Merge pull request #5355 from cash/oom2

Fixes the DB query cache out of memory issues

21 files changed, 277 insertions, 124 deletions

diff --git a/engine/classes/ElggBatch.php b/engine/classes/ElggBatch.php
index 5d59425d0..1912f89a2 100644
--- a/engine/classes/ElggBatch.php
+++ b/engine/classes/ElggBatch.php
@@ -229,8 +229,9 @@ class ElggBatch
 	private function getNextResultsChunk() {
 		// reset memory caches after first chunk load
 		if ($this->chunkIndex > 0) {
-			global $DB_QUERY_CACHE, $ENTITY_CACHE;
-			$DB_QUERY_CACHE = $ENTITY_CACHE = array();
+			global $ENTITY_CACHE;
+			$ENTITY_CACHE = array();
+			_elgg_invalidate_query_cache();
 		}
 
 		// always reset results.
diff --git a/engine/classes/ElggEntity.php b/engine/classes/ElggEntity.php
index 5a63c7b15..8b3ceb551 100644
--- a/engine/classes/ElggEntity.php
+++ b/engine/classes/ElggEntity.php
@@ -1270,7 +1270,7 @@ abstract class ElggEntity extends ElggData implements
 	public function save() {
 		$guid = $this->getGUID();
 		if ($guid > 0) {
-			cache_entity($this);
+			_elgg_cache_entity($this);
 
 			return update_entity(
 				$guid,
@@ -1320,7 +1320,7 @@ abstract class ElggEntity extends ElggData implements
 			$this->attributes['subtype'] = get_subtype_id($this->attributes['type'],
 				$this->attributes['subtype']);
 
-			cache_entity($this);
+			_elgg_cache_entity($this);
 
 			return $this->attributes['guid'];
 		}
@@ -1362,7 +1362,7 @@ abstract class ElggEntity extends ElggData implements
 
 			// Cache object handle
 			if ($this->attributes['guid']) {
-				cache_entity($this);
+				_elgg_cache_entity($this);
 			}
 
 			return true;
diff --git a/engine/classes/ElggGroup.php b/engine/classes/ElggGroup.php
index 7ab0bfa48..61f9163d5 100644
--- a/engine/classes/ElggGroup.php
+++ b/engine/classes/ElggGroup.php
@@ -335,7 +335,7 @@ class ElggGroup extends ElggEntity
 
 		$this->attributes = $attrs;
 		$this->attributes['tables_loaded'] = 2;
-		cache_entity($this);
+		_elgg_cache_entity($this);
 
