applying patch to version 1.15.0

1 files changed, 232 insertions, 0 deletions

diff --git a/includes/BacklinkCache.php b/includes/BacklinkCache.php
new file mode 100644
index 00000000..a7bcd858
--- /dev/null
+++ b/includes/BacklinkCache.php
@@ -0,0 +1,232 @@
+<?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;
+	}
+
+	/**
+	 * 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 string $table
+	 * @return TitleArray
+	 */
+	public function getLinks( $table, $startId = false, $endId = false ) {
+		wfProfileIn( __METHOD__ );
+
+		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.
+			$fromField = $this->getPrefix( $table ) . '_from';
+			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') );
+			$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') );
+			$this->fullResultCache[$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 string $table The links table name
+	 * @param integer $batchSize
+	 * @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;
+			}
+			$batches[] = array( $start, $end );
+		}
+		return array( 'numRows' => $numRows, 'batches' => $batches );
+	}
+}