From af89b09a067095027e64094423bc54f1b7e8499c Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Mon, 3 Sep 2012 12:45:50 -0700
Subject: [PATCH] Limit the Title backlink cache to two instances.

Change-Id: I1e17a3de20d7c84a9818a850d4b7cc2898f72dc2
---
 includes/BacklinkCache.php | 28 ++++++++++++++++++++++++----
 includes/Title.php         |  8 ++------
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/includes/BacklinkCache.php b/includes/BacklinkCache.php
index 2aba29f65b..824c38a216 100644
--- a/includes/BacklinkCache.php
+++ b/includes/BacklinkCache.php
@@ -41,6 +41,8 @@
  * @internal documentation reviewed on 18 Mar 2011 by hashar
  */
 class BacklinkCache {
+	/** @var ProcessCacheLRU */
+	protected static $cache;
 
 	/**
 	 * Multi dimensions array representing batches. Keys are:
@@ -81,12 +83,30 @@ class BacklinkCache {
 
 	/**
 	 * Create a new BacklinkCache
-	 * @param Title $title : Title object to create a backlink cache for.
+	 *
+	 * @param Title $title : Title object to create a backlink cache for
 	 */
-	function __construct( $title ) {
+	public function __construct( Title $title ) {
 		$this->title = $title;
 	}
 
+	/**
+	 * Create a new BacklinkCache or reuse any existing one
+	 *
+	 * @param Title $title : Title object to get a backlink cache for
+	 * @return BacklinkCache
+	 */
+	public static function get( Title $title ) {
+		if ( !self::$cache ) { // init cache
+			self::$cache = new ProcessCacheLRU( 2 );
+		}
+		$dbKey = $title->getPrefixedDBkey();
+		if ( !self::$cache->has( $dbKey, 'obj' ) ) {
+			self::$cache->set( $dbKey, 'obj', new self( $title ) );
+		}
+		return self::$cache->get( $dbKey, 'obj' );
+	}
+
 	/**
 	 * Serialization handler, diasallows to serialize the database to prevent
 	 * failures after this class is deserialized from cache with dead DB
@@ -303,7 +323,7 @@ class BacklinkCache {
 	 */
 	public function partition( $table, $batchSize ) {
 
-		// 1) try partition cache ... 
+		// 1) try partition cache ...
 
 		if ( isset( $this->partitionCache[$table][$batchSize] ) ) {
 			wfDebug( __METHOD__ . ": got from partition cache\n" );
@@ -358,7 +378,7 @@ class BacklinkCache {
 	 * Partition a DB result with backlinks in it into batches
 	 * @param $res ResultWrapper database result
 	 * @param $batchSize integer
-	 * @return array @see 
+	 * @return array @see
 	 */
 	protected function partitionResult( $res, $batchSize ) {
 		$batches = array();
diff --git a/includes/Title.php b/includes/Title.php
index eccae70a49..98961f818d 100644
--- a/includes/Title.php
+++ b/includes/Title.php
@@ -84,7 +84,6 @@ class Title {
 	var $mLength = -1;                // /< The page length, 0 for special pages
 	var $mRedirect = null;            // /< Is the article at this title a redirect?
 	var $mNotificationTimestamp = array(); // /< Associative array of user ID -> timestamp/false
-	var $mBacklinkCache = null;       // /< Cache of links to this title
 	var $mHasSubpage;                 // /< Whether a page has any subpages
 	// @}
 
@@ -4477,11 +4476,8 @@ class Title {
 	 *
 	 * @return BacklinkCache
 	 */
-	function getBacklinkCache() {
-		if ( is_null( $this->mBacklinkCache ) ) {
-			$this->mBacklinkCache = new BacklinkCache( $this );
-		}
-		return $this->mBacklinkCache;
+	public function getBacklinkCache() {
+		return BacklinkCache::get( $this );
 	}
 
 	/**
-- 
2.20.1