Merge "Update docs/hooks.txt for ShowSearchHitTitle"

[mediawiki.git] / maintenance / dumpTextPass.php

<?php
/**
 * BackupDumper that postprocesses XML dumps from dumpBackup.php to add page text
 *
 * Copyright (C) 2005 Brion Vibber <brion@pobox.com>
 * https://www.mediawiki.org/
 *
 * 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
 */

require_once __DIR__ . '/backup.inc';
require_once __DIR__ . '/../includes/export/WikiExporter.php';

/**
 * @ingroup Maintenance
 */
class TextPassDumper extends BackupDumper {
        public $prefetch = null;

        // when we spend more than maxTimeAllowed seconds on this run, we continue
        // processing until we write out the next complete page, then save output file(s),
        // rename it/them and open new one(s)
        public $maxTimeAllowed = 0; // 0 = no limit

        protected $input = "php://stdin";
        protected $history = WikiExporter::FULL;
        protected $fetchCount = 0;
        protected $prefetchCount = 0;
        protected $prefetchCountLast = 0;
        protected $fetchCountLast = 0;

        protected $maxFailures = 5;
        protected $maxConsecutiveFailedTextRetrievals = 200;
        protected $failureTimeout = 5; // Seconds to sleep after db failure

        protected $bufferSize = 524288; // In bytes. Maximum size to read from the stub in on go.

        protected $php = "php";
        protected $spawn = false;

        /**
         * @var bool|resource
         */
        protected $spawnProc = false;

        /**
         * @var bool|resource
         */
        protected $spawnWrite = false;

        /**
         * @var bool|resource
         */
        protected $spawnRead = false;

        /**
         * @var bool|resource
         */
        protected $spawnErr = false;

        /**
         * @var bool|XmlDumpWriter
         */
        protected $xmlwriterobj = false;

        protected $timeExceeded = false;
        protected $firstPageWritten = false;
        protected $lastPageWritten = false;
        protected $checkpointJustWritten = false;
        protected $checkpointFiles = [];

        /**
         * @var Database
         */
        protected $db;

        /**
         * @param array $args For backward compatibility
         */
        function __construct( $args = null ) {
                parent::__construct();

                $this->addDescription( <<<TEXT
This script postprocesses XML dumps from dumpBackup.php to add
page text which was stubbed out (using --stub).

XML input is accepted on stdin.
XML output is sent to stdout; progress reports are sent to stderr.
TEXT
                );
                $this->stderr = fopen( "php://stderr", "wt" );

                $this->addOption( 'stub', 'To load a compressed stub dump instead of stdin. ' .
                        'Specify as --stub=<type>:<file>.', false, true );
                $this->addOption( 'prefetch', 'Use a prior dump file as a text source, to savepressure on the ' .
                        'database. (Requires the XMLReader extension). Specify as --prefetch=<type>:<file>',
                        false, true );
                $this->addOption( 'maxtime', 'Write out checkpoint file after this many minutes (writing' .
                        'out complete page, closing xml file properly, and opening new one' .
                        'with header).  This option requires the checkpointfile option.', false, true );
                $this->addOption( 'checkpointfile', 'Use this string for checkpoint filenames,substituting ' .
                        'first pageid written for the first %s (required) and the last pageid written for the ' .
                        'second %s if it exists.', false, true, false, true ); // This can be specified multiple times
                $this->addOption( 'quiet', 'Don\'t dump status reports to stderr.' );
                $this->addOption( 'current', 'Base ETA on number of pages in database instead of all revisions' );
                $this->addOption( 'spawn', 'Spawn a subprocess for loading text records' );
                $this->addOption( 'buffersize', 'Buffer size in bytes to use for reading the stub. ' .
                        '(Default: 512KB, Minimum: 4KB)', false, true );

                if ( $args ) {
                        $this->loadWithArgv( $args );
                        $this->processOptions();
                }
        }

        function execute() {
                $this->processOptions();
                $this->dump( true );
        }

        function processOptions() {
                global $IP;

                parent::processOptions();

                if ( $this->hasOption( 'buffersize' ) ) {
                        $this->bufferSize = max( intval( $this->getOption( 'buffersize' ) ), 4 * 1024 );
                }

