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[mediawiki.git] / includes / specialpage / QueryPage.php

<?php
/**
 * Base code for "query" special pages.
 *
 * 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
 * @ingroup SpecialPage
 */

namespace MediaWiki\SpecialPage;

use Exception;
use MediaWiki\Cache\LinkBatchFactory;
use MediaWiki\Config\Config;
use MediaWiki\HookContainer\HookRunner;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MainConfigNames;
use MediaWiki\MediaWikiServices;
use MediaWiki\Output\OutputPage;
use MediaWiki\Specials\SpecialAncientPages;
use MediaWiki\Specials\SpecialBrokenRedirects;
use MediaWiki\Specials\SpecialDeadendPages;
use MediaWiki\Specials\SpecialDoubleRedirects;
use MediaWiki\Specials\SpecialFewestRevisions;
use MediaWiki\Specials\SpecialLinkSearch;
use MediaWiki\Specials\SpecialListDuplicatedFiles;
use MediaWiki\Specials\SpecialListRedirects;
use MediaWiki\Specials\SpecialLonelyPages;
use MediaWiki\Specials\SpecialLongPages;
use MediaWiki\Specials\SpecialMediaStatistics;
use MediaWiki\Specials\SpecialMIMESearch;
use MediaWiki\Specials\SpecialMostCategories;
use MediaWiki\Specials\SpecialMostImages;
use MediaWiki\Specials\SpecialMostInterwikis;
use MediaWiki\Specials\SpecialMostLinked;
use MediaWiki\Specials\SpecialMostLinkedCategories;
use MediaWiki\Specials\SpecialMostLinkedTemplates;
use MediaWiki\Specials\SpecialMostRevisions;
use MediaWiki\Specials\SpecialShortPages;
use MediaWiki\Specials\SpecialUncategorizedCategories;
use MediaWiki\Specials\SpecialUncategorizedImages;
use MediaWiki\Specials\SpecialUncategorizedPages;
use MediaWiki\Specials\SpecialUncategorizedTemplates;
use MediaWiki\Specials\SpecialUnusedCategories;
use MediaWiki\Specials\SpecialUnusedImages;
use MediaWiki\Specials\SpecialUnusedTemplates;
use MediaWiki\Specials\SpecialUnwatchedPages;
use MediaWiki\Specials\SpecialWantedCategories;
use MediaWiki\Specials\SpecialWantedFiles;
use MediaWiki\Specials\SpecialWantedPages;
use MediaWiki\Specials\SpecialWantedTemplates;
use MediaWiki\Specials\SpecialWithoutInterwiki;
use MediaWiki\Xml\Xml;
use Skin;
use stdClass;
use Wikimedia\Rdbms\DBError;
use Wikimedia\Rdbms\IConnectionProvider;
use Wikimedia\Rdbms\IDatabase;
use Wikimedia\Rdbms\ILoadBalancer;
use Wikimedia\Rdbms\IReadableDatabase;
use Wikimedia\Rdbms\IResultWrapper;
use Wikimedia\Rdbms\SelectQueryBuilder;

/**
 * This is a class for doing query pages; since they're almost all the same,
 * we factor out some of the functionality into a superclass, and let
 * subclasses derive from it.
 *
 * @stable to extend
 *
 * @ingroup SpecialPage
 */
abstract class QueryPage extends SpecialPage {
        /** @var bool Whether or not we want plain listoutput rather than an ordered list */
        protected $listoutput = false;

        /** @var int The offset and limit in use, as passed to the query() function */
        protected $offset = 0;

        /** @var int */
        protected $limit = 0;

        /**
         * The number of rows returned by the query. Reading this variable
         * only makes sense in functions that are run after the query has been
         * done, such as preprocessResults() and formatRow().
         *
         * @var int
         */
        protected $numRows;

        /**
         * @var string|null|false
         */
        protected $cachedTimestamp = null;

        /**
         * @var bool Whether to show prev/next links
         */
        protected $shownavigation = true;

        /** @var ILoadBalancer|null */
        private $loadBalancer = null;

        /** @var IConnectionProvider|null */
        private $databaseProvider = null;

        /** @var LinkBatchFactory|null */
        private $linkBatchFactory = null;

