fixBug20757.php

Go to the documentation of this file.

<?php
require_once( __DIR__ . '/../Maintenance.php' );

class FixBug20757 extends Maintenance {
        public $batchSize = 10000;
        public $mapCache = array();
        public $mapCacheSize = 0;
        public $maxMapCacheSize = 1000000;

        function __construct() {
                parent::__construct();
                $this->mDescription = 'Script to fix bug 20757 assuming that blob_tracking is intact';
                $this->addOption( 'dry-run', 'Report only' );
                $this->addOption( 'start', 'old_id to start at', false, true );
        }

        function execute() {
                $dbr = wfGetDB( DB_SLAVE );
                $dbw = wfGetDB( DB_MASTER );

                $dryRun = $this->getOption( 'dry-run' );
                if ( $dryRun ) {
                        print "Dry run only.\n";
                }

                $startId = $this->getOption( 'start', 0 );
                $numGood = 0;
                $numFixed = 0;
                $numBad = 0;

                $totalRevs = $dbr->selectField( 'text', 'MAX(old_id)', false, __METHOD__ );

                if ( $dbr->getType() == 'mysql'
                        && version_compare( $dbr->getServerVersion(), '4.1.0', '>=' ) )
                {
                        // In MySQL 4.1+, the binary field old_text has a non-working LOWER() function
                        $lowerLeft = 'LOWER(CONVERT(LEFT(old_text,22) USING latin1))';
                } else {
                        // No CONVERT() in MySQL 4.0
                        $lowerLeft = 'LOWER(LEFT(old_text,22))';
                }

                while ( true ) {
                        print "ID: $startId / $totalRevs\r";

                        $res = $dbr->select(
                                'text',
                                array( 'old_id', 'old_flags', 'old_text' ),
                                array(
                                        'old_id > ' . intval( $startId ),
                                        'old_flags LIKE \'%object%\' AND old_flags NOT LIKE \'%external%\'',
                                        "$lowerLeft = 'o:15:\"historyblobstub\"'",
                                ),
                                __METHOD__,
                                array(
                                        'ORDER BY' => 'old_id',
                                        'LIMIT' => $this->batchSize,
                                )
                        );

                        if ( !$res->numRows() ) {
                                break;
                        }

                        $secondaryIds = array();
                        $stubs = array();

                        foreach ( $res as $row ) {
                                $startId = $row->old_id;

                                // Basic sanity checks
                                $obj = unserialize( $row->old_text );
                                if ( $obj === false ) {
                                        print "{$row->old_id}: unrecoverable: cannot unserialize\n";
                                        ++$numBad;
                                        continue;
                                }

                                if ( !is_object( $obj ) ) {
                                        print "{$row->old_id}: unrecoverable: unserialized to type " .
                                                gettype( $obj ) . ", possible double-serialization\n";
                                        ++$numBad;
                                        continue;
                                }

                                if ( strtolower( get_class( $obj ) ) !== 'historyblobstub' ) {
                                        print "{$row->old_id}: unrecoverable: unexpected object class " .
                                                get_class( $obj ) . "\n";
                                        ++$numBad;
                                        continue;
                                }

                                // Process flags
                                $flags = explode( ',', $row->old_flags );
                                if ( in_array( 'utf-8', $flags ) || in_array( 'utf8', $flags ) ) {
                                        $legacyEncoding = false;
                                } else {
                                        $legacyEncoding = true;
                                }

                                // Queue the stub for future batch processing
                                $id = intval( $obj->mOldId );
                                $secondaryIds[] = $id;
                                $stubs[$row->old_id] = array(
                                        'legacyEncoding' => $legacyEncoding,
                                        'secondaryId' => $id,
                                        'hash' => $obj->mHash,
                                );
                        }

                        $secondaryIds = array_unique( $secondaryIds );

                        if ( !count( $secondaryIds ) ) {
                                continue;
                        }

                        // Run the batch query on blob_tracking
                        $res = $dbr->select(
                                'blob_tracking',
                                '*',
                                array(
                                        'bt_text_id' => $secondaryIds,
                                ),
                                __METHOD__
                        );
                        $trackedBlobs = array();
                        foreach ( $res as $row ) {
                                $trackedBlobs[$row->bt_text_id] = $row;
                        }

                        // Process the stubs
                        foreach ( $stubs as $primaryId => $stub ) {
                                $secondaryId = $stub['secondaryId'];
                                if ( !isset( $trackedBlobs[$secondaryId] ) ) {
                                        // No tracked blob. Work out what went wrong
                                        $secondaryRow = $dbr->selectRow(
                                                'text',
                                                array( 'old_flags', 'old_text' ),
                                                array( 'old_id' => $secondaryId ),
                                                __METHOD__
                                        );
                                        if ( !$secondaryRow ) {
                                                print "$primaryId: unrecoverable: secondary row is missing\n";
                                                ++$numBad;
                                        } elseif ( $this->isUnbrokenStub( $stub, $secondaryRow ) ) {
                                                // Not broken yet, and not in the tracked clusters so it won't get
                                                // broken by the current RCT run.
                                                ++$numGood;
                                        } elseif ( strpos( $secondaryRow->old_flags, 'external' ) !== false ) {
                                                print "$primaryId: unrecoverable: secondary gone to {$secondaryRow->old_text}\n";
                                                ++$numBad;
                                        } else {
                                                print "$primaryId: unrecoverable: miscellaneous corruption of secondary row\n";
                                                ++$numBad;
                                        }
                                        unset( $stubs[$primaryId] );
                                        continue;
                                }
                                $trackRow = $trackedBlobs[$secondaryId];

