includes/LinkCache.php

   1 <?php
   2 /**
   3  * Cache for article titles (prefixed DB keys) and ids linked from one source
   4  *
   5  * @addtogroup 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 $mPageLinks;
  13         /* private */ var $mGoodLinks, $mBadLinks;
  14         /* private */ var $mForUpdate;
  15
  16         /**
  17          * Get an instance of this class
  18          */
  19         static function &singleton() {
  20                 static $instance;
  21                 if ( !isset( $instance ) ) {
  22                         $instance = new LinkCache;
  23                 }
  24                 return $instance;
  25         }
  26
  27         function __construct() {
  28                 $this->mForUpdate = false;
  29                 $this->mPageLinks = array();
  30                 $this->mGoodLinks = array();
  31                 $this->mGoodLinkFields = array();
  32                 $this->mBadLinks = array();
  33         }
  34
  35         /* private */ function getKey( $title ) {
  36                 return wfMemcKey( 'lc', 'title', $title );
  37         }
  38
  39         /**
  40          * General accessor to get/set whether SELECT FOR UPDATE should be used
  41          */
  42         function forUpdate( $update = NULL ) {
  43                 return wfSetVar( $this->mForUpdate, $update );
  44         }
  45
  46         function getGoodLinkID( $title ) {
  47                 if ( array_key_exists( $title, $this->mGoodLinks ) ) {
  48                         return $this->mGoodLinks[$title];
  49                 } else {
  50                         return 0;
  51                 }
  52         }
  53
  54         /**
  55          * Get a field of a title object from cache.
  56          * If this link is not good, it will return NULL.
  57          * @param Title $title
  58          * @param string $field ('length','redirect')
  59          * @return mixed
  60          */
  61         function getGoodLinkFieldObj( $title, $field ) {
  62                 $dbkey = $title->getPrefixedDbKey();
  63                 if ( array_key_exists( $dbkey, $this->mGoodLinkFields ) ) {
  64                         return $this->mGoodLinkFields[$dbkey][$field];
  65                 } else {
  66                         return NULL;
  67                 }
  68         }
  69
  70         function isBadLink( $title ) {
  71                 return array_key_exists( $title, $this->mBadLinks );
  72         }
  73
  74         /**
  75          * Add a link for the title to the link cache
  76          * @param int $id
  77          * @param Title $title
  78          * @param int $len
  79          * @param int $redir
  80          */
  81         function addGoodLinkObj( $id, $title, $len = -1, $redir = NULL ) {
  82                 $dbkey = $title->getPrefixedDbKey();
  83                 $this->mGoodLinks[$dbkey] = $id;
  84                 $this->mGoodLinkFields[$dbkey] = array( 'length' => $len, 'redirect' => $redir );
  85                 $this->mPageLinks[$dbkey] = $title;
  86         }
  87
  88         function addBadLinkObj( $title ) {
  89                 $dbkey = $title->getPrefixedDbKey();
  90                 if ( ! $this->isBadLink( $dbkey ) ) {
  91                         $this->mBadLinks[$dbkey] = 1;
  92                         $this->mPageLinks[$dbkey] = $title;
  93                 }
  94         }
  95
  96         function clearBadLink( $title ) {
  97                 unset( $this->mBadLinks[$title] );
  98                 $this->clearLink( $title );
  99         }
 100
 101         function clearLink( $title ) {
 102                 global $wgMemc, $wgLinkCacheMemcached;
 103                 if( $wgLinkCacheMemcached )
 104                         $wgMemc->delete( $this->getKey( $title ) );
 105         }
 106
 107         function getPageLinks() { return $this->mPageLinks; }
 108         function getGoodLinks() { return $this->mGoodLinks; }
 109         function getBadLinks() { return array_keys( $this->mBadLinks ); }
 110
 111         /**
 112          * Add a title to the link cache, return the page_id or zero if non-existent
 113          * @param $title String: title to add
 114          * @param $len int, page size
 115          * @param $redir bool, is redirect?
 116          * @return integer
 117          */
 118         function addLink( $title, $len = -1, $redir = NULL ) {
 119                 $nt = Title::newFromDBkey( $title );
 120                 if( $nt ) {
 121                         return $this->addLinkObj( $nt, $len, $redir );
 122                 } else {
 123                         return 0;
 124                 }
 125         }
 126
 127         /**
 128          * Add a title to the link cache, return the page_id or zero if non-existent
 129          * @param $nt Title to add.
 130          * @param $len int, page size
 131          * @param $redir bool, is redirect?
 132          * @return integer
 133          */
 134         function addLinkObj( &$nt, $len = -1, $redirect = NULL ) {
 135                 global $wgMemc, $wgLinkCacheMemcached, $wgAntiLockFlags;
 136                 $title = $nt->getPrefixedDBkey();
 137                 if ( $this->isBadLink( $title ) ) { return 0; }
 138                 $id = $this->getGoodLinkID( $title );
 139                 if ( 0 != $id ) { return $id; }
 140
 141                 $fname = 'LinkCache::addLinkObj';
 142                 global $wgProfiler;
 143                 if ( isset( $wgProfiler ) ) {
 144                         $fname .= ' (' . $wgProfiler->getCurrentSection() . ')';
 145                 }
 146
 147                 wfProfileIn( $fname );
 148
 149                 $ns = $nt->getNamespace();
 150                 $t = $nt->getDBkey();
 151
 152                 if ( '' == $title ) {
 153                         wfProfileOut( $fname );
 154                         return 0;
 155                 }
 156                 # Some fields heavily used for linking...
 157                 $id = NULL;
 158
 159                 if( $wgLinkCacheMemcached ) {
 160                         $id = $wgMemc->get( $key = $this->getKey( $title ) );
 161                 }
 162                 if( !is_integer( $id ) ) {
 163                         if ( $this->mForUpdate ) {
 164                                 $db = wfGetDB( DB_MASTER );
 165                                 if ( !( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) ) {
 166                                         $options = array( 'FOR UPDATE' );
 167                                 } else {
 168                                         $options = array();
 169                                 }
 170                         } else {
 171                                 $db = wfGetDB( DB_SLAVE );
 172                                 $options = array();
 173                         }
 174
 175                         $s = $db->selectRow( 'page',
 176                                 array( 'page_id', 'page_len', 'page_is_redirect' ),
 177                                 array( 'page_namespace' => $ns, 'page_title' => $t ),
 178                                 $fname, $options );
 179                         # Set fields...
 180                         $id = $s ? $s->page_id : 0;
 181                         $len = $s ? $s->page_len : -1;
 182                         $redirect = $s ? $s->page_is_redirect : 0;
 183
 184                         if( $wgLinkCacheMemcached ) {
 185                                 $wgMemc->add( $key, $id, 3600*24 );
 186                         }
 187                 }
 188
 189                 if( 0 == $id ) {
 190                         $this->addBadLinkObj( $nt );
 191                 } else {
 192                         $this->addGoodLinkObj( $id, $nt, $len, $redirect );
 193                 }
 194                 wfProfileOut( $fname );
 195                 return $id;
 196         }
 197
 198         /**
 199          * Clears cache
 200          */
 201         function clear() {
 202                 $this->mPageLinks = array();
 203                 $this->mGoodLinks = array();
 204                 $this->mGoodLinkFields = array();
 205                 $this->mBadLinks = array();
 206         }
 207 }
 208