1 files changed, 253 insertions, 0 deletions
diff --git a/www/wiki/includes/jobqueue/jobs/CategoryMembershipChangeJob.php b/www/wiki/includes/jobqueue/jobs/CategoryMembershipChangeJob.php
new file mode 100644
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--- /dev/null
+++ b/www/wiki/includes/jobqueue/jobs/CategoryMembershipChangeJob.php
@@ -0,0 +1,253 @@
+<?php
+/**
+ * Updater for link tracking tables after a page edit.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ * http://www.gnu.org/copyleft/gpl.html
+ *
+ * @file
+ */
+use MediaWiki\MediaWikiServices;
+use Wikimedia\Rdbms\LBFactory;
+
+/**
+ * Job to add recent change entries mentioning category membership changes
+ *
+ * This allows users to easily scan categories for recent page membership changes
+ *
+ * Parameters include:
+ *   - pageId : page ID
+ *   - revTimestamp : timestamp of the triggering revision
+ *
+ * Category changes will be mentioned for revisions at/after the timestamp for this page
+ *
+ * @since 1.27
+ */
+class CategoryMembershipChangeJob extends Job {
+	/** @var int|null */
+	private $ticket;
+
+	const ENQUEUE_FUDGE_SEC = 60;
+
+	public function __construct( Title $title, array $params ) {
+		parent::__construct( 'categoryMembershipChange', $title, $params );
+		// Only need one job per page. Note that ENQUEUE_FUDGE_SEC handles races where an
+		// older revision job gets inserted while the newer revision job is de-duplicated.
+		$this->removeDuplicates = true;
+	}
+
+	public function run() {
+		$lbFactory = MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
+		$lb = $lbFactory->getMainLB();
+		$dbw = $lb->getConnection( DB_MASTER );
+
+		$this->ticket = $lbFactory->getEmptyTransactionTicket( __METHOD__ );
+
+		$page = WikiPage::newFromID( $this->params['pageId'], WikiPage::READ_LATEST );
+		if ( !$page ) {
+			$this->setLastError( "Could not find page #{$this->params['pageId']}" );
+			return false; // deleted?
+		}
+
+		// Cut down on the time spent in safeWaitForMasterPos() in the critical section
+		$dbr = $lb->getConnection( DB_REPLICA, [ 'recentchanges' ] );
+		if ( !$lb->safeWaitForMasterPos( $dbr ) ) {
+			$this->setLastError( "Timed out while pre-waiting for replica DB to catch up" );
+			return false;
+		}
+
+		// Use a named lock so that jobs for this page see each others' changes
+		$lockKey = "CategoryMembershipUpdates:{$page->getId()}";
+		$scopedLock = $dbw->getScopedLockAndFlush( $lockKey, __METHOD__, 3 );
+		if ( !$scopedLock ) {
+			$this->setLastError( "Could not acquire lock '$lockKey'" );
+			return false;
+		}
+
+		// Wait till replica DB is caught up so that jobs for this page see each others' changes
+		if ( !$lb->safeWaitForMasterPos( $dbr ) ) {
+			$this->setLastError( "Timed out while waiting for replica DB to catch up" );
+			return false;
+		}
+		// Clear any stale REPEATABLE-READ snapshot
+		$dbr->flushSnapshot( __METHOD__ );
+
+		$cutoffUnix = wfTimestamp( TS_UNIX, $this->params['revTimestamp'] );
+		// Using ENQUEUE_FUDGE_SEC handles jobs inserted out of revision order due to the delay
+		// between COMMIT and actual enqueueing of the CategoryMembershipChangeJob job.
+		$cutoffUnix -= self::ENQUEUE_FUDGE_SEC;
+
+		// Get the newest page revision that has a SRC_CATEGORIZE row.
+		// Assume that category changes before it were already handled.
+		$row = $dbr->selectRow(
+			'revision',
+			[ 'rev_timestamp', 'rev_id' ],
+			[
+				'rev_page' => $page->getId(),
+				'rev_timestamp >= ' . $dbr->addQuotes( $dbr->timestamp( $cutoffUnix ) ),
+				'EXISTS (' . $dbr->selectSQLText(
+					'recentchanges',
+					'1',
+					[
+						'rc_this_oldid = rev_id',
+						'rc_source' => RecentChange::SRC_CATEGORIZE,
+						// Allow rc_cur_id or rc_timestamp index usage
+						'rc_cur_id = rev_page',
+						'rc_timestamp = rev_timestamp'
+					]
+				) . ')'
+			],
+			__METHOD__,
+			[ 'ORDER BY' => 'rev_timestamp DESC, rev_id DESC' ]
+		);
+		// Only consider revisions newer than any such revision
+		if ( $row ) {
+			$cutoffUnix = wfTimestamp( TS_UNIX, $row->rev_timestamp );
+			$lastRevId = (int)$row->rev_id;
+		} else {
+			$lastRevId = 0;
+		}
+
+		// Find revisions to this page made around and after this revision which lack category
+		// notifications in recent changes. This lets jobs pick up were the last one left off.
