WatchedItemStore.php

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<?php
 
use Liuggio\StatsdClient\Factory\StatsdDataFactoryInterface;
use MediaWiki\Cache\LinkBatchFactory;
use MediaWiki\Config\ServiceOptions;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MainConfigNames;
use MediaWiki\Page\PageIdentity;
use MediaWiki\Revision\RevisionLookup;
use MediaWiki\User\UserIdentity;
use Wikimedia\Assert\Assert;
use Wikimedia\ParamValidator\TypeDef\ExpiryDef;
use Wikimedia\Rdbms\IDatabase;
use Wikimedia\Rdbms\ILBFactory;
use Wikimedia\Rdbms\IResultWrapper;
use Wikimedia\Rdbms\ReadOnlyMode;
use Wikimedia\Rdbms\SelectQueryBuilder;
use Wikimedia\ScopedCallback;
 
class WatchedItemStore implements WatchedItemStoreInterface, StatsdAwareInterface {
 
    public const CONSTRUCTOR_OPTIONS = [
        MainConfigNames::UpdateRowsPerQuery,
        MainConfigNames::WatchlistExpiry,
        MainConfigNames::WatchlistExpiryMaxDuration,
        MainConfigNames::WatchlistPurgeRate,
    ];
 
    private $lbFactory;
 
    private $queueGroup;
 
    private $stash;
 
    private $readOnlyMode;
 
    private $cache;
 
    private $latestUpdateCache;
 
    private $cacheIndex = [];
 
    private $deferredUpdatesAddCallableUpdateCallback;
 
    private $updateRowsPerQuery;
 
    private $nsInfo;
 
    private $revisionLookup;
 
    private $stats;
 
    private $expiryEnabled;
 
    private $linkBatchFactory;
 
    private $maxExpiryDuration;
 
    private $watchlistPurgeRate;
 
    public function __construct(
        ServiceOptions $options,
        ILBFactory $lbFactory,
        JobQueueGroup $queueGroup,
        BagOStuff $stash,
        HashBagOStuff $cache,
        ReadOnlyMode $readOnlyMode,
        NamespaceInfo $nsInfo,
        RevisionLookup $revisionLookup,
        LinkBatchFactory $linkBatchFactory
    ) {
        $options->assertRequiredOptions( self::CONSTRUCTOR_OPTIONS );
        $this->updateRowsPerQuery = $options->get( MainConfigNames::UpdateRowsPerQuery );
        $this->expiryEnabled = $options->get( MainConfigNames::WatchlistExpiry );
        $this->maxExpiryDuration = $options->get( MainConfigNames::WatchlistExpiryMaxDuration );
        $this->watchlistPurgeRate = $options->get( MainConfigNames::WatchlistPurgeRate );
 
        $this->lbFactory = $lbFactory;
        $this->queueGroup = $queueGroup;
        $this->stash = $stash;
        $this->cache = $cache;
        $this->readOnlyMode = $readOnlyMode;
        $this->stats = new NullStatsdDataFactory();
        $this->deferredUpdatesAddCallableUpdateCallback =
            [ DeferredUpdates::class, 'addCallableUpdate' ];
        $this->nsInfo = $nsInfo;
        $this->revisionLookup = $revisionLookup;
        $this->linkBatchFactory = $linkBatchFactory;
 
        $this->latestUpdateCache = new HashBagOStuff( [ 'maxKeys' => 3 ] );
    }
 
    public function setStatsdDataFactory( StatsdDataFactoryInterface $stats ) {
        $this->stats = $stats;
    }
 
    public function overrideDeferredUpdatesAddCallableUpdateCallback( callable $callback ) {
        if ( !defined( 'MW_PHPUNIT_TEST' ) ) {
            throw new MWException(
                'Cannot override DeferredUpdates::addCallableUpdate callback in operation.'
            );
        }
        $previousValue = $this->deferredUpdatesAddCallableUpdateCallback;
        $this->deferredUpdatesAddCallableUpdateCallback = $callback;
        return new ScopedCallback( function () use ( $previousValue ) {
            $this->deferredUpdatesAddCallableUpdateCallback = $previousValue;
        } );
    }
 
    private function getCacheKey( UserIdentity $user, $target ): string {
        return $this->cache->makeKey(
            (string)$target->getNamespace(),
            $target->getDBkey(),
            (string)$user->getId()
        );
    }
 
    private function cache( WatchedItem $item ) {
        $user = $item->getUserIdentity();
        $target = $item->getTarget();
        $key = $this->getCacheKey( $user, $target );
        $this->cache->set( $key, $item );
        $this->cacheIndex[$target->getNamespace()][$target->getDBkey()][$user->getId()] = $key;
        $this->stats->increment( 'WatchedItemStore.cache' );
    }
 
    private function uncache( UserIdentity $user, $target ) {
        $this->cache->delete( $this->getCacheKey( $user, $target ) );
        unset( $this->cacheIndex[$target->getNamespace()][$target->getDBkey()][$user->getId()] );
        $this->stats->increment( 'WatchedItemStore.uncache' );
    }
 
    private function uncacheLinkTarget( $target ) {
        $this->stats->increment( 'WatchedItemStore.uncacheLinkTarget' );
        if ( !isset( $this->cacheIndex[$target->getNamespace()][$target->getDBkey()] ) ) {
            return;
        }
        foreach ( $this->cacheIndex[$target->getNamespace()][$target->getDBkey()] as $key ) {
            $this->stats->increment( 'WatchedItemStore.uncacheLinkTarget.items' );
            $this->cache->delete( $key );
        }
    }
 
    private function uncacheUser( UserIdentity $user ) {
        $this->stats->increment( 'WatchedItemStore.uncacheUser' );
        foreach ( $this->cacheIndex as $dbKeyArray ) {
            foreach ( $dbKeyArray as $userArray ) {
                if ( isset( $userArray[$user->getId()] ) ) {
                    $this->stats->increment( 'WatchedItemStore.uncacheUser.items' );
                    $this->cache->delete( $userArray[$user->getId()] );
                }
            }
        }
 