 		return true;
 	}
diff --git a/engine/classes/ElggLRUCache.php b/engine/classes/ElggLRUCache.php
new file mode 100644
index 000000000..f51af2ed7
--- /dev/null
+++ b/engine/classes/ElggLRUCache.php
@@ -0,0 +1,181 @@
+<?php
+
+/**
+ * Least Recently Used Cache
+ *
+ * A fixed sized cache that removes the element used last when it reaches its
+ * size limit.
+ * 
+ * Based on https://github.com/cash/LRUCache
+ * 
+ * @access private
+ * 
+ * @package    Elgg.Core
+ * @subpackage Cache
+ */
+class ElggLRUCache implements ArrayAccess {
+	/** @var int */
+	protected $maximumSize;
+
+	/**
+	 * The front of the array contains the LRU element
+	 *
+	 * @var array
+	 */
+	protected $data = array();
+
+	/**
+	 * Create a LRU Cache
+	 *
+	 * @param int $size The size of the cache
+	 * @throws InvalidArgumentException
+	 */
+	public function __construct($size) {
+		if (!is_int($size) || $size <= 0) {
+			throw new InvalidArgumentException();
+		}
+		$this->maximumSize = $size;
+	}
+
+	/**
+	 * Get the value cached with this key
+	 *
+	 * @param int|string $key     The key. Strings that are ints are cast to ints.
+	 * @param mixed      $default The value to be returned if key not found. (Optional)
+	 * @return mixed
+	 */
+	public function get($key, $default = null) {
+		if (isset($this->data[$key])) {
+			$this->recordAccess($key);
+			return $this->data[$key];
+		} else {
+			return $default;
+		}
+	}
+
+	/**
+	 * Add something to the cache
+	 *
+	 * @param int|string $key   The key. Strings that are ints are cast to ints.
+	 * @param mixed      $value The value to cache
+	 * @return void
+	 */
+	public function set($key, $value) {
+		if (isset($this->data[$key])) {
+			$this->data[$key] = $value;
+			$this->recordAccess($key);
+		} else {
+			$this->data[$key] = $value;
+			if ($this->size() > $this->maximumSize) {
+				// remove least recently used element (front of array)
+				reset($this->data);
+				unset($this->data[key($this->data)]);
+			}
+		}
+	}
+
+	/**
+	 * Get the number of elements in the cache
+	 *
+	 * @return int
+	 */
+	public function size() {
+		return count($this->data);
+	}
+
+	/**
+	 * Does the cache contain an element with this key
+	 *
+	 * @param int|string $key The key
+	 * @return boolean
+	 */
+	public function containsKey($key) {
+		return isset($this->data[$key]);
+	}
+
+	/**
+	 * Remove the element with this key.
+	 *
+	 * @param int|string $key The key
+	 * @return mixed Value or null if not set
+	 */
+	public function remove($key) {
+		if (isset($this->data[$key])) {
+			$value = $this->data[$key];
+			unset($this->data[$key]);
+			return $value;
+		} else {
+			return null;
+		}
+	}
+
+	/**
+	 * Clear the cache
+	 * 
+	 * @return void
+	 */
+	public function clear() {
+		$this->data = array();
+	}
+
+	/**
+	 * Moves the element from current position to end of array
+	 * 
+	 * @param int|string $key The key
+	 * @return void
+	 */
+	protected function recordAccess($key) {
+		$value = $this->data[$key];
+		unset($this->data[$key]);
+		$this->data[$key] = $value;
+	}
+
+	/**
+	 * Assigns a value for the specified key
+	 *
+	 * @see ArrayAccess::offsetSet()
+	 *
+	 * @param int|string $key   The key to assign the value to.
+	 * @param mixed      $value The value to set.
+	 * @return void
+	 */
+	public function offsetSet($key, $value) {
+		$this->set($key, $value);
+	}
+
+	/**
+	 * Get the value for specified key
+	 *
+	 * @see ArrayAccess::offsetGet()
+	 *
+	 * @param int|string $key The key to retrieve.
+	 * @return mixed
+	 */
+	public function offsetGet($key) {
+		return $this->get($key);
+	}
+
+	/**
+	 * Unsets a key.
+	 *
+	 * @see ArrayAccess::offsetUnset()
+	 *
+	 * @param int|string $key The key to unset.
+	 * @return void
+	 */
+	public function offsetUnset($key) {
+		$this->remove($key);
+	}
+
+	/**
+	 * Does key exist?
+	 *
+	 * @see ArrayAccess::offsetExists()
+	 *
+	 * @param int|string $key A key to check for.
+	 * @return boolean
+	 */
+	public function offsetExists($key) {
+		return $this->containsKey($key);
+	}
+}
diff --git a/engine/classes/ElggObject.php b/engine/classes/ElggObject.php
index 3cb76ffaf..d54752dca 100644
--- a/engine/classes/ElggObject.php
+++ b/engine/classes/ElggObject.php
@@ -107,7 +107,7 @@ class ElggObject extends ElggEntity {
 
 		$this->attributes = $attrs;
 		$this->attributes['tables_loaded'] = 2;
-		cache_entity($this);
+		_elgg_cache_entity($this);
 
 		return true;
 	}
diff --git a/engine/classes/ElggSite.php b/engine/classes/ElggSite.php
index deba5087e..dd996fe98 100644
--- a/engine/classes/ElggSite.php
+++ b/engine/classes/ElggSite.php
@@ -124,7 +124,7 @@ class ElggSite extends ElggEntity {
 
 		$this->attributes = $attrs;
 		$this->attributes['tables_loaded'] = 2;
-		cache_entity($this);
+		_elgg_cache_entity($this);
 
 		return true;
 	}
diff --git a/engine/classes/ElggStaticVariableCache.php b/engine/classes/ElggStaticVariableCache.php
index 17d849400..9c14fdfba 100644
--- a/engine/classes/ElggStaticVariableCache.php
+++ b/engine/classes/ElggStaticVariableCache.php
@@ -11,7 +11,7 @@ class ElggStaticVariableCache extends ElggSharedMemoryCache {
 	/**
 	 * The cache.
 	 *
-	 * @var unknown_type
+	 * @var array
 	 */
 	private static $__cache;
 