                if ( $this->hasOption( 'prefetch' ) ) {
                        require_once "$IP/maintenance/backupPrefetch.inc";
                        $url = $this->processFileOpt( $this->getOption( 'prefetch' ) );
                        $this->prefetch = new BaseDump( $url );
                }

                if ( $this->hasOption( 'stub' ) ) {
                        $this->input = $this->processFileOpt( $this->getOption( 'stub' ) );
                }

                if ( $this->hasOption( 'maxtime' ) ) {
                        $this->maxTimeAllowed = intval( $this->getOption( 'maxtime' ) ) * 60;
                }

                if ( $this->hasOption( 'checkpointfile' ) ) {
                        $this->checkpointFiles = $this->getOption( 'checkpointfile' );
                }

                if ( $this->hasOption( 'current' ) ) {
                        $this->history = WikiExporter::CURRENT;
                }

                if ( $this->hasOption( 'full' ) ) {
                        $this->history = WikiExporter::FULL;
                }

                if ( $this->hasOption( 'spawn' ) ) {
                        $this->spawn = true;
                        $val = $this->getOption( 'spawn' );
                        if ( $val !== 1 ) {
                                $this->php = $val;
                        }
                }
        }

        /**
         * Drop the database connection $this->db and try to get a new one.
         *
         * This function tries to get a /different/ connection if this is
         * possible. Hence, (if this is possible) it switches to a different
         * failover upon each call.
         *
         * This function resets $this->lb and closes all connections on it.
         *
         * @throws MWException
         */
        function rotateDb() {
                // Cleaning up old connections
                if ( isset( $this->lb ) ) {
                        $this->lb->closeAll();
                        unset( $this->lb );
                }

                if ( $this->forcedDb !== null ) {
                        $this->db = $this->forcedDb;

                        return;
                }

                if ( isset( $this->db ) && $this->db->isOpen() ) {
                        throw new MWException( 'DB is set and has not been closed by the Load Balancer' );
                }

                unset( $this->db );

                // Trying to set up new connection.
                // We do /not/ retry upon failure, but delegate to encapsulating logic, to avoid
                // individually retrying at different layers of code.

                // 1. The LoadBalancer.
                try {
                        $this->lb = wfGetLBFactory()->newMainLB();
                } catch ( Exception $e ) {
                        throw new MWException( __METHOD__
                                . " rotating DB failed to obtain new load balancer (" . $e->getMessage() . ")" );
                }

                // 2. The Connection, through the load balancer.
                try {
                        $this->db = $this->lb->getConnection( DB_REPLICA, 'dump' );
                } catch ( Exception $e ) {
                        throw new MWException( __METHOD__
                                . " rotating DB failed to obtain new database (" . $e->getMessage() . ")" );
                }
        }

        function initProgress( $history = WikiExporter::FULL ) {
                parent::initProgress();
                $this->timeOfCheckpoint = $this->startTime;
        }

        function dump( $history, $text = WikiExporter::TEXT ) {
                // Notice messages will foul up your XML output even if they're
                // relatively harmless.
                if ( ini_get( 'display_errors' ) ) {
                        ini_set( 'display_errors', 'stderr' );
                }

                $this->initProgress( $this->history );

                // We are trying to get an initial database connection to avoid that the
                // first try of this request's first call to getText fails. However, if
                // obtaining a good DB connection fails it's not a serious issue, as
                // getText does retry upon failure and can start without having a working
                // DB connection.
                try {
                        $this->rotateDb();
                } catch ( Exception $e ) {
                        // We do not even count this as failure. Just let eventual
                        // watchdogs know.
                        $this->progress( "Getting initial DB connection failed (" .
                                $e->getMessage() . ")" );
                }

                $this->egress = new ExportProgressFilter( $this->sink, $this );

                // it would be nice to do it in the constructor, oh well. need egress set
                $this->finalOptionCheck();

                // we only want this so we know how to close a stream :-P
                $this->xmlwriterobj = new XmlDumpWriter();