        $pageSeenKey = $this->getPageSeenTimestampsKey( $user );
        $this->latestUpdateCache->delete( $pageSeenKey );
        $this->stash->delete( $pageSeenKey );
    }
 
    private function getCached( UserIdentity $user, $target ) {
        return $this->cache->get( $this->getCacheKey( $user, $target ) );
    }
 
    private function modifyQueryBuilderForExpiry(
        SelectQueryBuilder $queryBuilder,
        IDatabase $db
    ) {
        if ( $this->expiryEnabled ) {
            $queryBuilder->where( 'we_expiry IS NULL OR we_expiry > ' . $db->addQuotes( $db->timestamp() ) );
            $queryBuilder->leftJoin( 'watchlist_expiry', null, 'wl_id = we_item' );
        }
    }
 
    public function clearUserWatchedItems( UserIdentity $user ): bool {
        if ( $this->mustClearWatchedItemsUsingJobQueue( $user ) ) {
            return false;
        }
 
        $dbw = $this->lbFactory->getPrimaryDatabase();
 
        if ( $this->expiryEnabled ) {
            $ticket = $this->lbFactory->getEmptyTransactionTicket( __METHOD__ );
            // First fetch the wl_ids.
            $wlIds = $dbw->newSelectQueryBuilder()
                ->select( 'wl_id' )
                ->from( 'watchlist' )
                ->where( [ 'wl_user' => $user->getId() ] )
                ->caller( __METHOD__ )
                ->fetchFieldValues();
            if ( $wlIds ) {
                // Delete rows from both the watchlist and watchlist_expiry tables.
                $dbw->delete(
                    'watchlist',
                    [ 'wl_id' => $wlIds ],
                    __METHOD__
                );
 
                $dbw->delete(
                    'watchlist_expiry',
                    [ 'we_item' => $wlIds ],
                    __METHOD__
                );
            }
            $this->lbFactory->commitAndWaitForReplication( __METHOD__, $ticket );
        } else {
            $dbw->delete(
                'watchlist',
                [ 'wl_user' => $user->getId() ],
                __METHOD__
            );
        }
 
        $this->uncacheAllItemsForUser( $user );
 
        return true;
    }
 
    public function mustClearWatchedItemsUsingJobQueue( UserIdentity $user ): bool {
        return $this->countWatchedItems( $user ) > $this->updateRowsPerQuery;
    }
 
    private function uncacheAllItemsForUser( UserIdentity $user ) {
        $userId = $user->getId();
        foreach ( $this->cacheIndex as $ns => $dbKeyIndex ) {
            foreach ( $dbKeyIndex as $dbKey => $userIndex ) {
                if ( array_key_exists( $userId, $userIndex ) ) {
                    $this->cache->delete( $userIndex[$userId] );
                    unset( $this->cacheIndex[$ns][$dbKey][$userId] );
                }
            }
        }
 
        // Cleanup empty cache keys
        foreach ( $this->cacheIndex as $ns => $dbKeyIndex ) {
            foreach ( $dbKeyIndex as $dbKey => $userIndex ) {
                if ( empty( $this->cacheIndex[$ns][$dbKey] ) ) {
                    unset( $this->cacheIndex[$ns][$dbKey] );
                }
            }
            if ( empty( $this->cacheIndex[$ns] ) ) {
                unset( $this->cacheIndex[$ns] );
            }
        }
    }
 
    public function clearUserWatchedItemsUsingJobQueue( UserIdentity $user ) {
        $job = ClearUserWatchlistJob::newForUser( $user, $this->getMaxId() );
        $this->queueGroup->push( $job );
    }
 
    public function maybeEnqueueWatchlistExpiryJob(): void {
        if ( !$this->expiryEnabled ) {
            // No need to purge expired entries if there are none
            return;
        }
 
        $max = mt_getrandmax();
        if ( mt_rand( 0, $max ) < $max * $this->watchlistPurgeRate ) {
            // The higher the watchlist purge rate, the more likely we are to enqueue a job.
            $this->queueGroup->lazyPush( new WatchlistExpiryJob() );
        }
    }
 
    public function getMaxId(): int {
        return (int)$this->lbFactory->getReplicaDatabase()->newSelectQueryBuilder()
            ->select( 'MAX(wl_id)' )
            ->from( 'watchlist' )
            ->caller( __METHOD__ )
            ->fetchField();
    }
 
    public function countWatchedItems( UserIdentity $user ): int {
        $dbr = $this->lbFactory->getReplicaDatabase();
        $queryBuilder = $this->lbFactory->getReplicaDatabase()->newSelectQueryBuilder()
            ->select( 'COUNT(*)' )
            ->from( 'watchlist' )
            ->where( [ 'wl_user' => $user->getId() ] )
            ->caller( __METHOD__ );
 
        $this->modifyQueryBuilderForExpiry( $queryBuilder, $dbr );
 
        return (int)$queryBuilder->fetchField();
    }
 
    public function countWatchers( $target ): int {
        $dbr = $this->lbFactory->getReplicaDatabase();
        $queryBuilder = $dbr->newSelectQueryBuilder()
            ->select( 'COUNT(*)' )
            ->from( 'watchlist' )
            ->where( [
                'wl_namespace' => $target->getNamespace(),
                'wl_title' => $target->getDBkey()
            ] )
            ->caller( __METHOD__ );
 
        $this->modifyQueryBuilderForExpiry( $queryBuilder, $dbr );
 
        return (int)$queryBuilder->fetchField();
    }
 
    public function countVisitingWatchers( $target, $threshold ): int {
        $dbr = $this->lbFactory->getReplicaDatabase();
        $queryBuilder = $dbr->newSelectQueryBuilder()
            ->select( 'COUNT(*)' )
            ->from( 'watchlist' )
            ->where( [
                'wl_namespace' => $target->getNamespace(),
                'wl_title' => $target->getDBkey(),
                'wl_notificationtimestamp >= ' .
                $dbr->addQuotes( $dbr->timestamp( $threshold ) ) .
                ' OR wl_notificationtimestamp IS NULL'
            ] )
            ->caller( __METHOD__ );
 
        $this->modifyQueryBuilderForExpiry( $queryBuilder, $dbr );
 
        return (int)$queryBuilder->fetchField();
    }
 
    public function removeWatchBatchForUser( UserIdentity $user, array $titles ): bool {
        if ( $this->readOnlyMode->isReadOnly() ) {
            return false;
        }
        if ( !$user->isRegistered() ) {
            return false;
        }
        if ( !$titles ) {
            return true;
        }
 
        $rows = $this->getTitleDbKeysGroupedByNamespace( $titles );
        $this->uncacheTitlesForUser( $user, $titles );
 