@@ -22,7 +22,7 @@ class ElggStaticVariableCache extends ElggSharedMemoryCache {
 	 * memory, optionally with a given namespace (to avoid overlap).
 	 *
 	 * @param string $namespace The namespace for this cache to write to.
-	 * @note namespaces of the same name are shared!
+	 * @warning namespaces of the same name are shared!
 	 */
 	function __construct($namespace = 'default') {
 		$this->setNamespace($namespace);
@@ -80,7 +80,7 @@ class ElggStaticVariableCache extends ElggSharedMemoryCache {
 	}
 
 	/**
-	 * This was probably meant to delete everything?
+	 * Clears the cache for a particular namespace
 	 *
 	 * @return void
 	 */
diff --git a/engine/classes/ElggUser.php b/engine/classes/ElggUser.php
index b80065b27..6d9f10b57 100644
--- a/engine/classes/ElggUser.php
+++ b/engine/classes/ElggUser.php
@@ -112,7 +112,7 @@ class ElggUser extends ElggEntity
 
 		$this->attributes = $attrs;
 		$this->attributes['tables_loaded'] = 2;
-		cache_entity($this);
+		_elgg_cache_entity($this);
 
 		return true;
 	}
diff --git a/engine/lib/database.php b/engine/lib/database.php
index 2b348366d..3553d787d 100644
--- a/engine/lib/database.php
+++ b/engine/lib/database.php
@@ -12,17 +12,19 @@
 /**
  * Query cache for all queries.
  *
- * Each query and its results are stored in this array as:
+ * Each query and its results are stored in this cache as:
  * <code>
- * $DB_QUERY_CACHE[$query] => array(result1, result2, ... resultN)
+ * $DB_QUERY_CACHE[query hash] => array(result1, result2, ... resultN)
  * </code>
+ * @see elgg_query_runner() for details on the hash.
  *
- * @warning be array this var may be an array or ElggStaticVariableCache depending on when called :(
+ * @warning Elgg used to set this as an empty array to turn off the cache
  *
- * @global ElggStaticVariableCache|array $DB_QUERY_CACHE
+ * @global ElggLRUCache|null $DB_QUERY_CACHE
+ * @access private
  */
 global $DB_QUERY_CACHE;
-$DB_QUERY_CACHE = array();
+$DB_QUERY_CACHE = null;
 
 /**
  * Queries to be executed upon shutdown.
@@ -40,6 +42,7 @@ $DB_QUERY_CACHE = array();
  * </code>
  *
  * @global array $DB_DELAYED_QUERIES
+ * @access private
  */
 global $DB_DELAYED_QUERIES;
 $DB_DELAYED_QUERIES = array();
@@ -51,6 +54,7 @@ $DB_DELAYED_QUERIES = array();
  * $dblink as $dblink[$name] => resource.  Use get_db_link($name) to retrieve it.
  *
  * @global resource[] $dblink
+ * @access private
  */
 global $dblink;
 $dblink = array();
@@ -61,6 +65,7 @@ $dblink = array();
  * Each call to the database increments this counter.
  *
  * @global integer $dbcalls
+ * @access private
  */
 global $dbcalls;
 $dbcalls = 0;
@@ -123,9 +128,8 @@ function establish_db_link($dblinkname = "readwrite") {
 
 	// Set up cache if global not initialized and query cache not turned off
 	if ((!$DB_QUERY_CACHE) && (!$db_cache_off)) {
-		// @todo everywhere else this is assigned to array(), making it dangerous to call
-		// object methods on this. We should consider making this an plain array
-		$DB_QUERY_CACHE = new ElggStaticVariableCache('db_query_cache');
+		// @todo if we keep this cache in 1.9, expose the size as a config parameter
+		$DB_QUERY_CACHE = new ElggLRUCache(200);		
 	}
 }
 
@@ -400,11 +404,9 @@ function elgg_query_runner($query, $callback = null, $single = false) {
 
