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 /**
  25  * Cache for article titles (prefixed DB keys) and ids linked from one source
  26  *
  27  * @ingroup Cache
  28  */
  29 class LinkCache {
  30         /**
  31          * @var MapCacheLRU
  32          */
  33         private $mGoodLinks;
  34         /**
  35          * @var MapCacheLRU
  36          */
  37         private $mBadLinks;
  38         private $mForUpdate = false;
  39
  40         /**
  41          * How many Titles to store. There are two caches, so the amount actually
  42          * stored in memory can be up to twice this.
  43          */
  44         const MAX_SIZE = 10000;
  45
  46         /**
  47          * @var LinkCache
  48          */
  49         protected static $instance;
  50
  51         public function __construct() {
  52                 $this->mGoodLinks = new MapCacheLRU( self::MAX_SIZE );
  53                 $this->mBadLinks = new MapCacheLRU( self::MAX_SIZE );
  54         }
  55
  56         /**
  57          * Get an instance of this class.
  58          *
  59          * @return LinkCache
  60          */
  61         public static function &singleton() {
  62                 if ( !self::$instance ) {
  63                         self::$instance = new LinkCache;
  64                 }
  65
  66                 return self::$instance;
  67         }
  68
  69         /**
  70          * Destroy the singleton instance
  71          *
  72          * A new one will be created next time singleton() is called.
  73          *
  74          * @since 1.22
  75          */
  76         public static function destroySingleton() {
  77                 self::$instance = null;
  78         }
  79
  80         /**
  81          * Set the singleton instance to a given object.
  82          *
  83          * Since we do not have an interface for LinkCache, you have to be sure the
  84          * given object implements all the LinkCache public methods.
  85          *
  86          * @param LinkCache $instance
  87          * @since 1.22
  88          */
  89         public static function setSingleton( LinkCache $instance ) {
  90                 self::$instance = $instance;
  91         }
  92
  93         /**
  94          * General accessor to get/set whether the master DB should be used
  95          *
  96          * This used to also set the FOR UPDATE option (locking the rows read
  97          * in order to avoid link table inconsistency), which was later removed
  98          * for performance on wikis with a high edit rate.
  99          *
 100          * @param bool $update
 101          * @return bool
 102          */
 103         public function forUpdate( $update = null ) {
 104                 return wfSetVar( $this->mForUpdate, $update );
 105         }
 106
 107         /**
 108          * @param string $title
 109          * @return int Page ID or zero
 110          */
 111         public function getGoodLinkID( $title ) {
 112                 if ( !$this->mGoodLinks->has( $title ) ) {
 113                         return 0;
 114                 }
 115                 $info = $this->mGoodLinks->get( $title );
 116                 return $info['id'];
 117         }
 118
 119         /**
 120          * Get a field of a title object from cache.
 121          * If this link is not a cached good title, it will return NULL.
 122          * @param Title $title
 123          * @param string $field ('length','redirect','revision','model')
 124          * @return string|int|null
 125          */
 126         public function getGoodLinkFieldObj( $title, $field ) {
 127                 $dbkey = $title->getPrefixedDBkey();
 128                 if ( !$this->mGoodLinks->has( $dbkey ) ) {
 129                         return null;
 130                 }
 131                 $info = $this->mGoodLinks->get( $dbkey );
 132                 return $info[$field];
 133         }
 134
 135         /**
 136          * @param string $title
 137          * @return bool
 138          */
 139         public function isBadLink( $title ) {
 140                 // Use get() to ensure it records as used for LRU.
 141                 return $this->mBadLinks->get( $title ) !== null;
 142         }
 143
 144         /**
 145          * Add a link for the title to the link cache
 146          *
 147          * @param int $id Page's ID
 148          * @param Title $title
 149          * @param int $len Text's length
 150          * @param int $redir Whether the page is a redirect
 151          * @param int $revision Latest revision's ID
 152          * @param string|null $model Latest revision's content model ID
 153          */
 154         public function addGoodLinkObj( $id, Title $title, $len = -1, $redir = null,
 155                 $revision = 0, $model = null
 156         ) {
 157                 $dbkey = $title->getPrefixedDBkey();
 158                 $this->mGoodLinks->set( $dbkey, array(
 159                         'id' => (int)$id,
 160                         'length' => (int)$len,
 161                         'redirect' => (int)$redir,
 162                         'revision' => (int)$revision,
 163                         'model' => $model ? (string)$model : null,
 164                 ) );
 165         }
 166
 167         /**
 168          * Same as above with better interface.