        $dbw = $this->lbFactory->getPrimaryDatabase();
        $ticket = count( $titles ) > $this->updateRowsPerQuery ?
            $this->lbFactory->getEmptyTransactionTicket( __METHOD__ ) : null;
        $affectedRows = 0;
 
        // Batch delete items per namespace.
        foreach ( $rows as $namespace => $namespaceTitles ) {
            $rowBatches = array_chunk( $namespaceTitles, $this->updateRowsPerQuery );
            foreach ( $rowBatches as $toDelete ) {
                // First fetch the wl_ids.
                $wlIds = $dbw->newSelectQueryBuilder()
                    ->select( 'wl_id' )
                    ->from( 'watchlist' )
                    ->where(
                        [
                            'wl_user' => $user->getId(),
                            'wl_namespace' => $namespace,
                            'wl_title' => $toDelete
                        ]
                    )
                    ->caller( __METHOD__ )
                    ->fetchFieldValues();
 
                if ( $wlIds ) {
                    // Delete rows from both the watchlist and watchlist_expiry tables.
                    $dbw->delete(
                        'watchlist',
                        [ 'wl_id' => $wlIds ],
                        __METHOD__
                    );
                    $affectedRows += $dbw->affectedRows();
 
                    if ( $this->expiryEnabled ) {
                        $dbw->delete(
                            'watchlist_expiry',
                            [ 'we_item' => $wlIds ],
                            __METHOD__
                        );
                        $affectedRows += $dbw->affectedRows();
                    }
                }
 
                if ( $ticket ) {
                    $this->lbFactory->commitAndWaitForReplication( __METHOD__, $ticket );
                }
            }
        }
 
        return (bool)$affectedRows;
    }
 
    public function countWatchersMultiple( array $targets, array $options = [] ): array {
        $linkTargets = array_map( static function ( $target ) {
            if ( !$target instanceof LinkTarget ) {
                return new TitleValue( $target->getNamespace(), $target->getDBkey() );
            }
            return $target;
        }, $targets );
        $lb = $this->linkBatchFactory->newLinkBatch( $linkTargets );
        $dbr = $this->lbFactory->getReplicaDatabase();
        $queryBuilder = $dbr->newSelectQueryBuilder();
        $queryBuilder
            ->select( [ 'wl_title', 'wl_namespace', 'watchers' => 'COUNT(*)' ] )
            ->from( 'watchlist' )
            ->where( [ $lb->constructSet( 'wl', $dbr ) ] )
            ->groupBy( [ 'wl_namespace', 'wl_title' ] )
            ->caller( __METHOD__ );
 
        if ( array_key_exists( 'minimumWatchers', $options ) ) {
            $queryBuilder->having( 'COUNT(*) >= ' . (int)$options['minimumWatchers'] );
        }
 
        $this->modifyQueryBuilderForExpiry( $queryBuilder, $dbr );
 
        $res = $queryBuilder->fetchResultSet();
 
        $watchCounts = [];
        foreach ( $targets as $linkTarget ) {
            $watchCounts[$linkTarget->getNamespace()][$linkTarget->getDBkey()] = 0;
        }
 
        foreach ( $res as $row ) {
            $watchCounts[$row->wl_namespace][$row->wl_title] = (int)$row->watchers;
        }
 
        return $watchCounts;
    }
 
    public function countVisitingWatchersMultiple(
        array $targetsWithVisitThresholds,
        $minimumWatchers = null
    ): array {
        if ( $targetsWithVisitThresholds === [] ) {
            // No titles requested => no results returned
            return [];
        }
 
        $dbr = $this->lbFactory->getReplicaDatabase();
        $queryBuilder = $dbr->newSelectQueryBuilder()
            ->select( [ 'wl_namespace', 'wl_title', 'watchers' => 'COUNT(*)' ] )
            ->from( 'watchlist' )
            ->where( [ $this->getVisitingWatchersCondition( $dbr, $targetsWithVisitThresholds ) ] )
            ->groupBy( [ 'wl_namespace', 'wl_title' ] )
            ->caller( __METHOD__ );
        if ( $minimumWatchers !== null ) {
            $queryBuilder->having( 'COUNT(*) >= ' . (int)$minimumWatchers );
        }
        $this->modifyQueryBuilderForExpiry( $queryBuilder, $dbr );
 
        $res = $queryBuilder->fetchResultSet();
 
        $watcherCounts = [];
        foreach ( $targetsWithVisitThresholds as [ $target ] ) {
            $watcherCounts[$target->getNamespace()][$target->getDBkey()] = 0;
        }
 
        foreach ( $res as $row ) {
            $watcherCounts[$row->wl_namespace][$row->wl_title] = (int)$row->watchers;
        }
 
        return $watcherCounts;
    }
 
    private function getVisitingWatchersCondition(
        IDatabase $db,
        array $targetsWithVisitThresholds
    ): string {
        $missingTargets = [];
        $namespaceConds = [];
        foreach ( $targetsWithVisitThresholds as [ $target, $threshold ] ) {
            if ( $threshold === null ) {
                $missingTargets[] = $target;
                continue;
            }
            $namespaceConds[$target->getNamespace()][] = $db->makeList( [
                'wl_title = ' . $db->addQuotes( $target->getDBkey() ),
                $db->makeList( [
                    'wl_notificationtimestamp >= ' . $db->addQuotes( $db->timestamp( $threshold ) ),
                    'wl_notificationtimestamp IS NULL'
                ], LIST_OR )
            ], LIST_AND );
        }
 
        $conds = [];
        foreach ( $namespaceConds as $namespace => $pageConds ) {
            $conds[] = $db->makeList( [
                'wl_namespace = ' . $namespace,
                '(' . $db->makeList( $pageConds, LIST_OR ) . ')'
            ], LIST_AND );
        }
 
        if ( $missingTargets ) {
            $lb = $this->linkBatchFactory->newLinkBatch( $missingTargets );
            $conds[] = $lb->constructSet( 'wl', $db );
        }
 
        return $db->makeList( $conds, LIST_OR );
    }
 
    public function getWatchedItem( UserIdentity $user, $target ) {
        if ( !$user->isRegistered() ) {
            return false;
        }
 
