includes/export/BaseDump.php

   1 <?php
   2 /**
   3  * Helper class for the --prefetch option of dumpTextPass.php
   4  *
   5  * Copyright © 2005 Brion Vibber <brion@pobox.com>
   6  * https://www.mediawiki.org/
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Maintenance
  25  */
  26
  27 /**
  28  * Readahead helper for making large MediaWiki data dumps;
  29  * reads in a previous XML dump to sequentially prefetch text
  30  * records already normalized and decompressed.
  31  *
  32  * This can save load on the external database servers, hopefully.
  33  *
  34  * Assumes that dumps will be recorded in the canonical order:
  35  * - ascending by page_id
  36  * - ascending by rev_id within each page
  37  * - text contents are immutable and should not change once
  38  *   recorded, so the previous dump is a reliable source
  39  *
  40  * @ingroup Maintenance
  41  */
  42 class BaseDump {
  43         /** @var XMLReader */
  44         protected $reader = null;
  45         protected $atEnd = false;
  46         protected $atPageEnd = false;
  47         protected $lastPage = 0;
  48         protected $lastRev = 0;
  49         protected $infiles = null;
  50
  51         public function __construct( $infile ) {
  52                 $this->infiles = explode( ';', $infile );
  53                 $this->reader = new XMLReader();
  54                 $infile = array_shift( $this->infiles );
  55                 $this->reader->open( $infile, null, LIBXML_PARSEHUGE );
  56         }
  57
  58         /**
  59          * Attempts to fetch the text of a particular page revision
  60          * from the dump stream. May return null if the page is
  61          * unavailable.
  62          *
  63          * @param int $page ID number of page to read
  64          * @param int $rev ID number of revision to read
  65          * @return string|null
  66          */
  67         function prefetch( $page, $rev ) {
  68                 $page = intval( $page );
  69                 $rev = intval( $rev );
  70                 while ( $this->lastPage < $page && !$this->atEnd ) {
  71                         $this->debug( "BaseDump::prefetch at page $this->lastPage, looking for $page" );
  72                         $this->nextPage();
  73                 }
  74                 if ( $this->lastPage > $page || $this->atEnd ) {
  75                         $this->debug( "BaseDump::prefetch already past page $page "
  76                                 . "looking for rev $rev  [$this->lastPage, $this->lastRev]" );
  77
  78                         return null;
  79                 }
  80                 while ( $this->lastRev < $rev && !$this->atEnd && !$this->atPageEnd ) {
  81                         $this->debug( "BaseDump::prefetch at page $this->lastPage, rev $this->lastRev, "
  82                                 . "looking for $page, $rev" );
  83                         $this->nextRev();
  84                 }
  85                 if ( $this->lastRev == $rev && !$this->atEnd ) {
  86                         $this->debug( "BaseDump::prefetch hit on $page, $rev [$this->lastPage, $this->lastRev]" );
  87
  88                         return $this->nextText();
  89                 } else {
  90                         $this->debug( "BaseDump::prefetch already past rev $rev on page $page "
  91                                 . "[$this->lastPage, $this->lastRev]" );
  92
  93                         return null;
  94                 }
  95         }
  96
  97         function debug( $str ) {
  98                 wfDebug( $str . "\n" );
  99                 // global $dumper;
 100                 // $dumper->progress( $str );
 101         }
 102
 103         /**
 104          * @private
 105          */
 106         function nextPage() {
 107                 if ( $this->skipTo( 'page', 'mediawiki' ) ) {
 108                         if ( $this->skipTo( 'id' ) ) {
 109                                 $this->lastPage = intval( $this->nodeContents() );
 110                                 $this->lastRev = 0;
 111                                 $this->atPageEnd = false;
 112                         }
 113                 } else {
 114                         $this->close();
 115                         if ( count( $this->infiles ) ) {
 116                                 $infile = array_shift( $this->infiles );
 117                                 $this->reader->open( $infile );
 118                                 $this->atEnd = false;
 119                         }
 120                 }
 121         }
 122
 123         /**
 124          * @private
 125          */
 126         function nextRev() {
 127                 if ( $this->skipTo( 'revision' ) ) {
 128                         if ( $this->skipTo( 'id' ) ) {
 129                                 $this->lastRev = intval( $this->nodeContents() );
 130                         }
 131                 } else {
 132                         $this->atPageEnd = true;
 133                 }
 134         }
 135
 136         /**
 137          * @private
 138          * @return string
 139          */
 140         function nextText() {
 141                 $this->skipTo( 'text' );
 142
 143                 return strval( $this->nodeContents() );
 144         }
 145
 146         /**
 147          * @private
 148          * @param string $name
 149          * @param string $parent
 150          * @return bool|null
 151          */
 152         function skipTo( $name, $parent = 'page' ) {
 153                 if ( $this->atEnd ) {
 154                         return false;
 155                 }
 156                 while ( $this->reader->read() ) {
 157                         if ( $this->reader->nodeType == XMLReader::ELEMENT
 158                                 && $this->reader->name == $name
 159                         ) {
 160                                 return true;
 161                         }
 162                         if ( $this->reader->nodeType == XMLReader::END_ELEMENT
 163                                 && $this->reader->name == $parent
 164                         ) {
 165                                 $this->debug( "BaseDump::skipTo found </$parent> searching for <$name>" );
 166
 167                                 return false;
 168                         }
 169                 }
 170
 171                 return $this->close();
 172         }
 173
 174         /**
 175          * Shouldn't something like this be built-in to XMLReader?
 176          * Fetches text contents of the current element, assuming
 177          * no sub-elements or such scary things.
 178          *
 179          * @return string
 180          * @private
 181          */
 182         function nodeContents() {
 183                 if ( $this->atEnd ) {
 184                         return null;
 185                 }
 186                 if ( $this->reader->isEmptyElement ) {
 187                         return "";
 188                 }
 189                 $buffer = "";
 190                 while ( $this->reader->read() ) {
 191                         switch ( $this->reader->nodeType ) {
 192                                 case XMLReader::TEXT:
 193                                 // case XMLReader::WHITESPACE:
 194                                 case XMLReader::SIGNIFICANT_WHITESPACE:
 195                                         $buffer .= $this->reader->value;
 196                                         break;
 197                                 case XMLReader::END_ELEMENT:
 198                                         return $buffer;
 199                         }
 200                 }
 201
 202                 return $this->close();
 203         }
 204
 205         /**
 206          * @private
 207          * @return null
 208          */
 209         function close() {
 210                 $this->reader->close();
 211                 $this->atEnd = true;
 212
 213                 return null;
 214         }
 215 }