namespaceDupes.php

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<?php
// @codeCoverageIgnoreStart
require_once __DIR__ . '/Maintenance.php';
// @codeCoverageIgnoreEnd
 
use MediaWiki\Deferred\DeferredUpdates;
use MediaWiki\Deferred\LinksUpdate\ImageLinksTable;
use MediaWiki\Deferred\LinksUpdate\LinksDeletionUpdate;
use MediaWiki\Deferred\LinksUpdate\PageLinksTable;
use MediaWiki\Deferred\LinksUpdate\TemplateLinksTable;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MainConfigNames;
use MediaWiki\Maintenance\Maintenance;
use MediaWiki\Page\PageIdentity;
use MediaWiki\Revision\SlotRecord;
use MediaWiki\Status\Status;
use MediaWiki\Title\Title;
use MediaWiki\Title\TitleValue;
use Wikimedia\Rdbms\IDBAccessObject;
use Wikimedia\Rdbms\IExpression;
use Wikimedia\Rdbms\IResultWrapper;
use Wikimedia\Rdbms\LikeValue;
 
class NamespaceDupes extends Maintenance {
 
    private $resolvablePages = 0;
 
    private $totalPages = 0;
 
    private $resolvableLinks = 0;
 
    private $totalLinks = 0;
 
    private $deletedLinks = 0;
 
    public function __construct() {
        parent::__construct();
        $this->addDescription( 'Find and fix pages affected by namespace addition/removal' );
        $this->addOption( 'fix', 'Attempt to automatically fix errors and delete broken links' );
        $this->addOption( 'merge', "Instead of renaming conflicts, do a history merge with " .
            "the correct title" );
        $this->addOption( 'add-suffix', "Dupes will be renamed with correct namespace with " .
            "<text> appended after the article name", false, true );
        $this->addOption( 'add-prefix', "Dupes will be renamed with correct namespace with " .
            "<text> prepended before the article name", false, true );
        $this->addOption( 'source-pseudo-namespace', "Move all pages with the given source " .
            "prefix (with an implied colon following it). If --dest-namespace is not specified, " .
            "the colon will be replaced with a hyphen.",
            false, true );
        $this->addOption( 'dest-namespace', "In combination with --source-pseudo-namespace, " .
            "specify the namespace ID of the destination.", false, true );
        $this->addOption( 'move-talk', "If this is specified, pages in the Talk namespace that " .
            "begin with a conflicting prefix will be renamed, for example " .
            "Talk:File:Foo -> File_Talk:Foo" );
    }
 
    public function execute() {
        $options = [
            'fix' => $this->hasOption( 'fix' ),
            'merge' => $this->hasOption( 'merge' ),
            'add-suffix' => $this->getOption( 'add-suffix', '' ),
            'add-prefix' => $this->getOption( 'add-prefix', '' ),
            'move-talk' => $this->hasOption( 'move-talk' ),
            'source-pseudo-namespace' => $this->getOption( 'source-pseudo-namespace', '' ),
            'dest-namespace' => intval( $this->getOption( 'dest-namespace', 0 ) )
        ];
 
        if ( $options['source-pseudo-namespace'] !== '' ) {
            $retval = $this->checkPrefix( $options );
        } else {
            $retval = $this->checkAll( $options );
        }
 
        if ( $retval ) {
            $this->output( "\nLooks good!\n" );
        } else {
            $this->output( "\nOh noeees\n" );
        }
    }
 
    private function checkAll( $options ) {
        $contLang = $this->getServiceContainer()->getContentLanguage();
        $spaces = [];
 
        // List interwikis first, so they'll be overridden
        // by any conflicting local namespaces.
        foreach ( $this->getInterwikiList() as $prefix ) {
            $name = $contLang->ucfirst( $prefix );
            $spaces[$name] = 0;
        }
 
        // Now pull in all canonical and alias namespaces...
        foreach (
            $this->getServiceContainer()->getNamespaceInfo()->getCanonicalNamespaces()
            as $ns => $name
        ) {
            // This includes $wgExtraNamespaces
            if ( $name !== '' ) {
                $spaces[$name] = $ns;
            }
        }
        foreach ( $contLang->getNamespaces() as $ns => $name ) {
            if ( $name !== '' ) {
                $spaces[$name] = $ns;
            }
        }
        foreach ( $contLang->getNamespaceAliases() as $name => $ns ) {
            $spaces[$name] = $ns;
        }
 
