includes/cache/LinkCache.php

   1 <?php
   2 /**
   3  * Page existence cache.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache
  22  */
  23
  24 use Wikimedia\Rdbms\Database;
  25 use Wikimedia\Rdbms\IDatabase;
  26 use MediaWiki\Linker\LinkTarget;
  27 use MediaWiki\MediaWikiServices;
  28
  29 /**
  30  * Cache for article titles (prefixed DB keys) and ids linked from one source
  31  *
  32  * @ingroup Cache
  33  */
  34 class LinkCache {
  35         /** @var MapCacheLRU */
  36         private $goodLinks;
  37         /** @var MapCacheLRU */
  38         private $badLinks;
  39         /** @var WANObjectCache */
  40         private $wanCache;
  41
  42         /** @var bool */
  43         private $mForUpdate = false;
  44
  45         /** @var TitleFormatter */
  46         private $titleFormatter;
  47
  48         /** @var NamespaceInfo */
  49         private $nsInfo;
  50
  51         /**
  52          * How many Titles to store. There are two caches, so the amount actually
  53          * stored in memory can be up to twice this.
  54          */
  55         const MAX_SIZE = 10000;
  56
  57         public function __construct(
  58                 TitleFormatter $titleFormatter,
  59                 WANObjectCache $cache,
  60                 NamespaceInfo $nsInfo = null
  61         ) {
  62                 if ( !$nsInfo ) {
  63                         wfDeprecated( __METHOD__ . ' with no NamespaceInfo argument', '1.34' );
  64                         $nsInfo = MediaWikiServices::getInstance()->getNamespaceInfo();
  65                 }
  66                 $this->goodLinks = new MapCacheLRU( self::MAX_SIZE );
  67                 $this->badLinks = new MapCacheLRU( self::MAX_SIZE );
  68                 $this->wanCache = $cache;
  69                 $this->titleFormatter = $titleFormatter;
  70                 $this->nsInfo = $nsInfo;
  71         }
  72
  73         /**
  74          * Get an instance of this class.
  75          *
  76          * @return LinkCache
  77          * @deprecated since 1.28, use MediaWikiServices instead
  78          */
  79         public static function singleton() {
  80                 return MediaWikiServices::getInstance()->getLinkCache();
  81         }
  82
  83         /**
  84          * General accessor to get/set whether the master DB should be used
  85          *
  86          * This used to also set the FOR UPDATE option (locking the rows read
  87          * in order to avoid link table inconsistency), which was later removed
  88          * for performance on wikis with a high edit rate.
  89          *
  90          * @param bool|null $update
  91          * @return bool
  92          * @deprecated Since 1.34
  93          */
  94         public function forUpdate( $update = null ) {
  95                 return wfSetVar( $this->mForUpdate, $update );
  96         }
  97
  98         /**
  99          * @param string $title Prefixed DB key
 100          * @return int Page ID or zero
 101          */
 102         public function getGoodLinkID( $title ) {
 103                 $info = $this->goodLinks->get( $title );
 104                 if ( !$info ) {
 105                         return 0;
 106                 }
 107                 return $info['id'];
 108         }
 109
 110         /**
 111          * Get a field of a title object from cache.
 112          * If this link is not a cached good title, it will return NULL.
 113          * @param LinkTarget $target
 114          * @param string $field ('length','redirect','revision','model')
 115          * @return string|int|null
 116          */
 117         public function getGoodLinkFieldObj( LinkTarget $target, $field ) {
 118                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 119                 $info = $this->goodLinks->get( $dbkey );
 120                 if ( !$info ) {
 121                         return null;
 122                 }
 123                 return $info[$field];
 124         }
 125
 126         /**
 127          * @param string $title Prefixed DB key
 128          * @return bool
 129          */
 130         public function isBadLink( $title ) {
 131                 // Use get() to ensure it records as used for LRU.
