Fix typo reported at twn

[mediawiki.git] / includes / Revision.php

<?php
/**
 * @todo document
 * @file
 */

/**
 * @todo document
 */
class Revision {
        const DELETED_TEXT = 1;
        const DELETED_COMMENT = 2;
        const DELETED_USER = 4;
        const DELETED_RESTRICTED = 8;
        // Convenience field
        const SUPPRESSED_USER = 12;
        // Audience options for Revision::getText()
        const FOR_PUBLIC = 1;
        const FOR_THIS_USER = 2;
        const RAW = 3;

        /**
         * Load a page revision from a given revision ID number.
         * Returns null if no such revision can be found.
         *
         * @param int $id
         * @access public
         * @static
         */
        public static function newFromId( $id ) {
                return Revision::newFromConds(
                        array( 'page_id=rev_page',
                               'rev_id' => intval( $id ) ) );
        }

        /**
         * Load either the current, or a specified, revision
         * that's attached to a given title. If not attached
         * to that title, will return null.
         *
         * @param Title $title
         * @param int $id
         * @return Revision
         */
        public static function newFromTitle( $title, $id = 0 ) {
                $conds = array( 
                        'page_namespace' => $title->getNamespace(), 
                        'page_title' => $title->getDBkey()
                );
                if ( $id ) {
                        // Use the specified ID
                        $conds['rev_id'] = $id;
                } elseif ( wfGetLB()->getServerCount() > 1 ) {
                        // Get the latest revision ID from the master
                        $dbw = wfGetDB( DB_MASTER );
                        $latest = $dbw->selectField( 'page', 'page_latest', $conds, __METHOD__ );
                        if ( $latest === false ) {
                                // Page does not exist
                                return null;
                        }
                        $conds['rev_id'] = $latest;
                } else {
                        // Use a join to get the latest revision
                        $conds[] = 'rev_id=page_latest';
                }
                $conds[] = 'page_id=rev_page';
                return Revision::newFromConds( $conds );
        }

        /**
         * Make a fake revision object from an archive table row. This is queried
         * for permissions or even inserted (as in Special:Undelete)
         * @fixme: should be a subclass for RevisionDelete. [TS]
         */
        public static function newFromArchiveRow( $row, $overrides = array() ) {
                $attribs = $overrides + array(
                        'page'       => isset( $row->page_id ) ? $row->page_id : null,
                        'id'         => isset( $row->ar_rev_id ) ? $row->ar_rev_id : null,
                        'comment'    => $row->ar_comment,
                        'user'       => $row->ar_user,
                        'user_text'  => $row->ar_user_text,
                        'timestamp'  => $row->ar_timestamp,
                        'minor_edit' => $row->ar_minor_edit,
                        'text_id'    => isset( $row->ar_text_id ) ? $row->ar_text_id : null,
                        'deleted'    => $row->ar_deleted,
                        'len'        => $row->ar_len);
                if ( isset( $row->ar_text ) && !$row->ar_text_id ) {
                        // Pre-1.5 ar_text row
                        $attribs['text'] = self::getRevisionText( $row, 'ar_' );
                }
                return new self( $attribs );
        }

        /**
         * Load a page revision from a given revision ID number.
         * Returns null if no such revision can be found.
         *
         * @param Database $db
         * @param int $id
         * @access public
         * @static
         */
        public static function loadFromId( $db, $id ) {
                return Revision::loadFromConds( $db,
                        array( 'page_id=rev_page',
                               'rev_id' => intval( $id ) ) );
        }

        /**
         * Load either the current, or a specified, revision
         * that's attached to a given page. If not attached
         * to that page, will return null.
         *
         * @param Database $db
         * @param int $pageid
         * @param int $id
         * @return Revision
         * @access public
         * @static
         */
        public static function loadFromPageId( $db, $pageid, $id = 0 ) {
                $conds=array('page_id=rev_page','rev_page'=>intval( $pageid ), 'page_id'=>intval( $pageid ));
                if( $id ) {
                        $conds['rev_id']=intval($id);
                } else {
                        $conds[]='rev_id=page_latest';
                }
                return Revision::loadFromConds( $db, $conds );
        }

