+++ /dev/null
-<?php
-/**
- * Class for fetching backlink lists, approximate backlink counts and partitions.
- * Instances of this class should typically be fetched with $title->getBacklinkCache().
- *
- * Ideally you should only get your backlinks from here when you think there is some
- * advantage in caching them. Otherwise it's just a waste of memory.
- */
-class BacklinkCache {
- var $partitionCache = array();
- var $fullResultCache = array();
- var $title;
- var $db;
-
- const CACHE_EXPIRY = 3600;
-
- /**
- * Create a new BacklinkCache
- */
- function __construct( $title ) {
- $this->title = $title;
- }
-
- /**
- * Serialization handler, diasallows to serialize the database to prevent
- * failures after this class is deserialized from cache with dead DB connection.
- */
- function __sleep() {
- return array( 'partitionCache', 'fullResultCache', 'title' );
- }
-
- /**
- * Clear locally stored data
- */
- function clear() {
- $this->partitionCache = array();
- $this->fullResultCache = array();
- unset( $this->db );
- }
-
- /**
- * Set the Database object to use
- */
- public function setDB( $db ) {
- $this->db = $db;
- }
-
- protected function getDB() {
- if ( !isset( $this->db ) ) {
- $this->db = wfGetDB( DB_SLAVE );
- }
-
- return $this->db;
- }
-
- /**
- * Get the backlinks for a given table. Cached in process memory only.
- * @param $table String
- * @param $startId Integer or false
- * @param $endId Integer or false
- * @return TitleArray
- */
- public function getLinks( $table, $startId = false, $endId = false ) {
- wfProfileIn( __METHOD__ );
-
- $fromField = $this->getPrefix( $table ) . '_from';
-
- if ( $startId || $endId ) {
- // Partial range, not cached
- wfDebug( __METHOD__ . ": from DB (uncacheable range)\n" );
- $conds = $this->getConditions( $table );
-
- // Use the from field in the condition rather than the joined page_id,
- // because databases are stupid and don't necessarily propagate indexes.
- if ( $startId ) {
- $conds[] = "$fromField >= " . intval( $startId );
- }
-
- if ( $endId ) {
- $conds[] = "$fromField <= " . intval( $endId );
- }
-
- $res = $this->getDB()->select(
- array( $table, 'page' ),
- array( 'page_namespace', 'page_title', 'page_id' ),
- $conds,
- __METHOD__,
- array(
- 'STRAIGHT_JOIN',
- 'ORDER BY' => $fromField
- ) );
- $ta = TitleArray::newFromResult( $res );
-
- wfProfileOut( __METHOD__ );
- return $ta;
- }
-
- if ( !isset( $this->fullResultCache[$table] ) ) {
- wfDebug( __METHOD__ . ": from DB\n" );
- $res = $this->getDB()->select(
- array( $table, 'page' ),
- array( 'page_namespace', 'page_title', 'page_id' ),
- $this->getConditions( $table ),
- __METHOD__,
- array(
- 'STRAIGHT_JOIN',
- 'ORDER BY' => $fromField,
- ) );
- $this->fullResultCache[$table] = $res;
- }
-
- $ta = TitleArray::newFromResult( $this->fullResultCache[$table] );
-
- wfProfileOut( __METHOD__ );
- return $ta;
- }
-
- /**
- * Get the field name prefix for a given table
- */
- protected function getPrefix( $table ) {
- static $prefixes = array(
- 'pagelinks' => 'pl',
- 'imagelinks' => 'il',
- 'categorylinks' => 'cl',
- 'templatelinks' => 'tl',
- 'redirect' => 'rd',
- );
-
- if ( isset( $prefixes[$table] ) ) {
- return $prefixes[$table];
- } else {
- throw new MWException( "Invalid table \"$table\" in " . __CLASS__ );
- }
- }
-
- /**
- * Get the SQL condition array for selecting backlinks, with a join on the page table
- */
- protected function getConditions( $table ) {
- $prefix = $this->getPrefix( $table );
-
- switch ( $table ) {
- case 'pagelinks':
- case 'templatelinks':
- case 'redirect':
- $conds = array(
- "{$prefix}_namespace" => $this->title->getNamespace(),
- "{$prefix}_title" => $this->title->getDBkey(),
- "page_id={$prefix}_from"
- );
- break;
- case 'imagelinks':
- $conds = array(
- 'il_to' => $this->title->getDBkey(),
- 'page_id=il_from'
- );
- break;
- case 'categorylinks':
- $conds = array(
- 'cl_to' => $this->title->getDBkey(),
- 'page_id=cl_from',
- );
- break;
- default:
- throw new MWException( "Invalid table \"$table\" in " . __CLASS__ );
- }
-
- return $conds;
- }
-
- /**
- * Get the approximate number of backlinks
- */
- public function getNumLinks( $table ) {
- if ( isset( $this->fullResultCache[$table] ) ) {
- return $this->fullResultCache[$table]->numRows();
- }
-
- if ( isset( $this->partitionCache[$table] ) ) {
- $entry = reset( $this->partitionCache[$table] );
- return $entry['numRows'];
- }
-
- $titleArray = $this->getLinks( $table );
-
- return $titleArray->count();
- }
-
- /**
- * Partition the backlinks into batches.
