Merge "Tweaked WikiPage::clear() comment a bit"

[mediawiki.git] / includes / cache / LinkCache.php

<?php
/**
 * Page existence cache.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Cache
 */

/**
 * Cache for article titles (prefixed DB keys) and ids linked from one source
 *
 * @ingroup Cache
 */
class LinkCache {
        // Increment $mClassVer whenever old serialized versions of this class
        // becomes incompatible with the new version.
        private $mClassVer = 4;

        private $mGoodLinks = array();
        private $mGoodLinkFields = array();
        private $mBadLinks = array();
        private $mForUpdate = false;

        /**
         * @var LinkCache
         */
        protected static $instance;

        /**
         * Get an instance of this class.
         *
         * @return LinkCache
         */
        static function &singleton() {
                if ( self::$instance ) {
                        return self::$instance;
                }
                self::$instance = new LinkCache;

                return self::$instance;
        }

        /**
         * Destroy the singleton instance, a new one will be created next time
         * singleton() is called.
         * @since 1.22
         */
        static function destroySingleton() {
                self::$instance = null;
        }

        /**
         * Set the singleton instance to a given object.
         * Since we do not have an interface for LinkCache, you have to be sure the
         * given object implements all the LinkCache public methods.
         * @param LinkCache $instance
         * @since 1.22
         */
        static function setSingleton( LinkCache $instance ) {
                self::$instance = $instance;
        }

        /**
         * General accessor to get/set whether SELECT FOR UPDATE should be used
         *
         * @return bool
         */
        public function forUpdate( $update = null ) {
                return wfSetVar( $this->mForUpdate, $update );
        }

        /**
         * @param $title
         * @return array|int
         */
        public function getGoodLinkID( $title ) {
                if ( array_key_exists( $title, $this->mGoodLinks ) ) {
                        return $this->mGoodLinks[$title];
                } else {
                        return 0;
                }
        }

        /**
         * Get a field of a title object from cache.
         * If this link is not good, it will return NULL.
         * @param $title Title
         * @param string $field ('length','redirect','revision','model')
         * @return mixed
         */
        public function getGoodLinkFieldObj( $title, $field ) {
                $dbkey = $title->getPrefixedDBkey();
                if ( array_key_exists( $dbkey, $this->mGoodLinkFields ) ) {
                        return $this->mGoodLinkFields[$dbkey][$field];
                } else {
                        return null;
                }
        }

        /**
         * @param $title
         * @return bool
         */
        public function isBadLink( $title ) {
                return array_key_exists( $title, $this->mBadLinks );
        }

        /**
         * Add a link for the title to the link cache
         *
         * @param $id Integer: page's ID
         * @param $title Title object
         * @param $len Integer: text's length
         * @param $redir Integer: whether the page is a redirect
         * @param $revision Integer: latest revision's ID
         * @param $model Integer: latest revision's content model ID
         */
        public function addGoodLinkObj( $id, $title, $len = -1, $redir = null, $revision = false, $model = false ) {
                $dbkey = $title->getPrefixedDBkey();
                $this->mGoodLinks[$dbkey] = intval( $id );
                $this->mGoodLinkFields[$dbkey] = array(
                        'length' => intval( $len ),
                        'redirect' => intval( $redir ),
                        'revision' => intval( $revision ),
                        'model' => intval( $model ) );
        }

        /**
         * Same as above with better interface.
         * @since 1.19
         * @param $title Title
         * @param $row object which has the fields page_id, page_is_redirect,
         *  page_latest and page_content_model
         */
        public function addGoodLinkObjFromRow( $title, $row ) {
                $dbkey = $title->getPrefixedDBkey();
                $this->mGoodLinks[$dbkey] = intval( $row->page_id );
                $this->mGoodLinkFields[$dbkey] = array(
                        '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,
                );
        }

        /**
         * @param $title Title
         */
        public function addBadLinkObj( $title ) {
                $dbkey = $title->getPrefixedDBkey();
                if ( !$this->isBadLink( $dbkey ) ) {
                        $this->mBadLinks[$dbkey] = 1;
                }
        }

        public function clearBadLink( $title ) {
                unset( $this->mBadLinks[$title] );
        }

        /**
         * @param $title Title
         */
        public function clearLink( $title ) {
                $dbkey = $title->getPrefixedDBkey();
                unset( $this->mBadLinks[$dbkey] );
                unset( $this->mGoodLinks[$dbkey] );
                unset( $this->mGoodLinkFields[$dbkey] );
        }

        public function getGoodLinks() {
                return $this->mGoodLinks;
        }

        public function getBadLinks() {
                return array_keys( $this->mBadLinks );
        }

        /**
         * Add a title to the link cache, return the page_id or zero if non-existent
         *
         * @param string $title title to add
         * @return Integer
         */
        public function addLink( $title ) {
                $nt = Title::newFromDBkey( $title );
                if ( $nt ) {
                        return $this->addLinkObj( $nt );
                } else {
                        return 0;
                }
        }

        /**
         * Add a title to the link cache, return the page_id or zero if non-existent
         *
         * @param $nt Title object to add
         * @return Integer
         */
        public function addLinkObj( $nt ) {
                global $wgAntiLockFlags, $wgContentHandlerUseDB;

                wfProfileIn( __METHOD__ );

                $key = $nt->getPrefixedDBkey();
                if ( $this->isBadLink( $key ) || $nt->isExternal() ) {
                        wfProfileOut( __METHOD__ );

                        return 0;
                }
                $id = $this->getGoodLinkID( $key );
                if ( $id != 0 ) {
                        wfProfileOut( __METHOD__ );

                        return $id;
                }

                if ( $key === '' ) {
                        wfProfileOut( __METHOD__ );

                        return 0;
                }

                # Some fields heavily used for linking...
                if ( $this->mForUpdate ) {
                        $db = wfGetDB( DB_MASTER );
                        if ( !( $wgAntiLockFlags & ALF_NO_LINK_LOCK ) ) {
                                $options = array( 'FOR UPDATE' );
                        } else {
                                $options = array();
                        }
                } else {
                        $db = wfGetDB( DB_SLAVE );
                        $options = array();
                }

                $f = array( 'page_id', 'page_len', 'page_is_redirect', 'page_latest' );
                if ( $wgContentHandlerUseDB ) {
                        $f[] = 'page_content_model';
                }

                $s = $db->selectRow( 'page', $f,
                        array( 'page_namespace' => $nt->getNamespace(), 'page_title' => $nt->getDBkey() ),
                        __METHOD__, $options );
                # Set fields...
                if ( $s !== false ) {
                        $this->addGoodLinkObjFromRow( $nt, $s );
                        $id = intval( $s->page_id );
                } else {
                        $this->addBadLinkObj( $nt );
                        $id = 0;
                }

                wfProfileOut( __METHOD__ );

                return $id;
        }

        /**
         * Clears cache
         */
        public function clear() {
                $this->mGoodLinks = array();
                $this->mGoodLinkFields = array();
                $this->mBadLinks = array();
        }
}