                                // Check that the specified text really is available in the tracked source row
                                $url = "DB://{$trackRow->bt_cluster}/{$trackRow->bt_blob_id}/{$stub['hash']}";
                                $text = ExternalStore::fetchFromURL( $url );
                                if ( $text === false ) {
                                        print "$primaryId: unrecoverable: source text missing\n";
                                        ++$numBad;
                                        unset( $stubs[$primaryId] );
                                        continue;
                                }
                                if ( md5( $text ) !== $stub['hash'] ) {
                                        print "$primaryId: unrecoverable: content hashes do not match\n";
                                        ++$numBad;
                                        unset( $stubs[$primaryId] );
                                        continue;
                                }

                                // Find the page_id and rev_id
                                // The page is probably the same as the page of the secondary row
                                $pageId = intval( $trackRow->bt_page );
                                if ( !$pageId ) {
                                        $revId = $pageId = 0;
                                } else {
                                        $revId = $this->findTextIdInPage( $pageId, $primaryId );
                                        if ( !$revId ) {
                                                // Actually an orphan
                                                $pageId = $revId = 0;
                                        }
                                }

                                $newFlags = $stub['legacyEncoding'] ? 'external' : 'external,utf-8';

                                if ( !$dryRun ) {
                                        // Reset the text row to point to the original copy
                                        $dbw->begin( __METHOD__ );
                                        $dbw->update(
                                                'text',
                                                // SET
                                                array(
                                                        'old_flags' => $newFlags,
                                                        'old_text' => $url
                                                ),
                                                // WHERE
                                                array( 'old_id' => $primaryId ),
                                                __METHOD__
                                        );

                                        // Add a blob_tracking row so that the new reference can be recompressed
                                        // without needing to run trackBlobs.php again
                                        $dbw->insert( 'blob_tracking',
                                                array(
                                                        'bt_page' => $pageId,
                                                        'bt_rev_id' => $revId,
                                                        'bt_text_id' => $primaryId,
                                                        'bt_cluster' => $trackRow->bt_cluster,
                                                        'bt_blob_id' => $trackRow->bt_blob_id,
                                                        'bt_cgz_hash' => $stub['hash'],
                                                        'bt_new_url' => null,
                                                        'bt_moved' => 0,
                                                ),
                                                __METHOD__
                                        );
                                        $dbw->commit( __METHOD__ );
                                        $this->waitForSlaves();
                                }

                                print "$primaryId: resolved to $url\n";
                                ++$numFixed;
                        }
                }

                print "\n";
                print "Fixed: $numFixed\n";
                print "Unrecoverable: $numBad\n";
                print "Good stubs: $numGood\n";
        }

        function waitForSlaves() {
                static $iteration = 0;
                ++$iteration;
                if ( ++$iteration > 50 == 0 ) {
                        wfWaitForSlaves();
                        $iteration = 0;
                }
        }

        function findTextIdInPage( $pageId, $textId ) {
                $ids = $this->getRevTextMap( $pageId );
                if ( !isset( $ids[$textId] ) ) {
                        return null;
                } else {
                        return $ids[$textId];
                }
        }

        function getRevTextMap( $pageId ) {
                if ( !isset( $this->mapCache[$pageId] ) ) {
                        // Limit cache size
                        while ( $this->mapCacheSize > $this->maxMapCacheSize ) {
                                $key = key( $this->mapCache );
                                $this->mapCacheSize -= count( $this->mapCache[$key] );
                                unset( $this->mapCache[$key] );
                        }

                        $dbr = wfGetDB( DB_SLAVE );
                        $map = array();
                        $res = $dbr->select( 'revision',
                                array( 'rev_id', 'rev_text_id' ),
                                array( 'rev_page' => $pageId ),
                                __METHOD__
                        );
                        foreach ( $res as $row ) {
                                $map[$row->rev_text_id] = $row->rev_id;
                        }
                        $this->mapCache[$pageId] = $map;
                        $this->mapCacheSize += count( $map );
                }
                return $this->mapCache[$pageId];
        }

        function isUnbrokenStub( $stub, $secondaryRow ) {
                $flags = explode( ',', $secondaryRow->old_flags );
                $text = $secondaryRow->old_text;
                if ( in_array( 'external', $flags ) ) {
                        $url = $text;
                        @list( /* $proto */ , $path ) = explode( '://', $url, 2 );
                        if ( $path == "" ) {
                                return false;
                        }
                        $text = ExternalStore::fetchFromUrl( $url );
                }
                if ( !in_array( 'object', $flags ) ) {
                        return false;
                }

                if ( in_array( 'gzip', $flags ) ) {
                        $obj = unserialize( gzinflate( $text ) );
                } else {
                        $obj = unserialize( $text );
                }

                if ( !is_object( $obj ) ) {
                        // Correct for old double-serialization bug.
                        $obj = unserialize( $obj );
                }

                if ( !is_object( $obj ) ) {
                        return false;
                }

                $obj->uncompress();
                $text = $obj->getItem( $stub['hash'] );
                return $text !== false;
        }
}

$maintClass = 'FixBug20757';
require_once( RUN_MAINTENANCE_IF_MAIN );