        $cached = $this->getCached( $user, $target );
        if ( $cached && !$cached->isExpired() ) {
            $this->stats->increment( 'WatchedItemStore.getWatchedItem.cached' );
            return $cached;
        }
        $this->stats->increment( 'WatchedItemStore.getWatchedItem.load' );
        return $this->loadWatchedItem( $user, $target );
    }
 
    public function loadWatchedItem( UserIdentity $user, $target ) {
        $item = $this->loadWatchedItemsBatch( $user, [ $target ] );
        return $item ? $item[0] : false;
    }
 
    public function loadWatchedItemsBatch( UserIdentity $user, array $targets ) {
        // Only registered user can have a watchlist
        if ( !$user->isRegistered() ) {
            return false;
        }
 
        $dbr = $this->lbFactory->getReplicaDatabase();
 
        $rows = $this->fetchWatchedItems(
            $dbr,
            $user,
            [ 'wl_namespace', 'wl_title', 'wl_notificationtimestamp' ],
            [],
            $targets
        );
 
        if ( !$rows ) {
            return false;
        }
 
        $items = [];
        foreach ( $rows as $row ) {
            // TODO: convert to PageIdentity
            $target = new TitleValue( (int)$row->wl_namespace, $row->wl_title );
            $item = $this->getWatchedItemFromRow( $user, $target, $row );
            $this->cache( $item );
            $items[] = $item;
        }
 
        return $items;
    }
 
    public function getWatchedItemsForUser( UserIdentity $user, array $options = [] ): array {
        $options += [ 'forWrite' => false ];
        $vars = [ 'wl_namespace', 'wl_title', 'wl_notificationtimestamp' ];
        $orderBy = [];
        if ( $options['forWrite'] ) {
            $db = $this->lbFactory->getPrimaryDatabase();
        } else {
            $db = $this->lbFactory->getReplicaDatabase();
        }
        if ( array_key_exists( 'sort', $options ) ) {
            Assert::parameter(
                ( in_array( $options['sort'], [ self::SORT_ASC, self::SORT_DESC ] ) ),
                '$options[\'sort\']',
                'must be SORT_ASC or SORT_DESC'
            );
            $orderBy[] = "wl_namespace {$options['sort']}";
            if ( $this->expiryEnabled
                && array_key_exists( 'sortByExpiry', $options )
                && $options['sortByExpiry']
            ) {
                // Add `wl_has_expiry` column to allow sorting by watched titles that have an expiration date first.
                $vars['wl_has_expiry'] = $db->conditional( 'we_expiry IS NULL', '0', '1' );
                // Display temporarily watched titles first.
                // Order by expiration date, with the titles that will expire soonest at the top.
                $orderBy[] = "wl_has_expiry DESC";
                $orderBy[] = "we_expiry ASC";
            }
 
            $orderBy[] = "wl_title {$options['sort']}";
        }
 
        $res = $this->fetchWatchedItems(
            $db,
            $user,
            $vars,
            $orderBy
        );
 
        $watchedItems = [];
        foreach ( $res as $row ) {
            // TODO: convert to PageIdentity
            $target = new TitleValue( (int)$row->wl_namespace, $row->wl_title );
            // @todo: Should we add these to the process cache?
            $watchedItems[] = $this->getWatchedItemFromRow( $user, $target, $row );
        }
 
        return $watchedItems;
    }
 
    private function getWatchedItemFromRow(
        UserIdentity $user,
        $target,
        stdClass $row
    ): WatchedItem {
        return new WatchedItem(
            $user,
            $target,
            $this->getLatestNotificationTimestamp(
                $row->wl_notificationtimestamp, $user, $target ),
            wfTimestampOrNull( TS_ISO_8601, $row->we_expiry ?? null )
        );
    }
 
    private function fetchWatchedItems(
        IDatabase $db,
        UserIdentity $user,
        array $vars,
        array $orderBy = [],
        $target = null
    ) {
        $dbMethod = 'select';
        $queryBuilder = $db->newSelectQueryBuilder()
            ->select( $vars )
            ->from( 'watchlist' )
            ->where( [ 'wl_user' => $user->getId() ] )
            ->caller( __METHOD__ );
        if ( $target ) {
            if ( $target instanceof LinkTarget || $target instanceof PageIdentity ) {
                $queryBuilder->where( [
                    'wl_namespace' => $target->getNamespace(),
                    'wl_title' => $target->getDBkey(),
                ] );
                $dbMethod = 'selectRow';
            } else {
                $titleConds = [];
                foreach ( $target as $linkTarget ) {
                    $titleConds[] = $db->makeList(
                        [
                            'wl_namespace' => $linkTarget->getNamespace(),
                            'wl_title' => $linkTarget->getDBkey(),
                        ],
                        $db::LIST_AND
                    );
                }
                $queryBuilder->where( $db->makeList( $titleConds, $db::LIST_OR ) );
            }
        }
 
        $this->modifyQueryBuilderForExpiry( $queryBuilder, $db );
        if ( $this->expiryEnabled ) {
            $queryBuilder->field( 'we_expiry' );
        }
        if ( $orderBy ) {
            $queryBuilder->orderBy( $orderBy );
        }
 
        if ( $dbMethod == 'selectRow' ) {
            return $queryBuilder->fetchRow();
        }
        return $queryBuilder->fetchResultSet();
    }
 
    public function isWatched( UserIdentity $user, $target ): bool {
        return (bool)$this->getWatchedItem( $user, $target );
    }
 
    public function isTempWatched( UserIdentity $user, $target ): bool {
        $item = $this->getWatchedItem( $user, $target );
        return $item && $item->getExpiry();
    }
 
    public function getNotificationTimestampsBatch( UserIdentity $user, array $targets ): array {
        $timestamps = [];
        foreach ( $targets as $target ) {
            $timestamps[$target->getNamespace()][$target->getDBkey()] = false;
        }
 
        if ( !$user->isRegistered() ) {
            return $timestamps;
        }
 
        $targetsToLoad = [];
        foreach ( $targets as $target ) {
            $cachedItem = $this->getCached( $user, $target );
            if ( $cachedItem ) {
                $timestamps[$target->getNamespace()][$target->getDBkey()] =
                    $cachedItem->getNotificationTimestamp();
            } else {
                $targetsToLoad[] = $target;
            }
        }
 
        if ( !$targetsToLoad ) {
            return $timestamps;
        }
 
        $dbr = $this->lbFactory->getReplicaDatabase();
 