 132                 return $this->badLinks->has( $title );
 133         }
 134
 135         /**
 136          * Add a link for the title to the link cache
 137          *
 138          * @param int $id Page's ID
 139          * @param LinkTarget $target
 140          * @param int $len Text's length
 141          * @param int|null $redir Whether the page is a redirect
 142          * @param int $revision Latest revision's ID
 143          * @param string|null $model Latest revision's content model ID
 144          * @param string|null $lang Language code of the page, if not the content language
 145          */
 146         public function addGoodLinkObj( $id, LinkTarget $target, $len = -1, $redir = null,
 147                 $revision = 0, $model = null, $lang = null
 148         ) {
 149                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 150                 $this->goodLinks->set( $dbkey, [
 151                         'id' => (int)$id,
 152                         'length' => (int)$len,
 153                         'redirect' => (int)$redir,
 154                         'revision' => (int)$revision,
 155                         'model' => $model ? (string)$model : null,
 156                         'lang' => $lang ? (string)$lang : null,
 157                         'restrictions' => null
 158                 ] );
 159         }
 160
 161         /**
 162          * Same as above with better interface.
 163          * @since 1.19
 164          * @param LinkTarget $target
 165          * @param stdClass $row Object which has the fields page_id, page_is_redirect,
 166          *  page_latest and page_content_model
 167          */
 168         public function addGoodLinkObjFromRow( LinkTarget $target, $row ) {
 169                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 170                 $this->goodLinks->set( $dbkey, [
 171                         'id' => intval( $row->page_id ),
 172                         'length' => intval( $row->page_len ),
 173                         'redirect' => intval( $row->page_is_redirect ),
 174                         'revision' => intval( $row->page_latest ),
 175                         'model' => !empty( $row->page_content_model )
 176                                 ? strval( $row->page_content_model )
 177                                 : null,
 178                         'lang' => !empty( $row->page_lang )
 179                                 ? strval( $row->page_lang )
 180                                 : null,
 181                         'restrictions' => !empty( $row->page_restrictions )
 182                                 ? strval( $row->page_restrictions )
 183                                 : null
 184                 ] );
 185         }
 186
 187         /**
 188          * @param LinkTarget $target
 189          */
 190         public function addBadLinkObj( LinkTarget $target ) {
 191                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 192                 if ( !$this->isBadLink( $dbkey ) ) {
 193                         $this->badLinks->set( $dbkey, 1 );
 194                 }
 195         }
 196
 197         /**
 198          * @param string $title Prefixed DB key
 199          */
 200         public function clearBadLink( $title ) {
 201                 $this->badLinks->clear( $title );
 202         }
 203
 204         /**
 205          * @param LinkTarget $target
 206          */
 207         public function clearLink( LinkTarget $target ) {
 208                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 209                 $this->badLinks->clear( $dbkey );
 210                 $this->goodLinks->clear( $dbkey );
 211         }
 212
 213         /**
 214          * Fields that LinkCache needs to select
 215          *
 216          * @since 1.28
 217          * @return array
 218          */
 219         public static function getSelectFields() {
 220                 global $wgContentHandlerUseDB, $wgPageLanguageUseDB;
 221
 222                 $fields = [
 223                         'page_id',
 224                         'page_len',
 225                         'page_is_redirect',
 226                         'page_latest',
 227                         'page_restrictions'
 228                 ];
 229                 if ( $wgContentHandlerUseDB ) {
 230                         $fields[] = 'page_content_model';
 231                 }
 232                 if ( $wgPageLanguageUseDB ) {
 233                         $fields[] = 'page_lang';
 234                 }
 235
 236                 return $fields;
 237         }
 238
 239         /**
 240          * Add a title to the link cache, return the page_id or zero if non-existent
 241          *
 242          * @param LinkTarget $nt LinkTarget object to add
 243          * @return int Page ID or zero
 244          */
 245         public function addLinkObj( LinkTarget $nt ) {
