rdbms: Avoid selectDB() call in LoadMonitor new connections

[mediawiki.git] / includes / export / WikiExporter.php

<?php
/**
 * Base class for exporting
 *
 * Copyright © 2003, 2005, 2006 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
 */

/**
 * @defgroup Dump Dump
 */

use Wikimedia\Rdbms\ResultWrapper;
use Wikimedia\Rdbms\IDatabase;

/**
 * @ingroup SpecialPage Dump
 */
class WikiExporter {
        /** @var bool Return distinct author list (when not returning full history) */
        public $list_authors = false;

        /** @var bool */
        public $dumpUploads = false;

        /** @var bool */
        public $dumpUploadFileContents = false;

        /** @var string */
        public $author_list = "";

        const FULL = 1;
        const CURRENT = 2;
        const STABLE = 4; // extension defined
        const LOGS = 8;
        const RANGE = 16;

        const BUFFER = 0;
        const STREAM = 1;

        const TEXT = 0;
        const STUB = 1;

        /** @var int */
        public $buffer;

        /** @var int */
        public $text;

        /** @var DumpOutput */
        public $sink;

        /**
         * Returns the export schema version.
         * @return string
         */
        public static function schemaVersion() {
                return "0.10";
        }

        /**
         * If using WikiExporter::STREAM to stream a large amount of data,
         * provide a database connection which is not managed by
         * LoadBalancer to read from: some history blob types will
         * make additional queries to pull source data while the
         * main query is still running.
         *
         * @param IDatabase $db
         * @param int|array $history One of WikiExporter::FULL, WikiExporter::CURRENT,
         *   WikiExporter::RANGE or WikiExporter::STABLE, or an associative array:
         *   - offset: non-inclusive offset at which to start the query
         *   - limit: maximum number of rows to return
         *   - dir: "asc" or "desc" timestamp order
         * @param int $buffer One of WikiExporter::BUFFER or WikiExporter::STREAM
         * @param int $text One of WikiExporter::TEXT or WikiExporter::STUB
         */
        function __construct( $db, $history = self::CURRENT,
                        $buffer = self::BUFFER, $text = self::TEXT ) {
                $this->db = $db;
                $this->history = $history;
                $this->buffer = $buffer;
                $this->writer = new XmlDumpWriter();
                $this->sink = new DumpOutput();
                $this->text = $text;
        }

        /**
         * Set the DumpOutput or DumpFilter object which will receive
         * various row objects and XML output for filtering. Filters
         * can be chained or used as callbacks.
         *
         * @param DumpOutput &$sink
         */
        public function setOutputSink( &$sink ) {
                $this->sink =& $sink;
        }

        public function openStream() {
                $output = $this->writer->openStream();
                $this->sink->writeOpenStream( $output );
        }

        public function closeStream() {
                $output = $this->writer->closeStream();
                $this->sink->writeCloseStream( $output );
        }

        /**
         * Dumps a series of page and revision records for all pages
         * in the database, either including complete history or only
         * the most recent version.
         */
        public function allPages() {
                $this->dumpFrom( '' );
        }

        /**
         * Dumps a series of page and revision records for those pages
         * in the database falling within the page_id range given.
         * @param int $start Inclusive lower limit (this id is included)
         * @param int $end Exclusive upper limit (this id is not included)
         *   If 0, no upper limit.
         * @param bool $orderRevs order revisions within pages in ascending order
         */
        public function pagesByRange( $start, $end, $orderRevs ) {
                if ( $orderRevs ) {
                        $condition = 'rev_page >= ' . intval( $start );
                        if ( $end ) {
                                $condition .= ' AND rev_page < ' . intval( $end );
                        }
                } else {
                        $condition = 'page_id >= ' . intval( $start );
                        if ( $end ) {
                                $condition .= ' AND page_id < ' . intval( $end );
                        }
                }
                $this->dumpFrom( $condition, $orderRevs );
        }

