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 HashBagOStuff */
  36         private $mGoodLinks;
  37         /** @var HashBagOStuff */
  38         private $mBadLinks;
  39         /** @var WANObjectCache */
  40         private $wanCache;
  41
  42         /** @var bool */
  43         private $mForUpdate = false;
  44
  45         /** @var TitleFormatter */
  46         private $titleFormatter;
  47
  48         /**
  49          * How many Titles to store. There are two caches, so the amount actually
  50          * stored in memory can be up to twice this.
  51          */
  52         const MAX_SIZE = 10000;
  53
  54         public function __construct( TitleFormatter $titleFormatter, WANObjectCache $cache ) {
  55                 $this->mGoodLinks = new HashBagOStuff( [ 'maxKeys' => self::MAX_SIZE ] );
  56                 $this->mBadLinks = new HashBagOStuff( [ 'maxKeys' => self::MAX_SIZE ] );
  57                 $this->wanCache = $cache;
  58                 $this->titleFormatter = $titleFormatter;
  59         }
  60
  61         /**
  62          * Get an instance of this class.
  63          *
  64          * @return LinkCache
  65          * @deprecated since 1.28, use MediaWikiServices instead
  66          */
  67         public static function singleton() {
  68                 return MediaWikiServices::getInstance()->getLinkCache();
  69         }
  70
  71         /**
  72          * General accessor to get/set whether the master DB should be used
  73          *
  74          * This used to also set the FOR UPDATE option (locking the rows read
  75          * in order to avoid link table inconsistency), which was later removed
  76          * for performance on wikis with a high edit rate.
  77          *
  78          * @param bool $update
  79          * @return bool
  80          */
  81         public function forUpdate( $update = null ) {
  82                 return wfSetVar( $this->mForUpdate, $update );
  83         }
  84
  85         /**
  86          * @param string $title Prefixed DB key
  87          * @return int Page ID or zero
  88          */
  89         public function getGoodLinkID( $title ) {
  90                 $info = $this->mGoodLinks->get( $title );
  91                 if ( !$info ) {
  92                         return 0;
  93                 }
  94                 return $info['id'];
  95         }
  96
  97         /**
  98          * Get a field of a title object from cache.
  99          * If this link is not a cached good title, it will return NULL.
 100          * @param LinkTarget $target
 101          * @param string $field ('length','redirect','revision','model')
 102          * @return string|int|null
 103          */
 104         public function getGoodLinkFieldObj( LinkTarget $target, $field ) {
 105                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 106                 $info = $this->mGoodLinks->get( $dbkey );
 107                 if ( !$info ) {
 108                         return null;
 109                 }
 110                 return $info[$field];
 111         }
 112
 113         /**
 114          * @param string $title Prefixed DB key
 115          * @return bool
 116          */
 117         public function isBadLink( $title ) {
 118                 // Use get() to ensure it records as used for LRU.
 119                 return $this->mBadLinks->get( $title ) !== false;
 120         }
 121
 122         /**
 123          * Add a link for the title to the link cache
 124          *
 125          * @param int $id Page's ID
 126          * @param LinkTarget $target
 127          * @param int $len Text's length
 128          * @param int $redir Whether the page is a redirect
 129          * @param int $revision Latest revision's ID
 130          * @param string|null $model Latest revision's content model ID
 131          * @param string|null $lang Language code of the page, if not the content language
 132          */
 133         public function addGoodLinkObj( $id, LinkTarget $target, $len = -1, $redir = null,
 134                 $revision = 0, $model = null, $lang = null
 135         ) {
 136                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 137                 $this->mGoodLinks->set( $dbkey, [
 138                         'id' => (int)$id,
 139                         'length' => (int)$len,
 140                         'redirect' => (int)$redir,
 141                         'revision' => (int)$revision,
 142                         'model' => $model ? (string)$model : null,
 143                         'lang' => $lang ? (string)$lang : null,
 144                 ] );
 145         }
 146
 147         /**
 148          * Same as above with better interface.