                $input = fopen( $this->input, "rt" );
                $this->readDump( $input );

                if ( $this->spawnProc ) {
                        $this->closeSpawn();
                }

                $this->report( true );
        }

        function processFileOpt( $opt ) {
                $split = explode( ':', $opt, 2 );
                $val = $split[0];
                $param = '';
                if ( count( $split ) === 2 ) {
                        $param = $split[1];
                }
                $fileURIs = explode( ';', $param );
                foreach ( $fileURIs as $URI ) {
                        switch ( $val ) {
                                case "file":
                                        $newURI = $URI;
                                        break;
                                case "gzip":
                                        $newURI = "compress.zlib://$URI";
                                        break;
                                case "bzip2":
                                        $newURI = "compress.bzip2://$URI";
                                        break;
                                case "7zip":
                                        $newURI = "mediawiki.compress.7z://$URI";
                                        break;
                                default:
                                        $newURI = $URI;
                        }
                        $newFileURIs[] = $newURI;
                }
                $val = implode( ';', $newFileURIs );

                return $val;
        }

        /**
         * Overridden to include prefetch ratio if enabled.
         */
        function showReport() {
                if ( !$this->prefetch ) {
                        parent::showReport();

                        return;
                }

                if ( $this->reporting ) {
                        $now = wfTimestamp( TS_DB );
                        $nowts = microtime( true );
                        $deltaAll = $nowts - $this->startTime;
                        $deltaPart = $nowts - $this->lastTime;
                        $this->pageCountPart = $this->pageCount - $this->pageCountLast;
                        $this->revCountPart = $this->revCount - $this->revCountLast;

                        if ( $deltaAll ) {
                                $portion = $this->revCount / $this->maxCount;
                                $eta = $this->startTime + $deltaAll / $portion;
                                $etats = wfTimestamp( TS_DB, intval( $eta ) );
                                if ( $this->fetchCount ) {
                                        $fetchRate = 100.0 * $this->prefetchCount / $this->fetchCount;
                                } else {
                                        $fetchRate = '-';
                                }
                                $pageRate = $this->pageCount / $deltaAll;
                                $revRate = $this->revCount / $deltaAll;
                        } else {
                                $pageRate = '-';
                                $revRate = '-';
                                $etats = '-';
                                $fetchRate = '-';
                        }
                        if ( $deltaPart ) {
                                if ( $this->fetchCountLast ) {
                                        $fetchRatePart = 100.0 * $this->prefetchCountLast / $this->fetchCountLast;
                                } else {
                                        $fetchRatePart = '-';
                                }
                                $pageRatePart = $this->pageCountPart / $deltaPart;
                                $revRatePart = $this->revCountPart / $deltaPart;
                        } else {
                                $fetchRatePart = '-';
                                $pageRatePart = '-';
                                $revRatePart = '-';
                        }
                        $this->progress( sprintf(
                                "%s: %s (ID %d) %d pages (%0.1f|%0.1f/sec all|curr), "
                                        . "%d revs (%0.1f|%0.1f/sec all|curr), %0.1f%%|%0.1f%% "
                                        . "prefetched (all|curr), ETA %s [max %d]",
                                $now, wfWikiID(), $this->ID, $this->pageCount, $pageRate,
                                $pageRatePart, $this->revCount, $revRate, $revRatePart,
                                $fetchRate, $fetchRatePart, $etats, $this->maxCount
                        ) );
                        $this->lastTime = $nowts;
                        $this->revCountLast = $this->revCount;
                        $this->prefetchCountLast = $this->prefetchCount;
                        $this->fetchCountLast = $this->fetchCount;
                }
        }

        function setTimeExceeded() {
                $this->timeExceeded = true;
        }

        function checkIfTimeExceeded() {
                if ( $this->maxTimeAllowed
                        && ( $this->lastTime - $this->timeOfCheckpoint > $this->maxTimeAllowed )
                ) {
                        return true;
                }

