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