From 12b76fcabbdeb3be937c5ed4af8eb334d0d91317 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Tue, 27 Nov 2012 09:26:02 -0800
Subject: [PATCH] Made BackLinkCache use object caching better.

* This way, we can actually get persistent cache hits for
the HTMLCacheUpdate queries rather than always hitting a DB.
* Also moved BacklinkCache under the /cache directory.

Change-Id: I0666ee575fb42675f1a7dd9cb52665f0a12a66a9
---
 includes/AutoLoader.php                |  2 +-
 includes/{ => cache}/BacklinkCache.php | 42 ++++++++++++++++----------
 2 files changed, 27 insertions(+), 17 deletions(-)
 rename includes/{ => cache}/BacklinkCache.php (94%)

diff --git a/includes/AutoLoader.php b/includes/AutoLoader.php
index 9bdf3778cd..31c1571987 100644
--- a/includes/AutoLoader.php
+++ b/includes/AutoLoader.php
@@ -38,7 +38,6 @@ $wgAutoloadLocalClasses = array(
 	'AuthPlugin' => 'includes/AuthPlugin.php',
 	'AuthPluginUser' => 'includes/AuthPlugin.php',
 	'Autopromote' => 'includes/Autopromote.php',
-	'BacklinkCache' => 'includes/BacklinkCache.php',
 	'BadTitleError' => 'includes/Exception.php',
 	'BaseTemplate' => 'includes/SkinTemplate.php',
 	'Block' => 'includes/Block.php',
@@ -425,6 +424,7 @@ $wgAutoloadLocalClasses = array(
 	'UsageException' => 'includes/api/ApiMain.php',
 
 	# includes/cache
+	'BacklinkCache' => 'includes/cache/BacklinkCache.php',
 	'CacheDependency' => 'includes/cache/CacheDependency.php',
 	'ConstantDependency' => 'includes/cache/CacheDependency.php',
 	'DependencyWrapper' => 'includes/cache/CacheDependency.php',
diff --git a/includes/BacklinkCache.php b/includes/cache/BacklinkCache.php
similarity index 94%
rename from includes/BacklinkCache.php
rename to includes/cache/BacklinkCache.php
index ba8691b292..c4f8762a24 100644
--- a/includes/BacklinkCache.php
+++ b/includes/cache/BacklinkCache.php
@@ -303,18 +303,32 @@ class BacklinkCache {
 	 * @return integer
 	 */
 	public function getNumLinks( $table ) {
-		if ( isset( $this->fullResultCache[$table] ) ) {
-			return $this->fullResultCache[$table]->numRows();
-		}
+		global $wgMemc;
 
+		// 1) try partition cache ...
 		if ( isset( $this->partitionCache[$table] ) ) {
 			$entry = reset( $this->partitionCache[$table] );
 			return $entry['numRows'];
 		}
 
-		$titleArray = $this->getLinks( $table );
+		// 2) ... then try full result cache ...
+		if ( isset( $this->fullResultCache[$table] ) ) {
+			return $this->fullResultCache[$table]->numRows();
+		}
+
+		$memcKey = wfMemcKey( 'numbacklinks', md5( $this->title->getPrefixedDBkey() ), $table );
+
+		// 3) ... fallback to memcached ...
+		$count = $wgMemc->get( $memcKey );
+		if ( $count ) {
+			return $count;
+		}
+
+		// 4) fetch from the database ...
+		$count = $this->getLinks( $table )->count();
+		$wgMemc->set( $memcKey, $count, self::CACHE_EXPIRY );
 
-		return $titleArray->count();
+		return $count;
 	}
 
 	/**
@@ -327,9 +341,9 @@ class BacklinkCache {
 	 * @return Array
 	 */
 	public function partition( $table, $batchSize ) {
+		global $wgMemc;
 
 		// 1) try partition cache ...
-
 		if ( isset( $this->partitionCache[$table][$batchSize] ) ) {
 			wfDebug( __METHOD__ . ": got from partition cache\n" );
 			return $this->partitionCache[$table][$batchSize]['batches'];
@@ -339,18 +353,12 @@ class BacklinkCache {
 		$cacheEntry =& $this->partitionCache[$table][$batchSize];
 
 		// 2) ... then try full result cache ...
-
 		if ( isset( $this->fullResultCache[$table] ) ) {
 			$cacheEntry = $this->partitionResult( $this->fullResultCache[$table], $batchSize );
 			wfDebug( __METHOD__ . ": got from full result cache\n" );
-
 			return $cacheEntry['batches'];
 		}
 
-		// 3) ... fallback to memcached ...
-
-		global $wgMemc;
-
 		$memcKey = wfMemcKey(
 			'backlinks',
 			md5( $this->title->getPrefixedDBkey() ),
@@ -358,23 +366,25 @@ class BacklinkCache {
 			$batchSize
 		);
 
+		// 3) ... fallback to memcached ...
 		$memcValue = $wgMemc->get( $memcKey );
-
 		if ( is_array( $memcValue ) ) {
 			$cacheEntry = $memcValue;
 			wfDebug( __METHOD__ . ": got from memcached $memcKey\n" );
-
 			return $cacheEntry['batches'];
 		}
 
 
 		// 4) ... finally fetch from the slow database :(
-
 		$this->getLinks( $table );
 		$cacheEntry = $this->partitionResult( $this->fullResultCache[$table], $batchSize );
-		// Save to memcached
+		// Save partitions to memcached
 		$wgMemc->set( $memcKey, $cacheEntry, self::CACHE_EXPIRY );
 
+		// Save backlink count to memcached
+		$memcKey = wfMemcKey( 'numbacklinks', md5( $this->title->getPrefixedDBkey() ), $table );
+		$wgMemc->set( $memcKey, $cacheEntry['numRows'], self::CACHE_EXPIRY );
+
 		wfDebug( __METHOD__ . ": got from database\n" );
 		return $cacheEntry['batches'];
 	}
-- 
2.20.1