 	// Is cached?
 	if ($DB_QUERY_CACHE) {
-		$cached_query = $DB_QUERY_CACHE[$hash];
-
-		if ($cached_query !== FALSE) {
+		if (isset($DB_QUERY_CACHE[$hash])) {
 			elgg_log("DB query $query results returned from cache (hash: $hash)", 'NOTICE');
-			return $cached_query;
+			return $DB_QUERY_CACHE[$hash];			
 		}
 	}
 
@@ -456,19 +458,12 @@ function elgg_query_runner($query, $callback = null, $single = false) {
  * @access private
  */
 function insert_data($query) {
-	global $DB_QUERY_CACHE;
 
 	elgg_log("DB query $query", 'NOTICE');
 	
 	$dblink = get_db_link('write');
 
-	// Invalidate query cache
-	if ($DB_QUERY_CACHE) {
-		/* @var ElggStaticVariableCache $DB_QUERY_CACHE */
-		$DB_QUERY_CACHE->clear();
-	}
-
-	elgg_log("Query cache invalidated", 'NOTICE');
+	_elgg_invalidate_query_cache();
 
 	if (execute_query("$query", $dblink)) {
 		return mysql_insert_id($dblink);
@@ -488,18 +483,12 @@ function insert_data($query) {
  * @access private
  */
 function update_data($query) {
-	global $DB_QUERY_CACHE;
 
 	elgg_log("DB query $query", 'NOTICE');
 
 	$dblink = get_db_link('write');
 
-	// Invalidate query cache
-	if ($DB_QUERY_CACHE) {
-		/* @var ElggStaticVariableCache $DB_QUERY_CACHE */
-		$DB_QUERY_CACHE->clear();
-		elgg_log("Query cache invalidated", 'NOTICE');
-	}
+	_elgg_invalidate_query_cache();
 
 	if (execute_query("$query", $dblink)) {
 		return TRUE;
@@ -519,18 +508,12 @@ function update_data($query) {
  * @access private
  */
 function delete_data($query) {
-	global $DB_QUERY_CACHE;
 
 	elgg_log("DB query $query", 'NOTICE');
 
 	$dblink = get_db_link('write');
 
-	// Invalidate query cache
-	if ($DB_QUERY_CACHE) {
-		/* @var ElggStaticVariableCache $DB_QUERY_CACHE */
-		$DB_QUERY_CACHE->clear();
-		elgg_log("Query cache invalidated", 'NOTICE');
-	}
+	_elgg_invalidate_query_cache();
 
 	if (execute_query("$query", $dblink)) {
 		return mysql_affected_rows($dblink);
@@ -539,6 +522,22 @@ function delete_data($query) {
 	return FALSE;
 }
 
+/**
+ * Invalidate the query cache
+ * 
+ * @access private
+ */
+function _elgg_invalidate_query_cache() {
+	global $DB_QUERY_CACHE;
+	if ($DB_QUERY_CACHE instanceof ElggLRUCache) {
+		$DB_QUERY_CACHE->clear();
+		elgg_log("Query cache invalidated", 'NOTICE');
+	} elseif ($DB_QUERY_CACHE) {
+		// In case someone sets the cache to an array and primes it with data 
+		$DB_QUERY_CACHE = array();
+		elgg_log("Query cache invalidated", 'NOTICE');
+	}
+}
 
 /**
  * Return tables matching the database prefix {@link $CONFIG->dbprefix}% in the currently
diff --git a/engine/lib/entities.php b/engine/lib/entities.php
index 156eec040..cb972b282 100644
--- a/engine/lib/entities.php
+++ b/engine/lib/entities.php
@@ -30,10 +30,10 @@ $SUBTYPE_CACHE = null;
  *
  * @param int $guid The entity guid
  *
- * @return null
+ * @return void
  * @access private
  */
-function invalidate_cache_for_entity($guid) {
+function _elgg_invalidate_cache_for_entity($guid) {
 	global $ENTITY_CACHE;
 
 	$guid = (int)$guid;
@@ -50,13 +50,13 @@ function invalidate_cache_for_entity($guid) {
  *
  * @param ElggEntity $entity Entity to cache
  *
- * @return null
- * @see retrieve_cached_entity()
- * @see invalidate_cache_for_entity()
+ * @return void
+ * @see _elgg_retrieve_cached_entity()
+ * @see _elgg_invalidate_cache_for_entity()
  * @access private
- * TODO(evan): Use an ElggCache object
+ * @todo Use an ElggCache object
  */
-function cache_entity(ElggEntity $entity) {
+function _elgg_cache_entity(ElggEntity $entity) {
 	global $ENTITY_CACHE;
 