        // We'll need to check for lowercase keys as well,
        // since we're doing case-sensitive searches in the db.
        $capitalLinks = $this->getConfig()->get( MainConfigNames::CapitalLinks );
        foreach ( $spaces as $name => $ns ) {
            $moreNames = [
                $contLang->uc( $name ),
                $contLang->ucfirst( $contLang->lc( $name ) ),
                $contLang->ucwords( $name ),
                $contLang->ucwords( $contLang->lc( $name ) ),
                $contLang->ucwordbreaks( $name ),
                $contLang->ucwordbreaks( $contLang->lc( $name ) ),
            ];
            if ( !$capitalLinks ) {
                foreach ( $moreNames as $altName ) {
                    $moreNames[] = $contLang->lcfirst( $altName );
                }
                $moreNames[] = $contLang->lcfirst( $name );
            }
            foreach ( array_unique( $moreNames ) as $altName ) {
                if ( $altName !== $name ) {
                    $spaces[$altName] = $ns;
                }
            }
        }
 
        // Sort by namespace index, and if there are two with the same index,
        // break the tie by sorting by name
        $origSpaces = $spaces;
        uksort( $spaces, static function ( $a, $b ) use ( $origSpaces ) {
            return $origSpaces[$a] <=> $origSpaces[$b]
                ?: $a <=> $b;
        } );
 
        $ok = true;
        foreach ( $spaces as $name => $ns ) {
            $ok = $this->checkNamespace( $ns, $name, $options ) && $ok;
        }
 
        $this->output(
            "{$this->totalPages} pages to fix, " .
            "{$this->resolvablePages} were resolvable.\n\n"
        );
 
        foreach ( $spaces as $name => $ns ) {
            if ( $ns != 0 ) {
                /* Fix up link destinations for non-interwiki links only.
                 *
                 * For example if a page has [[Foo:Bar]] and then a Foo namespace
                 * is introduced, pagelinks needs to be updated to have
                 * page_namespace = NS_FOO.
                 *
                 * If instead an interwiki prefix was introduced called "Foo",
                 * the link should instead be moved to the iwlinks table. If a new
                 * language is introduced called "Foo", or if there is a pagelink
                 * [[fr:Bar]] when interlanguage magic links are turned on, the
                 * link would have to be moved to the langlinks table. Let's put
                 * those cases in the too-hard basket for now. The consequences are
                 * not especially severe.
                 * @fixme Handle interwiki links, and pagelinks to Category:, File:
                 * which probably need reparsing.
                 */
 
                $this->checkLinkTable( 'pagelinks', 'pl', $ns, $name, $options );
                $this->checkLinkTable( 'templatelinks', 'tl', $ns, $name, $options );
 
                // The redirect table has interwiki links randomly mixed in, we
                // need to filter those out. For example [[w:Foo:Bar]] would
                // have rd_interwiki=w and rd_namespace=0, which would match the
                // query for a conflicting namespace "Foo" if filtering wasn't done.
                $this->checkLinkTable( 'redirect', 'rd', $ns, $name, $options,
                    [ 'rd_interwiki' => '' ] );
            }
        }
 
        $this->output(
            "{$this->totalLinks} links to fix, " .
            "{$this->resolvableLinks} were resolvable, " .
            "{$this->deletedLinks} were deleted.\n"
        );
 
        return $ok;
    }
 
    private function getInterwikiList() {
        $result = $this->getServiceContainer()->getInterwikiLookup()->getAllPrefixes();
        return array_column( $result, 'iw_prefix' );
    }
 
    private function isSingleRevRedirectTo( Title $oldTitle, Title $newTitle ): bool {
        if ( !$oldTitle->isSingleRevRedirect() ) {
            return false;
        }
        $revStore = $this->getServiceContainer()->getRevisionStore();
        $rev = $revStore->getRevisionByTitle( $oldTitle, 0, IDBAccessObject::READ_LATEST );
        if ( !$rev ) {
            return false;
        }
        $content = $rev->getContent( SlotRecord::MAIN );
        if ( !$content ) {
            return false;
        }
        $target = $content->getRedirectTarget();
        return $target && $target->equals( $newTitle );
    }
 
