Update docs/hooks.txt for ShowSearchHitTitle

[mediawiki.git] / includes / jobqueue / jobs / CategoryMembershipChangeJob.php

<?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;

/**
 * Job to add recent change entries mentioning category 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 integer|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?
                }

                // 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;
                }

                $dbr = $lb->getConnection( DB_REPLICA, [ 'recentchanges' ] );
                // Wait till the replica DB is caught up so that jobs for this page see each others' changes
                if ( !$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 revision that has a SRC_CATEGORIZE row...
                $row = $dbr->selectRow(
                        [ 'revision', 'recentchanges' ],
                        [ 'rev_timestamp', 'rev_id' ],
                        [
                                'rev_page' => $page->getId(),
                                'rev_timestamp >= ' . $dbr->addQuotes( $dbr->timestamp( $cutoffUnix ) )
                        ],
                        __METHOD__,
                        [ 'ORDER BY' => 'rev_timestamp DESC, rev_id DESC' ],
                        [
                                'recentchanges' => [
                                        'INNER JOIN',
                                        [
                                                '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'
                                        ]
                                ]
                        ]
                );
                // 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 ) );
                $res = $dbr->select(
                        'revision',
                        Revision::selectFields(),
                        [
                                'rev_page' => $page->getId(),
                                "rev_timestamp > $encCutoff" .
                                        " OR (rev_timestamp = $encCutoff AND rev_id > $lastRevId)"
                        ],
                        __METHOD__,
                        [ 'ORDER BY' => 'rev_timestamp ASC, rev_id ASC' ]
                );

                // 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;
        }
}