        $lb = $this->linkBatchFactory->newLinkBatch( $targetsToLoad );
        $res = $dbr->newSelectQueryBuilder()
            ->select( [ 'wl_namespace', 'wl_title', 'wl_notificationtimestamp' ] )
            ->from( 'watchlist' )
            ->where( [
                $lb->constructSet( 'wl', $dbr ),
                'wl_user' => $user->getId(),
            ] )
            ->caller( __METHOD__ )
            ->fetchResultSet();
 
        foreach ( $res as $row ) {
            // TODO: convert to PageIdentity
            $target = new TitleValue( (int)$row->wl_namespace, $row->wl_title );
            $timestamps[$row->wl_namespace][$row->wl_title] =
                $this->getLatestNotificationTimestamp(
                    $row->wl_notificationtimestamp, $user, $target );
        }
 
        return $timestamps;
    }
 
    public function addWatch( UserIdentity $user, $target, ?string $expiry = null ) {
        $this->addWatchBatchForUser( $user, [ $target ], $expiry );
 
        if ( $this->expiryEnabled && !$expiry ) {
            // When re-watching a page with a null $expiry, any existing expiry is left unchanged.
            // However we must re-fetch the preexisting expiry or else the cached WatchedItem will
            // incorrectly have a null expiry. Note that loadWatchedItem() does the caching.
            // See T259379
            $this->loadWatchedItem( $user, $target );
        } else {
            // Create a new WatchedItem and add it to the process cache.
            // In this case we don't need to re-fetch the expiry.
            $expiry = ExpiryDef::normalizeUsingMaxExpiry( $expiry, $this->maxExpiryDuration, TS_ISO_8601 );
            $item = new WatchedItem(
                $user,
                $target,
                null,
                $expiry
            );
            $this->cache( $item );
        }
    }
 
    public function addWatchBatchForUser(
        UserIdentity $user,
        array $targets,
        ?string $expiry = null
    ): bool {
        if ( $this->readOnlyMode->isReadOnly() ) {
            return false;
        }
        // Only registered user can have a watchlist
        if ( !$user->isRegistered() ) {
            return false;
        }
 
        if ( !$targets ) {
            return true;
        }
        $expiry = ExpiryDef::normalizeUsingMaxExpiry( $expiry, $this->maxExpiryDuration, TS_ISO_8601 );
        $rows = [];
        foreach ( $targets as $target ) {
            $rows[] = [
                'wl_user' => $user->getId(),
                'wl_namespace' => $target->getNamespace(),
                'wl_title' => $target->getDBkey(),
                'wl_notificationtimestamp' => null,
            ];
            $this->uncache( $user, $target );
        }
 
        $dbw = $this->lbFactory->getPrimaryDatabase();
        $ticket = count( $targets ) > $this->updateRowsPerQuery ?
            $this->lbFactory->getEmptyTransactionTicket( __METHOD__ ) : null;
        $affectedRows = 0;
        $rowBatches = array_chunk( $rows, $this->updateRowsPerQuery );
        foreach ( $rowBatches as $toInsert ) {
            // Use INSERT IGNORE to avoid overwriting the notification timestamp
            // if there's already an entry for this page
            $dbw->insert( 'watchlist', $toInsert, __METHOD__, [ 'IGNORE' ] );
            $affectedRows += $dbw->affectedRows();
 
            if ( $this->expiryEnabled ) {
                $affectedRows += $this->updateOrDeleteExpiries( $dbw, $user->getId(), $toInsert, $expiry );
            }
 
            if ( $ticket ) {
                $this->lbFactory->commitAndWaitForReplication( __METHOD__, $ticket );
            }
        }
 
        return (bool)$affectedRows;
    }
 
    private function updateOrDeleteExpiries(
        IDatabase $dbw,
        int $userId,
        array $rows,
        ?string $expiry = null
    ): int {
        if ( !$expiry ) {
            // if expiry is null (shouldn't change), 0 rows affected.
            return 0;
        }
 
        // Build the giant `(...) OR (...)` part to be used with WHERE.
        $conds = [];
        foreach ( $rows as $row ) {
            $conds[] = $dbw->makeList(
                [
                    'wl_user' => $userId,
                    'wl_namespace' => $row['wl_namespace'],
                    'wl_title' => $row['wl_title']
                ],
                $dbw::LIST_AND
            );
        }
        $cond = $dbw->makeList( $conds, $dbw::LIST_OR );
 
        if ( wfIsInfinity( $expiry ) ) {
            // Rows should be deleted rather than updated.
            $dbw->deleteJoin(
                'watchlist_expiry',
                'watchlist',
                'we_item',
                'wl_id',
                [ $cond ],
                __METHOD__
            );
 
            return $dbw->affectedRows();
        }
 
        return $this->updateExpiries( $dbw, $expiry, $cond );
    }
 
    private function updateExpiries( IDatabase $dbw, string $expiry, string $cond ): int {
        // First fetch the wl_ids from the watchlist table.
        // We'd prefer to do a INSERT/SELECT in the same query with IDatabase::insertSelect(),
        // but it doesn't allow us to use the "ON DUPLICATE KEY UPDATE" clause.
        $wlIds = $dbw->newSelectQueryBuilder()
            ->select( 'wl_id' )
            ->from( 'watchlist' )
            ->where( $cond )
            ->caller( __METHOD__ )
            ->fetchFieldValues();
        $expiry = $dbw->timestamp( $expiry );
 
        $weRows = array_map( static function ( $wlId ) use ( $expiry ) {
            return [
                'we_item' => $wlId,
                'we_expiry' => $expiry
            ];
        }, $wlIds );
 
        // Insert into watchlist_expiry, updating the expiry for duplicate rows.
        $dbw->upsert(
            'watchlist_expiry',
            $weRows,
            'we_item',
            [ 'we_expiry' => $expiry ],
            __METHOD__
        );
 
        return $dbw->affectedRows();
    }
 
    public function removeWatch( UserIdentity $user, $target ): bool {
        return $this->removeWatchBatchForUser( $user, [ $target ] );
    }
 
    public function setNotificationTimestampsForUser(
        UserIdentity $user,
        $timestamp,
        array $targets = []
    ): bool {
        // Only registered user can have a watchlist
        if ( !$user->isRegistered() || $this->readOnlyMode->isReadOnly() ) {
            return false;
        }
 
        if ( !$targets ) {
            // Backwards compatibility
            $this->resetAllNotificationTimestampsForUser( $user, $timestamp );
            return true;
        }
 
        $rows = $this->getTitleDbKeysGroupedByNamespace( $targets );
 