 149          * @since 1.19
 150          * @param LinkTarget $target
 151          * @param stdClass $row Object which has the fields page_id, page_is_redirect,
 152          *  page_latest and page_content_model
 153          */
 154         public function addGoodLinkObjFromRow( LinkTarget $target, $row ) {
 155                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 156                 $this->mGoodLinks->set( $dbkey, [
 157                         'id' => intval( $row->page_id ),
 158                         'length' => intval( $row->page_len ),
 159                         'redirect' => intval( $row->page_is_redirect ),
 160                         'revision' => intval( $row->page_latest ),
 161                         'model' => !empty( $row->page_content_model ) ? strval( $row->page_content_model ) : null,
 162                         'lang' => !empty( $row->page_lang ) ? strval( $row->page_lang ) : null,
 163                 ] );
 164         }
 165
 166         /**
 167          * @param LinkTarget $target
 168          */
 169         public function addBadLinkObj( LinkTarget $target ) {
 170                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 171                 if ( !$this->isBadLink( $dbkey ) ) {
 172                         $this->mBadLinks->set( $dbkey, 1 );
 173                 }
 174         }
 175
 176         /**
 177          * @param string $title Prefixed DB key
 178          */
 179         public function clearBadLink( $title ) {
 180                 $this->mBadLinks->delete( $title );
 181         }
 182
 183         /**
 184          * @param LinkTarget $target
 185          */
 186         public function clearLink( LinkTarget $target ) {
 187                 $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
 188                 $this->mBadLinks->delete( $dbkey );
 189                 $this->mGoodLinks->delete( $dbkey );
 190         }
 191
 192         /**
 193          * Add a title to the link cache, return the page_id or zero if non-existent
 194          *
 195          * @deprecated since 1.27, unused
 196          * @param string $title Prefixed DB key
 197          * @return int Page ID or zero
 198          */
 199         public function addLink( $title ) {
 200                 $nt = Title::newFromDBkey( $title );
 201                 if ( !$nt ) {
 202                         return 0;
 203                 }
 204                 return $this->addLinkObj( $nt );
 205         }
 206
 207         /**
 208          * Fields that LinkCache needs to select
 209          *
 210          * @since 1.28
 211          * @return array
 212          */
 213         public static function getSelectFields() {
 214                 global $wgContentHandlerUseDB, $wgPageLanguageUseDB;
 215
 216                 $fields = [ 'page_id', 'page_len', 'page_is_redirect', 'page_latest' ];
 217                 if ( $wgContentHandlerUseDB ) {
 218                         $fields[] = 'page_content_model';
 219                 }
 220                 if ( $wgPageLanguageUseDB ) {
 221                         $fields[] = 'page_lang';
 222                 }
 223
 224                 return $fields;
 225         }
 226
 227         /**
 228          * Add a title to the link cache, return the page_id or zero if non-existent
 229          *
 230          * @param LinkTarget $nt LinkTarget object to add
 231          * @return int Page ID or zero
 232          */
 233         public function addLinkObj( LinkTarget $nt ) {
 234                 $key = $this->titleFormatter->getPrefixedDBkey( $nt );
 235                 if ( $this->isBadLink( $key ) || $nt->isExternal()
 236                         || $nt->inNamespace( NS_SPECIAL )
 237                 ) {
 238                         return 0;
 239                 }
 240                 $id = $this->getGoodLinkID( $key );
 241                 if ( $id != 0 ) {
 242                         return $id;
 243                 }
 244
 245                 if ( $key === '' ) {
 246                         return 0;
 247                 }
 248
 249                 // Cache template/file pages as they are less often viewed but heavily used
 250                 if ( $this->mForUpdate ) {
 251                         $row = $this->fetchPageRow( wfGetDB( DB_MASTER ), $nt );
 252                 } elseif ( $this->isCacheable( $nt ) ) {
 253                         // These pages are often transcluded heavily, so cache them
 254                         $cache = $this->wanCache;
 255                         $row = $cache->getWithSetCallback(
 256                                 $cache->makeKey( 'page', $nt->getNamespace(), sha1( $nt->getDBkey() ) ),
 257                                 $cache::TTL_DAY,
 258                                 function ( $curValue, &$ttl, array &$setOpts ) use ( $cache, $nt ) {
 259                                         $dbr = wfGetDB( DB_REPLICA );
 260                                         $setOpts += Database::getCacheSetOptions( $dbr );
 261
 262                                         $row = $this->fetchPageRow( $dbr, $nt );
 263                                         $mtime = $row ? wfTimestamp( TS_UNIX, $row->page_touched ) : false;
 264                                         $ttl = $cache->adaptiveTTL( $mtime, $ttl );
 265
 266                                         return $row;
 267                                 }
 268                         );
 269                 } else {
 270                         $row = $this->fetchPageRow( wfGetDB( DB_REPLICA ), $nt );
 271                 }
 272
 273                 if ( $row ) {
 274                         $this->addGoodLinkObjFromRow( $nt, $row );
 275                         $id = intval( $row->page_id );
 276                 } else {
 277                         $this->addBadLinkObj( $nt );
 278                         $id = 0;
 279                 }
 280
 281                 return $id;
 282         }
 283
 284         /**
 285          * @param WANObjectCache $cache
 286          * @param TitleValue $t
 287          * @return string[]
 288          * @since 1.28
 289          */
 290         public function getMutableCacheKeys( WANObjectCache $cache, TitleValue $t ) {
 291                 if ( $this->isCacheable( $t ) ) {
 292                         return [ $cache->makeKey( 'page', $t->getNamespace(), sha1( $t->getDBkey() ) ) ];
 293                 }
 294
 295                 return [];
 296         }
 297
 298         private function isCacheable( LinkTarget $title ) {
 299                 return ( $title->inNamespace( NS_TEMPLATE ) || $title->inNamespace( NS_FILE ) );
 300         }
 301
 302         private function fetchPageRow( IDatabase $db, LinkTarget $nt ) {
 303                 $fields = self::getSelectFields();
 304                 if ( $this->isCacheable( $nt ) ) {
 305                         $fields[] = 'page_touched';
 306                 }
 307
 308                 return $db->selectRow(
 309                         'page',
 310                         $fields,
 311                         [ 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ],
 312                         __METHOD__
 313                 );
 314         }
 315
 316         /**
 317          * Purge the link cache for a title
 318          *
 319          * @param LinkTarget $title
 320          * @since 1.28
 321          */
 322         public function invalidateTitle( LinkTarget $title ) {
 323                 if ( $this->isCacheable( $title ) ) {
 324                         $cache = ObjectCache::getMainWANInstance();
 325                         $cache->delete(
 326                                 $cache->makeKey( 'page', $title->getNamespace(), sha1( $title->getDBkey() ) )
 327                         );
 328                 }
 329         }
 330
 331         /**
 332          * Clears cache
 333          */
 334         public function clear() {
 335                 $this->mGoodLinks->clear();
 336                 $this->mBadLinks->clear();
 337         }
 338 }