MDL-38165 cache: fixed issues purging peristent caches by event

cache/classes/factory.php

@@ -75,6 +75,12 @@ class cache_factory {
      */
     protected $cachesfromparams = array();
 
+    /**
+     * An array of stores organised by definitions.
+     * @var array
+     */
+    protected $definitionstores = array();
+
     /**
      * An array of instantiated stores.
      * @var array
@@ -272,9 +278,27 @@ public function create_store_from_config($name, array $details, cache_definition
         // order to address the issues.
         $store = $this->stores[$name]->create_clone($details);
         $store->initialise($definition);
+        $definitionid = $definition->get_id();
+        if (!isset($this->definitionstores[$definitionid])) {
+            $this->definitionstores[$definitionid] = array();
+        }
+        $this->definitionstores[$definitionid][] = $store;
         return $store;
     }
 
+    /**
+     * Returns an array of cache stores that have been initialised for use in definitions.
+     * @param cache_definition $definition
+     * @return array
+     */
+    public function get_store_instances_in_use(cache_definition $definition) {
+        $id = $definition->get_id();
+        if (!isset($this->definitionstores[$id])) {
+            return array();
+        }
+        return $this->definitionstores[$id];
+    }
+
     /**
      * Creates a cache config instance with the ability to write if required.
      *

cache/classes/helper.php

@@ -312,15 +312,18 @@ public static function purge_by_event($event) {
         foreach ($instance->get_definitions() as $name => $definitionarr) {
             $definition = cache_definition::load($name, $definitionarr);
             if ($definition->invalidates_on_event($event)) {
-                // Create the cache.
-                $cache = $factory->create_cache($definition);
-                // Initialise, in case of a store.
-                if ($cache instanceof cache_store) {
-                    $cache->initialise($definition);
+                // Check if this definition would result in a persistent loader being in use.
+                if ($definition->should_be_persistent()) {
+                    // There may be a persistent cache loader. Lets purge that first so that any persistent data is removed.
+                    $cache = $factory->create_cache_from_definition($definition->get_component(), $definition->get_area());
+                    $cache->purge();
+                }
+                // Get all of the store instances that are in use for this store.
+                $stores = $factory->get_store_instances_in_use($definition);
+                foreach ($stores as $store) {
+                    // Purge each store individually.
+                    $store->purge();
                 }
-                // Purge the cache.
-                $cache->purge();
-
                 // We need to flag the event in the "Event invalidation" cache if it hasn't already happened.
                 if ($invalidationeventset === false) {
                     // Get the event invalidation cache.