        /**
         * Get a list of query page classes and their associated special pages,
         * for periodic updates.
         *
         * DO NOT CHANGE THIS LIST without testing that
         * maintenance/updateSpecialPages.php still works.
         *
         * @return array[] List of [ string $class, string $specialPageName, ?int $limit (optional) ].
         *  Limit defaults to $wgQueryCacheLimit if not given.
         */
        public static function getPages() {
                static $qp = null;

                if ( $qp === null ) {
                        $qp = [
                                [ SpecialAncientPages::class, 'Ancientpages' ],
                                [ SpecialBrokenRedirects::class, 'BrokenRedirects' ],
                                [ SpecialDeadendPages::class, 'Deadendpages' ],
                                [ SpecialDoubleRedirects::class, 'DoubleRedirects' ],
                                [ SpecialListDuplicatedFiles::class, 'ListDuplicatedFiles' ],
                                [ SpecialLinkSearch::class, 'LinkSearch' ],
                                [ SpecialListRedirects::class, 'Listredirects' ],
                                [ SpecialLonelyPages::class, 'Lonelypages' ],
                                [ SpecialLongPages::class, 'Longpages' ],
                                [ SpecialMediaStatistics::class, 'MediaStatistics', SpecialMediaStatistics::MAX_LIMIT ],
                                [ SpecialMIMESearch::class, 'MIMEsearch' ],
                                [ SpecialMostCategories::class, 'Mostcategories' ],
                                [ SpecialMostImages::class, 'Mostimages' ],
                                [ SpecialMostInterwikis::class, 'Mostinterwikis' ],
                                [ SpecialMostLinkedCategories::class, 'Mostlinkedcategories' ],
                                [ SpecialMostLinkedTemplates::class, 'Mostlinkedtemplates' ],
                                [ SpecialMostLinked::class, 'Mostlinked' ],
                                [ SpecialMostRevisions::class, 'Mostrevisions' ],
                                [ SpecialFewestRevisions::class, 'Fewestrevisions' ],
                                [ SpecialShortPages::class, 'Shortpages' ],
                                [ SpecialUncategorizedCategories::class, 'Uncategorizedcategories' ],
                                [ SpecialUncategorizedPages::class, 'Uncategorizedpages' ],
                                [ SpecialUncategorizedImages::class, 'Uncategorizedimages' ],
                                [ SpecialUncategorizedTemplates::class, 'Uncategorizedtemplates' ],
                                [ SpecialUnusedCategories::class, 'Unusedcategories' ],
                                [ SpecialUnusedImages::class, 'Unusedimages' ],
                                [ SpecialWantedCategories::class, 'Wantedcategories' ],
                                [ SpecialWantedFiles::class, 'Wantedfiles' ],
                                [ SpecialWantedPages::class, 'Wantedpages' ],
                                [ SpecialWantedTemplates::class, 'Wantedtemplates' ],
                                [ SpecialUnwatchedPages::class, 'Unwatchedpages' ],
                                [ SpecialUnusedTemplates::class, 'Unusedtemplates' ],
                                [ SpecialWithoutInterwiki::class, 'Withoutinterwiki' ],
                        ];
                        ( new HookRunner( MediaWikiServices::getInstance()->getHookContainer() ) )->onWgQueryPages( $qp );
                }

                return $qp;
        }

        /**
         * @since 1.36
         * @param LinkBatchFactory $linkBatchFactory
         */
        final protected function setLinkBatchFactory( LinkBatchFactory $linkBatchFactory ) {
                $this->linkBatchFactory = $linkBatchFactory;
        }

        /**
         * @since 1.36
         * @return LinkBatchFactory
         */
        final protected function getLinkBatchFactory(): LinkBatchFactory {
                if ( $this->linkBatchFactory === null ) {
                        // Fallback if not provided
                        // TODO Change to wfWarn in a future release
                        $this->linkBatchFactory = MediaWikiServices::getInstance()->getLinkBatchFactory();
                }
                return $this->linkBatchFactory;
        }

        /**
         * Get a list of disabled query pages and their run mode
         * @param Config $config
         * @return string[]
         */
        public static function getDisabledQueryPages( Config $config ) {
                $disableQueryPageUpdate = $config->get( MainConfigNames::DisableQueryPageUpdate );

                if ( !is_array( $disableQueryPageUpdate ) ) {
                        return [];
                }

