Cache page content language in Title object

During the parsing process, $title->getPageLanguage() gets called
a large number of times for the same title. Apparently the value
can vary by user, but it should be safe to cache for the current
request (I believe).

On [[Commons:Commons:Featured_picture_candidates/Log/October_2013]],
it appears that this method is called 5118 times, and represents
20.58% (11.77 seconds) of the time to render the page.

Also checks if $wgLanguageCode has been changed, since Title
object are cached during a request, and the unit tests seem
to change $wgLanguageCode/$wgContLang while still using
the Title cache.

Bug: 55952
Change-Id: I84b2d86c7bcb32997acff47cfea0f789b5b960a6

diff --git a/includes/Title.php b/includes/Title.php
index 56e9b44..3418fa2 100644 (file)
--- a/includes/Title.php
+++ b/includes/Title.php
@@ -86,6 +86,7 @@ class Title {
        var $mRedirect = null;            // /< Is the article at this title a redirect?
        var $mNotificationTimestamp = array(); // /< Associative array of user ID -> timestamp/false
        var $mHasSubpage;                 // /< Whether a page has any subpages
+       private $mPageLanguage = false;   // /< The (string) language code of the page's language and content code.
        // @}
 
        /**
@@ -3110,6 +3111,7 @@ class Title {
                $this->mLatestID = false;
                $this->mContentModel = false;
                $this->mEstimateRevisions = null;
+               $this->mPageLanguage = false;
        }
 
        /**
@@ -4808,18 +4810,26 @@ class Title {
         * @return Language
         */
        public function getPageLanguage() {
-               global $wgLang;
+               global $wgLang, $wgLanguageCode;
+               wfProfileIn( __METHOD__ );
                if ( $this->isSpecialPage() ) {
                        // special pages are in the user language
+                       wfProfileOut( __METHOD__ );
                        return $wgLang;
                }
 
-               //TODO: use the LinkCache to cache this! Note that this may depend on user settings, so the cache should be only per-request.
-               //NOTE: ContentHandler::getPageLanguage() may need to load the content to determine the page language!
-               $contentHandler = ContentHandler::getForTitle( $this );
-               $pageLang = $contentHandler->getPageLanguage( $this );
-
-               return wfGetLangObj( $pageLang );
+               if ( !$this->mPageLanguage || $this->mPageLanguage[1] !== $wgLanguageCode ) {
+                       // Note that this may depend on user settings, so the cache should be only per-request.
+                       // NOTE: ContentHandler::getPageLanguage() may need to load the content to determine the page language!
+                       // Checking $wgLanguageCode hasn't changed for the benefit of unit tests.
+                       $contentHandler = ContentHandler::getForTitle( $this );
+                       $langObj = wfGetLangObj( $contentHandler->getPageLanguage( $this ) );
+                       $this->mPageLanguage = array( $langObj->getCode(), $wgLanguageCode );
+               } else {
+                       $langObj =  wfGetLangObj( $this->mPageLanguage[0] );
+               }
+               wfProfileOut( __METHOD__ );
+               return $langObj;
        }
 
        /**