        /**
         * Load either the current, or a specified, revision
         * that's attached to a given page. If not attached
         * to that page, will return null.
         *
         * @param Database $db
         * @param Title $title
         * @param int $id
         * @return Revision
         * @access public
         * @static
         */
        public static function loadFromTitle( $db, $title, $id = 0 ) {
                if( $id ) {
                        $matchId = intval( $id );
                } else {
                        $matchId = 'page_latest';
                }
                return Revision::loadFromConds(
                        $db,
                        array( "rev_id=$matchId",
                               'page_id=rev_page',
                               'page_namespace' => $title->getNamespace(),
                               'page_title'     => $title->getDBkey() ) );
        }

        /**
         * Load the revision for the given title with the given timestamp.
         * WARNING: Timestamps may in some circumstances not be unique,
         * so this isn't the best key to use.
         *
         * @param Database $db
         * @param Title $title
         * @param string $timestamp
         * @return Revision
         * @access public
         * @static
         */
        public static function loadFromTimestamp( $db, $title, $timestamp ) {
                return Revision::loadFromConds(
                        $db,
                        array( 'rev_timestamp'  => $db->timestamp( $timestamp ),
                               'page_id=rev_page',
                               'page_namespace' => $title->getNamespace(),
                               'page_title'     => $title->getDBkey() ) );
        }

        /**
         * Given a set of conditions, fetch a revision.
         *
         * @param array $conditions
         * @return Revision
         * @access private
         * @static
         */
        public static function newFromConds( $conditions ) {
                $db = wfGetDB( DB_SLAVE );
                $row = Revision::loadFromConds( $db, $conditions );
                if( is_null( $row ) && wfGetLB()->getServerCount() > 1 ) {
                        $dbw = wfGetDB( DB_MASTER );
                        $row = Revision::loadFromConds( $dbw, $conditions );
                }
                return $row;
        }

        /**
         * Given a set of conditions, fetch a revision from
         * the given database connection.
         *
         * @param Database $db
         * @param array $conditions
         * @return Revision
         * @access private
         * @static
         */
        private static function loadFromConds( $db, $conditions ) {
                $res = Revision::fetchFromConds( $db, $conditions );
                if( $res ) {
                        $row = $res->fetchObject();
                        $res->free();
                        if( $row ) {
                                $ret = new Revision( $row );
                                return $ret;
                        }
                }
                $ret = null;
                return $ret;
        }

        /**
         * Return a wrapper for a series of database rows to
         * fetch all of a given page's revisions in turn.
         * Each row can be fed to the constructor to get objects.
         *
         * @param Title $title
         * @return ResultWrapper
         * @access public
         * @static
         */
        public static function fetchRevision( $title ) {
                return Revision::fetchFromConds(
                        wfGetDB( DB_SLAVE ),
                        array( 'rev_id=page_latest',
                               'page_namespace' => $title->getNamespace(),
                               'page_title'     => $title->getDBkey(),
                               'page_id=rev_page' ) );
        }

        /**
         * Given a set of conditions, return a ResultWrapper
         * which will return matching database rows with the
         * fields necessary to build Revision objects.
         *
         * @param Database $db
         * @param array $conditions
         * @return ResultWrapper
         * @access private
         * @static
         */
        private static function fetchFromConds( $db, $conditions ) {
                $fields = self::selectFields();
                $fields[] = 'page_namespace';
                $fields[] = 'page_title';
                $fields[] = 'page_latest';
                $res = $db->select(
                        array( 'page', 'revision' ),
                        $fields,
                        $conditions,
                        __METHOD__,
                        array( 'LIMIT' => 1 ) );
                $ret = $db->resultObject( $res );
                return $ret;
        }

        /**
         * Return the list of revision fields that should be selected to create
         * a new revision.
         */
        static function selectFields() {
                return array(
                        'rev_id',
                        'rev_page',
                        'rev_text_id',
                        'rev_timestamp',
                        'rev_comment',
                        'rev_user_text,'.
                        'rev_user',
                        'rev_minor_edit',
                        'rev_deleted',
                        'rev_len',
                        'rev_parent_id'
                );
        }
        
        /**
         * Return the list of text fields that should be selected to read the 
         * revision text
         */
        static function selectTextFields() {
                return array(
                        'old_text',
                        'old_flags'
                );
        }
        /**
         * Return the list of page fields that should be selected from page table
         */
        static function selectPageFields() {
                return array(
                        'page_namespace',
                        'page_title',
                        'page_latest'
                );
        }