 246                 $key = $this->titleFormatter->getPrefixedDBkey( $nt );
 247                 if ( $this->isBadLink( $key ) || $nt->isExternal() || $nt->getNamespace() < 0 ) {
 248                         return 0;
 249                 }
 250                 $id = $this->getGoodLinkID( $key );
 251                 if ( $id != 0 ) {
 252                         return $id;
 253                 }
 254
 255                 if ( $key === '' ) {
 256                         return 0;
 257                 }
 258
 259                 // Cache template/file pages as they are less often viewed but heavily used
 260                 if ( $this->mForUpdate ) {
 261                         $row = $this->fetchPageRow( wfGetDB( DB_MASTER ), $nt );
 262                 } elseif ( $this->isCacheable( $nt ) ) {
 263                         // These pages are often transcluded heavily, so cache them
 264                         $cache = $this->wanCache;
 265                         $row = $cache->getWithSetCallback(
 266                                 $cache->makeKey( 'page', $nt->getNamespace(), sha1( $nt->getDBkey() ) ),
 267                                 $cache::TTL_DAY,
 268                                 function ( $curValue, &$ttl, array &$setOpts ) use ( $cache, $nt ) {
 269                                         $dbr = wfGetDB( DB_REPLICA );
 270                                         $setOpts += Database::getCacheSetOptions( $dbr );
 271
 272                                         $row = $this->fetchPageRow( $dbr, $nt );
 273                                         $mtime = $row ? wfTimestamp( TS_UNIX, $row->page_touched ) : false;
 274                                         $ttl = $cache->adaptiveTTL( $mtime, $ttl );
 275
 276                                         return $row;
 277                                 }
 278                         );
 279                 } else {
 280                         $row = $this->fetchPageRow( wfGetDB( DB_REPLICA ), $nt );
 281                 }
 282
 283                 if ( $row ) {
 284                         $this->addGoodLinkObjFromRow( $nt, $row );
 285                         $id = intval( $row->page_id );
 286                 } else {
 287                         $this->addBadLinkObj( $nt );
 288                         $id = 0;
 289                 }
 290
 291                 return $id;
 292         }
 293
 294         /**
 295          * @param WANObjectCache $cache
 296          * @param LinkTarget $t
 297          * @return string[]
 298          * @since 1.28
 299          */
 300         public function getMutableCacheKeys( WANObjectCache $cache, LinkTarget $t ) {
 301                 if ( $this->isCacheable( $t ) ) {
 302                         return [ $cache->makeKey( 'page', $t->getNamespace(), sha1( $t->getDBkey() ) ) ];
 303                 }
 304
 305                 return [];
 306         }
 307
 308         private function isCacheable( LinkTarget $title ) {
 309                 $ns = $title->getNamespace();
 310                 if ( in_array( $ns, [ NS_TEMPLATE, NS_FILE, NS_CATEGORY, NS_MEDIAWIKI ] ) ) {
 311                         return true;
 312                 }
 313                 // Focus on transcluded pages more than the main content
 314                 if ( $this->nsInfo->isContent( $ns ) ) {
 315                         return false;
 316                 }
 317                 // Non-talk extension namespaces (e.g. NS_MODULE)
 318                 return ( $ns >= 100 && $this->nsInfo->isSubject( $ns ) );
 319         }
 320
 321         private function fetchPageRow( IDatabase $db, LinkTarget $nt ) {
 322                 $fields = self::getSelectFields();
 323                 if ( $this->isCacheable( $nt ) ) {
 324                         $fields[] = 'page_touched';
 325                 }
 326
 327                 return $db->selectRow(
 328                         'page',
 329                         $fields,
 330                         [ 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ],
 331                         __METHOD__
 332                 );
 333         }
 334
 335         /**
 336          * Purge the link cache for a title
 337          *
 338          * @param LinkTarget $title
 339          * @since 1.28
 340          */
 341         public function invalidateTitle( LinkTarget $title ) {
 342                 if ( $this->isCacheable( $title ) ) {
 343                         $cache = $this->wanCache;
 344                         $cache->delete(
 345                                 $cache->makeKey( 'page', $title->getNamespace(), sha1( $title->getDBkey() ) )
 346                         );
 347                 }
 348         }
 349
 350         /**
 351          * Clears cache
 352          */
 353         public function clear() {
 354                 $this->goodLinks->clear();
 355                 $this->badLinks->clear();
 356         }
 357 }