    private function deletePage( Title $pageToDelete, string $reason ): Status {
        $services = $this->getServiceContainer();
        $page = $services->getWikiPageFactory()->newFromTitle( $pageToDelete );
        $user = User::newSystemUser( "Maintenance script" );
        $deletePage = $services->getDeletePageFactory()->newDeletePage( $page, $user );
        return $deletePage->deleteUnsafe( $reason );
    }
 
    private function checkNamespace( $ns, $name, $options ) {
        $targets = $this->getTargetList( $ns, $name, $options );
        $count = $targets->numRows();
        $this->totalPages += $count;
        if ( $count == 0 ) {
            return true;
        }
 
        $dryRunNote = $options['fix'] ? '' : ' DRY RUN ONLY';
 
        $ok = true;
        foreach ( $targets as $row ) {
            // Find the new title and determine the action to take
 
            $newTitle = $this->getDestinationTitle(
                $ns, $name, $row->page_namespace, $row->page_title );
            $logStatus = false;
            // $oldTitle is not a valid title by definition but the methods I use here
            // shouldn't care
            $oldTitle = Title::makeTitle( $row->page_namespace, $row->page_title );
            if ( !$newTitle ) {
                if ( $options['add-prefix'] == '' && $options['add-suffix'] == '' ) {
                    $logStatus = 'invalid title and --add-prefix not specified';
                    $action = 'abort';
                } else {
                    $action = 'alternate';
                }
            } elseif ( $newTitle->exists( IDBAccessObject::READ_LATEST ) ) {
                if ( $this->isSingleRevRedirectTo( $newTitle, $newTitle ) ) {
                    // Conceptually this is the new title redirecting to the old title
                    // except that the redirect target is parsed as wikitext so is actually
                    // appears to redirect to itself
                    $action = 'delete-new';
                } elseif ( $options['merge'] ) {
                    if ( $this->canMerge( $row->page_id, $newTitle, $logStatus ) ) {
                        $action = 'merge';
                    } else {
                        $action = 'abort';
                    }
                } elseif ( $options['add-prefix'] == '' && $options['add-suffix'] == '' ) {
                    $action = 'abort';
                    $logStatus = 'dest title exists and --add-prefix not specified';
                } else {
                    $action = 'alternate';
                }
            } else {
                $action = 'move';
                $logStatus = 'no conflict';
            }
            if ( $action === 'alternate' ) {
                [ $ns, $dbk ] = $this->getDestination( $ns, $name, $row->page_namespace,
                    $row->page_title );
                $altTitle = $this->getAlternateTitle( $ns, $dbk, $options );
                if ( !$altTitle ) {
                    $action = 'abort';
                    $logStatus = 'alternate title is invalid';
                } elseif ( $altTitle->exists() ) {
                    $action = 'abort';
                    $logStatus = 'alternate title conflicts';
                } elseif ( $this->isSingleRevRedirectTo( $oldTitle, $newTitle ) ) {
                    $action = 'delete-old';
                    $newTitle = $altTitle;
                } else {
                    $action = 'move';
                    $logStatus = 'alternate';
                    $newTitle = $altTitle;
                }
            }
 
            // Take the action or log a dry run message
 
            $logTitle = "id={$row->page_id} ns={$row->page_namespace} dbk={$row->page_title}";
            $pageOK = true;
 
            switch ( $action ) {
                case 'delete-old':
                    $this->output( "$logTitle move to " . $newTitle->getPrefixedDBKey() .
                        " then delete as single-revision redirect to new home$dryRunNote\n" );
                    if ( $options['fix'] ) {
                        // First move the page so the delete command gets a valid title
                        $pageOK = $this->movePage( $row->page_id, $newTitle );
                        if ( $pageOK ) {
                            $status = $this->deletePage(
                                $newTitle,
                                "Non-normalized title already redirects to new form"
                            );
                            if ( !$status->isOK() ) {
                                $this->error( $status );
                                $pageOK = false;
                            }
                        }
                    }
                    break;
                case "delete-new":
                    $this->output( "$logTitle -> " .
                    $newTitle->getPrefixedDBkey() . " delete existing page $dryRunNote\n" );
                    if ( $options['fix'] ) {
                        $status = $this->deletePage( $newTitle, "Delete circular redirect to make way for move" );
                        $pageOK = $status->isOK();
                        if ( $pageOK ) {
                            $pageOK = $this->movePage( $row->page_id, $newTitle );
                        } else {
                            $this->error( $status );
                        }
                    }
                    break;
                case 'abort':
                    $this->output( "$logTitle *** $logStatus\n" );
                    $pageOK = false;
                    break;
                case 'move':
                    $this->output( "$logTitle -> " .
                        $newTitle->getPrefixedDBkey() . " ($logStatus)$dryRunNote\n" );
 
