UserCache.php

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<?php
class UserCache {
        protected $cache = array(); // (uid => property => value)
        protected $typesCached = array(); // (uid => cache type => 1)

        public static function singleton() {
                static $instance = null;
                if ( $instance === null ) {
                        $instance = new self();
                }
                return $instance;
        }

        protected function __construct() {}

        public function getProp( $userId, $prop ) {
                if ( !isset( $this->cache[$userId][$prop] ) ) {
                        wfDebug( __METHOD__ . ": querying DB for prop '$prop' for user ID '$userId'.\n" );
                        $this->doQuery( array( $userId ) ); // cache miss
                }
                return isset( $this->cache[$userId][$prop] )
                        ? $this->cache[$userId][$prop]
                        : false; // user does not exist?
        }

        public function doQuery( array $userIds, $options = array(), $caller = '' ) {
                wfProfileIn( __METHOD__ );

                $usersToCheck = array();
                $usersToQuery = array();

                foreach ( $userIds as $userId ) {
                        $userId = (int)$userId;
                        if ( $userId <= 0 ) {
                                continue; // skip anons
                        }
                        if ( isset( $this->cache[$userId]['name'] ) ) {
                                $usersToCheck[$userId] = $this->cache[$userId]['name']; // already have name
                        } else {
                                $usersToQuery[] = $userId; // we need to get the name
                        }
                }

                // Lookup basic info for users not yet loaded...
                if ( count( $usersToQuery ) ) {
                        $dbr = wfGetDB( DB_SLAVE );
                        $table = array( 'user' );
                        $conds = array( 'user_id' => $usersToQuery );
                        $fields = array( 'user_name', 'user_real_name', 'user_registration', 'user_id' );

                        $comment = __METHOD__;
                        if ( strval( $caller ) !== '' ) {
                                $comment .= "/$caller";
                        }

                        $res = $dbr->select( $table, $fields, $conds, $comment );
                        foreach ( $res as $row ) { // load each user into cache
                                $userId = (int)$row->user_id;
                                $this->cache[$userId]['name'] = $row->user_name;
                                $this->cache[$userId]['real_name'] = $row->user_real_name;
                                $this->cache[$userId]['registration'] = $row->user_registration;
                                $usersToCheck[$userId] = $row->user_name;
                        }
                }

                $lb = new LinkBatch();
                foreach ( $usersToCheck as $userId => $name ) {
                        if ( $this->queryNeeded( $userId, 'userpage', $options ) ) {
                                $lb->add( NS_USER, str_replace( ' ', '_', $row->user_name ) );
                                $this->typesCached[$userId]['userpage'] = 1;
                        }
                        if ( $this->queryNeeded( $userId, 'usertalk', $options ) ) {
                                $lb->add( NS_USER_TALK, str_replace( ' ', '_', $row->user_name ) );
                                $this->typesCached[$userId]['usertalk'] = 1;
                        }
                }
                $lb->execute();

                wfProfileOut( __METHOD__ );
        }

        protected function queryNeeded( $uid, $type, array $options ) {
                return ( in_array( $type, $options ) && !isset( $this->typesCached[$uid][$type] ) );
        }
}