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 use Wikimedia\Rdbms\IDatabase;
  24 use MediaWiki\Linker\LinkTarget;
  25 use MediaWiki\MediaWikiServices;
  26
  27 /**
  28  * Cache for article titles (prefixed DB keys) and ids linked from one source
  29  *
  30  * @ingroup Cache
  31  */
  32 class LinkCache {
  33         /** @var HashBagOStuff */
  34         private $mGoodLinks;
  35         /** @var HashBagOStuff */
  36         private $mBadLinks;
  37         /** @var WANObjectCache */
  38         private $wanCache;
  39
  40         /** @var bool */
  41         private $mForUpdate = false;
  42
  43         /** @var TitleFormatter */
  44         private $titleFormatter;
  45
  46         /**
  47          * How many Titles to store. There are two caches, so the amount actually
  48          * stored in memory can be up to twice this.
  49          */
  50         const MAX_SIZE = 10000;
  51
  52         public function __construct( TitleFormatter $titleFormatter, WANObjectCache $cache ) {
  53                 $this->mGoodLinks = new HashBagOStuff( [ 'maxKeys' => self::MAX_SIZE ] );
  54                 $this->mBadLinks = new HashBagOStuff( [ 'maxKeys' => self::MAX_SIZE ] );
  55                 $this->wanCache = $cache;
  56                 $this->titleFormatter = $titleFormatter;
  57         }
  58
  59         /**
  60          * Get an instance of this class.
  61          *
  62          * @return LinkCache
  63          * @deprecated since 1.28, use MediaWikiServices instead
  64          */
  65         public static function singleton() {
  66                 return MediaWikiServices::getInstance()->getLinkCache();
  67         }
  68
  69         /**
  70          * General accessor to get/set whether the master DB should be used
  71          *
  72          * This used to also set the FOR UPDATE option (locking the rows read
  73          * in order to avoid link table inconsistency), which was later removed
  74          * for performance on wikis with a high edit rate.
  75          *
  76          * @param bool $update
  77          * @return bool
  78          */
  79         public function forUpdate( $update = null ) {
  80                 return wfSetVar( $this->mForUpdate, $update );
  81         }
  82
  83         /**
  84          * @param string $title Prefixed DB key
  85          * @return int Page ID or zero
  86          */
  87         public function getGoodLinkID( $title ) {
  88                 $info = $this->mGoodLinks->get( $title );
  89                 if ( !$info ) {
  90                         return 0;
  91                 }
  92                 return $info['id'];
  93         }
  94
  95         /**
  96          * Get a field of a title object from cache.
  97          * If this link is not a cached good title, it will return NULL.
  98          * @param LinkTarget $target
  99          * @param string $field ('length','redirect','revision','model')
 100          * @return string|int|null
 101          */
 102         public function getGoodLinkFieldObj( LinkTarget $target, $field ) {
 103                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 104                 $info = $this->mGoodLinks->get( $dbkey );
 105                 if ( !$info ) {
 106                         return null;
 107                 }
 108                 return $info[$field];
 109         }
 110
 111         /**
 112          * @param string $title Prefixed DB key
 113          * @return bool
 114          */
 115         public function isBadLink( $title ) {
 116                 // Use get() to ensure it records as used for LRU.
 117                 return $this->mBadLinks->get( $title ) !== false;
 118         }
 119
 120         /**
 121          * Add a link for the title to the link cache
 122          *
 123          * @param int $id Page's ID
 124          * @param LinkTarget $target
 125          * @param int $len Text's length
 126          * @param int $redir Whether the page is a redirect
 127          * @param int $revision Latest revision's ID
 128          * @param string|null $model Latest revision's content model ID
 129          * @param string|null $lang Language code of the page, if not the content language
 130          */
 131         public function addGoodLinkObj( $id, LinkTarget $target, $len = -1, $redir = null,
 132                 $revision = 0, $model = null, $lang = null
 133         ) {
 134                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 135                 $this->mGoodLinks->set( $dbkey, [
 136                         'id' => (int)$id,
 137                         'length' => (int)$len,
 138                         'redirect' => (int)$redir,
 139                         'revision' => (int)$revision,
 140                         'model' => $model ? (string)$model : null,
 141                         'lang' => $lang ? (string)$lang : null,
 142                 ] );
 143         }
 144
 145         /**
 146          * Same as above with better interface.