                    if ( $options['fix'] ) {
                        $pageOK = $this->movePage( $row->page_id, $newTitle );
                    }
                    break;
                case 'merge':
                    $this->output( "$logTitle => " .
                        $newTitle->getPrefixedDBkey() . " (merge)$dryRunNote\n" );
 
                    if ( $options['fix'] ) {
                        $pageOK = $this->mergePage( $row, $newTitle );
                    }
                    break;
            }
 
            if ( $pageOK ) {
                $this->resolvablePages++;
            } else {
                $ok = false;
            }
        }
 
        return $ok;
    }
 
    private function checkLinkTable( $table, $fieldPrefix, $ns, $name, $options,
        $extraConds = []
    ) {
        $domainMap = [
            'templatelinks' => TemplateLinksTable::VIRTUAL_DOMAIN,
            'imagelinks' => ImageLinksTable::VIRTUAL_DOMAIN,
            'pagelinks' => PageLinksTable::VIRTUAL_DOMAIN,
        ];
 
        if ( isset( $domainMap[$table] ) ) {
            $dbw = $this->getServiceContainer()->getConnectionProvider()->getPrimaryDatabase( $domainMap[$table] );
        } else {
            $dbw = $this->getPrimaryDB();
        }
 
        $batchConds = [];
        $fromField = "{$fieldPrefix}_from";
        $batchSize = 100;
        $sqb = $dbw->newSelectQueryBuilder()
            ->select( $fromField )
            ->where( $extraConds )
            ->limit( $batchSize );
 
        $linksMigration = $this->getServiceContainer()->getLinksMigration();
        if ( isset( $linksMigration::$mapping[$table] ) ) {
            $sqb->queryInfo( $linksMigration->getQueryInfo( $table ) );
            [ $namespaceField, $titleField ] = $linksMigration->getTitleFields( $table );
            $schemaMigrationStage = $linksMigration::$mapping[$table]['config'] === -1
                ? MIGRATION_NEW
                : $this->getConfig()->get( $linksMigration::$mapping[$table]['config'] );
            $linkTargetLookup = $this->getServiceContainer()->getLinkTargetLookup();
            $targetIdField = $linksMigration::$mapping[$table]['target_id'];
        } else {
            $sqb->table( $table );
            $namespaceField = "{$fieldPrefix}_namespace";
            $titleField = "{$fieldPrefix}_title";
            $sqb->fields( [ $namespaceField, $titleField ] );
            // Variables only used for links migration, init only
            $schemaMigrationStage = -1;
            $linkTargetLookup = null;
            $targetIdField = '';
        }
        $sqb->andWhere( [
                $namespaceField => 0,
                $dbw->expr( $titleField, IExpression::LIKE, new LikeValue( "$name:", $dbw->anyString() ) ),
            ] )
            ->orderBy( [ $titleField, $fromField ] )
            ->caller( __METHOD__ );
 
        $updateRowsPerQuery = $this->getConfig()->get( MainConfigNames::UpdateRowsPerQuery );
        while ( true ) {
            $res = ( clone $sqb )
                ->andWhere( $batchConds )
                ->fetchResultSet();
            if ( $res->numRows() == 0 ) {
                break;
            }
 