                $pages = [];
                foreach ( $disableQueryPageUpdate as $name => $runMode ) {
                        if ( is_int( $name ) ) {
                                // The run mode may be omitted
                                $pages[$runMode] = 'disabled';
                        } else {
                                $pages[$name] = $runMode;
                        }
                }
                return $pages;
        }

        /**
         * A mutator for $this->listoutput;
         *
         * @param bool $bool
         */
        protected function setListoutput( $bool ) {
                $this->listoutput = $bool;
        }

        /**
         * Subclasses return an SQL query here, formatted as an array with the
         * following keys:
         *    tables => Table(s) for passing to Database::select()
         *    fields => Field(s) for passing to Database::select(), may be *
         *    conds => WHERE conditions
         *    options => options
         *    join_conds => JOIN conditions
         *
         * Note that the query itself should return the following three columns:
         * 'namespace', 'title', and 'value'. 'value' is used for sorting.
         *
         * These may be stored in the querycache table for expensive queries,
         * and that cached data will be returned sometimes, so the presence of
         * extra fields can't be relied upon. The cached 'value' column will be
         * an integer; non-numeric values are useful only for sorting the
         * initial query (except if they're timestamps, see usesTimestamps()).
         *
         * Don't include an ORDER or LIMIT clause, they will be added.
         *
         * @return array
         * @since 1.18, abstract since 1.43
         */
        abstract public function getQueryInfo();

        /**
         * Subclasses return an array of fields to order by here. Don't append
         * DESC to the field names, that'll be done automatically if
         * sortDescending() returns true.
         * @stable to override
         * @return string[]
         * @since 1.18
         */
        protected function getOrderFields() {
                return [ 'value' ];
        }

        /**
         * Does this query return timestamps rather than integers in its
         * 'value' field? If true, this class will convert 'value' to a
         * UNIX timestamp for caching.
         * NOTE: formatRow() may get timestamps in TS_MW (mysql), TS_DB (pgsql)
         *       or TS_UNIX (querycache) format, so be sure to always run them
         *       through wfTimestamp()
         * @stable to override
         * @return bool
         * @since 1.18
         */
        public function usesTimestamps() {
                return false;
        }

        /**
         * Override to sort by increasing values
         *
         * @stable to override
         * @return bool
         */
        protected function sortDescending() {
                return true;
        }

        /**
         * Should this query page only be updated offline on large wikis?
         *
         * If the query for this page is considered too expensive to run on-demand
         * for large wikis (e.g. every time the special page is viewed), then
         * implement this as returning true.
         *
         * "Large wikis" are those that enable $wgMiserMode. The value of
         * ::isExpensive() has no effect by default when $wgMiserMode is off.
         *
         * It is expected that such large wikis, periodically run the
         * UpdateSpecialPages maintenance script to update these query pages.
         *
         * By enabling $wgDisableQueryPages, all query pages will be considered
         * as expensive and updated offline only, even query pages that do not
         * mark themselves as expensive.
         *
         * @stable to override
         * @return bool
         */
        public function isExpensive() {
                return $this->getConfig()->get( MainConfigNames::DisableQueryPages );
        }

        /**
         * Is the output of this query cacheable? Non-cacheable expensive pages
         * will be disabled in miser mode and will not have their results written
         * to the querycache table.
         * @stable to override
         * @return bool
         * @since 1.18
         */
        public function isCacheable() {
                return true;
        }

        /**
         * Whether or not the output of the page in question is retrieved from
         * the database cache.
         *
         * @stable to override
         * @return bool
         */
        public function isCached() {
                return $this->isExpensive() && $this->getConfig()->get( MainConfigNames::MiserMode );
        }

        /**
         * Sometimes we don't want to build rss / atom feeds.
         *
         * @stable to override
         * @return bool
         */
        public function isSyndicated() {
                return true;
        }

        /**
         * Formats the results of the query for display. The skin is the current
         * skin; you can use it for making links. The result is a single row of
         * result data. You should be able to grab SQL results from it.
         * If the function returns false, the line output will be skipped.
         * @param Skin $skin
         * @param stdClass $result Result row
         * @return string|bool String or false to skip
         */
        abstract protected function formatResult( $skin, $result );