        /**
         * Dumps a series of page and revision records for those pages
         * in the database with revisions falling within the rev_id range given.
         * @param int $start Inclusive lower limit (this id is included)
         * @param int $end Exclusive upper limit (this id is not included)
         *   If 0, no upper limit.
         */
        public function revsByRange( $start, $end ) {
                $condition = 'rev_id >= ' . intval( $start );
                if ( $end ) {
                        $condition .= ' AND rev_id < ' . intval( $end );
                }
                $this->dumpFrom( $condition );
        }

        /**
         * @param Title $title
         */
        public function pageByTitle( $title ) {
                $this->dumpFrom(
                        'page_namespace=' . $title->getNamespace() .
                        ' AND page_title=' . $this->db->addQuotes( $title->getDBkey() ) );
        }

        /**
         * @param string $name
         * @throws MWException
         */
        public function pageByName( $name ) {
                $title = Title::newFromText( $name );
                if ( is_null( $title ) ) {
                        throw new MWException( "Can't export invalid title" );
                } else {
                        $this->pageByTitle( $title );
                }
        }

        /**
         * @param array $names
         */
        public function pagesByName( $names ) {
                foreach ( $names as $name ) {
                        $this->pageByName( $name );
                }
        }

        public function allLogs() {
                $this->dumpFrom( '' );
        }

        /**
         * @param int $start
         * @param int $end
         */
        public function logsByRange( $start, $end ) {
                $condition = 'log_id >= ' . intval( $start );
                if ( $end ) {
                        $condition .= ' AND log_id < ' . intval( $end );
                }
                $this->dumpFrom( $condition );
        }

        /**
         * Generates the distinct list of authors of an article
         * Not called by default (depends on $this->list_authors)
         * Can be set by Special:Export when not exporting whole history
         *
         * @param array $cond
         */
        protected function do_list_authors( $cond ) {
                $this->author_list = "<contributors>";
                // rev_deleted

                $res = $this->db->select(
                        [ 'page', 'revision' ],
                        [ 'DISTINCT rev_user_text', 'rev_user' ],
                        [
                                $this->db->bitAnd( 'rev_deleted', Revision::DELETED_USER ) . ' = 0',
                                $cond,
                                'page_id = rev_id',
                        ],
                        __METHOD__
                );

                foreach ( $res as $row ) {
                        $this->author_list .= "<contributor>" .
                                "<username>" .
                                htmlentities( $row->rev_user_text ) .
                                "</username>" .
                                "<id>" .
                                $row->rev_user .
                                "</id>" .
                                "</contributor>";
                }
                $this->author_list .= "</contributors>";
        }

        /**
         * @param string $cond
         * @param bool $orderRevs
         * @throws MWException
         * @throws Exception
         */
        protected function dumpFrom( $cond = '', $orderRevs = false ) {
                # For logging dumps...
                if ( $this->history & self::LOGS ) {
                        $where = [ 'user_id = log_user' ];
                        # Hide private logs
                        $hideLogs = LogEventsList::getExcludeClause( $this->db );
                        if ( $hideLogs ) {
                                $where[] = $hideLogs;
                        }
                        # Add on any caller specified conditions
                        if ( $cond ) {
                                $where[] = $cond;
                        }
                        # Get logging table name for logging.* clause
                        $logging = $this->db->tableName( 'logging' );

                        if ( $this->buffer == self::STREAM ) {
                                $prev = $this->db->bufferResults( false );
                        }
                        $result = null; // Assuring $result is not undefined, if exception occurs early
                        try {
                                $result = $this->db->select( [ 'logging', 'user' ],
                                        [ "{$logging}.*", 'user_name' ], // grab the user name
                                        $where,
                                        __METHOD__,
                                        [ 'ORDER BY' => 'log_id', 'USE INDEX' => [ 'logging' => 'PRIMARY' ] ]
                                );
                                $this->outputLogStream( $result );
                                if ( $this->buffer == self::STREAM ) {
                                        $this->db->bufferResults( $prev );
                                }
                        } catch ( Exception $e ) {
                                // Throwing the exception does not reliably free the resultset, and
                                // would also leave the connection in unbuffered mode.

