--- /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;
+ }
+
+ /**
+ * 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 );
+ }
+}
scripts.mit.edu / autoinstallsdev / mediawiki.git / blobdiff