        /**
         * The content returned by this function will be output before any result
         *
         * @stable to override
         * @return string
         */
        protected function getPageHeader() {
                return '';
        }

        /**
         * Outputs some kind of an informative message (via OutputPage) to let the
         * user know that the query returned nothing and thus there's nothing to
         * show.
         *
         * @since 1.26
         */
        protected function showEmptyText() {
                $this->getOutput()->addWikiMsg( 'specialpage-empty' );
        }

        /**
         * If using extra form wheely-dealies, return a set of parameters here
         * as an associative array. They will be encoded and added to the paging
         * links (prev/next/lengths).
         *
         * @stable to override
         * @return array
         */
        protected function linkParameters() {
                return [];
        }

        /**
         * Clear the cache and save new results
         *
         * @stable to override
         *
         * @param int|false $limit Limit for SQL statement or false for no limit
         * @param bool $unused Unused since 1.43, kept for backwards-compatibility
         * @throws DBError|Exception
         * @return bool|int
         */
        public function recache( $limit, $unused = true ) {
                if ( !$this->isCacheable() ) {
                        return 0;
                }

                $fname = static::class . '::recache';
                $dbw = $this->getDatabaseProvider()->getPrimaryDatabase();

                // Do query
                $res = $this->reallyDoQuery( $limit, false );
                $num = false;
                if ( $res ) {
                        $num = $res->numRows();
                        // Fetch results
                        $vals = [];
                        foreach ( $res as $i => $row ) {
                                if ( isset( $row->value ) ) {
                                        if ( $this->usesTimestamps() ) {
                                                $value = (int)wfTimestamp( TS_UNIX, $row->value );
                                        } else {
                                                $value = intval( $row->value ); // T16414
                                        }
                                } else {
                                        $value = $i;
                                }

                                $vals[] = [
                                        'qc_type' => $this->getName(),
                                        'qc_namespace' => $row->namespace,
                                        'qc_title' => $row->title,
                                        'qc_value' => $value
                                ];
                        }

                        $dbw->doAtomicSection(
                                $fname,
                                function ( IDatabase $dbw, $fname ) use ( $vals ) {
                                        // Clear out any old cached data
                                        $dbw->newDeleteQueryBuilder()
                                                ->deleteFrom( 'querycache' )
                                                ->where( [ 'qc_type' => $this->getName() ] )
                                                ->caller( $fname )->execute();
                                        // Update the querycache_info record for the page
                                        $dbw->newInsertQueryBuilder()
                                                ->insertInto( 'querycache_info' )
                                                ->row( [ 'qci_type' => $this->getName(), 'qci_timestamp' => $dbw->timestamp() ] )
                                                ->onDuplicateKeyUpdate()
                                                ->uniqueIndexFields( [ 'qci_type' ] )
                                                ->set( [ 'qci_timestamp' => $dbw->timestamp() ] )
                                                ->caller( $fname )->execute();
                                }
                        );
                        // Save results into the querycache table on the primary DB
                        if ( count( $vals ) ) {
                                foreach ( array_chunk( $vals, 500 ) as $chunk ) {
                                        $dbw->newInsertQueryBuilder()
                                                ->insertInto( 'querycache' )
                                                ->rows( $chunk )
                                                ->caller( $fname )->execute();
                                }
                        }
                }

                return $num;
        }

        /**
         * Get a DB connection to be used for slow recache queries
         * @stable to override
         * @return IDatabase
         */
        protected function getRecacheDB() {
                return $this->getDBLoadBalancer()
                        ->getConnection( ILoadBalancer::DB_REPLICA, 'vslow' );
        }

        /**
         * Remove a cached result.
         * Useful for interactive backlogs where the user can fix problems in-place.
         * @param LinkTarget $title The page to remove.
         * @since 1.34
         */
        public function delete( LinkTarget $title ) {
                if ( $this->isCached() ) {
                        $dbw = $this->getDatabaseProvider()->getPrimaryDatabase();
                        $dbw->newDeleteQueryBuilder()
                                ->deleteFrom( 'querycache' )
                                ->where( [
                                        'qc_type' => $this->getName(),
                                        'qc_namespace' => $title->getNamespace(),
                                        'qc_title' => $title->getDBkey(),
                                ] )
                                ->caller( __METHOD__ )->execute();
                }
        }