                return false;
        }

        function finalOptionCheck() {
                if ( ( $this->checkpointFiles && !$this->maxTimeAllowed )
                        || ( $this->maxTimeAllowed && !$this->checkpointFiles )
                ) {
                        throw new MWException( "Options checkpointfile and maxtime must be specified together.\n" );
                }
                foreach ( $this->checkpointFiles as $checkpointFile ) {
                        $count = substr_count( $checkpointFile, "%s" );
                        if ( $count != 2 ) {
                                throw new MWException( "Option checkpointfile must contain two '%s' "
                                        . "for substitution of first and last pageids, count is $count instead, "
                                        . "file is $checkpointFile.\n" );
                        }
                }

                if ( $this->checkpointFiles ) {
                        $filenameList = (array)$this->egress->getFilenames();
                        if ( count( $filenameList ) != count( $this->checkpointFiles ) ) {
                                throw new MWException( "One checkpointfile must be specified "
                                        . "for each output option, if maxtime is used.\n" );
                        }
                }
        }

        /**
         * @throws MWException Failure to parse XML input
         * @param string $input
         * @return bool
         */
        function readDump( $input ) {
                $this->buffer = "";
                $this->openElement = false;
                $this->atStart = true;
                $this->state = "";
                $this->lastName = "";
                $this->thisPage = 0;
                $this->thisRev = 0;
                $this->thisRevModel = null;
                $this->thisRevFormat = null;

                $parser = xml_parser_create( "UTF-8" );
                xml_parser_set_option( $parser, XML_OPTION_CASE_FOLDING, false );

                xml_set_element_handler(
                        $parser,
                        [ $this, 'startElement' ],
                        [ $this, 'endElement' ]
                );
                xml_set_character_data_handler( $parser, [ $this, 'characterData' ] );

                $offset = 0; // for context extraction on error reporting
                do {
                        if ( $this->checkIfTimeExceeded() ) {
                                $this->setTimeExceeded();
                        }
                        $chunk = fread( $input, $this->bufferSize );
                        if ( !xml_parse( $parser, $chunk, feof( $input ) ) ) {
                                wfDebug( "TextDumpPass::readDump encountered XML parsing error\n" );

                                $byte = xml_get_current_byte_index( $parser );
                                $msg = wfMessage( 'xml-error-string',
                                        'XML import parse failure',
                                        xml_get_current_line_number( $parser ),
                                        xml_get_current_column_number( $parser ),
                                        $byte . ( is_null( $chunk ) ? null : ( '; "' . substr( $chunk, $byte - $offset, 16 ) . '"' ) ),
                                        xml_error_string( xml_get_error_code( $parser ) ) )->escaped();

                                xml_parser_free( $parser );

                                throw new MWException( $msg );
                        }
                        $offset += strlen( $chunk );
                } while ( $chunk !== false && !feof( $input ) );
                if ( $this->maxTimeAllowed ) {
                        $filenameList = (array)$this->egress->getFilenames();
                        // we wrote some stuff after last checkpoint that needs renamed
                        if ( file_exists( $filenameList[0] ) ) {
                                $newFilenames = [];
                                # we might have just written the header and footer and had no
                                # pages or revisions written... perhaps they were all deleted
                                # there's no pageID 0 so we use that. the caller is responsible
                                # for deciding what to do with a file containing only the
                                # siteinfo information and the mw tags.
                                if ( !$this->firstPageWritten ) {
                                        $firstPageID = str_pad( 0, 9, "0", STR_PAD_LEFT );
                                        $lastPageID = str_pad( 0, 9, "0", STR_PAD_LEFT );
                                } else {
                                        $firstPageID = str_pad( $this->firstPageWritten, 9, "0", STR_PAD_LEFT );
                                        $lastPageID = str_pad( $this->lastPageWritten, 9, "0", STR_PAD_LEFT );
                                }

