includes/LinkCache.php

   1 <?php
   2 /**
   3  * Cache for article titles (prefixed DB keys) and ids linked from one source
   4  *
   5  * @ingroup Cache
   6  */
   7 class LinkCache {
   8         // Increment $mClassVer whenever old serialized versions of this class
   9         // becomes incompatible with the new version.
  10         /* private */ var $mClassVer = 4;
  11
  12         /* private */ var $mGoodLinks, $mBadLinks;
  13         /* private */ var $mForUpdate;
  14
  15         /**
  16          * Get an instance of this class
  17          */
  18         static function &singleton() {
  19                 static $instance;
  20                 if ( !isset( $instance ) ) {
  21                         $instance = new LinkCache;
  22                 }
  23                 return $instance;
  24         }
  25
  26         function __construct() {
  27                 $this->mForUpdate = false;
  28                 $this->mGoodLinks = array();
  29                 $this->mGoodLinkFields = array();
  30                 $this->mBadLinks = array();
  31         }
  32
  33         /**
  34          * General accessor to get/set whether SELECT FOR UPDATE should be used
  35          */
  36         public function forUpdate( $update = NULL ) {
  37                 return wfSetVar( $this->mForUpdate, $update );
  38         }
  39
  40         public function getGoodLinkID( $title ) {
  41                 if ( array_key_exists( $title, $this->mGoodLinks ) ) {
  42                         return $this->mGoodLinks[$title];
  43                 } else {
  44                         return 0;
  45                 }
  46         }
  47
  48         /**
  49          * Get a field of a title object from cache.
  50          * If this link is not good, it will return NULL.
  51          * @param Title $title
  52          * @param string $field ('length','redirect')
  53          * @return mixed
  54          */
  55         public function getGoodLinkFieldObj( $title, $field ) {
  56                 $dbkey = $title->getPrefixedDbKey();
  57                 if ( array_key_exists( $dbkey, $this->mGoodLinkFields ) ) {
  58                         return $this->mGoodLinkFields[$dbkey][$field];
  59                 } else {
  60                         return NULL;
  61                 }
  62         }
  63
  64         public function isBadLink( $title ) {
  65                 return array_key_exists( $title, $this->mBadLinks );
  66         }
  67
  68         /**
  69          * Add a link for the title to the link cache
  70          * @param int $id
  71          * @param Title $title
  72          * @param int $len
  73          * @param int $redir
  74          */
  75         public function addGoodLinkObj( $id, $title, $len = -1, $redir = NULL ) {
  76                 $dbkey = $title->getPrefixedDbKey();
  77                 $this->mGoodLinks[$dbkey] = $id;
  78                 $this->mGoodLinkFields[$dbkey] = array( 'length' => $len, 'redirect' => $redir );
  79         }
  80
  81         public function addBadLinkObj( $title ) {
  82                 $dbkey = $title->getPrefixedDbKey();
  83                 if ( !$this->isBadLink( $dbkey ) ) {
  84                         $this->mBadLinks[$dbkey] = 1;
  85                 }
  86         }
  87
  88         public function clearBadLink( $title ) {
  89                 unset( $this->mBadLinks[$title] );
  90         }
  91
  92         /* obsolete, for old $wgLinkCacheMemcached stuff */
  93         public function clearLink( $title ) {}
  94
  95         public function getGoodLinks() { return $this->mGoodLinks; }
  96         public function getBadLinks() { return array_keys( $this->mBadLinks ); }
  97
  98         /**
  99          * Add a title to the link cache, return the page_id or zero if non-existent
 100          * @param $title String: title to add
 101          * @param $len int, page size
 102          * @param $redir bool, is redirect?
 103          * @return integer
 104          */
 105         public function addLink( $title, $len = -1, $redir = NULL ) {
 106                 $nt = Title::newFromDBkey( $title );
 107                 if( $nt ) {
 108                         return $this->addLinkObj( $nt, $len, $redir );
 109                 } else {
 110                         return 0;
 111                 }
 112         }
 113
 114         /**
 115          * Add a title to the link cache, return the page_id or zero if non-existent
 116          * @param $nt Title to add.
 117          * @param $len int, page size
 118          * @param $redir bool, is redirect?
 119          * @return integer
 120          */
 121         public function addLinkObj( &$nt, $len = -1, $redirect = NULL ) {
 122                 global $wgAntiLockFlags, $wgProfiler;
 123                 wfProfileIn( __METHOD__ );
 124
 125                 $key = $nt->getPrefixedDBkey();
 126                 if ( $this->isBadLink( $key ) ) {
 127                         wfProfileOut( __METHOD__ );
 128                         return 0;
 129                 }
 130                 $id = $this->getGoodLinkID( $key );
 131                 if ( $id != 0 ) {
 132                         wfProfileOut( __METHOD__ );
 133                         return $id;
 134                 }
 135
 136                 if ( $key === '' ) {
 137                         wfProfileOut( __METHOD__ );
 138                         return 0;
 139                 }
 140
 141                 # Some fields heavily used for linking...
 142                 if ( $this->mForUpdate ) {
 143                         $db = wfGetDB( DB_MASTER );
 144                         if ( !( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) ) {
 145                                 $options = array( 'FOR UPDATE' );
 146                         } else {
 147                                 $options = array();
 148                         }
 149                 } else {
 150                         $db = wfGetDB( DB_SLAVE );
 151                         $options = array();
 152                 }
 153
 154                 $s = $db->selectRow( 'page',
 155                         array( 'page_id', 'page_len', 'page_is_redirect' ),
 156                         array( 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ),
 157                         __METHOD__, $options );
 158                 # Set fields...
 159                 if ( $s !== false ) {
 160                         $id = $s->page_id;
 161                         $len = $s->page_len;
 162                         $redirect = $s->page_is_redirect;
 163                 } else {
 164                         $len = -1;
 165                         $redirect = 0;
 166                 }
 167
 168                 if ( $id == 0 ) {
 169                         $this->addBadLinkObj( $nt );
 170                 } else {
 171                         $this->addGoodLinkObj( $id, $nt, $len, $redirect );
 172                 }
 173                 wfProfileOut( __METHOD__ );
 174                 return $id;
 175         }
 176
 177         /**
 178          * Clears cache
 179          */
 180         public function clear() {
 181                 $this->mGoodLinks = array();
 182                 $this->mGoodLinkFields = array();
 183                 $this->mBadLinks = array();
 184         }
 185 }