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         // Increment $mClassVer whenever old serialized versions of this class
  31         // becomes incompatible with the new version.
  32         private $mClassVer = 4;
  33
  34         private $mGoodLinks = array();
  35         private $mGoodLinkFields = array();
  36         private $mBadLinks = array();
  37         private $mForUpdate = false;
  38
  39         /**
  40          * Get an instance of this class
  41          *
  42          * @return LinkCache
  43          */
  44         static function &singleton() {
  45                 static $instance;
  46                 if ( !isset( $instance ) ) {
  47                         $instance = new LinkCache;
  48                 }
  49                 return $instance;
  50         }
  51
  52         /**
  53          * General accessor to get/set whether SELECT FOR UPDATE should be used
  54          *
  55          * @return bool
  56          */
  57         public function forUpdate( $update = null ) {
  58                 return wfSetVar( $this->mForUpdate, $update );
  59         }
  60
  61         /**
  62          * @param $title
  63          * @return array|int
  64          */
  65         public function getGoodLinkID( $title ) {
  66                 if ( array_key_exists( $title, $this->mGoodLinks ) ) {
  67                         return $this->mGoodLinks[$title];
  68                 } else {
  69                         return 0;
  70                 }
  71         }
  72
  73         /**
  74          * Get a field of a title object from cache.
  75          * If this link is not good, it will return NULL.
  76          * @param $title Title
  77          * @param $field String: ('length','redirect','revision')
  78          * @return mixed
  79          */
  80         public function getGoodLinkFieldObj( $title, $field ) {
  81                 $dbkey = $title->getPrefixedDbKey();
  82                 if ( array_key_exists( $dbkey, $this->mGoodLinkFields ) ) {
  83                         return $this->mGoodLinkFields[$dbkey][$field];
  84                 } else {
  85                         return null;
  86                 }
  87         }
  88
  89         /**
  90          * @param $title
  91          * @return bool
  92          */
  93         public function isBadLink( $title ) {
  94                 return array_key_exists( $title, $this->mBadLinks );
  95         }
  96
  97         /**
  98          * Add a link for the title to the link cache
  99          *
 100          * @param $id Integer: page's ID
 101          * @param $title Title object
 102          * @param $len Integer: text's length
 103          * @param $redir Integer: whether the page is a redirect
 104          * @param $revision Integer: latest revision's ID
 105          */
 106         public function addGoodLinkObj( $id, $title, $len = -1, $redir = null, $revision = false ) {
 107                 $dbkey = $title->getPrefixedDbKey();
 108                 $this->mGoodLinks[$dbkey] = intval( $id );
 109                 $this->mGoodLinkFields[$dbkey] = array(
 110                         'length' => intval( $len ),
 111                         'redirect' => intval( $redir ),
 112                         'revision' => intval( $revision ) );
 113         }
 114
 115         /**
 116          * Same as above with better interface.
 117          * @since 1.19
 118          * @param $title Title
 119          * @param $row object which has the fields page_id, page_is_redirect,
 120          *  page_latest
 121          */
 122         public function addGoodLinkObjFromRow( $title, $row ) {
 123                 $dbkey = $title->getPrefixedDbKey();
 124                 $this->mGoodLinks[$dbkey] = intval( $row->page_id );
 125                 $this->mGoodLinkFields[$dbkey] = array(
 126                         'length' => intval( $row->page_len ),
 127                         'redirect' => intval( $row->page_is_redirect ),
 128                         'revision' => intval( $row->page_latest ),
 129                 );
 130         }
 131
 132         /**
 133          * @param $title Title
 134          */
 135         public function addBadLinkObj( $title ) {
 136                 $dbkey = $title->getPrefixedDbKey();
 137                 if ( !$this->isBadLink( $dbkey ) ) {
 138                         $this->mBadLinks[$dbkey] = 1;
 139                 }
 140         }
 141
 142         public function clearBadLink( $title ) {
 143                 unset( $this->mBadLinks[$title] );
 144         }
 145
 146         /**
 147          * @param $title Title
 148          */
 149         public function clearLink( $title ) {
 150                 $dbkey = $title->getPrefixedDbKey();
 151                 unset( $this->mBadLinks[$dbkey] );
 152                 unset( $this->mGoodLinks[$dbkey] );
 153                 unset( $this->mGoodLinkFields[$dbkey] );
 154         }
 155
 156         public function getGoodLinks() { return $this->mGoodLinks; }
 157         public function getBadLinks() { return array_keys( $this->mBadLinks ); }
 158
 159         /**
 160          * Add a title to the link cache, return the page_id or zero if non-existent
 161          *
 162          * @param $title String: title to add
 163          * @return Integer
 164          */
 165         public function addLink( $title ) {
 166                 $nt = Title::newFromDBkey( $title );
 167                 if( $nt ) {
 168                         return $this->addLinkObj( $nt );
 169                 } else {
 170                         return 0;
 171                 }
 172         }
 173
 174         /**
 175          * Add a title to the link cache, return the page_id or zero if non-existent
 176          *
 177          * @param $nt Title object to add
 178          * @return Integer
 179          */
 180         public function addLinkObj( $nt ) {
 181                 global $wgAntiLockFlags;
 182                 wfProfileIn( __METHOD__ );
 183
 184                 $key = $nt->getPrefixedDBkey();
 185                 if ( $this->isBadLink( $key ) || $nt->isExternal() ) {
 186                         wfProfileOut( __METHOD__ );
 187                         return 0;
 188                 }
 189                 $id = $this->getGoodLinkID( $key );
 190                 if ( $id != 0 ) {
 191                         wfProfileOut( __METHOD__ );
 192                         return $id;
 193                 }
 194
 195                 if ( $key === '' ) {
 196                         wfProfileOut( __METHOD__ );
 197                         return 0;
 198                 }
 199
 200                 # Some fields heavily used for linking...
 201                 if ( $this->mForUpdate ) {
 202                         $db = wfGetDB( DB_MASTER );
 203                         if ( !( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) ) {
 204                                 $options = array( 'FOR UPDATE' );
 205                         } else {
 206                                 $options = array();
 207                         }
 208                 } else {
 209                         $db = wfGetDB( DB_SLAVE );
 210                         $options = array();
 211                 }
 212
 213                 $s = $db->selectRow( 'page',
 214                         array( 'page_id', 'page_len', 'page_is_redirect', 'page_latest' ),
 215                         array( 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ),
 216                         __METHOD__, $options );
 217                 # Set fields...
 218                 if ( $s !== false ) {
 219                         $this->addGoodLinkObjFromRow( $nt, $s );
 220                         $id = intval( $s->page_id );
 221                 } else {
 222                         $this->addBadLinkObj( $nt );
 223                         $id = 0;
 224                 }
 225
 226                 wfProfileOut( __METHOD__ );
 227                 return $id;
 228         }
 229
 230         /**
 231          * Clears cache
 232          */
 233         public function clear() {
 234                 $this->mGoodLinks = array();
 235                 $this->mGoodLinkFields = array();
 236                 $this->mBadLinks = array();
 237         }
 238 }