        /**
         * Remove all cached value
         * This is needed when the page is no longer using the cache
         * @since 1.36
         */
        public function deleteAllCachedData() {
                $fname = static::class . '::' . __FUNCTION__;
                $dbw = $this->getDatabaseProvider()->getPrimaryDatabase();
                $dbw->newDeleteQueryBuilder()
                        ->deleteFrom( 'querycache' )
                        ->where( [ 'qc_type' => $this->getName() ] )
                        ->caller( $fname )->execute();
                $dbw->newDeleteQueryBuilder()
                        ->deleteFrom( 'querycachetwo' )
                        ->where( [ 'qcc_type' => $this->getName() ] )
                        ->caller( $fname )->execute();
                $dbw->newDeleteQueryBuilder()
                        ->deleteFrom( 'querycache_info' )
                        ->where( [ 'qci_type' => $this->getName() ] )
                        ->caller( $fname )->execute();
        }

        /**
         * Run the query and return the result
         * @stable to override
         * @param int|false $limit Numerical limit or false for no limit
         * @param int|false $offset Numerical offset or false for no offset
         * @return IResultWrapper
         * @since 1.18
         */
        public function reallyDoQuery( $limit, $offset = false ) {
                $fname = static::class . '::reallyDoQuery';
                $dbr = $this->getRecacheDB();
                $query = $this->getQueryInfo();
                $order = $this->getOrderFields();

                if ( $this->sortDescending() ) {
                        foreach ( $order as &$field ) {
                                $field .= ' DESC';
                        }
                }

                $tables = isset( $query['tables'] ) ? (array)$query['tables'] : [];
                $fields = isset( $query['fields'] ) ? (array)$query['fields'] : [];
                $conds = isset( $query['conds'] ) ? (array)$query['conds'] : [];
                $options = isset( $query['options'] ) ? (array)$query['options'] : [];
                $join_conds = isset( $query['join_conds'] ) ? (array)$query['join_conds'] : [];

                $queryBuilder = $dbr->newSelectQueryBuilder()
                        ->tables( $tables )
                        ->fields( $fields )
                        ->conds( $conds )
                        ->caller( $fname )
                        ->options( $options )
                        ->joinConds( $join_conds );
                if ( $order ) {
                        $queryBuilder->orderBy( $order );
                }

                if ( $limit !== false ) {
                        $queryBuilder->limit( intval( $limit ) );
                }

                if ( $offset !== false ) {
                        $queryBuilder->offset( intval( $offset ) );
                }

                return $queryBuilder->fetchResultSet();
        }

        /**
         * Somewhat deprecated, you probably want to be using execute()
         * @param int|false $offset
         * @param int|false $limit
         * @return IResultWrapper
         */
        public function doQuery( $offset = false, $limit = false ) {
                if ( $this->isCached() && $this->isCacheable() ) {
                        return $this->fetchFromCache( $limit, $offset );
                } else {
                        return $this->reallyDoQuery( $limit, $offset );
                }
        }

        /**
         * Fetch the query results from the query cache
         * @stable to override
         *
         * @param int|false $limit Numerical limit or false for no limit
         * @param int|false $offset Numerical offset or false for no offset
         * @return IResultWrapper
         * @since 1.18
         */
        public function fetchFromCache( $limit, $offset = false ) {
                $dbr = $this->getDatabaseProvider()->getReplicaDatabase();
                $queryBuilder = $dbr->newSelectQueryBuilder()
                        ->select( [ 'qc_type', 'namespace' => 'qc_namespace', 'title' => 'qc_title', 'value' => 'qc_value' ] )
                        ->from( 'querycache' )
                        ->where( [ 'qc_type' => $this->getName() ] );

                if ( $limit !== false ) {
                        $queryBuilder->limit( intval( $limit ) );
                }

                if ( $offset !== false ) {
                        $queryBuilder->offset( intval( $offset ) );
                }