        $dbw = $this->lbFactory->getPrimaryDatabase();
        if ( $timestamp !== null ) {
            $timestamp = $dbw->timestamp( $timestamp );
        }
        $ticket = $this->lbFactory->getEmptyTransactionTicket( __METHOD__ );
        $affectedSinceWait = 0;
 
        // Batch update items per namespace
        foreach ( $rows as $namespace => $namespaceTitles ) {
            $rowBatches = array_chunk( $namespaceTitles, $this->updateRowsPerQuery );
            foreach ( $rowBatches as $toUpdate ) {
                // First fetch the wl_ids.
                $wlIds = $dbw->newSelectQueryBuilder()
                    ->select( 'wl_id' )
                    ->from( 'watchlist' )
                    ->where( [
                        'wl_user' => $user->getId(),
                        'wl_namespace' => $namespace,
                        'wl_title' => $toUpdate
                    ] )
                    ->caller( __METHOD__ )
                    ->fetchFieldValues();
                if ( $wlIds ) {
                    $wlIds = array_map( 'intval', $wlIds );
                    $dbw->update(
                        'watchlist',
                        [ 'wl_notificationtimestamp' => $timestamp ],
                        [ 'wl_id' => $wlIds ],
                        __METHOD__
                    );
                    $affectedSinceWait += $dbw->affectedRows();
                    // Wait for replication every time we've touched updateRowsPerQuery rows
                    if ( $affectedSinceWait >= $this->updateRowsPerQuery ) {
                        $this->lbFactory->commitAndWaitForReplication( __METHOD__, $ticket );
                        $affectedSinceWait = 0;
                    }
                }
            }
        }
 
        $this->uncacheUser( $user );
 
        return true;
    }
 
    public function getLatestNotificationTimestamp(
        $timestamp,
        UserIdentity $user,
        $target
    ) {
        $timestamp = wfTimestampOrNull( TS_MW, $timestamp );
        if ( $timestamp === null ) {
            return null; // no notification
        }
 
        $seenTimestamps = $this->getPageSeenTimestamps( $user );
        if ( $seenTimestamps ) {
            $seenKey = $this->getPageSeenKey( $target );
            if ( isset( $seenTimestamps[$seenKey] ) && $seenTimestamps[$seenKey] >= $timestamp ) {
                // If a reset job did not yet run, then the "seen" timestamp will be higher
                return null;
            }
        }
 
        return $timestamp;
    }
 
    public function resetAllNotificationTimestampsForUser( UserIdentity $user, $timestamp = null ) {
        // Only registered user can have a watchlist
        if ( !$user->isRegistered() ) {
            return;
        }
 
        // If the page is watched by the user (or may be watched), update the timestamp
        $job = new ClearWatchlistNotificationsJob( [
            'userId'  => $user->getId(), 'timestamp' => $timestamp, 'casTime' => time()
        ] );
 
        // Try to run this post-send
        // Calls DeferredUpdates::addCallableUpdate in normal operation
        call_user_func(
            $this->deferredUpdatesAddCallableUpdateCallback,
            static function () use ( $job ) {
                $job->run();
            }
        );
    }
 
    public function updateNotificationTimestamp(
        UserIdentity $editor,
        $target,
        $timestamp
    ): array {
        $dbw = $this->lbFactory->getPrimaryDatabase();
        $queryBuilder = $dbw->newSelectQueryBuilder()
            ->select( [ 'wl_id', 'wl_user' ] )
            ->from( 'watchlist' )
            ->where(
                [
                    'wl_user != ' . $editor->getId(),
                    'wl_namespace' => $target->getNamespace(),
                    'wl_title' => $target->getDBkey(),
                    'wl_notificationtimestamp' => null,
                ]
            )
            ->caller( __METHOD__ );
 
        $this->modifyQueryBuilderForExpiry( $queryBuilder, $dbw );
 
        $res = $queryBuilder->fetchResultSet();
        $watchers = [];
        $wlIds = [];
        foreach ( $res as $row ) {
            $watchers[] = (int)$row->wl_user;
            $wlIds[] = (int)$row->wl_id;
        }
 
        if ( $wlIds ) {
            $fname = __METHOD__;
            // Try to run this post-send
            // Calls DeferredUpdates::addCallableUpdate in normal operation
            call_user_func(
                $this->deferredUpdatesAddCallableUpdateCallback,
                function () use ( $timestamp, $wlIds, $target, $fname ) {
                    $dbw = $this->lbFactory->getPrimaryDatabase();
                    $ticket = $this->lbFactory->getEmptyTransactionTicket( $fname );
 
                    $wlIdsChunks = array_chunk( $wlIds, $this->updateRowsPerQuery );
                    foreach ( $wlIdsChunks as $wlIdsChunk ) {
                        $dbw->update(
                            'watchlist',
                            [ 'wl_notificationtimestamp' => $dbw->timestamp( $timestamp ) ],
                            [ 'wl_id' => $wlIdsChunk ],
                            $fname
                        );
                        if ( count( $wlIdsChunks ) > 1 ) {
                            $this->lbFactory->commitAndWaitForReplication(
                                $fname, $ticket, [ 'domain' => $dbw->getDomainID() ]
                            );
                        }
                    }
                    $this->uncacheLinkTarget( $target );
                },
                DeferredUpdates::POSTSEND,
                $dbw
            );
        }
 
        return $watchers;
    }
 
    public function resetNotificationTimestamp(
        UserIdentity $user,
        $title,
        $force = '',
        $oldid = 0
    ): bool {
        $time = time();
 
        // Only registered user can have a watchlist
        if ( $this->readOnlyMode->isReadOnly() || !$user->isRegistered() ) {
            return false;
        }
 
        $item = null;
        if ( $force != 'force' ) {
            $item = $this->getWatchedItem( $user, $title );
            if ( !$item || $item->getNotificationTimestamp() === null ) {
                return false;
            }
        }
 
        // Get the timestamp (TS_MW) of this revision to track the latest one seen
        $id = $oldid;
        $seenTime = null;
        if ( !$id ) {
            $latestRev = $this->revisionLookup->getRevisionByTitle( $title );
            if ( $latestRev ) {
                $id = $latestRev->getId();
                // Save a DB query
                $seenTime = $latestRev->getTimestamp();
            }
        }
        if ( $seenTime === null ) {
            // @phan-suppress-next-line PhanTypeMismatchArgumentNullable getId does not return null here
            $seenTime = $this->revisionLookup->getTimestampFromId( $id );
        }
 
