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