                                // Freeing result
                                try {
                                        if ( $result ) {
                                                $result->free();
                                        }
                                } catch ( Exception $e2 ) {
                                        // Already in panic mode -> ignoring $e2 as $e has
                                        // higher priority
                                }

                                // Putting database back in previous buffer mode
                                try {
                                        if ( $this->buffer == self::STREAM ) {
                                                $this->db->bufferResults( $prev );
                                        }
                                } catch ( Exception $e2 ) {
                                        // Already in panic mode -> ignoring $e2 as $e has
                                        // higher priority
                                }

                                // Inform caller about problem
                                throw $e;
                        }
                # For page dumps...
                } else {
                        $tables = [ 'page', 'revision' ];
                        $opts = [ 'ORDER BY' => 'page_id ASC' ];
                        $opts['USE INDEX'] = [];
                        $join = [];
                        if ( is_array( $this->history ) ) {
                                # Time offset/limit for all pages/history...
                                $revJoin = 'page_id=rev_page';
                                # Set time order
                                if ( $this->history['dir'] == 'asc' ) {
                                        $op = '>';
                                        $opts['ORDER BY'] = 'rev_timestamp ASC';
                                } else {
                                        $op = '<';
                                        $opts['ORDER BY'] = 'rev_timestamp DESC';
                                }
                                # Set offset
                                if ( !empty( $this->history['offset'] ) ) {
                                        $revJoin .= " AND rev_timestamp $op " .
                                                $this->db->addQuotes( $this->db->timestamp( $this->history['offset'] ) );
                                }
                                $join['revision'] = [ 'INNER JOIN', $revJoin ];
                                # Set query limit
                                if ( !empty( $this->history['limit'] ) ) {
                                        $opts['LIMIT'] = intval( $this->history['limit'] );
                                }
                        } elseif ( $this->history & self::FULL ) {
                                # Full history dumps...
                                # query optimization for history stub dumps
                                if ( $this->text == self::STUB && $orderRevs ) {
                                        $tables = [ 'revision', 'page' ];
                                        $opts[] = 'STRAIGHT_JOIN';
                                        $opts['ORDER BY'] = [ 'rev_page ASC', 'rev_id ASC' ];
                                        $opts['USE INDEX']['revision'] = 'rev_page_id';
                                        $join['page'] = [ 'INNER JOIN', 'rev_page=page_id' ];
                                } else {
                                        $join['revision'] = [ 'INNER JOIN', 'page_id=rev_page' ];
                                }
                        } elseif ( $this->history & self::CURRENT ) {
                                # Latest revision dumps...
                                if ( $this->list_authors && $cond != '' ) { // List authors, if so desired
                                        $this->do_list_authors( $cond );
                                }
                                $join['revision'] = [ 'INNER JOIN', 'page_id=rev_page AND page_latest=rev_id' ];
                        } elseif ( $this->history & self::STABLE ) {
                                # "Stable" revision dumps...
                                # Default JOIN, to be overridden...
                                $join['revision'] = [ 'INNER JOIN', 'page_id=rev_page AND page_latest=rev_id' ];
                                # One, and only one hook should set this, and return false
                                if ( Hooks::run( 'WikiExporter::dumpStableQuery', [ &$tables, &$opts, &$join ] ) ) {
                                        throw new MWException( __METHOD__ . " given invalid history dump type." );
                                }
                        } elseif ( $this->history & self::RANGE ) {
                                # Dump of revisions within a specified range
                                $join['revision'] = [ 'INNER JOIN', 'page_id=rev_page' ];
                                $opts['ORDER BY'] = [ 'rev_page ASC', 'rev_id ASC' ];
                        } else {
                                # Unknown history specification parameter?
                                throw new MWException( __METHOD__ . " given invalid history dump type." );
                        }
                        # Query optimization hacks
                        if ( $cond == '' ) {
                                $opts[] = 'STRAIGHT_JOIN';
                                $opts['USE INDEX']['page'] = 'PRIMARY';
                        }
                        # Build text join options
                        if ( $this->text != self::STUB ) { // 1-pass
                                $tables[] = 'text';
                                $join['text'] = [ 'INNER JOIN', 'rev_text_id=old_id' ];
                        }

