wikimedia/mediawiki-core

<?php
/**
 * Convert history stubs that point to an external row to direct external
 * pointers.
 *
 * 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 Maintenance ExternalStorage
 */

use MediaWiki\Maintenance\UndoLog;
use MediaWiki\Storage\SqlBlobStore;

require_once __DIR__ . '/../Maintenance.php';

class ResolveStubs extends Maintenance {
    /** @var UndoLog|null */
    private $undoLog;

    public function __construct() {
        parent::__construct();
        $this->setBatchSize( 1000 );
        $this->addOption( 'dry-run', 'Don\'t update any rows' );
        $this->addOption( 'undo', 'Undo log location', false, true );
    }

    /**
     * Convert history stubs that point to an external row to direct
     * external pointers
     */
    public function execute() {
        $dbw = $this->getPrimaryDB();
        $dbr = $this->getReplicaDB();
        $maxID = $dbr->newSelectQueryBuilder()
            ->select( 'MAX(old_id)' )
            ->from( 'text' )
            ->caller( __METHOD__ )->fetchField();
        $blockSize = $this->getBatchSize();
        $dryRun = $this->getOption( 'dry-run' );
        $this->setUndoLog( new UndoLog( $this->getOption( 'undo' ), $dbw ) );

        $numBlocks = intval( $maxID / $blockSize ) + 1;
        $numResolved = 0;
        $numTotal = 0;

        for ( $b = 0; $b < $numBlocks; $b++ ) {
            $this->waitForReplication();

            $this->output( sprintf( "%5.2f%%\n", $b / $numBlocks * 100 ) );
            $start = $blockSize * $b + 1;
            $end = $blockSize * ( $b + 1 );

            $res = $dbr->newSelectQueryBuilder()
                ->select( [ 'old_id', 'old_text', 'old_flags' ] )
                ->from( 'text' )
                ->where(
                    "old_id>=$start AND old_id<=$end " .
                    "AND old_flags LIKE '%object%' AND old_flags NOT LIKE '%external%' " .
                    // LOWER() doesn't work on binary text, need to convert
                    'AND LOWER(CONVERT(LEFT(old_text,22) USING latin1)) = \'o:15:"historyblobstub"\''
                )
                ->caller( __METHOD__ )->fetchResultSet();
            foreach ( $res as $row ) {
                $numResolved += $this->resolveStub( $row, $dryRun ) ? 1 : 0;
                $numTotal++;
            }
        }
        $this->output( "100%\n" );
        $this->output( "$numResolved of $numTotal stubs resolved\n" );
    }

    /**
     * @param UndoLog $undoLog
     */
    public function setUndoLog( UndoLog $undoLog ) {
        $this->undoLog = $undoLog;
    }

    /**
     * Resolve a history stub.
     *
     * This is called by MoveToExternal
     *
     * @param stdClass $row The existing text row
     * @param bool $dryRun
     * @return bool
     */
    public function resolveStub( $row, $dryRun ) {
        $id = $row->old_id;
        $stub = unserialize( $row->old_text );
        $flags = SqlBlobStore::explodeFlags( $row->old_flags );

        $dbr = $this->getReplicaDB();

        if ( !( $stub instanceof HistoryBlobStub ) ) {
            print "Error at old_id $id: found object of class " . get_class( $stub ) .
                ", expecting HistoryBlobStub\n";
            return false;
        }

        $mainId = $stub->getLocation();
        if ( !$mainId ) {
            print "Error at old_id $id: falsey location\n";
            return false;
        }

        # Get the main text row
        $mainTextRow = $dbr->newSelectQueryBuilder()
            ->select( [ 'old_text', 'old_flags' ] )
            ->from( 'text' )
            ->where( [ 'old_id' => $mainId ] )
            ->caller( __METHOD__ )->fetchRow();

        if ( !$mainTextRow ) {
            print "Error at old_id $id: can't find main text row old_id $mainId\n";
            return false;
        }

        $mainFlags = SqlBlobStore::explodeFlags( $mainTextRow->old_flags );
        $mainText = $mainTextRow->old_text;

        if ( !in_array( 'external', $mainFlags ) ) {
            print "Error at old_id $id: target $mainId is not external\n";
            return false;
        }
        if ( preg_match( '!^DB://([^/]*)/([^/]*)/[0-9a-f]{32}$!', $mainText ) ) {
            print "Error at old_id $id: target $mainId is a CGZ pointer\n";
            return false;
        }
        if ( preg_match( '!^DB://([^/]*)/([^/]*)/[0-9]{1,6}$!', $mainText ) ) {
            print "Error at old_id $id: target $mainId is a DHB pointer\n";
            return false;
        }
        if ( !preg_match( '!^DB://([^/]*)/([^/]*)$!', $mainText ) ) {
            print "Error at old_id $id: target $mainId has unrecognised text\n";
            return false;
        }

        # Preserve the legacy encoding flag, but switch from object to external
        if ( in_array( 'utf-8', $flags ) ) {
            $newFlags = 'utf-8,external';
        } else {
            $newFlags = 'external';
        }
        $newText = $mainText . '/' . $stub->getHash();

        # Update the row
        if ( $dryRun ) {
            $this->output( "Resolve $id => $newFlags $newText\n" );
        } else {
            $updated = $this->undoLog->update(
                'text',
                [
                    'old_flags' => $newFlags,
                    'old_text' => $newText
                ],
                (array)$row,
                __METHOD__
            );
            if ( !$updated ) {
                $this->output( "Updated of old_id $id failed to match\n" );
                return false;
            }
        }
        return true;
    }
}

$maintClass = ResolveStubs::class;
require_once RUN_MAINTENANCE_IF_MAIN;