            $rowsToDeleteIfStillExists = [];
 
            foreach ( $res as $row ) {
                $logTitle = "from={$row->$fromField} ns={$row->$namespaceField} " .
                    "dbk={$row->$titleField}";
                $destTitle = $this->getDestinationTitle(
                    $ns, $name, $row->$namespaceField, $row->$titleField );
                $this->totalLinks++;
                if ( !$destTitle ) {
                    $this->output( "$table $logTitle *** INVALID\n" );
                    continue;
                }
                $this->resolvableLinks++;
                if ( !$options['fix'] ) {
                    $this->output( "$table $logTitle -> " .
                        $destTitle->getPrefixedDBkey() . " DRY RUN\n" );
                    continue;
                }
 
                if ( isset( $linksMigration::$mapping[$table] ) ) {
                    $setValue = [];
                    if ( $schemaMigrationStage & SCHEMA_COMPAT_WRITE_NEW ) {
                        $setValue[$targetIdField] = $linkTargetLookup->acquireLinkTargetId( $destTitle, $dbw );
                    }
                    if ( $schemaMigrationStage & SCHEMA_COMPAT_WRITE_OLD ) {
                        $setValue["{$fieldPrefix}_namespace"] = $destTitle->getNamespace();
                        $setValue["{$fieldPrefix}_title"] = $destTitle->getDBkey();
                    }
                    $whereCondition = $linksMigration->getLinksConditions(
                        $table,
                        new TitleValue( 0, $row->$titleField )
                    );
                    $deleteCondition = $linksMigration->getLinksConditions(
                        $table,
                        new TitleValue( (int)$row->$namespaceField, $row->$titleField )
                    );
                } else {
                    $setValue = [
                        $namespaceField => $destTitle->getNamespace(),
                        $titleField => $destTitle->getDBkey()
                    ];
                    $whereCondition = [
                        $namespaceField => 0,
                        $titleField => $row->$titleField
                    ];
                    $deleteCondition = [
                        $namespaceField => $row->$namespaceField,
                        $titleField => $row->$titleField,
                    ];
                }
 
                $dbw->newUpdateQueryBuilder()
                    ->update( $table )
                    ->ignore()
                    ->set( $setValue )
                    ->where( [ $fromField => $row->$fromField ] )
                    ->andWhere( $whereCondition )
                    ->caller( __METHOD__ )
                    ->execute();
 
                // In case there is a key conflict on UPDATE IGNORE the row needs deletion
                $rowsToDeleteIfStillExists[] = array_merge( [ $fromField => $row->$fromField ], $deleteCondition );
 
                $this->output( "$table $logTitle -> " .
                    $destTitle->getPrefixedDBkey() . "\n"
                );
            }
 
            if ( $options['fix'] && count( $rowsToDeleteIfStillExists ) > 0 ) {
                $affectedRows = 0;
                $deleteBatches = array_chunk( $rowsToDeleteIfStillExists, $updateRowsPerQuery );
                foreach ( $deleteBatches as $deleteBatch ) {
                    $dbw->newDeleteQueryBuilder()
                        ->deleteFrom( $table )
                        ->where( $dbw->factorConds( $deleteBatch ) )
                        ->caller( __METHOD__ )
                        ->execute();
                    $affectedRows += $dbw->affectedRows();
                    if ( count( $deleteBatches ) > 1 ) {
                        $this->waitForReplication();
                    }
                }
 
                $this->deletedLinks += $affectedRows;
                $this->resolvableLinks -= $affectedRows;
            }
 
            $batchConds = [
                $dbw->buildComparison( '>', [
                    // @phan-suppress-next-line PhanPossiblyUndeclaredVariable rows contains at least one item
                    $titleField => $row->$titleField,
                    // @phan-suppress-next-line PhanPossiblyUndeclaredVariable rows contains at least one item
                    $fromField => $row->$fromField,
                ] )
            ];
 
            $this->waitForReplication();
        }
    }
 
    private function checkPrefix( $options ) {
        $prefix = $options['source-pseudo-namespace'];
        $ns = $options['dest-namespace'];
        $this->output( "Checking prefix \"$prefix\" vs namespace $ns\n" );
 
        return $this->checkNamespace( $ns, $prefix, $options );
    }
 
    private function getTargetList( $ns, $name, $options ) {
        $dbw = $this->getPrimaryDB();
 
        if (
            $options['move-talk'] &&
            $this->getServiceContainer()->getNamespaceInfo()->isSubject( $ns )
        ) {
            $checkNamespaces = [ NS_MAIN, NS_TALK ];
        } else {
            $checkNamespaces = NS_MAIN;
        }
 