+		$encCutoff = $dbr->addQuotes( $dbr->timestamp( $cutoffUnix ) );
+		$revQuery = Revision::getQueryInfo();
+		$res = $dbr->select(
+			$revQuery['tables'],
+			$revQuery['fields'],
+			[
+				'rev_page' => $page->getId(),
+				"rev_timestamp > $encCutoff" .
+					" OR (rev_timestamp = $encCutoff AND rev_id > $lastRevId)"
+			],
+			__METHOD__,
+			[ 'ORDER BY' => 'rev_timestamp ASC, rev_id ASC' ],
+			$revQuery['joins']
+		);
+
+		// Apply all category updates in revision timestamp order
+		foreach ( $res as $row ) {
+			$this->notifyUpdatesForRevision( $lbFactory, $page, Revision::newFromRow( $row ) );
+		}
+
+		return true;
+	}
+
+	/**
+	 * @param LBFactory $lbFactory
+	 * @param WikiPage $page
+	 * @param Revision $newRev
+	 * @throws MWException
+	 */
+	protected function notifyUpdatesForRevision(
+		LBFactory $lbFactory, WikiPage $page, Revision $newRev
+	) {
+		$config = RequestContext::getMain()->getConfig();
+		$title = $page->getTitle();
+
+		// Get the new revision
+		if ( !$newRev->getContent() ) {
+			return; // deleted?
+		}
+
+		// Get the prior revision (the same for null edits)
+		if ( $newRev->getParentId() ) {
+			$oldRev = Revision::newFromId( $newRev->getParentId(), Revision::READ_LATEST );
+			if ( !$oldRev->getContent() ) {
+				return; // deleted?
+			}
+		} else {
+			$oldRev = null;
+		}
+
+		// Parse the new revision and get the categories
+		$categoryChanges = $this->getExplicitCategoriesChanges( $title, $newRev, $oldRev );
+		list( $categoryInserts, $categoryDeletes ) = $categoryChanges;
+		if ( !$categoryInserts && !$categoryDeletes ) {
+			return; // nothing to do
+		}
+
+		$catMembChange = new CategoryMembershipChange( $title, $newRev );
+		$catMembChange->checkTemplateLinks();
+
+		$batchSize = $config->get( 'UpdateRowsPerQuery' );
+		$insertCount = 0;
+
+		foreach ( $categoryInserts as $categoryName ) {
+			$categoryTitle = Title::makeTitle( NS_CATEGORY, $categoryName );
+			$catMembChange->triggerCategoryAddedNotification( $categoryTitle );
+			if ( $insertCount++ && ( $insertCount % $batchSize ) == 0 ) {
+				$lbFactory->commitAndWaitForReplication( __METHOD__, $this->ticket );
+			}
+		}
+
+		foreach ( $categoryDeletes as $categoryName ) {
+			$categoryTitle = Title::makeTitle( NS_CATEGORY, $categoryName );
+			$catMembChange->triggerCategoryRemovedNotification( $categoryTitle );
+			if ( $insertCount++ && ( $insertCount++ % $batchSize ) == 0 ) {
+				$lbFactory->commitAndWaitForReplication( __METHOD__, $this->ticket );
+			}
+		}
+	}
+
+	private function getExplicitCategoriesChanges(
+		Title $title, Revision $newRev, Revision $oldRev = null
+	) {
+		// Inject the same timestamp for both revision parses to avoid seeing category changes
+		// due to time-based parser functions. Inject the same page title for the parses too.
+		// Note that REPEATABLE-READ makes template/file pages appear unchanged between parses.
+		$parseTimestamp = $newRev->getTimestamp();
+		// Parse the old rev and get the categories. Do not use link tables as that
+		// assumes these updates are perfectly FIFO and that link tables are always
+		// up to date, neither of which are true.
+		$oldCategories = $oldRev
+			? $this->getCategoriesAtRev( $title, $oldRev, $parseTimestamp )
+			: [];
+		// Parse the new revision and get the categories
+		$newCategories = $this->getCategoriesAtRev( $title, $newRev, $parseTimestamp );
+
+		$categoryInserts = array_values( array_diff( $newCategories, $oldCategories ) );
+		$categoryDeletes = array_values( array_diff( $oldCategories, $newCategories ) );
+
+		return [ $categoryInserts, $categoryDeletes ];
+	}
+
+	/**
+	 * @param Title $title
+	 * @param Revision $rev
+	 * @param string $parseTimestamp TS_MW
+	 *
+	 * @return string[] category names
+	 */
+	private function getCategoriesAtRev( Title $title, Revision $rev, $parseTimestamp ) {
+		$content = $rev->getContent();
+		$options = $content->getContentHandler()->makeParserOptions( 'canonical' );
+		$options->setTimestamp( $parseTimestamp );
+		// This could possibly use the parser cache if it checked the revision ID,
+		// but that's more complicated than it's worth.
+		$output = $content->getParserOutput( $title, $rev->getId(), $options );
+
+		// array keys will cast numeric category names to ints
+		// so we need to cast them back to strings to avoid breaking things!
+		return array_map( 'strval', array_keys( $output->getCategories() ) );
+	}
+
+	public function getDeduplicationInfo() {
+		$info = parent::getDeduplicationInfo();
+		unset( $info['params']['revTimestamp'] ); // first job wins
+
+		return $info;
+	}
+}