                                $filenameCount = count( $filenameList );
                                for ( $i = 0; $i < $filenameCount; $i++ ) {
                                        $checkpointNameFilledIn = sprintf( $this->checkpointFiles[$i], $firstPageID, $lastPageID );
                                        $fileinfo = pathinfo( $filenameList[$i] );
                                        $newFilenames[] = $fileinfo['dirname'] . '/' . $checkpointNameFilledIn;
                                }
                                $this->egress->closeAndRename( $newFilenames );
                        }
                }
                xml_parser_free( $parser );

                return true;
        }

        /**
         * Applies applicable export transformations to $text.
         *
         * @param string $text
         * @param string $model
         * @param string|null $format
         *
         * @return string
         */
        private function exportTransform( $text, $model, $format = null ) {
                try {
                        $handler = ContentHandler::getForModelID( $model );
                        $text = $handler->exportTransform( $text, $format );
                }
                catch ( MWException $ex ) {
                        $this->progress(
                                "Unable to apply export transformation for content model '$model': " .
                                $ex->getMessage()
                        );
                }

                return $text;
        }

        /**
         * Tries to get the revision text for a revision id.
         * Export transformations are applied if the content model can is given or can be
         * determined from the database.
         *
         * Upon errors, retries (Up to $this->maxFailures tries each call).
         * If still no good revision get could be found even after this retrying, "" is returned.
         * If no good revision text could be returned for
         * $this->maxConsecutiveFailedTextRetrievals consecutive calls to getText, MWException
         * is thrown.
         *
         * @param string $id The revision id to get the text for
         * @param string|bool|null $model The content model used to determine
         *  applicable export transformations.
         *  If $model is null, it will be determined from the database.
         * @param string|null $format The content format used when applying export transformations.
         *
         * @throws MWException
         * @return string The revision text for $id, or ""
         */
        function getText( $id, $model = null, $format = null ) {
                global $wgContentHandlerUseDB;

                $prefetchNotTried = true; // Whether or not we already tried to get the text via prefetch.
                $text = false; // The candidate for a good text. false if no proper value.
                $failures = 0; // The number of times, this invocation of getText already failed.

                // The number of times getText failed without yielding a good text in between.
                static $consecutiveFailedTextRetrievals = 0;

                $this->fetchCount++;

                // To allow to simply return on success and do not have to worry about book keeping,
                // we assume, this fetch works (possible after some retries). Nevertheless, we koop
                // the old value, so we can restore it, if problems occur (See after the while loop).
                $oldConsecutiveFailedTextRetrievals = $consecutiveFailedTextRetrievals;
                $consecutiveFailedTextRetrievals = 0;

                if ( $model === null && $wgContentHandlerUseDB ) {
                        $row = $this->db->selectRow(
                                'revision',
                                [ 'rev_content_model', 'rev_content_format' ],
                                [ 'rev_id' => $this->thisRev ],
                                __METHOD__
                        );

                        if ( $row ) {
                                $model = $row->rev_content_model;
                                $format = $row->rev_content_format;
                        }
                }

                if ( $model === null || $model === '' ) {
                        $model = false;
                }

                while ( $failures < $this->maxFailures ) {

                        // As soon as we found a good text for the $id, we will return immediately.
                        // Hence, if we make it past the try catch block, we know that we did not
                        // find a good text.

                        try {
                                // Step 1: Get some text (or reuse from previous iteratuon if checking
                                //         for plausibility failed)

                                // Trying to get prefetch, if it has not been tried before
                                if ( $text === false && isset( $this->prefetch ) && $prefetchNotTried ) {
                                        $prefetchNotTried = false;
                                        $tryIsPrefetch = true;
                                        $text = $this->prefetch->prefetch( intval( $this->thisPage ),
                                                intval( $this->thisRev ) );

                                        if ( $text === null ) {
                                                $text = false;
                                        }

                                        if ( is_string( $text ) && $model !== false ) {
                                                // Apply export transformation to text coming from an old dump.
                                                // The purpose of this transformation is to convert up from legacy
                                                // formats, which may still be used in the older dump that is used
                                                // for pre-fetching. Applying the transformation again should not
                                                // interfere with content that is already in the correct form.
                                                $text = $this->exportTransform( $text, $model, $format );
                                        }
                                }

                                if ( $text === false ) {
                                        // Fallback to asking the database
                                        $tryIsPrefetch = false;
                                        if ( $this->spawn ) {
                                                $text = $this->getTextSpawned( $id );
                                        } else {
                                                $text = $this->getTextDb( $id );
                                        }