        /**
         * @param object $row
         * @access private
         */
        function Revision( $row ) {
                if( is_object( $row ) ) {
                        $this->mId        = intval( $row->rev_id );
                        $this->mPage      = intval( $row->rev_page );
                        $this->mTextId    = intval( $row->rev_text_id );
                        $this->mComment   =         $row->rev_comment;
                        $this->mUserText  =         $row->rev_user_text;
                        $this->mUser      = intval( $row->rev_user );
                        $this->mMinorEdit = intval( $row->rev_minor_edit );
                        $this->mTimestamp =         $row->rev_timestamp;
                        $this->mDeleted   = intval( $row->rev_deleted );

                        if( !isset( $row->rev_parent_id ) )
                                $this->mParentId = is_null($row->rev_parent_id) ? null : 0;
                        else
                                $this->mParentId  = intval( $row->rev_parent_id );

                        if( !isset( $row->rev_len ) || is_null( $row->rev_len ) )
                                $this->mSize = null;
                        else
                                $this->mSize = intval( $row->rev_len );

                        if( isset( $row->page_latest ) ) {
                                $this->mCurrent = ( $row->rev_id == $row->page_latest );
                                $this->mTitle = Title::makeTitle( $row->page_namespace, $row->page_title );
                                $this->mTitle->resetArticleID( $this->mPage );
                        } else {
                                $this->mCurrent = false;
                                $this->mTitle = null;
                        }

                        // Lazy extraction...
                        $this->mText      = null;
                        if( isset( $row->old_text ) ) {
                                $this->mTextRow = $row;
                        } else {
                                // 'text' table row entry will be lazy-loaded
                                $this->mTextRow = null;
                        }
                } elseif( is_array( $row ) ) {
                        // Build a new revision to be saved...
                        global $wgUser;

                        $this->mId        = isset( $row['id']         ) ? intval( $row['id']         ) : null;
                        $this->mPage      = isset( $row['page']       ) ? intval( $row['page']       ) : null;
                        $this->mTextId    = isset( $row['text_id']    ) ? intval( $row['text_id']    ) : null;
                        $this->mUserText  = isset( $row['user_text']  ) ? strval( $row['user_text']  ) : $wgUser->getName();
                        $this->mUser      = isset( $row['user']       ) ? intval( $row['user']       ) : $wgUser->getId();
                        $this->mMinorEdit = isset( $row['minor_edit'] ) ? intval( $row['minor_edit'] ) : 0;
                        $this->mTimestamp = isset( $row['timestamp']  ) ? strval( $row['timestamp']  ) : wfTimestamp( TS_MW );
                        $this->mDeleted   = isset( $row['deleted']    ) ? intval( $row['deleted']    ) : 0;
                        $this->mSize      = isset( $row['len']        ) ? intval( $row['len']        ) : null;
                        $this->mParentId  = isset( $row['parent_id']  ) ? intval( $row['parent_id']  ) : null;

                        // Enforce spacing trimming on supplied text
                        $this->mComment   = isset( $row['comment']    ) ?  trim( strval( $row['comment'] ) ) : null;
                        $this->mText      = isset( $row['text']       ) ? rtrim( strval( $row['text']    ) ) : null;
                        $this->mTextRow   = null;

                        $this->mTitle     = null; # Load on demand if needed
                        $this->mCurrent   = false;
                        # If we still have no len_size, see it we have the text to figure it out
                        if ( !$this->mSize )
                                $this->mSize      = is_null($this->mText) ? null : strlen($this->mText);
                } else {
                        throw new MWException( 'Revision constructor passed invalid row format.' );
                }
                $this->mUnpatrolled = NULL;
        }

        /**#@+
         * @access public
         */

        /**
         * Get revision ID
         * @return int
         */
        public function getId() {
                return $this->mId;
        }

        /**
         * Get text row ID
         * @return int
         */
        public function getTextId() {
                return $this->mTextId;
        }

        /**
         * Get parent revision ID (the original previous page revision)
         * @return int
         */
        public function getParentId() {
                return $this->mParentId;
        }

        /**
         * Returns the length of the text in this revision, or null if unknown.
         * @return int
         */
        public function getSize() {
                return $this->mSize;
        }