 147          * @since 1.19
 148          * @param LinkTarget $target
 149          * @param stdClass $row Object which has the fields page_id, page_is_redirect,
 150          *  page_latest and page_content_model
 151          */
 152         public function addGoodLinkObjFromRow( LinkTarget $target, $row ) {
 153                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 154                 $this->mGoodLinks->set( $dbkey, [
 155                         'id' => intval( $row->page_id ),
 156                         'length' => intval( $row->page_len ),
 157                         'redirect' => intval( $row->page_is_redirect ),
 158                         'revision' => intval( $row->page_latest ),
 159                         'model' => !empty( $row->page_content_model ) ? strval( $row->page_content_model ) : null,
 160                         'lang' => !empty( $row->page_lang ) ? strval( $row->page_lang ) : null,
 161                 ] );
 162         }
 163
 164         /**
 165          * @param LinkTarget $target
 166          */
 167         public function addBadLinkObj( LinkTarget $target ) {
 168                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 169                 if ( !$this->isBadLink( $dbkey ) ) {
 170                         $this->mBadLinks->set( $dbkey, 1 );
 171                 }
 172         }
 173
 174         /**
 175          * @param string $title Prefixed DB key
 176          */
 177         public function clearBadLink( $title ) {
 178                 $this->mBadLinks->delete( $title );
 179         }
 180
 181         /**
 182          * @param LinkTarget $target
 183          */
 184         public function clearLink( LinkTarget $target ) {
 185                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 186                 $this->mBadLinks->delete( $dbkey );
 187                 $this->mGoodLinks->delete( $dbkey );
 188         }
 189
 190         /**
 191          * Add a title to the link cache, return the page_id or zero if non-existent
 192          *
 193          * @deprecated since 1.27, unused
 194          * @param string $title Prefixed DB key
 195          * @return int Page ID or zero
 196          */
 197         public function addLink( $title ) {
 198                 $nt = Title::newFromDBkey( $title );
 199                 if ( !$nt ) {
 200                         return 0;
 201                 }
 202                 return $this->addLinkObj( $nt );
 203         }
 204
 205         /**
 206          * Fields that LinkCache needs to select
 207          *
 208          * @since 1.28
 209          * @return array
 210          */
 211         public static function getSelectFields() {
 212                 global $wgContentHandlerUseDB, $wgPageLanguageUseDB;
 213
 214                 $fields = [ 'page_id', 'page_len', 'page_is_redirect', 'page_latest' ];
 215                 if ( $wgContentHandlerUseDB ) {
 216                         $fields[] = 'page_content_model';
 217                 }
 218                 if ( $wgPageLanguageUseDB ) {
 219                         $fields[] = 'page_lang';
 220                 }
 221
 222                 return $fields;
 223         }
 224
 225         /**
 226          * Add a title to the link cache, return the page_id or zero if non-existent
 227          *
 228          * @param LinkTarget $nt LinkTarget object to add
 229          * @return int Page ID or zero
 230          */
 231         public function addLinkObj( LinkTarget $nt ) {
 232                 $key = $this->titleFormatter->getPrefixedDBkey( $nt );
 233                 if ( $this->isBadLink( $key ) || $nt->isExternal()
 234                         || $nt->inNamespace( NS_SPECIAL )
 235                 ) {
 236                         return 0;
 237                 }
 238                 $id = $this->getGoodLinkID( $key );
 239                 if ( $id != 0 ) {
 240                         return $id;
 241                 }
 242
 243                 if ( $key === '' ) {
 244                         return 0;
 245                 }
 246
 247                 // Cache template/file pages as they are less often viewed but heavily used
 248                 if ( $this->mForUpdate ) {
 249                         $row = $this->fetchPageRow( wfGetDB( DB_MASTER ), $nt );
 250                 } elseif ( $this->isCacheable( $nt ) ) {
 251                         // These pages are often transcluded heavily, so cache them
 252                         $cache = $this->wanCache;
 253                         $row = $cache->getWithSetCallback(
 254                                 $cache->makeKey( 'page', $nt->getNamespace(), sha1( $nt->getDBkey() ) ),
 255                                 $cache::TTL_DAY,
 256                                 function ( $curValue, &$ttl, array &$setOpts ) use ( $cache, $nt ) {
 257                                         $dbr = wfGetDB( DB_REPLICA );
 258                                         $setOpts += Database::getCacheSetOptions( $dbr );
 259
 260                                         $row = $this->fetchPageRow( $dbr, $nt );
 261                                         $mtime = $row ? wfTimestamp( TS_UNIX, $row->page_touched ) : false;
 262                                         $ttl = $cache->adaptiveTTL( $mtime, $ttl );
 263
 264                                         return $row;
 265                                 }
 266                         );
 267                 } else {
 268                         $row = $this->fetchPageRow( wfGetDB( DB_REPLICA ), $nt );
 269                 }
 270
 271                 if ( $row ) {
 272                         $this->addGoodLinkObjFromRow( $nt, $row );
 273                         $id = intval( $row->page_id );
 274                 } else {
 275                         $this->addBadLinkObj( $nt );
 276                         $id = 0;
 277                 }
 278
 279                 return $id;
 280         }
 281
 282         /**
 283          * @param WANObjectCache $cache
 284          * @param TitleValue $t
 285          * @return string[]
 286          * @since 1.28
 287          */
 288         public function getMutableCacheKeys( WANObjectCache $cache, TitleValue $t ) {
 289                 if ( $this->isCacheable( $t ) ) {
 290                         return [ $cache->makeKey( 'page', $t->getNamespace(), sha1( $t->getDBkey() ) ) ];
 291                 }
 292
 293                 return [];
 294         }
 295
 296         private function isCacheable( LinkTarget $title ) {
 297                 return ( $title->inNamespace( NS_TEMPLATE ) || $title->inNamespace( NS_FILE ) );
 298         }
 299
 300         private function fetchPageRow( IDatabase $db, LinkTarget $nt ) {
 301                 $fields = self::getSelectFields();
 302                 if ( $this->isCacheable( $nt ) ) {
 303                         $fields[] = 'page_touched';
 304                 }
 305
 306                 return $db->selectRow(
 307                         'page',
 308                         $fields,
 309                         [ 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ],
 310                         __METHOD__
 311                 );
 312         }
 313
 314         /**
 315          * Purge the link cache for a title
 316          *
 317          * @param LinkTarget $title
 318          * @since 1.28
 319          */
 320         public function invalidateTitle( LinkTarget $title ) {
 321                 if ( $this->isCacheable( $title ) ) {
 322                         $cache = ObjectCache::getMainWANInstance();
 323                         $cache->delete(
 324                                 $cache->makeKey( 'page', $title->getNamespace(), sha1( $title->getDBkey() ) )
 325                         );
 326                 }
 327         }
 328
 329         /**
 330          * Clears cache
 331          */
 332         public function clear() {
 333                 $this->mGoodLinks->clear();
 334                 $this->mBadLinks->clear();
 335         }
 336 }