                                        if ( $text !== false && $model !== false ) {
                                                // Apply export transformation to text coming from the database.
                                                // Prefetched text should already have transformations applied.
                                                $text = $this->exportTransform( $text, $model, $format );
                                        }

                                        // No more checks for texts from DB for now.
                                        // If we received something that is not false,
                                        // We treat it as good text, regardless of whether it actually is or is not
                                        if ( $text !== false ) {
                                                return $text;
                                        }
                                }

                                if ( $text === false ) {
                                        throw new MWException( "Generic error while obtaining text for id " . $id );
                                }

                                // We received a good candidate for the text of $id via some method

                                // Step 2: Checking for plausibility and return the text if it is
                                //         plausible
                                $revID = intval( $this->thisRev );
                                if ( !isset( $this->db ) ) {
                                        throw new MWException( "No database available" );
                                }

                                if ( $model !== CONTENT_MODEL_WIKITEXT ) {
                                        $revLength = strlen( $text );
                                } else {
                                        $revLength = $this->db->selectField( 'revision', 'rev_len', [ 'rev_id' => $revID ] );
                                }

                                if ( strlen( $text ) == $revLength ) {
                                        if ( $tryIsPrefetch ) {
                                                $this->prefetchCount++;
                                        }

                                        return $text;
                                }

                                $text = false;
                                throw new MWException( "Received text is unplausible for id " . $id );
                        } catch ( Exception $e ) {
                                $msg = "getting/checking text " . $id . " failed (" . $e->getMessage() . ")";
                                if ( $failures + 1 < $this->maxFailures ) {
                                        $msg .= " (Will retry " . ( $this->maxFailures - $failures - 1 ) . " more times)";
                                }
                                $this->progress( $msg );
                        }

                        // Something went wrong; we did not a text that was plausible :(
                        $failures++;

                        // A failure in a prefetch hit does not warrant resetting db connection etc.
                        if ( !$tryIsPrefetch ) {
                                // After backing off for some time, we try to reboot the whole process as
                                // much as possible to not carry over failures from one part to the other
                                // parts
                                sleep( $this->failureTimeout );
                                try {
                                        $this->rotateDb();
                                        if ( $this->spawn ) {
                                                $this->closeSpawn();
                                                $this->openSpawn();
                                        }
                                } catch ( Exception $e ) {
                                        $this->progress( "Rebooting getText infrastructure failed (" . $e->getMessage() . ")" .
                                                " Trying to continue anyways" );
                                }
                        }
                }

                // Retirieving a good text for $id failed (at least) maxFailures times.
                // We abort for this $id.

                // Restoring the consecutive failures, and maybe aborting, if the dump
                // is too broken.
                $consecutiveFailedTextRetrievals = $oldConsecutiveFailedTextRetrievals + 1;
                if ( $consecutiveFailedTextRetrievals > $this->maxConsecutiveFailedTextRetrievals ) {
                        throw new MWException( "Graceful storage failure" );
                }

                return "";
        }

        /**
         * May throw a database error if, say, the server dies during query.
         * @param int $id
         * @return bool|string
         * @throws MWException
         */
        private function getTextDb( $id ) {
                global $wgContLang;
                if ( !isset( $this->db ) ) {
                        throw new MWException( __METHOD__ . "No database available" );
                }
                $row = $this->db->selectRow( 'text',
                        [ 'old_text', 'old_flags' ],
                        [ 'old_id' => $id ],
                        __METHOD__ );
                $text = Revision::getRevisionText( $row );
                if ( $text === false ) {
                        return false;
                }
                $stripped = str_replace( "\r", "", $text );
                $normalized = $wgContLang->normalize( $stripped );

                return $normalized;
        }

        private function getTextSpawned( $id ) {
                MediaWiki\suppressWarnings();
                if ( !$this->spawnProc ) {
                        // First time?
                        $this->openSpawn();
                }
                $text = $this->getTextSpawnedOnce( $id );
                MediaWiki\restoreWarnings();

                return $text;
        }

        function openSpawn() {
                global $IP;

                if ( file_exists( "$IP/../multiversion/MWScript.php" ) ) {
                        $cmd = implode( " ",
                                array_map( 'wfEscapeShellArg',
                                        [
                                                $this->php,
                                                "$IP/../multiversion/MWScript.php",
                                                "fetchText.php",
                                                '--wiki', wfWikiID() ] ) );
                } else {
                        $cmd = implode( " ",
                                array_map( 'wfEscapeShellArg',
                                        [
                                                $this->php,
                                                "$IP/maintenance/fetchText.php",
                                                '--wiki', wfWikiID() ] ) );
                }
                $spec = [
                        0 => [ "pipe", "r" ],
                        1 => [ "pipe", "w" ],
                        2 => [ "file", "/dev/null", "a" ] ];
                $pipes = [];

