diff --git a/phpBB/phpbb/cache/driver/memory.php b/phpBB/phpbb/cache/driver/memory.php
index 0b0e323e3d..56308be8da 100644
--- a/phpBB/phpbb/cache/driver/memory.php
+++ b/phpBB/phpbb/cache/driver/memory.php
@@ -208,24 +208,12 @@ abstract class memory extends \phpbb\cache\driver\base
 		// determine which tables this query belongs to
 		// Some queries use backticks, namely the get_database_size() query
 		// don't check for conformity, the SQL would error and not reach here.
-		if (!preg_match_all('/(?:FROM \\(?(`?\\w+`?(?: \\w+)?(?:, ?`?\\w+`?(?: \\w+)?)*)\\)?)|(?:JOIN (`?\\w+`?(?: \\w+)?))/', $query, $regs, PREG_SET_ORDER))
+		if (!preg_match('/FROM \\(?(`?\\w+`?(?: \\w+)?(?:, ?`?\\w+`?(?: \\w+)?)*)\\)?/', $query, $regs))
 		{
 			// Bail out if the match fails.
 			return $query_result;
 		}
-
-		$tables = array();
-		foreach ($regs as $match)
-		{
-			if ($match[0][0] == 'F')
-			{
-				$tables = array_merge($tables, array_map('trim', explode(',', $match[1])));
-			}
-			else
-			{
-				$tables[] = $match[2];
-			}
-		}
+		$tables = array_map('trim', explode(',', $regs[1]));
 
 		foreach ($tables as $table_name)
 		{
diff --git a/tests/cache/cache_memory.php b/tests/cache/cache_memory.php
deleted file mode 100644
index c468cb4658..0000000000
--- a/tests/cache/cache_memory.php
+++ /dev/null
@@ -1,62 +0,0 @@
-<?php
-/**
-*
-* @package testing
-* @copyright (c) 2014 phpBB Group
-* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
-*
-*/
-
-require_once dirname(__FILE__) . '/../../phpBB/includes/acm/acm_memory.php';
-
-class phpbb_cache_memory extends acm_memory
-{
-	protected $data = array();
-
-	/**
-	* Set cache path
-	*/
-	function phpbb_cache_memory()
-	{
-	}
-
-	/**
-	* Fetch an item from the cache
-	*
-	* @access protected
-	* @param string $var Cache key
-	* @return mixed Cached data
-	*/
-	function _read($var)
-	{
-		return $this->data[$var];
-	}
-
-	/**
-	* Store data in the cache
-	*
-	* @access protected
-	* @param string $var Cache key
-	* @param mixed $data Data to store
-	* @param int $ttl Time-to-live of cached data
-	* @return bool True if the operation succeeded
-	*/
-	function _write($var, $data, $ttl = 2592000)
-	{
-		$this->data[$var] = $data;
-		return true;
-	}
-
-	/**
-	* Remove an item from the cache
-	*
-	* @access protected
-	* @param string $var Cache key
-	* @return bool True if the operation succeeded
-	*/
-	function _delete($var)
-	{
-		unset($this->data[$var]);
-		return true;
-	}
-}
diff --git a/tests/cache/cache_memory_test.php b/tests/cache/cache_memory_test.php
deleted file mode 100644
index 7a529c1d04..0000000000
--- a/tests/cache/cache_memory_test.php
+++ /dev/null
@@ -1,125 +0,0 @@
-<?php
-/**
-*
-* @package testing
-* @copyright (c) 2014 phpBB Group
-* @license http://opensource.org/licenses/gpl-2.0.php GNU General Public License v2
-*
-*/
-
-require_once dirname(__FILE__) . '/cache_memory.php';
-
-class phpbb_cache_memory_test extends phpbb_database_test_case
-{
-	protected $cache;
-
-	public function getDataSet()
-	{
-		return $this->createXMLDataSet(dirname(__FILE__).'/fixtures/cache_memory.xml');
-	}
-
-	protected function setUp()
-	{
-		global $db;
-		parent::setUp();
-
-		$this->cache = new phpbb_cache_memory();
-		$db = $this->new_dbal();
-	}
-
-	static public function cache_single_query_data()
-	{
-		return array(
-			array(
-				array(
-					array(
-						'SELECT * FROM ' . POSTS_TABLE,
-						3,
-					),
-				),
-				POSTS_TABLE,
-			),
-			array(
-				array(
-					array(
-						'SELECT * FROM ' . POSTS_TABLE,
-						3,
-					),
-					array(
-						'SELECT * FROM ' . POSTS_TABLE . ' p
-							LEFT JOIN ' . TOPICS_TABLE . ' t ON p.topic_id = t.topic_id',
-						3,
-					),
-				),
-				POSTS_TABLE,