        return $dbw->newSelectQueryBuilder()
            ->select( [ 'page_id', 'page_title', 'page_namespace' ] )
            ->from( 'page' )
            ->where( [
                'page_namespace' => $checkNamespaces,
                $dbw->expr( 'page_title', IExpression::LIKE, new LikeValue( "$name:", $dbw->anyString() ) ),
            ] )
            ->caller( __METHOD__ )->fetchResultSet();
    }
 
    private function getDestination( $ns, $name, $sourceNs, $sourceDbk ) {
        $dbk = substr( $sourceDbk, strlen( "$name:" ) );
        if ( $ns <= 0 ) {
            // An interwiki or an illegal namespace like "Special" or "Media"
            // try an alternate encoding with '-' for ':'
            $dbk = "$name-" . $dbk;
            $ns = 0;
        }
        $destNS = $ns;
        $nsInfo = $this->getServiceContainer()->getNamespaceInfo();
        if ( $sourceNs == NS_TALK && $nsInfo->isSubject( $ns ) ) {
            // This is an associated talk page moved with the --move-talk feature.
            $destNS = $nsInfo->getTalk( $destNS );
        }
        return [ $destNS, $dbk ];
    }
 
    private function getDestinationTitle( $ns, $name, $sourceNs, $sourceDbk ) {
        [ $destNS, $dbk ] = $this->getDestination( $ns, $name, $sourceNs, $sourceDbk );
        $newTitle = Title::makeTitleSafe( $destNS, $dbk );
        if ( !$newTitle || !$newTitle->canExist() ) {
            return false;
        }
        return $newTitle;
    }
 
    private function getAlternateTitle( $ns, $dbk, $options ) {
        $prefix = $options['add-prefix'];
        $suffix = $options['add-suffix'];
        if ( $prefix == '' && $suffix == '' ) {
            return false;
        }
        $newDbk = $prefix . $dbk . $suffix;
        return Title::makeTitleSafe( $ns, $newDbk );
    }
 
    private function movePage( $id, LinkTarget $newLinkTarget ) {
        $dbw = $this->getPrimaryDB();
 
        $update = $dbw->newUpdateQueryBuilder()
            ->update( 'page' )
            ->set( [
                "page_namespace" => $newLinkTarget->getNamespace(),
                "page_title" => $newLinkTarget->getDBkey(),
            ] )
            ->where( [
                "page_id" => $id,
            ] )
            ->caller( __METHOD__ );
        $update->execute();
        $this->getServiceContainer()->getLinkWriteDuplicator()->duplicate( $update );
 
        // Update *_from_namespace in links tables
        $fromNamespaceTables = [
            [ 'templatelinks', 'tl', [ 'tl_target_id' ] ],
            [ 'pagelinks', 'pl', [ 'pl_target_id' ] ],
        ];
        if ( $this->getConfig()->get( MainConfigNames::ImageLinksSchemaMigrationStage ) & SCHEMA_COMPAT_READ_OLD ) {
            $fromNamespaceTables[] = [ 'imagelinks', 'il', [ 'il_to' ] ];
        } else {
            $fromNamespaceTables[] = [ 'imagelinks', 'il', [ 'il_target_id' ] ];
        }
 
        $updateRowsPerQuery = $this->getConfig()->get( MainConfigNames::UpdateRowsPerQuery );
 
        foreach ( $fromNamespaceTables as [ $table, $fieldPrefix, $additionalPrimaryKeyFields ] ) {
            $domainMap = [
                'templatelinks' => TemplateLinksTable::VIRTUAL_DOMAIN,
                'imagelinks' => ImageLinksTable::VIRTUAL_DOMAIN,
                'pagelinks' => PageLinksTable::VIRTUAL_DOMAIN,
            ];
 
            if ( isset( $domainMap[$table] ) ) {
                $dbw = $this->getServiceContainer()->getConnectionProvider()->getPrimaryDatabase( $domainMap[$table] );
            } else {
                $dbw = $this->getPrimaryDB();
            }
 
            $fromField = "{$fieldPrefix}_from";
            $fromNamespaceField = "{$fieldPrefix}_from_namespace";
 
            $res = $dbw->newSelectQueryBuilder()
                ->select( $additionalPrimaryKeyFields )
                ->from( $table )
                ->where( [ $fromField => $id ] )
                ->andWhere( $dbw->expr( $fromNamespaceField, '!=', $newLinkTarget->getNamespace() ) )
                ->caller( __METHOD__ )
                ->fetchResultSet();
            if ( !$res ) {
                continue;
            }
 