 	// Don't cache non-plugin entities while access control is off, otherwise they could be
@@ -66,7 +66,7 @@ function cache_entity(ElggEntity $entity) {
 	}
 
 	// Don't store too many or we'll have memory problems
-	// TODO(evan): Pick a less arbitrary limit
+	// @todo Pick a less arbitrary limit
 	if (count($ENTITY_CACHE) > 256) {
 		$random_guid = array_rand($ENTITY_CACHE);
 
@@ -88,11 +88,11 @@ function cache_entity(ElggEntity $entity) {
  * @param int $guid The guid
  *
  * @return ElggEntity|bool false if entity not cached, or not fully loaded
- * @see cache_entity()
- * @see invalidate_cache_for_entity()
+ * @see _elgg_cache_entity()
+ * @see _elgg_invalidate_cache_for_entity()
  * @access private
  */
-function retrieve_cached_entity($guid) {
+function _elgg_retrieve_cached_entity($guid) {
 	global $ENTITY_CACHE;
 
 	if (isset($ENTITY_CACHE[$guid])) {
@@ -105,31 +105,6 @@ function retrieve_cached_entity($guid) {
 }
 
 /**
- * As retrieve_cached_entity, but returns the result as a stdClass
- * (compatible with load functions that expect a database row.)
- *
- * @param int $guid The guid
- *
- * @return mixed
- * @todo unused
- * @access private
- */
-function retrieve_cached_entity_row($guid) {
-	$obj = retrieve_cached_entity($guid);
-	if ($obj) {
-		$tmp = new stdClass;
-
-		foreach ($obj as $k => $v) {
-			$tmp->$k = $v;
-		}
-
-		return $tmp;
-	}
-
-	return false;
-}
-
-/**
  * Return the id for a given subtype.
  *
  * ElggEntity objects have a type and a subtype.  Subtypes
@@ -745,7 +720,7 @@ function get_entity($guid) {
 	}
 	
 	// Check local cache first
-	$new_entity = retrieve_cached_entity($guid);
+	$new_entity = _elgg_retrieve_cached_entity($guid);
 	if ($new_entity) {
 		return $new_entity;
 	}
@@ -782,7 +757,7 @@ function get_entity($guid) {
 	}
 
 	if ($new_entity) {
-		cache_entity($new_entity);
+		_elgg_cache_entity($new_entity);
 	}
 	return $new_entity;
 }
@@ -1037,7 +1012,7 @@ function elgg_get_entities(array $options = array()) {
 			foreach ($dt as $item) {
 				// A custom callback could result in items that aren't ElggEntity's, so check for them
 				if ($item instanceof ElggEntity) {
-					cache_entity($item);
+					_elgg_cache_entity($item);
 					// plugins usually have only settings
 					if (!$item instanceof ElggPlugin) {
 						$guids[] = $item->guid;
@@ -1102,7 +1077,7 @@ function _elgg_fetch_entities_from_sql($sql) {
 		if (empty($row->guid) || empty($row->type)) {
 			throw new LogicException('Entity row missing guid or type');
 		}
-		if ($entity = retrieve_cached_entity($row->guid)) {
+		if ($entity = _elgg_retrieve_cached_entity($row->guid)) {
 			$rows[$i] = $entity;
 			continue;
 		}
@@ -1628,7 +1603,7 @@ function disable_entity($guid, $reason = "", $recursive = true) {
 
 				$entity->disableMetadata();
 				$entity->disableAnnotations();
-				invalidate_cache_for_entity($guid);
+				_elgg_invalidate_cache_for_entity($guid);
 
 				$res = update_data("UPDATE {$CONFIG->dbprefix}entities
 					SET enabled = 'no'
@@ -1726,7 +1701,7 @@ function delete_entity($guid, $recursive = true) {
 
 				// delete cache
 				if (isset($ENTITY_CACHE[$guid])) {
-					invalidate_cache_for_entity($guid);
+					_elgg_invalidate_cache_for_entity($guid);
 				}
 				
