LinkCache.php

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<?php
use Wikimedia\Rdbms\Database;
use Wikimedia\Rdbms\IDatabase;
use MediaWiki\Linker\LinkTarget;
use MediaWiki\MediaWikiServices;

class LinkCache {
    private $goodLinks;
    private $badLinks;
    private $wanCache;

    private $mForUpdate = false;

    private $titleFormatter;

    const MAX_SIZE = 10000;

    public function __construct( TitleFormatter $titleFormatter, WANObjectCache $cache ) {
        $this->goodLinks = new MapCacheLRU( self::MAX_SIZE );
        $this->badLinks = new MapCacheLRU( self::MAX_SIZE );
        $this->wanCache = $cache;
        $this->titleFormatter = $titleFormatter;
    }

    public static function singleton() {
        return MediaWikiServices::getInstance()->getLinkCache();
    }

    public function forUpdate( $update = null ) {
        return wfSetVar( $this->mForUpdate, $update );
    }

    public function getGoodLinkID( $title ) {
        $info = $this->goodLinks->get( $title );
        if ( !$info ) {
            return 0;
        }
        return $info['id'];
    }

    public function getGoodLinkFieldObj( LinkTarget $target, $field ) {
        $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
        $info = $this->goodLinks->get( $dbkey );
        if ( !$info ) {
            return null;
        }
        return $info[$field];
    }

    public function isBadLink( $title ) {
        // Use get() to ensure it records as used for LRU.
        return $this->badLinks->has( $title );
    }

    public function addGoodLinkObj( $id, LinkTarget $target, $len = -1, $redir = null,
        $revision = 0, $model = null, $lang = null
    ) {
        $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
        $this->goodLinks->set( $dbkey, [
            'id' => (int)$id,
            'length' => (int)$len,
            'redirect' => (int)$redir,
            'revision' => (int)$revision,
            'model' => $model ? (string)$model : null,
            'lang' => $lang ? (string)$lang : null,
            'restrictions' => null
        ] );
    }

    public function addGoodLinkObjFromRow( LinkTarget $target, $row ) {
        $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
        $this->goodLinks->set( $dbkey, [
            'id' => intval( $row->page_id ),
            'length' => intval( $row->page_len ),
            'redirect' => intval( $row->page_is_redirect ),
            'revision' => intval( $row->page_latest ),
            'model' => !empty( $row->page_content_model )
                ? strval( $row->page_content_model )
                : null,
            'lang' => !empty( $row->page_lang )
                ? strval( $row->page_lang )
                : null,
            'restrictions' => !empty( $row->page_restrictions )
                ? strval( $row->page_restrictions )
                : null
        ] );
    }

    public function addBadLinkObj( LinkTarget $target ) {
        $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
        if ( !$this->isBadLink( $dbkey ) ) {
            $this->badLinks->set( $dbkey, 1 );
        }
    }

    public function clearBadLink( $title ) {
        $this->badLinks->clear( $title );
    }

    public function clearLink( LinkTarget $target ) {
        $dbkey = $this->titleFormatter->getPrefixedDBkey( $target );
        $this->badLinks->clear( $dbkey );
        $this->goodLinks->clear( $dbkey );
    }

    public static function getSelectFields() {
        global $wgContentHandlerUseDB, $wgPageLanguageUseDB;

        $fields = [
            'page_id',
            'page_len',
            'page_is_redirect',
            'page_latest',
            'page_restrictions'
        ];
        if ( $wgContentHandlerUseDB ) {
            $fields[] = 'page_content_model';
        }
        if ( $wgPageLanguageUseDB ) {
            $fields[] = 'page_lang';
        }

        return $fields;
    }

    public function addLinkObj( LinkTarget $nt ) {
        $key = $this->titleFormatter->getPrefixedDBkey( $nt );
        if ( $this->isBadLink( $key ) || $nt->isExternal()
            || $nt->inNamespace( NS_SPECIAL )
        ) {
            return 0;
        }
        $id = $this->getGoodLinkID( $key );
        if ( $id != 0 ) {
            return $id;
        }

        if ( $key === '' ) {
            return 0;
        }

        // Cache template/file pages as they are less often viewed but heavily used
        if ( $this->mForUpdate ) {
            $row = $this->fetchPageRow( wfGetDB( DB_MASTER ), $nt );
        } elseif ( $this->isCacheable( $nt ) ) {
            // These pages are often transcluded heavily, so cache them
            $cache = $this->wanCache;
            $row = $cache->getWithSetCallback(
                $cache->makeKey( 'page', $nt->getNamespace(), sha1( $nt->getDBkey() ) ),
                $cache::TTL_DAY,
                function ( $curValue, &$ttl, array &$setOpts ) use ( $cache, $nt ) {
                    $dbr = wfGetDB( DB_REPLICA );
                    $setOpts += Database::getCacheSetOptions( $dbr );

                    $row = $this->fetchPageRow( $dbr, $nt );
                    $mtime = $row ? wfTimestamp( TS_UNIX, $row->page_touched ) : false;
                    $ttl = $cache->adaptiveTTL( $mtime, $ttl );

                    return $row;
                }
            );
        } else {
            $row = $this->fetchPageRow( wfGetDB( DB_REPLICA ), $nt );
        }

        if ( $row ) {
            $this->addGoodLinkObjFromRow( $nt, $row );
            $id = intval( $row->page_id );
        } else {
            $this->addBadLinkObj( $nt );
            $id = 0;
        }

        return $id;
    }

    public function getMutableCacheKeys( WANObjectCache $cache, LinkTarget $t ) {
        if ( $this->isCacheable( $t ) ) {
            return [ $cache->makeKey( 'page', $t->getNamespace(), sha1( $t->getDBkey() ) ) ];
        }

        return [];
    }

    private function isCacheable( LinkTarget $title ) {
        $ns = $title->getNamespace();
        if ( in_array( $ns, [ NS_TEMPLATE, NS_FILE, NS_CATEGORY ] ) ) {
            return true;
        }
        // Focus on transcluded pages more than the main content
        if ( MWNamespace::isContent( $ns ) ) {
            return false;
        }
        // Non-talk extension namespaces (e.g. NS_MODULE)
        return ( $ns >= 100 && MWNamespace::isSubject( $ns ) );
    }

    private function fetchPageRow( IDatabase $db, LinkTarget $nt ) {
        $fields = self::getSelectFields();
        if ( $this->isCacheable( $nt ) ) {
            $fields[] = 'page_touched';
        }

        return $db->selectRow(
            'page',
            $fields,
            [ 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ],
            __METHOD__
        );
    }

    public function invalidateTitle( LinkTarget $title ) {
        if ( $this->isCacheable( $title ) ) {
            $cache = $this->wanCache;
            $cache->delete(
                $cache->makeKey( 'page', $title->getNamespace(), sha1( $title->getDBkey() ) )
            );
        }
    }

    public function clear() {
        $this->goodLinks->clear();
        $this->badLinks->clear();
    }
}