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                 $this->mBadLinks = new MapCacheLRU( self::MAX_SIZE );
  54         }
  55
  56         /**
  57          * Get an instance of this class.
  58          *
  59          * @return LinkCache
  60          */
  61         static function &singleton() {
  62                 if ( self::$instance ) {
  63                         return self::$instance;
  64                 }
  65                 self::$instance = new LinkCache;
  66
  67                 return self::$instance;
  68         }
  69
  70         /**
  71          * Destroy the singleton instance, a new one will be created next time
  72          * singleton() is called.
  73          * @since 1.22
  74          */
  75         static function destroySingleton() {
  76                 self::$instance = null;
  77         }
  78
  79         /**
  80          * Set the singleton instance to a given object.
  81          * Since we do not have an interface for LinkCache, you have to be sure the
  82          * given object implements all the LinkCache public methods.
  83          * @param LinkCache $instance
  84          * @since 1.22
  85          */
  86         static function setSingleton( LinkCache $instance ) {
  87                 self::$instance = $instance;
  88         }
  89
  90         /**
  91          * General accessor to get/set whether the master DB should be used
  92          *
  93          * This used to also set the FOR UPDATE option (locking the rows read
  94          * in order to avoid link table inconsistency), which was later removed
  95          * for performance on wikis with a high edit rate.
  96          *
  97          * @param bool $update
  98          * @return bool
  99          */
 100         public function forUpdate( $update = null ) {
 101                 return wfSetVar( $this->mForUpdate, $update );
 102         }
 103
 104         /**
 105          * @param string $title
 106          * @return int
 107          */
 108         public function getGoodLinkID( $title ) {
 109                 if ( $this->mGoodLinks->has( $title ) ) {
 110                         $info = $this->mGoodLinks->get( $title );
 111                         return $info['id'];
 112                 } else {
 113                         return 0;
 114                 }
 115         }
 116
 117         /**
 118          * Get a field of a title object from cache.
 119          * If this link is not good, it will return NULL.
 120          * @param Title $title
 121          * @param string $field ('length','redirect','revision','model')
 122          * @return string|null
 123          */
 124         public function getGoodLinkFieldObj( $title, $field ) {
 125                 $dbkey = $title->getPrefixedDBkey();
 126                 if ( $this->mGoodLinks->has( $dbkey ) ) {
 127                         $info = $this->mGoodLinks->get( $dbkey );
 128                         return $info[$field];
 129                 } else {
 130                         return null;
 131                 }
 132         }
 133
 134         /**
 135          * @param string $title
 136          * @return bool
 137          */
 138         public function isBadLink( $title ) {
 139                 // We need to use get here since has will not call ping.
 140                 return $this->mBadLinks->get( $title ) !== null;
 141         }
 142
 143         /**
 144          * Add a link for the title to the link cache
 145          *
 146          * @param int $id Page's ID
 147          * @param Title $title
 148          * @param int $len Text's length
 149          * @param int $redir Whether the page is a redirect
 150          * @param int $revision Latest revision's ID
 151          * @param string|null $model Latest revision's content model ID
 152          */
 153         public function addGoodLinkObj( $id, $title, $len = -1, $redir = null,
 154                 $revision = 0, $model = null
 155         ) {
 156                 $dbkey = $title->getPrefixedDBkey();
 157                 $this->mGoodLinks->set( $dbkey, array(
 158                         'id' => (int)$id,
 159                         'length' => (int)$len,
 160                         'redirect' => (int)$redir,
 161                         'revision' => (int)$revision,
 162                         'model' => $model ? (string)$model : null,
 163                 ) );
 164         }
 165
 166         /**
 167          * Same as above with better interface.
 168          * @since 1.19
 169          * @param Title $title
 170          * @param stdClass $row Object which has the fields page_id, page_is_redirect,
 171          *  page_latest and page_content_model
 172          */
 173         public function addGoodLinkObjFromRow( $title, $row ) {
 174                 $dbkey = $title->getPrefixedDBkey();
 175                 $this->mGoodLinks->set( $dbkey, array(
 176                         'id' => intval( $row->page_id ),
 177                         'length' => intval( $row->page_len ),
 178                         'redirect' => intval( $row->page_is_redirect ),
 179                         'revision' => intval( $row->page_latest ),
 180                         'model' => !empty( $row->page_content_model ) ? strval( $row->page_content_model ) : null,
 181                 ) );
 182         }
 183
 184         /**
 185          * @param Title $title
 186          */
 187         public function addBadLinkObj( $title ) {
 188                 $dbkey = $title->getPrefixedDBkey();
 189                 if ( !$this->isBadLink( $dbkey ) ) {
 190                         $this->mBadLinks->set( $dbkey, 1 );
 191                 }
 192         }
 193
 194         public function clearBadLink( $title ) {
 195                 $this->mBadLinks->clear( array( $title ) );
 196         }
 197
 198         /**
 199          * @param Title $title
 200          */
 201         public function clearLink( $title ) {
 202                 $dbkey = $title->getPrefixedDBkey();
 203                 $this->mBadLinks->clear( array( $dbkey ) );
 204                 $this->mGoodLinks->clear( array( $dbkey ) );
 205         }
 206
 207         /**
 208          * Add a title to the link cache, return the page_id or zero if non-existent
 209          *
 210          * @param string $title Title to add
 211          * @return int
 212          */
 213         public function addLink( $title ) {
 214                 $nt = Title::newFromDBkey( $title );
 215                 if ( $nt ) {
 216                         return $this->addLinkObj( $nt );
 217                 } else {
 218                         return 0;
 219                 }
 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
 227          */
 228         public function addLinkObj( $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                 if ( $this->mForUpdate ) {
 246                         $db = wfGetDB( DB_MASTER );
 247                 } else {
 248                         $db = wfGetDB( DB_SLAVE );
 249                 }
 250
 251                 $f = array( 'page_id', 'page_len', 'page_is_redirect', 'page_latest' );
 252                 if ( $wgContentHandlerUseDB ) {
 253                         $f[] = 'page_content_model';
 254                 }
 255
 256                 $s = $db->selectRow( 'page', $f,
 257                         array( 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ),
 258                         __METHOD__ );
 259                 # Set fields...
 260                 if ( $s !== false ) {
 261                         $this->addGoodLinkObjFromRow( $nt, $s );
 262                         $id = intval( $s->page_id );
 263                 } else {
 264                         $this->addBadLinkObj( $nt );
 265                         $id = 0;
 266                 }
 267
 268                 return $id;
 269         }
 270
 271         /**
 272          * Clears cache
 273          */
 274         public function clear() {
 275                 $this->mGoodLinks->clear();
 276                 $this->mBadLinks->clear();
 277         }
 278 }