                $this->progress( "Spawning database subprocess: $cmd" );
                $this->spawnProc = proc_open( $cmd, $spec, $pipes );
                if ( !$this->spawnProc ) {
                        $this->progress( "Subprocess spawn failed." );

                        return false;
                }
                list(
                        $this->spawnWrite, // -> stdin
                        $this->spawnRead, // <- stdout
                ) = $pipes;

                return true;
        }

        private function closeSpawn() {
                MediaWiki\suppressWarnings();
                if ( $this->spawnRead ) {
                        fclose( $this->spawnRead );
                }
                $this->spawnRead = false;
                if ( $this->spawnWrite ) {
                        fclose( $this->spawnWrite );
                }
                $this->spawnWrite = false;
                if ( $this->spawnErr ) {
                        fclose( $this->spawnErr );
                }
                $this->spawnErr = false;
                if ( $this->spawnProc ) {
                        pclose( $this->spawnProc );
                }
                $this->spawnProc = false;
                MediaWiki\restoreWarnings();
        }

        private function getTextSpawnedOnce( $id ) {
                global $wgContLang;

                $ok = fwrite( $this->spawnWrite, "$id\n" );
                // $this->progress( ">> $id" );
                if ( !$ok ) {
                        return false;
                }

                $ok = fflush( $this->spawnWrite );
                // $this->progress( ">> [flush]" );
                if ( !$ok ) {
                        return false;
                }

                // check that the text id they are sending is the one we asked for
                // this avoids out of sync revision text errors we have encountered in the past
                $newId = fgets( $this->spawnRead );
                if ( $newId === false ) {
                        return false;
                }
                if ( $id != intval( $newId ) ) {
                        return false;
                }

                $len = fgets( $this->spawnRead );
                // $this->progress( "<< " . trim( $len ) );
                if ( $len === false ) {
                        return false;
                }

                $nbytes = intval( $len );
                // actual error, not zero-length text
                if ( $nbytes < 0 ) {
                        return false;
                }

                $text = "";

                // Subprocess may not send everything at once, we have to loop.
                while ( $nbytes > strlen( $text ) ) {
                        $buffer = fread( $this->spawnRead, $nbytes - strlen( $text ) );
                        if ( $buffer === false ) {
                                break;
                        }
                        $text .= $buffer;
                }

                $gotbytes = strlen( $text );
                if ( $gotbytes != $nbytes ) {
                        $this->progress( "Expected $nbytes bytes from database subprocess, got $gotbytes " );

                        return false;
                }

                // Do normalization in the dump thread...
                $stripped = str_replace( "\r", "", $text );
                $normalized = $wgContLang->normalize( $stripped );

                return $normalized;
        }

        function startElement( $parser, $name, $attribs ) {
                $this->checkpointJustWritten = false;

                $this->clearOpenElement( null );
                $this->lastName = $name;

                if ( $name == 'revision' ) {
                        $this->state = $name;
                        $this->egress->writeOpenPage( null, $this->buffer );
                        $this->buffer = "";
                } elseif ( $name == 'page' ) {
                        $this->state = $name;
                        if ( $this->atStart ) {
                                $this->egress->writeOpenStream( $this->buffer );
                                $this->buffer = "";
                                $this->atStart = false;
                        }
                }

                if ( $name == "text" && isset( $attribs['id'] ) ) {
                        $id = $attribs['id'];
                        $model = trim( $this->thisRevModel );
                        $format = trim( $this->thisRevFormat );

                        $model = $model === '' ? null : $model;
                        $format = $format === '' ? null : $format;