        // Mark the item as read immediately in lightweight storage
        $this->stash->merge(
            $this->getPageSeenTimestampsKey( $user ),
            function ( $cache, $key, $current ) use ( $title, $seenTime ) {
                if ( !$current ) {
                    $value = new MapCacheLRU( 300 );
                } elseif ( is_array( $current ) ) {
                    $value = MapCacheLRU::newFromArray( $current, 300 );
                } else {
                    // Backwards compatibility for T282105
                    $value = $current;
                }
                $subKey = $this->getPageSeenKey( $title );
 
                if ( $seenTime > $value->get( $subKey ) ) {
                    // Revision is newer than the last one seen
                    $value->set( $subKey, $seenTime );
 
                    $this->latestUpdateCache->set( $key, $value->toArray(), BagOStuff::TTL_PROC_LONG );
                } elseif ( $seenTime === false ) {
                    // Revision does not exist
                    $value->set( $subKey, wfTimestamp( TS_MW ) );
                    $this->latestUpdateCache->set( $key,
                        $value->toArray(),
                        BagOStuff::TTL_PROC_LONG );
                } else {
                    return false; // nothing to update
                }
 
                return $value->toArray();
            },
            BagOStuff::TTL_HOUR
        );
 
        // If the page is watched by the user (or may be watched), update the timestamp
        // ActivityUpdateJob accepts both LinkTarget and PageReference
        $job = new ActivityUpdateJob(
            $title,
            [
                'type'      => 'updateWatchlistNotification',
                'userid'    => $user->getId(),
                'notifTime' => $this->getNotificationTimestamp( $user, $title, $item, $force, $oldid ),
                'curTime'   => $time
            ]
        );
        // Try to enqueue this post-send
        $this->queueGroup->lazyPush( $job );
 
        $this->uncache( $user, $title );
 
        return true;
    }
 
    private function getPageSeenTimestamps( UserIdentity $user ) {
        $key = $this->getPageSeenTimestampsKey( $user );
 
        $cache = $this->latestUpdateCache->getWithSetCallback(
            $key,
            BagOStuff::TTL_PROC_LONG,
            function () use ( $key ) {
                return $this->stash->get( $key ) ?: null;
            }
        );
        // Backwards compatibility for T282105
        if ( $cache instanceof MapCacheLRU ) {
            $cache = $cache->toArray();
        }
        return $cache;
    }
 
    private function getPageSeenTimestampsKey( UserIdentity $user ): string {
        return $this->stash->makeGlobalKey(
            'watchlist-recent-updates',
            $this->lbFactory->getLocalDomainID(),
            $user->getId()
        );
    }
 
    private function getPageSeenKey( $target ): string {
        return "{$target->getNamespace()}:{$target->getDBkey()}";
    }
 
    private function getNotificationTimestamp(
        UserIdentity $user,
        $title,
        $item,
        $force,
        $oldid
    ) {
        if ( !$oldid ) {
            // No oldid given, assuming latest revision; clear the timestamp.
            return null;
        }
 
        $oldRev = $this->revisionLookup->getRevisionById( $oldid );
        if ( !$oldRev ) {
            // Oldid given but does not exist (probably deleted)
            return false;
        }
 
        $nextRev = $this->revisionLookup->getNextRevision( $oldRev );
        if ( !$nextRev ) {
            // Oldid given and is the latest revision for this title; clear the timestamp.
            return null;
        }
 
        if ( $item === null ) {
            $item = $this->loadWatchedItem( $user, $title );
        }
 
        if ( !$item ) {
            // This can only happen if $force is enabled.
            return null;
        }
 
        // Oldid given and isn't the latest; update the timestamp.
        // This will result in no further notification emails being sent!
        $notificationTimestamp = $this->revisionLookup->getTimestampFromId( $oldid );
        // @FIXME: this should use getTimestamp() for consistency with updates on new edits
        // $notificationTimestamp = $nextRev->getTimestamp(); // first unseen revision timestamp
 
        // We need to go one second to the future because of various strict comparisons
        // throughout the codebase
        $ts = new MWTimestamp( $notificationTimestamp );
        $ts->timestamp->add( new DateInterval( 'PT1S' ) );
        $notificationTimestamp = $ts->getTimestamp( TS_MW );
 
        if ( $notificationTimestamp < $item->getNotificationTimestamp() ) {
            if ( $force != 'force' ) {
                return false;
            } else {
                // This is a little silly…
                return $item->getNotificationTimestamp();
            }
        }
 
        return $notificationTimestamp;
    }
 
    public function countUnreadNotifications( UserIdentity $user, $unreadLimit = null ) {
        $queryBuilder = $this->lbFactory->getReplicaDatabase()->newSelectQueryBuilder()
            ->select( '1' )
            ->from( 'watchlist' )
            ->where( [
                'wl_user' => $user->getId(),
                'wl_notificationtimestamp IS NOT NULL'
            ] )
            ->caller( __METHOD__ );
        if ( $unreadLimit !== null ) {
            $unreadLimit = (int)$unreadLimit;
            $queryBuilder->limit( $unreadLimit );
        }
 
        $rowCount = $queryBuilder->fetchRowCount();
 
        if ( $unreadLimit === null ) {
            return $rowCount;
        }
 
        if ( $rowCount >= $unreadLimit ) {
            return true;
        }
 
        return $rowCount;
    }
 
    public function duplicateAllAssociatedEntries( $oldTarget, $newTarget ) {
        // Duplicate first the subject page, then the talk page
        // TODO: convert to PageIdentity
        $this->duplicateEntry(
            new TitleValue( $this->nsInfo->getSubject( $oldTarget->getNamespace() ), $oldTarget->getDBkey() ),
            new TitleValue( $this->nsInfo->getSubject( $newTarget->getNamespace() ), $newTarget->getDBkey() )
        );
        $this->duplicateEntry(
            new TitleValue( $this->nsInfo->getTalk( $oldTarget->getNamespace() ), $oldTarget->getDBkey() ),
            new TitleValue( $this->nsInfo->getTalk( $newTarget->getNamespace() ), $newTarget->getDBkey() )
        );
    }
 
    public function duplicateEntry( $oldTarget, $newTarget ) {
        $dbw = $this->lbFactory->getPrimaryDatabase();
        $result = $this->fetchWatchedItemsForPage( $dbw, $oldTarget );
        $newNamespace = $newTarget->getNamespace();
        $newDBkey = $newTarget->getDBkey();
 