 				// If memcache is available then delete this entry from the cache
diff --git a/engine/lib/river.php b/engine/lib/river.php
index f2ec1e101..4926a85c4 100644
--- a/engine/lib/river.php
+++ b/engine/lib/river.php
@@ -380,10 +380,10 @@ function _elgg_prefetch_river_entities(array $river_items) {
 	// prefetch objects and subjects
 	$guids = array();
 	foreach ($river_items as $item) {
-		if ($item->subject_guid && !retrieve_cached_entity($item->subject_guid)) {
+		if ($item->subject_guid && !_elgg_retrieve_cached_entity($item->subject_guid)) {
 			$guids[$item->subject_guid] = true;
 		}
-		if ($item->object_guid && !retrieve_cached_entity($item->object_guid)) {
+		if ($item->object_guid && !_elgg_retrieve_cached_entity($item->object_guid)) {
 			$guids[$item->object_guid] = true;
 		}
 	}
@@ -402,7 +402,7 @@ function _elgg_prefetch_river_entities(array $river_items) {
 	$guids = array();
 	foreach ($river_items as $item) {
 		$object = $item->getObjectEntity();
-		if ($object->container_guid && !retrieve_cached_entity($object->container_guid)) {
+		if ($object->container_guid && !_elgg_retrieve_cached_entity($object->container_guid)) {
 			$guids[$object->container_guid] = true;
 		}
 	}
diff --git a/engine/lib/upgrade.php b/engine/lib/upgrade.php
index d684af862..0cc1e64dc 100644
--- a/engine/lib/upgrade.php
+++ b/engine/lib/upgrade.php
@@ -354,16 +354,12 @@ function _elgg_upgrade_unlock() {
  * @access private
  */
 function _elgg_upgrade_is_locked() {
-	global $CONFIG, $DB_QUERY_CACHE;
-	
+	global $CONFIG;
+
 	$is_locked = count(get_data("show tables like '{$CONFIG->dbprefix}upgrade_lock'"));
-	
-	// Invalidate query cache
-	if ($DB_QUERY_CACHE) {
-		/* @var ElggStaticVariableCache $DB_QUERY_CACHE */
-		$DB_QUERY_CACHE->clear();
-		elgg_log("Query cache invalidated", 'NOTICE');
-	}
-	
+
+	// @todo why?
+	_elgg_invalidate_query_cache();
+
 	return $is_locked;
 }
diff --git a/engine/lib/upgrades/2009102801.php b/engine/lib/upgrades/2009102801.php
index cab9a6835..3ad113fb2 100644
--- a/engine/lib/upgrades/2009102801.php
+++ b/engine/lib/upgrades/2009102801.php
@@ -203,14 +203,15 @@ function user_file_matrix($guid) {
 	return "$time_created/$user->guid/";
 }
 
-global $DB_QUERY_CACHE, $DB_PROFILE, $ENTITY_CACHE;
+global $ENTITY_CACHE, $CONFIG;
 /**
  * Upgrade file locations
  */
 $users = mysql_query("SELECT guid, username
 	FROM {$CONFIG->dbprefix}users_entity WHERE username != ''");
 while ($user = mysql_fetch_object($users)) {
-	$DB_QUERY_CACHE = $DB_PROFILE = $ENTITY_CACHE = array();
+	$ENTITY_CACHE = array();
+	_elgg_invalidate_query_cache();
 
 	$to = $CONFIG->dataroot . user_file_matrix($user->guid);
 	foreach (array('1_0', '1_1', '1_6') as $version) {
diff --git a/engine/lib/upgrades/2010061501.php b/engine/lib/upgrades/2010061501.php
index 9ff7d3102..744c28fd5 100644
--- a/engine/lib/upgrades/2010061501.php
+++ b/engine/lib/upgrades/2010061501.php
@@ -45,7 +45,7 @@ if ($dbversion < 2009100701) {
 			}
 		}
 
-		global $DB_QUERY_CACHE, $DB_PROFILE, $ENTITY_CACHE;
+		global $ENTITY_CACHE;
 
 		/**
 			Upgrade file locations
@@ -60,7 +60,9 @@ if ($dbversion < 2009100701) {
 		$users = mysql_query("SELECT guid, username FROM {$CONFIG->dbprefix}users_entity
 			WHERE username != ''", $link);
 		while ($user = mysql_fetch_object($users)) {
-			$DB_QUERY_CACHE = $DB_PROFILE = $ENTITY_CACHE = array();
+			$ENTITY_CACHE = array();
+			_elgg_invalidate_query_cache();
+
 