                $order = $this->getCacheOrderFields();
                if ( $this->sortDescending() ) {
                        $queryBuilder->orderBy( $order, SelectQueryBuilder::SORT_DESC );
                } else {
                        $queryBuilder->orderBy( $order );
                }

                return $queryBuilder->caller( __METHOD__ )->fetchResultSet();
        }

        /**
         * Return the order fields for fetchFromCache. Default is to always use
         * "ORDER BY value" which was the default prior to this function.
         * @stable to override
         * @return array
         * @since 1.29
         */
        protected function getCacheOrderFields() {
                return [ 'value' ];
        }

        /**
         * @return string|false
         */
        public function getCachedTimestamp() {
                if ( $this->cachedTimestamp === null ) {
                        $dbr = $this->getDatabaseProvider()->getReplicaDatabase();
                        $fname = static::class . '::getCachedTimestamp';
                        $this->cachedTimestamp = $dbr->newSelectQueryBuilder()
                                ->select( 'qci_timestamp' )
                                ->from( 'querycache_info' )
                                ->where( [ 'qci_type' => $this->getName() ] )
                                ->caller( $fname )->fetchField();
                }
                return $this->cachedTimestamp;
        }

        /**
         * Returns limit and offset, as returned by $this->getRequest()->getLimitOffsetForUser().
         * Subclasses may override this to further restrict or modify limit and offset.
         *
         * @note Restricts the offset parameter, as most query pages have inefficient paging
         *
         * Its generally expected that the returned limit will not be 0, and the returned
         * offset will be less than the max results.
         *
         * @since 1.26
         * @return int[] list( $limit, $offset )
         */
        protected function getLimitOffset() {
                [ $limit, $offset ] = $this->getRequest()
                        ->getLimitOffsetForUser( $this->getUser() );
                if ( $this->getConfig()->get( MainConfigNames::MiserMode ) ) {
                        $maxResults = $this->getMaxResults();
                        // Can't display more than max results on a page
                        $limit = min( $limit, $maxResults );
                        // Can't skip over more than the end of $maxResults
                        $offset = min( $offset, $maxResults + 1 );
                }
                return [ $limit, $offset ];
        }

        /**
         * What is limit to fetch from DB
         *
         * Used to make it appear the DB stores less results then it actually does
         * @param int $uiLimit Limit from UI
         * @param int $uiOffset Offset from UI
         * @return int Limit to use for DB (not including extra row to see if at end)
         */
        protected function getDBLimit( $uiLimit, $uiOffset ) {
                $maxResults = $this->getMaxResults();
                if ( $this->getConfig()->get( MainConfigNames::MiserMode ) ) {
                        $limit = min( $uiLimit + 1, $maxResults - $uiOffset );
                        return max( $limit, 0 );
                } else {
                        return $uiLimit + 1;
                }
        }

        /**
         * Get max number of results we can return in miser mode.
         *
         * Most QueryPage subclasses use inefficient paging, so limit the max amount we return
         * This matters for uncached query pages that might otherwise accept an offset of 3 million
         *
         * @stable to override
         * @since 1.27
         * @return int
         */
        protected function getMaxResults() {
                // Max of 10000, unless we store more than 10000 in query cache.
                return max( $this->getConfig()->get( MainConfigNames::QueryCacheLimit ), 10000 );
        }

        /**
         * This is the actual workhorse. It does everything needed to make a
         * real, honest-to-gosh query page.
         * @stable to override
         * @param string|null $par
         */
        public function execute( $par ) {
                $this->checkPermissions();

                $this->setHeaders();
                $this->outputHeader();

                $out = $this->getOutput();

                if ( $this->isCached() && !$this->isCacheable() ) {
                        $out->addWikiMsg( 'querypage-disabled' );
                        return;
                }

                $out->setSyndicated( $this->isSyndicated() );

                if ( $this->limit == 0 && $this->offset == 0 ) {
                        [ $this->limit, $this->offset ] = $this->getLimitOffset();
                }
                $dbLimit = $this->getDBLimit( $this->limit, $this->offset );
                // @todo Use doQuery()
                if ( !$this->isCached() ) {
                        // select one extra row for navigation
                        $res = $this->reallyDoQuery( $dbLimit, $this->offset );
                } else {
                        // Get the cached result, select one extra row for navigation
                        $res = $this->fetchFromCache( $dbLimit, $this->offset );
                        if ( !$this->listoutput ) {
                                // Fetch the timestamp of this update
                                $ts = $this->getCachedTimestamp();
                                $lang = $this->getLanguage();
                                $maxResults = $lang->formatNum( $this->getConfig()->get(
                                        MainConfigNames::QueryCacheLimit ) );

