includes/HTMLCacheUpdate.php

   1 <?php
   2
   3 /**
   4  * Class to invalidate the HTML cache of all the pages linking to a given title.
   5  * Small numbers of links will be done immediately, large numbers are pushed onto
   6  * the job queue.
   7  *
   8  * This class is designed to work efficiently with small numbers of links, and
   9  * to work reasonably well with up to ~10^5 links. Above ~10^6 links, the memory
  10  * and time requirements of loading all backlinked IDs in doUpdate() might become
  11  * prohibitive. The requirements measured at Wikimedia are approximately:
  12  *
  13  *   memory: 48 bytes per row
  14  *   time: 16us per row for the query plus processing
  15  *
  16  * The reason this query is done is to support partitioning of the job
  17  * by backlinked ID. The memory issue could be allieviated by doing this query in
  18  * batches, but of course LIMIT with an offset is inefficient on the DB side.
  19  *
  20  * The class is nevertheless a vast improvement on the previous method of using
  21  * Image::getLinksTo() and Title::touchArray(), which uses about 2KB of memory per
  22  * link.
  23  *
  24  * @ingroup Cache
  25  */
  26 class HTMLCacheUpdate
  27 {
  28         public $mTitle, $mTable, $mPrefix;
  29         public $mRowsPerJob, $mRowsPerQuery;
  30
  31         function __construct( $titleTo, $table ) {
  32                 global $wgUpdateRowsPerJob, $wgUpdateRowsPerQuery;
  33
  34                 $this->mTitle = $titleTo;
  35                 $this->mTable = $table;
  36                 $this->mRowsPerJob = $wgUpdateRowsPerJob;
  37                 $this->mRowsPerQuery = $wgUpdateRowsPerQuery;
  38         }
  39
  40         public function doUpdate() {
  41                 # Fetch the IDs
  42                 $cond = $this->getToCondition();
  43                 $dbr = wfGetDB( DB_SLAVE );
  44                 $res = $dbr->select( $this->mTable, $this->getFromField(), $cond, __METHOD__ );
  45
  46                 if ( $dbr->numRows( $res ) != 0 ) {
  47                         if ( $dbr->numRows( $res ) > $this->mRowsPerJob ) {
  48                                 $this->insertJobs( $res );
  49                         } else {
  50                                 $this->invalidateIDs( $res );
  51                         }
  52                 }
  53                 wfRunHooks( 'HTMLCacheUpdate::doUpdate', array($this->mTitle) );
  54         }
  55
  56         protected function insertJobs( ResultWrapper $res ) {
  57                 $numRows = $res->numRows();
  58                 $numBatches = ceil( $numRows / $this->mRowsPerJob );
  59                 $realBatchSize = $numRows / $numBatches;
  60                 $start = false;
  61                 $jobs = array();
  62                 do {
  63                         for ( $i = 0; $i <= $realBatchSize - 1; $i++ ) {
  64                                 $row = $res->fetchRow();
  65                                 if ( $row ) {
  66                                         $id = $row[0];
  67                                 } else {
  68                                         $id = false;
  69                                         break;
  70                                 }
  71                         }
  72
  73                         $params = array(
  74                                 'table' => $this->mTable,
  75                                 'start' => $start,
  76                                 'end' => ( $id !== false ? $id - 1 : false ),
  77                         );
  78                         $jobs[] = new HTMLCacheUpdateJob( $this->mTitle, $params );
  79
  80                         $start = $id;
  81                 } while ( $start );
  82
  83                 Job::batchInsert( $jobs );
  84         }
  85
  86         protected function getPrefix() {
  87                 static $prefixes = array(
  88                         'pagelinks' => 'pl',
  89                         'imagelinks' => 'il',
  90                         'categorylinks' => 'cl',
  91                         'templatelinks' => 'tl',
  92                         'redirect' => 'rd',
  93                 );
  94
  95                 if ( is_null( $this->mPrefix ) ) {
  96                         $this->mPrefix = $prefixes[$this->mTable];
  97                         if ( is_null( $this->mPrefix ) ) {
  98                                 throw new MWException( "Invalid table type \"{$this->mTable}\" in " . __CLASS__ );
  99                         }
 100                 }
 101                 return $this->mPrefix;
 102         }
 103
 104         public function getFromField() {
 105                 return $this->getPrefix() . '_from';
 106         }
 107
 108         public function getToCondition() {
 109                 $prefix = $this->getPrefix();
 110                 switch ( $this->mTable ) {
 111                         case 'pagelinks':
