From e39dd4532c5fec33e0be2e327aad7378fcaeb277 Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@users.mediawiki.org>
Date: Thu, 25 Nov 2004 22:02:30 +0000
Subject: [PATCH] (bug 934) List each category on a page only once. Dan
 Keshet's patch
 (http://bugzilla.wikipedia.org/attachment.cgi?id=134&action=view) plus an
 added version check on parser cache objects, to automatically discard cached
 objects using the incompatible older format.

---
 includes/Parser.php      | 30 ++++++++++++++++++++++++++++--
 includes/ParserCache.php |  2 +-
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/includes/Parser.php b/includes/Parser.php
index 568bb21cf5..e17ad5a03c 100644
--- a/includes/Parser.php
+++ b/includes/Parser.php
@@ -7,6 +7,13 @@
  * @version $Id$
  */
 
+/**
+ * Update this version number when the ParserOutput format
+ * changes in an incompatible way, so the parser cache
+ * can automatically discard old data.
+ */
+define( 'MW_PARSER_VERSION', '1.4.0' );
+
 /**
  * Variable substitution O(N^2) attack
  *
@@ -1323,7 +1330,7 @@ class Parser
 						$sortkey = $text;
 					}
 					$wgLinkCache->addCategoryLinkObj( $nt, $sortkey );
-					$this->mOutput->mCategoryLinks[] = $t ;
+					$this->mOutput->addCategoryLink( $t );
 					$s .= $prefix . $trail ;
 					
 					wfProfileOut( "$fname-category" );
@@ -3063,6 +3070,7 @@ class ParserOutput
 {
 	var $mText, $mLanguageLinks, $mCategoryLinks, $mContainsOldMagic;
 	var $mCacheTime; # Used in ParserCache
+	var $mVersion;   # Compatibility check
 
 	function ParserOutput( $text = '', $languageLinks = array(), $categoryLinks = array(),
 		$containsOldMagic = false )
@@ -3072,11 +3080,12 @@ class ParserOutput
 		$this->mCategoryLinks = $categoryLinks;
 		$this->mContainsOldMagic = $containsOldMagic;
 		$this->mCacheTime = '';
+		$this->mVersion = MW_PARSER_VERSION;
 	}
 
 	function getText()                   { return $this->mText; }
 	function getLanguageLinks()          { return $this->mLanguageLinks; }
-	function getCategoryLinks()          { return $this->mCategoryLinks; }
+	function getCategoryLinks()          { return array_keys( $this->mCategoryLinks ); }
 	function getCacheTime()              { return $this->mCacheTime; }
 	function containsOldMagic()          { return $this->mContainsOldMagic; }
 	function setText( $text )            { return wfSetVar( $this->mText, $text ); }
@@ -3084,6 +3093,7 @@ class ParserOutput
 	function setCategoryLinks( $cl )     { return wfSetVar( $this->mCategoryLinks, $cl ); }
 	function setContainsOldMagic( $com ) { return wfSetVar( $this->mContainsOldMagic, $com ); }
 	function setCacheTime( $t )          { return wfSetVar( $this->mCacheTime, $t ); }
+	function addCategoryLink( $c )       { $this->mCategoryLinks[$c] = 1; }
 
 	function merge( $other ) {
 		$this->mLanguageLinks = array_merge( $this->mLanguageLinks, $other->mLanguageLinks );
@@ -3091,6 +3101,22 @@ class ParserOutput
 		$this->mContainsOldMagic = $this->mContainsOldMagic || $other->mContainsOldMagic;
 	}
 
+	/**
+	 * Return true if this cached output object predates the global or
+	 * per-article cache invalidation timestamps, or if it comes from
+	 * an incompatible older version.
+	 *
+	 * @param string $touched the affected article's last touched timestamp
+	 * @return bool
+	 * @access public
+	 */
+	function expired( $touched ) {
+		global $wgCacheEpoch;
+		return $this->getCacheTime() <= $touched ||
+		       $this->getCacheTime() <= $wgCacheEpoch ||
+		       !isset( $this->mVersion ) ||
+		       version_compare( $this->mVersion, MW_PARSER_VERSION, "lt" );
+	}
 }
 
 /**
diff --git a/includes/ParserCache.php b/includes/ParserCache.php
index fce8ed33cf..00ed003058 100644
--- a/includes/ParserCache.php
+++ b/includes/ParserCache.php
@@ -43,7 +43,7 @@ class ParserCache {
 			$canCache = $article->checkTouched();
 			$cacheTime = $value->getCacheTime();
 			$touched = $article->mTouched;
-			if ( !$canCache || $value->getCacheTime() <= $touched || $cacheTime < $wgCacheEpoch ) {
+			if ( !$canCache || $value->expired( $touched ) ) {
 				if ( !$canCache ) {
 					wfDebug( "Invalid cached redirect, touched $touched, epoch $wgCacheEpoch, cached $cacheTime\n" );
 				} else {
-- 
2.20.1