 169          * @since 1.19
 170          * @param Title $title
 171          * @param stdClass $row Object which has the fields page_id, page_is_redirect,
 172          *  page_latest and page_content_model
 173          */
 174         public function addGoodLinkObjFromRow( Title $title, $row ) {
 175                 $dbkey = $title->getPrefixedDBkey();
 176                 $this->mGoodLinks->set( $dbkey, array(
 177                         'id' => intval( $row->page_id ),
 178                         'length' => intval( $row->page_len ),
 179                         'redirect' => intval( $row->page_is_redirect ),
 180                         'revision' => intval( $row->page_latest ),
 181                         'model' => !empty( $row->page_content_model ) ? strval( $row->page_content_model ) : null,
 182                 ) );
 183         }
 184
 185         /**
 186          * @param Title $title
 187          */
 188         public function addBadLinkObj( Title $title ) {
 189                 $dbkey = $title->getPrefixedDBkey();
 190                 if ( !$this->isBadLink( $dbkey ) ) {
 191                         $this->mBadLinks->set( $dbkey, 1 );
 192                 }
 193         }
 194
 195         public function clearBadLink( $title ) {
 196                 $this->mBadLinks->clear( array( $title ) );
 197         }
 198
 199         /**
 200          * @param Title $title
 201          */
 202         public function clearLink( $title ) {
 203                 $dbkey = $title->getPrefixedDBkey();
 204                 $this->mBadLinks->clear( array( $dbkey ) );
 205                 $this->mGoodLinks->clear( array( $dbkey ) );
 206         }
 207
 208         /**
 209          * Add a title to the link cache, return the page_id or zero if non-existent
 210          *
 211          * @param string $title Title to add
 212          * @return int Page ID or zero
 213          */
 214         public function addLink( $title ) {
 215                 $nt = Title::newFromDBkey( $title );
 216                 if ( !$nt ) {
 217                         return 0;
 218                 }
 219                 return $this->addLinkObj( $nt );
 220         }
 221
 222         /**
 223          * Add a title to the link cache, return the page_id or zero if non-existent
 224          *
 225          * @param Title $nt Title object to add
 226          * @return int Page ID or zero
 227          */
 228         public function addLinkObj( Title $nt ) {
 229                 global $wgContentHandlerUseDB;
 230
 231                 $key = $nt->getPrefixedDBkey();
 232                 if ( $this->isBadLink( $key ) || $nt->isExternal() ) {
 233                         return 0;
 234                 }
 235                 $id = $this->getGoodLinkID( $key );
 236                 if ( $id != 0 ) {
 237                         return $id;
 238                 }
 239
 240                 if ( $key === '' ) {
 241                         return 0;
 242                 }
 243
 244                 // Some fields heavily used for linking...
 245                 $db = $this->mForUpdate ? wfGetDB( DB_MASTER ) : wfGetDB( DB_SLAVE );
 246
 247                 $fields = array( 'page_id', 'page_len', 'page_is_redirect', 'page_latest' );
 248                 if ( $wgContentHandlerUseDB ) {
 249                         $fields[] = 'page_content_model';
 250                 }
 251
 252                 $row = $db->selectRow( 'page', $fields,
 253                         array( 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ),
 254                         __METHOD__
 255                 );
 256
 257                 if ( $row !== false ) {
 258                         $this->addGoodLinkObjFromRow( $nt, $row );
 259                         $id = intval( $row->page_id );
 260                 } else {
 261                         $this->addBadLinkObj( $nt );
 262                         $id = 0;
 263                 }
 264
 265                 return $id;
 266         }
 267
 268         /**
 269          * Clears cache
 270          */
 271         public function clear() {
 272                 $this->mGoodLinks->clear();
 273                 $this->mBadLinks->clear();
 274         }
 275 }