                        if ( $this->buffer == self::STREAM ) {
                                $prev = $this->db->bufferResults( false );
                        }
                        $result = null; // Assuring $result is not undefined, if exception occurs early
                        try {
                                Hooks::run( 'ModifyExportQuery',
                                                [ $this->db, &$tables, &$cond, &$opts, &$join ] );

                                # Do the query!
                                $result = $this->db->select( $tables, '*', $cond, __METHOD__, $opts, $join );
                                # Output dump results
                                $this->outputPageStream( $result );

                                if ( $this->buffer == self::STREAM ) {
                                        $this->db->bufferResults( $prev );
                                }
                        } catch ( Exception $e ) {
                                // Throwing the exception does not reliably free the resultset, and
                                // would also leave the connection in unbuffered mode.

                                // Freeing result
                                try {
                                        if ( $result ) {
                                                $result->free();
                                        }
                                } catch ( Exception $e2 ) {
                                        // Already in panic mode -> ignoring $e2 as $e has
                                        // higher priority
                                }

                                // Putting database back in previous buffer mode
                                try {
                                        if ( $this->buffer == self::STREAM ) {
                                                $this->db->bufferResults( $prev );
                                        }
                                } catch ( Exception $e2 ) {
                                        // Already in panic mode -> ignoring $e2 as $e has
                                        // higher priority
                                }

                                // Inform caller about problem
                                throw $e;
                        }
                }
        }

        /**
         * Runs through a query result set dumping page and revision records.
         * The result set should be sorted/grouped by page to avoid duplicate
         * page records in the output.
         *
         * Should be safe for
         * streaming (non-buffered) queries, as long as it was made on a
         * separate database connection not managed by LoadBalancer; some
         * blob storage types will make queries to pull source data.
         *
         * @param ResultWrapper $resultset
         */
        protected function outputPageStream( $resultset ) {
                $last = null;
                foreach ( $resultset as $row ) {
                        if ( $last === null ||
                                $last->page_namespace != $row->page_namespace ||
                                $last->page_title != $row->page_title ) {
                                if ( $last !== null ) {
                                        $output = '';
                                        if ( $this->dumpUploads ) {
                                                $output .= $this->writer->writeUploads( $last, $this->dumpUploadFileContents );
                                        }
                                        $output .= $this->writer->closePage();
                                        $this->sink->writeClosePage( $output );
                                }
                                $output = $this->writer->openPage( $row );
                                $this->sink->writeOpenPage( $row, $output );
                                $last = $row;
                        }
                        $output = $this->writer->writeRevision( $row );
                        $this->sink->writeRevision( $row, $output );
                }
                if ( $last !== null ) {
                        $output = '';
                        if ( $this->dumpUploads ) {
                                $output .= $this->writer->writeUploads( $last, $this->dumpUploadFileContents );
                        }
                        $output .= $this->author_list;
                        $output .= $this->writer->closePage();
                        $this->sink->writeClosePage( $output );
                }
        }

        /**
         * @param ResultWrapper $resultset
         */
        protected function outputLogStream( $resultset ) {
                foreach ( $resultset as $row ) {
                        $output = $this->writer->writeLogItem( $row );
                        $this->sink->writeLogItem( $row, $output );
                }
        }
}