cache_flush + variable_get('cache_lifetime', 0)) {
                // Clear the cache for everyone, cache_lifetime seconds have
                // passed since the first request to clear the cache.
                db_delete($this->bin)
                    ->condition('expire', CACHE_PERMANENT, '<>')
                    ->condition('expire', REQUEST_TIME, '<')
                    ->execute();
                variable_set('cache_flush_' . $this->bin, 0);
            }
        }
        else {
            // No minimum cache lifetime, flush all temporary cache entries now.
            db_delete($this->bin)
                ->condition('expire', CACHE_PERMANENT, '<>')
                ->condition('expire', REQUEST_TIME, '<')
                ->execute();
        }
    }
    else {
        if ($wildcard) {
            if ($cid == '*') {
                // Check if $this->bin is a cache table before truncating. Other
                // cache_clear_all() operations throw a PDO error in this situation,
                // so we don't need to verify them first. This ensures that non-cache
                // tables cannot be truncated accidentally.
                if ($this->isValidBin()) {
                    db_truncate($this->bin)
                        ->execute();
                }
                else {
                    throw new Exception(t('Invalid or missing cache bin specified: %bin', array(
                        '%bin' => $this->bin,
                    )));
                }
            }
            else {
                db_delete($this->bin)
                    ->condition('cid', db_like($cid) . '%', 'LIKE')
                    ->execute();
            }
        }
        elseif (is_array($cid)) {
            // Delete in chunks when a large array is passed.
            do {
                db_delete($this->bin)
                    ->condition('cid', array_splice($cid, 0, 1000), 'IN')
                    ->execute();
            } while (count($cid));
        }
        else {
            db_delete($this->bin)
                ->condition('cid', $cid)
                ->execute();
        }
    }
}