maintenance/backupPrefetch.inc

   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         protected $reader = null;
  44         protected $atEnd = false;
  45         protected $atPageEnd = false;
  46         protected $lastPage = 0;
  47         protected $lastRev = 0;
  48         protected $infiles = null;
  49
  50         public function __construct( $infile ) {
  51                 $this->infiles = explode( ';', $infile );
  52                 $this->reader = new XMLReader();
  53                 $infile = array_shift( $this->infiles );
  54                 if ( defined( 'LIBXML_PARSEHUGE' ) ) {
  55                         $this->reader->open( $infile, null, LIBXML_PARSEHUGE );
  56                 } else {
  57                         $this->reader->open( $infile );
  58                 }
  59         }
  60
  61         /**
  62          * Attempts to fetch the text of a particular page revision
  63          * from the dump stream. May return null if the page is
  64          * unavailable.
  65          *
  66          * @param int $page ID number of page to read
  67          * @param int $rev ID number of revision to read
  68          * @return string|null
  69          */
  70         function prefetch( $page, $rev ) {
  71                 $page = intval( $page );
  72                 $rev = intval( $rev );
  73                 while ( $this->lastPage < $page && !$this->atEnd ) {
  74                         $this->debug( "BaseDump::prefetch at page $this->lastPage, looking for $page" );
  75                         $this->nextPage();
  76                 }
  77                 if ( $this->lastPage > $page || $this->atEnd ) {
  78                         $this->debug( "BaseDump::prefetch already past page $page "
  79                                 . "looking for rev $rev  [$this->lastPage, $this->lastRev]" );
  80
  81                         return null;
  82                 }
  83                 while ( $this->lastRev < $rev && !$this->atEnd && !$this->atPageEnd ) {
  84                         $this->debug( "BaseDump::prefetch at page $this->lastPage, rev $this->lastRev, "
  85                                 . "looking for $page, $rev" );
  86                         $this->nextRev();
  87                 }
  88                 if ( $this->lastRev == $rev && !$this->atEnd ) {
  89                         $this->debug( "BaseDump::prefetch hit on $page, $rev [$this->lastPage, $this->lastRev]" );
  90
  91                         return $this->nextText();
  92                 } else {
  93                         $this->debug( "BaseDump::prefetch already past rev $rev on page $page "
  94                                 . "[$this->lastPage, $this->lastRev]" );
  95
  96                         return null;
  97                 }
  98         }
  99
 100         function debug( $str ) {
 101                 wfDebug( $str . "\n" );
 102                 // global $dumper;
 103                 // $dumper->progress( $str );
 104         }
 105
 106         /**
 107          * @access private
 108          */
 109         function nextPage() {
 110                 if ( $this->skipTo( 'page', 'mediawiki' ) ) {
 111                         if ( $this->skipTo( 'id' ) ) {
 112                                 $this->lastPage = intval( $this->nodeContents() );
 113                                 $this->lastRev = 0;
 114                                 $this->atPageEnd = false;
 115                         }
 116                 } else {
 117                         $this->close();
 118                         if ( count( $this->infiles ) ) {
 119                                 $infile = array_shift( $this->infiles );
 120                                 $this->reader->open( $infile );
 121                                 $this->atEnd = false;
 122                         }
 123                 }
 124         }
 125
 126         /**
 127          * @access private
 128          */
 129         function nextRev() {
 130                 if ( $this->skipTo( 'revision' ) ) {
 131                         if ( $this->skipTo( 'id' ) ) {
 132                                 $this->lastRev = intval( $this->nodeContents() );
 133                         }
 134                 } else {
 135                         $this->atPageEnd = true;
 136                 }
 137         }
 138
 139         /**
 140          * @access private
 141          * @return string
 142          */
 143         function nextText() {
 144                 $this->skipTo( 'text' );
 145
 146                 return strval( $this->nodeContents() );
 147         }
 148
 149         /**
 150          * @access private
 151          * @param string $name
 152          * @param string $parent
 153          * @return bool|null
 154          */
 155         function skipTo( $name, $parent = 'page' ) {
 156                 if ( $this->atEnd ) {
 157                         return false;
 158                 }
 159                 while ( $this->reader->read() ) {
 160                         if ( $this->reader->nodeType == XMLReader::ELEMENT
 161                                 && $this->reader->name == $name
 162                         ) {
 163                                 return true;
 164                         }
 165                         if ( $this->reader->nodeType == XMLReader::END_ELEMENT
 166                                 && $this->reader->name == $parent
 167                         ) {
 168                                 $this->debug( "BaseDump::skipTo found </$parent> searching for <$name>" );
 169
 170                                 return false;
 171                         }
 172                 }
 173
 174                 return $this->close();
 175         }
 176
 177         /**
 178          * Shouldn't something like this be built-in to XMLReader?
 179          * Fetches text contents of the current element, assuming
 180          * no sub-elements or such scary things.
 181          *
 182          * @return string
 183          * @access private
 184          */
 185         function nodeContents() {
 186                 if ( $this->atEnd ) {
 187                         return null;
 188                 }
 189                 if ( $this->reader->isEmptyElement ) {
 190                         return "";
 191                 }
 192                 $buffer = "";
 193                 while ( $this->reader->read() ) {
 194                         switch ( $this->reader->nodeType ) {
 195                                 case XMLReader::TEXT:
 196                                 // case XMLReader::WHITESPACE:
 197                                 case XMLReader::SIGNIFICANT_WHITESPACE:
 198                                         $buffer .= $this->reader->value;
 199                                         break;
 200                                 case XMLReader::END_ELEMENT:
 201                                         return $buffer;
 202                         }
 203                 }
 204
 205                 return $this->close();
 206         }
 207
 208         /**
 209          * @access private
 210          * @return null
 211          */
 212         function close() {
 213                 $this->reader->close();
 214                 $this->atEnd = true;
 215
 216                 return null;
 217         }
 218 }