            $updateConds = [];
            foreach ( $res as $row ) {
                $updateConds[] = array_merge( [ $fromField => $id ], (array)$row );
            }
            $updateBatches = array_chunk( $updateConds, $updateRowsPerQuery );
            foreach ( $updateBatches as $updateBatch ) {
                $this->beginTransactionRound( __METHOD__ );
                $dbw->newUpdateQueryBuilder()
                    ->update( $table )
                    ->set( [ $fromNamespaceField => $newLinkTarget->getNamespace() ] )
                    ->where( $dbw->factorConds( $updateBatch ) )
                    ->caller( __METHOD__ )
                    ->execute();
                $this->commitTransactionRound( __METHOD__ );
            }
        }
 
        return true;
    }
 
    private function canMerge( $id, PageIdentity $page, &$logStatus ) {
        $revisionLookup = $this->getServiceContainer()->getRevisionLookup();
        $latestDest = $revisionLookup->getRevisionByTitle( $page, 0,
            IDBAccessObject::READ_LATEST );
        $latestSource = $revisionLookup->getRevisionByPageId( $id, 0,
            IDBAccessObject::READ_LATEST );
        if ( $latestSource->getTimestamp() > $latestDest->getTimestamp() ) {
            $logStatus = 'cannot merge since source is later';
            return false;
        } else {
            return true;
        }
    }
 
    private function mergePage( $row, Title $newTitle ) {
        $updateRowsPerQuery = $this->getConfig()->get( MainConfigNames::UpdateRowsPerQuery );
 
        $id = $row->page_id;
 
        // Construct the WikiPage object we will need later, while the
        // page_id still exists. Note that this cannot use makeTitleSafe(),
        // we are deliberately constructing an invalid title.
        $sourceTitle = Title::makeTitle( $row->page_namespace, $row->page_title );
        $sourceTitle->resetArticleID( $id );
        $wikiPage = $this->getServiceContainer()->getWikiPageFactory()->newFromTitle( $sourceTitle );
        $wikiPage->loadPageData( IDBAccessObject::READ_LATEST );
        $destId = $newTitle->getArticleID();
 
        $dbw = $this->getPrimaryDB();
        $this->beginTransactionRound( __METHOD__ );
        $revIds = $dbw->newSelectQueryBuilder()
            ->select( 'rev_id' )
            ->from( 'revision' )
            ->where( [ 'rev_page' => $id ] )
            ->caller( __METHOD__ )
            ->fetchFieldValues();
        $updateBatches = array_chunk( array_map( 'intval', $revIds ), $updateRowsPerQuery );
        foreach ( $updateBatches as $updateBatch ) {
            $dbw->newUpdateQueryBuilder()
                ->update( 'revision' )
                ->set( [ 'rev_page' => $destId ] )
                ->where( [ 'rev_id' => $updateBatch ] )
                ->caller( __METHOD__ )
                ->execute();
            if ( count( $updateBatches ) > 1 ) {
                $this->commitTransactionRound( __METHOD__ );
                $this->beginTransactionRound( __METHOD__ );
            }
        }
 
        $delete = $dbw->newDeleteQueryBuilder()
            ->deleteFrom( 'page' )
            ->where( [ 'page_id' => $id ] )
            ->caller( __METHOD__ );
        $delete->execute();
        $this->getServiceContainer()->getLinkWriteDuplicator()->duplicate( $delete );
        $this->commitTransactionRound( __METHOD__ );
 
        /* Call LinksDeletionUpdate to delete outgoing links from the old title,
         * and update category counts.
         *
         * Calling external code with a fake broken Title is a fairly dubious
         * idea. It's necessary because it's quite a lot of code to duplicate,
         * but that also makes it fragile since it would be easy for someone to
         * accidentally introduce an assumption of title validity to the code we
         * are calling.
         */
        DeferredUpdates::addUpdate( new LinksDeletionUpdate( $wikiPage ) );
        DeferredUpdates::doUpdates();
 
        return true;
    }
}
 
// @codeCoverageIgnoreStart
$maintClass = NamespaceDupes::class;
require_once RUN_MAINTENANCE_IF_MAIN;
// @codeCoverageIgnoreEnd