-			),
-			array(
-				array(
-					array(
-						'SELECT * FROM ' . POSTS_TABLE,
-						3,
-					),
-					array(
-						'SELECT * FROM ' . POSTS_TABLE . ' p
-							LEFT JOIN ' . TOPICS_TABLE . ' t ON p.topic_id = t.topic_id',
-						3,
-					),
-					array(
-						'SELECT * FROM ' . POSTS_TABLE . ' p
-							LEFT JOIN ' . TOPICS_TABLE . ' t ON p.topic_id = t.topic_id
-							LEFT JOIN ' . USERS_TABLE . ' u ON p.poster_id = u.user_id',
-						3,
-					),
-				),
-				POSTS_TABLE,
-			),
-			array(
-				array(
-					array(
-						'SELECT * FROM ' . POSTS_TABLE . ' p
-							LEFT JOIN ' . TOPICS_TABLE . ' t ON p.topic_id = t.topic_id',
-						3,
-					),
-					array(
-						'SELECT * FROM ' . POSTS_TABLE . ' p
-							LEFT JOIN ' . TOPICS_TABLE . ' t ON p.topic_id = t.topic_id
-							LEFT JOIN ' . USERS_TABLE . ' u ON p.poster_id = u.user_id',
-						3,
-					),
-				),
-				TOPICS_TABLE,
-			),
-		);
-	}
-
-	/**
-	* @dataProvider cache_single_query_data
-	*/
-	public function test_cache_single_query($sql_queries, $table)
-	{
-		global $db;
-
-		foreach ($sql_queries as $query)
-		{
-			$sql_request_res = $db->sql_query($query[0]);
-
-			$this->cache->sql_save($query[0], $sql_request_res, 1);
-
-			$results = array();
-			$query_id = $this->cache->sql_load($query[0]);
-			while ($row = $this->cache->sql_fetchrow($query_id))
-			{
-				$results[] = $row;
-			}
-			$this->cache->sql_freeresult($query_id);
-			$this->assertEquals($query[1], sizeof($results));
-		}
-
-		$this->cache->destroy('sql', $table);
-
-		foreach ($sql_queries as $query)
-		{
-			$this->assertNotEquals(false, $this->cache->sql_load($query[0]));
-		}
-	}
-}
diff --git a/tests/cache/fixtures/cache_memory.xml b/tests/cache/fixtures/cache_memory.xml
deleted file mode 100644
index 6954c7b76b..0000000000
--- a/tests/cache/fixtures/cache_memory.xml
+++ /dev/null
@@ -1,85 +0,0 @@
-<?xml version="1.0" encoding="UTF-8" ?>
-<dataset>
-	<table name="phpbb_topics">
-		<column>topic_id</column>
-		<column>forum_id</column>
-		<column>topic_title</column>
-		<column>topic_first_post_id</column>
-		<column>topic_last_post_id</column>
-		<row>
-			<value>1</value>
-			<value>1</value>
-			<value>Topic</value>
-			<value>2</value>
-			<value>2</value>
-		</row>
-	</table>
-	<table name="phpbb_posts">
-		<column>post_id</column>
-		<column>poster_id</column>
-		<column>topic_id</column>
-		<column>forum_id</column>
-		<column>post_text</column>
-		<row>
-			<value>1</value>
-			<value>1</value>
-			<value>1</value>
-			<value>1</value>
-			<value>Post 1</value>
-		</row>
-		<row>
-			<value>2</value>
-			<value>2</value>
-			<value>1</value>
-			<value>1</value>
-			<value>Post 2</value>
-		</row>
-		<row>
-			<value>3</value>
-			<value>3</value>
-			<value>1</value>
-			<value>1</value>
-			<value>Post 3</value>
-		</row>
-	</table>
-	<table name="phpbb_users">
-		<column>user_id</column>
-		<column>user_posts</column>
-		<column>username</column>
-		<column>username_clean</column>
-		<column>user_permissions</column>
-		<column>user_sig</column>
-		<column>user_occ</column>
-		<column>user_interests</column>
-		<row>
-			<value>1</value>
-			<value>1</value>
-			<value>user 1</value>
-			<value>user 1</value>
-			<value></value>
-			<value></value>
-			<value></value>
-			<value></value>
-		</row>
-		<row>
-			<value>2</value>
-			<value>1</value>
-			<value>user 2</value>
-			<value>user 2</value>
-			<value></value>
-			<value></value>
-			<value></value>
-			<value></value>
-		</row>
-		<row>
-			<value>3</value>
-			<value>1</value>
-			<value>user 3</value>
-			<value>user 3</value>
-			<value></value>
-			<value></value>
-			<value></value>
-			<value></value>
-		</row>
-	</table>
-</dataset>