 112                         case 'templatelinks':
 113                         case 'redirect':
 114                                 return array(
 115                                         "{$prefix}_namespace" => $this->mTitle->getNamespace(),
 116                                         "{$prefix}_title" => $this->mTitle->getDBkey()
 117                                 );
 118                         case 'imagelinks':
 119                                 return array( 'il_to' => $this->mTitle->getDBkey() );
 120                         case 'categorylinks':
 121                                 return array( 'cl_to' => $this->mTitle->getDBkey() );
 122                 }
 123                 throw new MWException( 'Invalid table type in ' . __CLASS__ );
 124         }
 125
 126         /**
 127          * Invalidate a set of IDs, right now
 128          */
 129         public function invalidateIDs( ResultWrapper $res ) {
 130                 global $wgUseFileCache, $wgUseSquid;
 131
 132                 if ( $res->numRows() == 0 ) {
 133                         return;
 134                 }
 135
 136                 $dbw = wfGetDB( DB_MASTER );
 137                 $timestamp = $dbw->timestamp();
 138                 $done = false;
 139
 140                 while ( !$done ) {
 141                         # Get all IDs in this query into an array
 142                         $ids = array();
 143                         for ( $i = 0; $i < $this->mRowsPerQuery; $i++ ) {
 144                                 $row = $res->fetchRow();
 145                                 if ( $row ) {
 146                                         $ids[] = $row[0];
 147                                 } else {
 148                                         $done = true;
 149                                         break;
 150                                 }
 151                         }
 152
 153                         if ( !count( $ids ) ) {
 154                                 break;
 155                         }
 156
 157                         # Update page_touched
 158                         $dbw->update( 'page',
 159                                 array( 'page_touched' => $timestamp ),
 160                                 array( 'page_id IN (' . $dbw->makeList( $ids ) . ')' ),
 161                                 __METHOD__
 162                         );
 163
 164                         # Update squid
 165                         if ( $wgUseSquid || $wgUseFileCache ) {
 166                                 $titles = Title::newFromIDs( $ids );
 167                                 if ( $wgUseSquid ) {
 168                                         $u = SquidUpdate::newFromTitles( $titles );
 169                                         $u->doUpdate();
 170                                 }
 171
 172                                 # Update file cache
 173                                 if  ( $wgUseFileCache ) {
 174                                         foreach ( $titles as $title ) {
 175                                                 $cm = new HTMLFileCache($title);
 176                                                 @unlink($cm->fileCacheName());
 177                                         }
 178                                 }
 179                         }
 180                 }
 181         }
 182 }
 183
 184 /**
 185  * @todo document (e.g. one-sentence top-level class description).
 186  * @ingroup JobQueue
 187  */
 188 class HTMLCacheUpdateJob extends Job {
 189         var $table, $start, $end;
 190
 191         /**
 192          * Construct a job
 193          * @param Title $title The title linked to
 194          * @param array $params Job parameters (table, start and end page_ids)
 195          * @param integer $id job_id
 196          */
 197         function __construct( $title, $params, $id = 0 ) {
 198                 parent::__construct( 'htmlCacheUpdate', $title, $params, $id );
 199                 $this->table = $params['table'];
 200                 $this->start = $params['start'];
 201                 $this->end = $params['end'];
 202         }
 203
 204         public function run() {
 205                 $update = new HTMLCacheUpdate( $this->title, $this->table );
 206
 207                 $fromField = $update->getFromField();
 208                 $conds = $update->getToCondition();
 209                 if ( $this->start ) {
 210                         $conds[] = "$fromField >= {$this->start}";
 211                 }
 212                 if ( $this->end ) {
 213                         $conds[] = "$fromField <= {$this->end}";
 214                 }
 215
 216                 $dbr = wfGetDB( DB_SLAVE );
 217                 $res = $dbr->select( $this->table, $fromField, $conds, __METHOD__ );
 218                 $update->invalidateIDs( $res );
 219
 220                 return true;
 221         }
 222 }