 			$to = $CONFIG->dataroot . user_file_matrix($user->guid);
 			foreach (array('1_0', '1_1', '1_6') as $version) {
diff --git a/engine/lib/upgrades/2010071001.php b/engine/lib/upgrades/2010071001.php
index 1b5d379d8..5594493a8 100644
--- a/engine/lib/upgrades/2010071001.php
+++ b/engine/lib/upgrades/2010071001.php
@@ -30,11 +30,12 @@ function user_file_matrix_2010071001($guid) {
 
 $sizes = array('large', 'medium', 'small', 'tiny', 'master', 'topbar');
 
-global $DB_QUERY_CACHE, $DB_PROFILE, $ENTITY_CACHE, $CONFIG;
+global $ENTITY_CACHE, $CONFIG;
 $users = mysql_query("SELECT guid, username FROM {$CONFIG->dbprefix}users_entity
 	WHERE username != ''");
 while ($user = mysql_fetch_object($users)) {
-	$DB_QUERY_CACHE = $DB_PROFILE = $ENTITY_CACHE = array();
+	$ENTITY_CACHE = array();
+	_elgg_invalidate_query_cache();
 
 	$user_directory = user_file_matrix_2010071001($user->guid);
 	if (!$user_directory) {
diff --git a/engine/lib/upgrades/2010071002.php b/engine/lib/upgrades/2010071002.php
index 30bd6538c..52aa15ef5 100644
--- a/engine/lib/upgrades/2010071002.php
+++ b/engine/lib/upgrades/2010071002.php
@@ -4,12 +4,13 @@
  */
 
 // loop through all users checking collections and notifications
-global $DB_QUERY_CACHE, $DB_PROFILE, $ENTITY_CACHE, $CONFIG;
+global $ENTITY_CACHE, $CONFIG;
 global $NOTIFICATION_HANDLERS;
 $users = mysql_query("SELECT guid, username FROM {$CONFIG->dbprefix}users_entity
 	WHERE username != ''");
 while ($user = mysql_fetch_object($users)) {
-	$DB_QUERY_CACHE = $DB_PROFILE = $ENTITY_CACHE = array();
+	$ENTITY_CACHE = array();
+	_elgg_invalidate_query_cache();
 
 	$user = get_entity($user->guid);
 	foreach ($NOTIFICATION_HANDLERS as $method => $foo) {
diff --git a/engine/lib/upgrades/2011052801.php b/engine/lib/upgrades/2011052801.php
index 8084bc06c..b5a8e1018 100644
--- a/engine/lib/upgrades/2011052801.php
+++ b/engine/lib/upgrades/2011052801.php
@@ -2,7 +2,7 @@
 /**
  * Make sure all users have the relationship member_of_site
  */
-global $DB_QUERY_CACHE, $DB_PROFILE, $ENTITY_CACHE, $CONFIG;
+global $ENTITY_CACHE;
 $db_prefix = get_config('dbprefix');
 
 $limit = 100;
@@ -17,7 +17,8 @@ $q = "SELECT e.* FROM {$db_prefix}entities e
 $users = get_data($q);
 
 while ($users) {
-	$DB_QUERY_CACHE = $DB_PROFILE = $ENTITY_CACHE = array();
+	$ENTITY_CACHE = array();
+	_elgg_invalidate_query_cache();
 
 	// do manually to not trigger any events because these aren't new users.
 	foreach ($users as $user) {
diff --git a/engine/lib/upgrades/2013030600-1.8.13-update_user_location-8999eb8bf1bdd9a3.php b/engine/lib/upgrades/2013030600-1.8.13-update_user_location-8999eb8bf1bdd9a3.php
index b38eb5100..8eccf05e2 100644
--- a/engine/lib/upgrades/2013030600-1.8.13-update_user_location-8999eb8bf1bdd9a3.php
+++ b/engine/lib/upgrades/2013030600-1.8.13-update_user_location-8999eb8bf1bdd9a3.php
@@ -7,8 +7,6 @@
  * This script turns that back into a string.
  */
 