                                if ( $ts ) {
                                        $user = $this->getUser();
                                        $updated = $lang->userTimeAndDate( $ts, $user );
                                        $updateddate = $lang->userDate( $ts, $user );
                                        $updatedtime = $lang->userTime( $ts, $user );
                                        $out->addMeta( 'Data-Cache-Time', $ts );
                                        $out->addJsConfigVars( 'dataCacheTime', $ts );
                                        $out->addWikiMsg( 'perfcachedts', $updated, $updateddate, $updatedtime, $maxResults );
                                } else {
                                        $out->addWikiMsg( 'perfcached', $maxResults );
                                }

                                // If updates on this page have been disabled, let the user know
                                // that the data set won't be refreshed for now
                                $disabledQueryPages = self::getDisabledQueryPages( $this->getConfig() );
                                if ( isset( $disabledQueryPages[$this->getName()] ) ) {
                                        $runMode = $disabledQueryPages[$this->getName()];
                                        if ( $runMode === 'disabled' ) {
                                                $out->wrapWikiMsg(
                                                        "<div class=\"mw-querypage-no-updates\">\n$1\n</div>",
                                                        'querypage-no-updates'
                                                );
                                        } else {
                                                // Messages used here: querypage-updates-periodical
                                                $out->wrapWikiMsg(
                                                        "<div class=\"mw-querypage-updates-" . $runMode . "\">\n$1\n</div>",
                                                        'querypage-updates-' . $runMode
                                                );
                                        }
                                }
                        }
                }

                $this->numRows = $res->numRows();

                $dbr = $this->getRecacheDB();
                $this->preprocessResults( $dbr, $res );

                $out->addHTML( Xml::openElement( 'div', [ 'class' => 'mw-spcontent' ] ) );

                // Top header and navigation
                if ( $this->shownavigation ) {
                        $out->addHTML( $this->getPageHeader() );
                        if ( $this->numRows > 0 ) {
                                $out->addHTML( $this->msg( 'showingresultsinrange' )->numParams(
                                        min( $this->numRows, $this->limit ), // do not show the one extra row, if exist
                                        $this->offset + 1, ( min( $this->numRows, $this->limit ) + $this->offset ) )->parseAsBlock() );
                                // Disable the "next" link when we reach the end
                                $miserMaxResults = $this->getConfig()->get( MainConfigNames::MiserMode )
                                        && ( $this->offset + $this->limit >= $this->getMaxResults() );
                                $atEnd = ( $this->numRows <= $this->limit ) || $miserMaxResults;
                                $paging = $this->buildPrevNextNavigation( $this->offset,
                                        $this->limit, $this->linkParameters(), $atEnd, $par );
                                $out->addHTML( '<p>' . $paging . '</p>' );
                        } else {
                                // No results to show, so don't bother with "showing X of Y" etc.
                                // -- just let the user know and give up now
                                $this->showEmptyText();
                                $out->addHTML( Xml::closeElement( 'div' ) );
                                return;
                        }
                }

                // The actual results; specialist subclasses will want to handle this
                // with more than a straight list, so we hand them the info, plus
                // an OutputPage, and let them get on with it
                $this->outputResults( $out,
                        $this->getSkin(),
                        $dbr, // Should use IResultWrapper for this
                        $res,
                        min( $this->numRows, $this->limit ), // do not format the one extra row, if exist
                        $this->offset );

                // Repeat the paging links at the bottom
                if ( $this->shownavigation ) {
                        // @phan-suppress-next-line PhanPossiblyUndeclaredVariable paging is set when used here
                        $out->addHTML( '<p>' . $paging . '</p>' );
                }