                        $text = $this->getText( $id, $model, $format );
                        $this->openElement = [ $name, [ 'xml:space' => 'preserve' ] ];
                        if ( strlen( $text ) > 0 ) {
                                $this->characterData( $parser, $text );
                        }
                } else {
                        $this->openElement = [ $name, $attribs ];
                }
        }

        function endElement( $parser, $name ) {
                $this->checkpointJustWritten = false;

                if ( $this->openElement ) {
                        $this->clearOpenElement( "" );
                } else {
                        $this->buffer .= "</$name>";
                }

                if ( $name == 'revision' ) {
                        $this->egress->writeRevision( null, $this->buffer );
                        $this->buffer = "";
                        $this->thisRev = "";
                        $this->thisRevModel = null;
                        $this->thisRevFormat = null;
                } elseif ( $name == 'page' ) {
                        if ( !$this->firstPageWritten ) {
                                $this->firstPageWritten = trim( $this->thisPage );
                        }
                        $this->lastPageWritten = trim( $this->thisPage );
                        if ( $this->timeExceeded ) {
                                $this->egress->writeClosePage( $this->buffer );
                                // nasty hack, we can't just write the chardata after the
                                // page tag, it will include leading blanks from the next line
                                $this->egress->sink->write( "\n" );

                                $this->buffer = $this->xmlwriterobj->closeStream();
                                $this->egress->writeCloseStream( $this->buffer );

                                $this->buffer = "";
                                $this->thisPage = "";
                                // this could be more than one file if we had more than one output arg

                                $filenameList = (array)$this->egress->getFilenames();
                                $newFilenames = [];
                                $firstPageID = str_pad( $this->firstPageWritten, 9, "0", STR_PAD_LEFT );
                                $lastPageID = str_pad( $this->lastPageWritten, 9, "0", STR_PAD_LEFT );
                                $filenamesCount = count( $filenameList );
                                for ( $i = 0; $i < $filenamesCount; $i++ ) {
                                        $checkpointNameFilledIn = sprintf( $this->checkpointFiles[$i], $firstPageID, $lastPageID );
                                        $fileinfo = pathinfo( $filenameList[$i] );
                                        $newFilenames[] = $fileinfo['dirname'] . '/' . $checkpointNameFilledIn;
                                }
                                $this->egress->closeRenameAndReopen( $newFilenames );
                                $this->buffer = $this->xmlwriterobj->openStream();
                                $this->timeExceeded = false;
                                $this->timeOfCheckpoint = $this->lastTime;
                                $this->firstPageWritten = false;
                                $this->checkpointJustWritten = true;
                        } else {
                                $this->egress->writeClosePage( $this->buffer );
                                $this->buffer = "";
                                $this->thisPage = "";
                        }
                } elseif ( $name == 'mediawiki' ) {
                        $this->egress->writeCloseStream( $this->buffer );
                        $this->buffer = "";
                }
        }

        function characterData( $parser, $data ) {
                $this->clearOpenElement( null );
                if ( $this->lastName == "id" ) {
                        if ( $this->state == "revision" ) {
                                $this->thisRev .= $data;
                        } elseif ( $this->state == "page" ) {
                                $this->thisPage .= $data;
                        }
                } elseif ( $this->lastName == "model" ) {
                        $this->thisRevModel .= $data;
                } elseif ( $this->lastName == "format" ) {
                        $this->thisRevFormat .= $data;
                }

                // have to skip the newline left over from closepagetag line of
                // end of checkpoint files. nasty hack!!
                if ( $this->checkpointJustWritten ) {
                        if ( $data[0] == "\n" ) {
                                $data = substr( $data, 1 );
                        }
                        $this->checkpointJustWritten = false;
                }
                $this->buffer .= htmlspecialchars( $data );
        }

        function clearOpenElement( $style ) {
                if ( $this->openElement ) {
                        $this->buffer .= Xml::element( $this->openElement[0], $this->openElement[1], $style );
                        $this->openElement = false;
                }
        }
}

$maintClass = 'TextPassDumper';
require_once RUN_MAINTENANCE_IF_MAIN;