        # Construct array to replace into the watchlist
        $values = [];
        $expiries = [];
        foreach ( $result as $row ) {
            $values[] = [
                'wl_user' => $row->wl_user,
                'wl_namespace' => $newNamespace,
                'wl_title' => $newDBkey,
                'wl_notificationtimestamp' => $row->wl_notificationtimestamp,
            ];
 
            if ( $this->expiryEnabled && $row->we_expiry ) {
                $expiries[$row->wl_user] = $row->we_expiry;
            }
        }
 
        if ( empty( $values ) ) {
            return;
        }
 
        // Perform a replace on the watchlist table rows.
        // Note that multi-row replace is very efficient for MySQL but may be inefficient for
        // some other DBMSes, mostly due to poor simulation by us.
        $dbw->replace(
            'watchlist',
            [ [ 'wl_user', 'wl_namespace', 'wl_title' ] ],
            $values,
            __METHOD__
        );
 
        if ( $this->expiryEnabled ) {
            $this->updateExpiriesAfterMove( $dbw, $expiries, $newNamespace, $newDBkey );
        }
    }
 
    private function fetchWatchedItemsForPage(
        IDatabase $dbw,
        $target
    ): IResultWrapper {
        $queryBuilder = $dbw->newSelectQueryBuilder()
            ->select( [ 'wl_user', 'wl_notificationtimestamp' ] )
            ->from( 'watchlist' )
            ->where( [
                'wl_namespace' => $target->getNamespace(),
                'wl_title' => $target->getDBkey(),
            ] )
            ->caller( __METHOD__ )
            ->forUpdate();
 
        if ( $this->expiryEnabled ) {
            $queryBuilder->leftJoin( 'watchlist_expiry', null, [ 'wl_id = we_item' ] )
                ->field( 'we_expiry' );
        }
 
        return $queryBuilder->fetchResultSet();
    }
 
    private function updateExpiriesAfterMove(
        IDatabase $dbw,
        array $expiries,
        int $namespace,
        string $dbKey
    ): void {
        $method = __METHOD__;
        DeferredUpdates::addCallableUpdate(
            function () use ( $dbw, $expiries, $namespace, $dbKey, $method ) {
                // First fetch new wl_ids.
                $res = $dbw->newSelectQueryBuilder()
                    ->select( [ 'wl_user', 'wl_id' ] )
                    ->from( 'watchlist' )
                    ->where( [
                        'wl_namespace' => $namespace,
                        'wl_title' => $dbKey,
                    ] )
                    ->caller( $method )
                    ->fetchResultSet();
 
                // Build new array to INSERT into multiple rows at once.
                $expiryData = [];
                foreach ( $res as $row ) {
                    if ( !empty( $expiries[$row->wl_user] ) ) {
                        $expiryData[] = [
                            'we_item' => $row->wl_id,
                            'we_expiry' => $expiries[$row->wl_user],
                        ];
                    }
                }
 
                // Batch the insertions.
                $batches = array_chunk( $expiryData, $this->updateRowsPerQuery );
                foreach ( $batches as $toInsert ) {
                    $dbw->replace(
                        'watchlist_expiry',
                        'we_item',
                        $toInsert,
                        $method
                    );
                }
            },
            DeferredUpdates::POSTSEND,
            $dbw
        );
    }
 
    private function getTitleDbKeysGroupedByNamespace( array $titles ) {
        $rows = [];
        foreach ( $titles as $title ) {
            // Group titles by namespace.
            $rows[ $title->getNamespace() ][] = $title->getDBkey();
        }
        return $rows;
    }
 
    private function uncacheTitlesForUser( UserIdentity $user, array $titles ) {
        foreach ( $titles as $title ) {
            $this->uncache( $user, $title );
        }
    }
 
    public function countExpired(): int {
        $dbr = $this->lbFactory->getReplicaDatabase();
        return $dbr->newSelectQueryBuilder()
            ->select( '*' )
            ->from( 'watchlist_expiry' )
            ->where( [ 'we_expiry <= ' . $dbr->addQuotes( $dbr->timestamp() ) ] )
            ->caller( __METHOD__ )
            ->fetchRowCount();
    }
 
    public function removeExpired( int $limit, bool $deleteOrphans = false ): void {
        $dbr = $this->lbFactory->getReplicaDatabase();
        $dbw = $this->lbFactory->getPrimaryDatabase();
        $ticket = $this->lbFactory->getEmptyTransactionTicket( __METHOD__ );
 
        // Get a batch of watchlist IDs to delete.
        $toDelete = $dbr->newSelectQueryBuilder()
            ->select( 'we_item' )
            ->from( 'watchlist_expiry' )
            ->where( [ 'we_expiry <= ' . $dbr->addQuotes( $dbr->timestamp() ) ] )
            ->limit( $limit )
            ->caller( __METHOD__ )
            ->fetchFieldValues();
 
        if ( count( $toDelete ) > 0 ) {
            // Delete them from the watchlist and watchlist_expiry table.
            $dbw->delete(
                'watchlist',
                [ 'wl_id' => $toDelete ],
                __METHOD__
            );
            $dbw->delete(
                'watchlist_expiry',
                [ 'we_item' => $toDelete ],
                __METHOD__
            );
        }
 
        // Also delete any orphaned or null-expiry watchlist_expiry rows
        // (they should not exist, but might because not everywhere knows about the expiry table yet).
        if ( $deleteOrphans ) {
            $expiryToDelete = $dbr->newSelectQueryBuilder()
                ->select( 'we_item' )
                ->from( 'watchlist_expiry' )
                ->leftJoin( 'watchlist', null, 'wl_id = we_item' )
                ->where( $dbr->makeList(
                    [ 'wl_id' => null, 'we_expiry' => null ],
                    $dbr::LIST_OR
                ) )
                ->caller( __METHOD__ )
                ->fetchFieldValues();
            if ( count( $expiryToDelete ) > 0 ) {
                $dbw->delete(
                    'watchlist_expiry',
                    [ 'we_item' => $expiryToDelete ],
                    __METHOD__
                );
            }
        }
 
        $this->lbFactory->commitAndWaitForReplication( __METHOD__, $ticket );
    }
}