                $out->addHTML( Xml::closeElement( 'div' ) );
        }

        /**
         * Format and output report results using the given information plus
         * OutputPage
         *
         * @stable to override
         *
         * @param OutputPage $out OutputPage to print to
         * @param Skin $skin User skin to use
         * @param IReadableDatabase $dbr Database (read) connection to use
         * @param IResultWrapper $res Result pointer
         * @param int $num Number of available result rows
         * @param int $offset Paging offset
         */
        protected function outputResults( $out, $skin, $dbr, $res, $num, $offset ) {
                if ( $num > 0 ) {
                        $html = [];
                        if ( !$this->listoutput ) {
                                $html[] = $this->openList( $offset );
                        }

                        // $res might contain the whole 1,000 rows, so we read up to
                        // $num [should update this to use a Pager]
                        // phpcs:ignore Generic.CodeAnalysis.AssignmentInCondition.Found
                        for ( $i = 0; $i < $num && $row = $res->fetchObject(); $i++ ) {
                                $line = $this->formatResult( $skin, $row );
                                if ( $line ) {
                                        $html[] = $this->listoutput
                                                ? $line
                                                : "<li>{$line}</li>\n";
                                }
                        }

                        if ( !$this->listoutput ) {
                                $html[] = $this->closeList();
                        }

                        $html = $this->listoutput
                                ? $this->getContentLanguage()->listToText( $html )
                                : implode( '', $html );

                        $out->addHTML( $html );
                }
        }

        /**
         * @param int $offset
         * @return string
         */
        protected function openList( $offset ) {
                return "\n<ol start='" . ( $offset + 1 ) . "' class='special'>\n";
        }

        /**
         * @return string
         */
        protected function closeList() {
                return "</ol>\n";
        }

        /**
         * Do any necessary preprocessing of the result object.
         * @stable to override
         * @param IDatabase $db
         * @param IResultWrapper $res
         */
        protected function preprocessResults( $db, $res ) {
        }

        /**
         * Creates a new LinkBatch object, adds all pages from the passed result wrapper (MUST include
         * title and optional the namespace field) and executes the batch. This operation will pre-cache
         * LinkCache information like page existence and information for stub color and redirect hints.
         *
         * @note Call self::setLinkBatchFactory from special page constructor when use
         *
         * @param IResultWrapper $res The result wrapper to process. Needs to include the title
         *  field and namespace field, if the $ns parameter isn't set.
         * @param int|null $ns Use this namespace for the given titles in the result wrapper,
         *  instead of the namespace value of $res.
         */
        protected function executeLBFromResultWrapper( IResultWrapper $res, $ns = null ) {
                if ( !$res->numRows() ) {
                        return;
                }

                $batch = $this->getLinkBatchFactory()->newLinkBatch();
                foreach ( $res as $row ) {
                        $batch->add( $ns ?? (int)$row->namespace, $row->title );
                }
                $batch->execute();

                $res->seek( 0 );
        }

        /**
         * @since 1.36
         * @deprecated since 1.43, use self::setDatabaseProvider
         * @param ILoadBalancer $loadBalancer
         */
        final protected function setDBLoadBalancer( ILoadBalancer $loadBalancer ) {
                $this->loadBalancer = $loadBalancer;
        }

        /**
         * @since 1.36
         * @deprecated since 1.43, use self::getDatabaseProvider
         * @return ILoadBalancer
         */
        final protected function getDBLoadBalancer(): ILoadBalancer {
                if ( $this->loadBalancer === null ) {
                        // Fallback if not provided
                        // TODO Change to wfWarn in a future release
                        $this->loadBalancer = MediaWikiServices::getInstance()->getDBLoadBalancer();
                }
                return $this->loadBalancer;
        }

        /**
         * @since 1.41
         * @param IConnectionProvider $databaseProvider
         */
        final protected function setDatabaseProvider( IConnectionProvider $databaseProvider ) {
                $this->databaseProvider = $databaseProvider;
        }

        /**
         * @since 1.41
         * @return IConnectionProvider
         */
        final protected function getDatabaseProvider(): IConnectionProvider {
                if ( $this->databaseProvider === null ) {
                        $this->databaseProvider = MediaWikiServices::getInstance()->getConnectionProvider();
                }
                return $this->databaseProvider;
        }
}

/** @deprecated class alias since 1.41 */
class_alias( QueryPage::class, 'QueryPage' );