-global $DB_QUERY_CACHE;
-
 $ia = elgg_set_ignore_access(true);
 $options = array(
 	'type' => 'user',
@@ -17,7 +15,7 @@ $options = array(
 $batch = new ElggBatch('elgg_get_entities', $options);
 
 foreach ($batch as $entity) {
-	$DB_QUERY_CACHE = array();
+	_elgg_invalidate_query_cache();
 	
 	if (is_array($entity->location)) {
 		$entity->location = implode(', ', $entity->location);
diff --git a/engine/lib/users.php b/engine/lib/users.php
index 4a585c07f..868cd7815 100644
--- a/engine/lib/users.php
+++ b/engine/lib/users.php
@@ -237,7 +237,7 @@ function make_user_admin($user_guid) {
 			}
 
 			$r = update_data("UPDATE {$CONFIG->dbprefix}users_entity set admin='yes' where guid=$user_guid");
-			invalidate_cache_for_entity($user_guid);
+			_elgg_invalidate_cache_for_entity($user_guid);
 			return $r;
 		}
 
@@ -273,7 +273,7 @@ function remove_user_admin($user_guid) {
 			}
 
 			$r = update_data("UPDATE {$CONFIG->dbprefix}users_entity set admin='no' where guid=$user_guid");
-			invalidate_cache_for_entity($user_guid);
+			_elgg_invalidate_cache_for_entity($user_guid);
 			return $r;
 		}
 
@@ -558,8 +558,8 @@ function get_user_by_username($username) {
 
 	// Caching
 	if ((isset($USERNAME_TO_GUID_MAP_CACHE[$username]))
-			&& (retrieve_cached_entity($USERNAME_TO_GUID_MAP_CACHE[$username]))) {
-		return retrieve_cached_entity($USERNAME_TO_GUID_MAP_CACHE[$username]);
+			&& (_elgg_retrieve_cached_entity($USERNAME_TO_GUID_MAP_CACHE[$username]))) {
+		return _elgg_retrieve_cached_entity($USERNAME_TO_GUID_MAP_CACHE[$username]);
 	}
 
 	$query = "SELECT e.* from {$CONFIG->dbprefix}users_entity u
@@ -592,9 +592,9 @@ function get_user_by_code($code) {
 
 	// Caching
 	if ((isset($CODE_TO_GUID_MAP_CACHE[$code]))
-	&& (retrieve_cached_entity($CODE_TO_GUID_MAP_CACHE[$code]))) {
+	&& (_elgg_retrieve_cached_entity($CODE_TO_GUID_MAP_CACHE[$code]))) {
 
-		return retrieve_cached_entity($CODE_TO_GUID_MAP_CACHE[$code]);
+		return _elgg_retrieve_cached_entity($CODE_TO_GUID_MAP_CACHE[$code]);
 	}
 
 	$query = "SELECT e.* from {$CONFIG->dbprefix}users_entity u
diff --git a/engine/tests/api/access_collections.php b/engine/tests/api/access_collections.php
index ebcd7d318..4acfae596 100644
--- a/engine/tests/api/access_collections.php
+++ b/engine/tests/api/access_collections.php
@@ -54,7 +54,6 @@ class ElggCoreAccessCollectionsTest extends ElggCoreUnitTest {
 	}
 
 	public function testCreateGetDeleteACL() {
-		global $DB_QUERY_CACHE;
 		
 		$acl_name = 'test access collection';
 		$acl_id = create_access_collection($acl_name);
@@ -67,8 +66,6 @@ class ElggCoreAccessCollectionsTest extends ElggCoreUnitTest {
 		$this->assertEqual($acl->id, $acl_id);
 
 		if ($acl) {
-			$DB_QUERY_CACHE = array();
-			
 			$this->assertEqual($acl->name, $acl_name);
 
 			$result = delete_access_collection($acl_id);
diff --git a/mod/pages/actions/pages/delete.php b/mod/pages/actions/pages/delete.php
index c99f15fbf..fd5791e4d 100644
--- a/mod/pages/actions/pages/delete.php
+++ b/mod/pages/actions/pages/delete.php
@@ -40,7 +40,7 @@ if (elgg_instanceof($page, 'object', 'page') || elgg_instanceof($page, 'object',
 						'metadata_name' => 'parent_guid',
 					));
 
-					invalidate_cache_for_entity($child_guid);
+					_elgg_invalidate_cache_for_entity($child_guid);
 					if ($newentity_cache) {
 						$newentity_cache->delete($child_guid);
 					}