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<?php
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/**
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* @file
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* Provides a stub cache implementation to be used during installation.
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*/
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/**
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* Defines a stub cache implementation to be used during installation.
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*
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* The stub implementation is needed when database access is not yet available.
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* Because Drupal's caching system never requires that cached data be present,
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* these stub functions can short-circuit the process and sidestep the need for
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* any persistent storage. Obviously, using this cache implementation during
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* normal operations would have a negative impact on performance.
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*/
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class DrupalFakeCache extends DrupalDatabaseCache implements DrupalCacheInterface {
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/**
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* Overrides DrupalDatabaseCache::get().
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*/
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function get($cid) {
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return FALSE;
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}
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/**
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* Overrides DrupalDatabaseCache::getMultiple().
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*/
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function getMultiple(&$cids) {
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return array();
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}
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/**
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* Overrides DrupalDatabaseCache::set().
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*/
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function set($cid, $data, $expire = CACHE_PERMANENT) {
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}
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/**
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* Overrides DrupalDatabaseCache::clear().
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*/
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function clear($cid = NULL, $wildcard = FALSE) {
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// If there is a database cache, attempt to clear it whenever possible. The
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// reason for doing this is that the database cache can accumulate data
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// during installation due to any full bootstraps that may occur at the
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// same time (for example, Ajax requests triggered by the installer). If we
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// didn't try to clear it whenever this function is called, the data in the
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// cache would become stale; for example, the installer sometimes calls
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// variable_set(), which updates the {variable} table and then clears the
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// cache to make sure that the next page request picks up the new value.
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// Not actually clearing the cache here therefore leads old variables to be
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// loaded on the first page requests after installation, which can cause
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// subtle bugs, some of which would not be fixed unless the site
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// administrator cleared the cache manually.
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try {
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if (class_exists('Database')) {
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parent::clear($cid, $wildcard);
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}
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}
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// If the attempt at clearing the cache causes an error, that means that
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// either the database connection is not set up yet or the relevant cache
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// table in the database has not yet been created, so we can safely do
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// nothing here.
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catch (Exception $e) {
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}
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}
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/**
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* Overrides DrupalDatabaseCache::isEmpty().
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*/
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function isEmpty() {
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return TRUE;
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}
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}
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