- * Returns an array giving the start and end of each range. The first batch has
- * a start of false, and the last batch has an end of false.
- *
- * @param $table String: the links table name
- * @param $batchSize Integer
- * @return Array
- */
- public function partition( $table, $batchSize ) {
- // Try cache
- if ( isset( $this->partitionCache[$table][$batchSize] ) ) {
- wfDebug( __METHOD__ . ": got from partition cache\n" );
- return $this->partitionCache[$table][$batchSize]['batches'];
- }
-
- $this->partitionCache[$table][$batchSize] = false;
- $cacheEntry =& $this->partitionCache[$table][$batchSize];
-
- // Try full result cache
- if ( isset( $this->fullResultCache[$table] ) ) {
- $cacheEntry = $this->partitionResult( $this->fullResultCache[$table], $batchSize );
- wfDebug( __METHOD__ . ": got from full result cache\n" );
-
- return $cacheEntry['batches'];
- }
-
- // Try memcached
- global $wgMemc;
-
- $memcKey = wfMemcKey(
- 'backlinks',
- md5( $this->title->getPrefixedDBkey() ),
- $table,
- $batchSize
- );
-
- $memcValue = $wgMemc->get( $memcKey );
-
- if ( is_array( $memcValue ) ) {
- $cacheEntry = $memcValue;
- wfDebug( __METHOD__ . ": got from memcached $memcKey\n" );
-
- return $cacheEntry['batches'];
- }
-
- // Fetch from database
- $this->getLinks( $table );
- $cacheEntry = $this->partitionResult( $this->fullResultCache[$table], $batchSize );
- // Save to memcached
- $wgMemc->set( $memcKey, $cacheEntry, self::CACHE_EXPIRY );
-
- wfDebug( __METHOD__ . ": got from database\n" );
- return $cacheEntry['batches'];
- }
-
- /**
- * Partition a DB result with backlinks in it into batches
- */
- protected function partitionResult( $res, $batchSize ) {
- $batches = array();
- $numRows = $res->numRows();
- $numBatches = ceil( $numRows / $batchSize );
-
- for ( $i = 0; $i < $numBatches; $i++ ) {
- if ( $i == 0 ) {
- $start = false;
- } else {
- $rowNum = intval( $numRows * $i / $numBatches );
- $res->seek( $rowNum );
- $row = $res->fetchObject();
- $start = $row->page_id;
- }
-
- if ( $i == $numBatches - 1 ) {
- $end = false;
- } else {
- $rowNum = intval( $numRows * ( $i + 1 ) / $numBatches );
- $res->seek( $rowNum );
- $row = $res->fetchObject();
- $end = $row->page_id - 1;
- }
-
- # Sanity check order
- if ( $start && $end && $start > $end ) {
- throw new MWException( __METHOD__ . ': Internal error: query result out of order' );
- }
-
- $batches[] = array( $start, $end );
- }
-
- return array( 'numRows' => $numRows, 'batches' => $batches );
- }
-}
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