        /**
         * Returns the title of the page associated with this entry.
         * @return Title
         */
        public function getTitle() {
                if( isset( $this->mTitle ) ) {
                        return $this->mTitle;
                }
                $dbr = wfGetDB( DB_SLAVE );
                $row = $dbr->selectRow(
                        array( 'page', 'revision' ),
                        array( 'page_namespace', 'page_title' ),
                        array( 'page_id=rev_page',
                               'rev_id' => $this->mId ),
                        'Revision::getTitle' );
                if( $row ) {
                        $this->mTitle = Title::makeTitle( $row->page_namespace,
                                                          $row->page_title );
                }
                return $this->mTitle;
        }

        /**
         * Set the title of the revision
         * @param Title $title
         */
        public function setTitle( $title ) {
                $this->mTitle = $title;
        }

        /**
         * Get the page ID
         * @return int
         */
        public function getPage() {
                return $this->mPage;
        }

        /**
         * Fetch revision's user id if it's available to the specified audience.
         * If the specified audience does not have access to it, zero will be 
         * returned.
         *
         * @param integer $audience One of:
         *      Revision::FOR_PUBLIC       to be displayed to all users
         *      Revision::FOR_THIS_USER    to be displayed to $wgUser
         *      Revision::RAW              get the ID regardless of permissions
         *
         *
         * @return int
         */
        public function getUser( $audience = self::FOR_PUBLIC ) {
                if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_USER ) ) {
                        return 0;
                } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_USER ) ) {
                        return 0;
                } else {
                        return $this->mUser;
                }
        }

        /**
         * Fetch revision's user id without regard for the current user's permissions
         * @return string
         */
        public function getRawUser() {
                return $this->mUser;
        }

        /**
         * Fetch revision's username if it's available to the specified audience.
         * If the specified audience does not have access to the username, an 
         * empty string will be returned.
         *
         * @param integer $audience One of:
         *      Revision::FOR_PUBLIC       to be displayed to all users
         *      Revision::FOR_THIS_USER    to be displayed to $wgUser
         *      Revision::RAW              get the text regardless of permissions
         *
         * @return string
         */
        public function getUserText( $audience = self::FOR_PUBLIC ) {
                if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_USER ) ) {
                        return "";
                } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_USER ) ) {
                        return "";
                } else {
                        return $this->mUserText;
                }
        }

        /**
         * Fetch revision's username without regard for view restrictions
         * @return string
         */
        public function getRawUserText() {
                return $this->mUserText;
        }

        /**
         * Fetch revision comment if it's available to the specified audience.
         * If the specified audience does not have access to the comment, an 
         * empty string will be returned.
         *
         * @param integer $audience One of:
         *      Revision::FOR_PUBLIC       to be displayed to all users
         *      Revision::FOR_THIS_USER    to be displayed to $wgUser
         *      Revision::RAW              get the text regardless of permissions
         *
         * @return string
         */
        function getComment( $audience = self::FOR_PUBLIC ) {
                if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_COMMENT ) ) {
                        return "";
                } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_COMMENT ) ) {
                        return "";
                } else {
                        return $this->mComment;
                }
        }

        /**
         * Fetch revision comment without regard for the current user's permissions
         * @return string
         */
        public function getRawComment() {
                return $this->mComment;
        }

        /**
         * @return bool
         */
        public function isMinor() {
                return (bool)$this->mMinorEdit;
        }
        
        /**
         * @return int rcid of the unpatrolled row, zero if there isn't one
         */
        public function isUnpatrolled() {
                if( $this->mUnpatrolled !== NULL ) {
                        return $this->mUnpatrolled;
                }
                $dbr = wfGetDB( DB_SLAVE );
                $this->mUnpatrolled = $dbr->selectField( 'recentchanges',
                        'rc_id',
                        array( // Add redundant user,timestamp condition so we can use the existing index
                                'rc_user_text'  => $this->getRawUserText(),
                                'rc_timestamp'  => $dbr->timestamp( $this->getTimestamp() ),
                                'rc_this_oldid' => $this->getId(),
                                'rc_patrolled'  => 0
                        ),
                        __METHOD__
                );
                return (int)$this->mUnpatrolled;
        }

        /**
         * int $field one of DELETED_* bitfield constants
         * @return bool
         */
        public function isDeleted( $field ) {
                return ($this->mDeleted & $field) == $field;
        }
        
        /**
         * Get the deletion bitfield of the revision
         */     
        public function getVisibility() {
                return (int)$this->mDeleted;
        }

        /**
         * Fetch revision text if it's available to the specified audience.
         * If the specified audience does not have the ability to view this 
         * revision, an empty string will be returned.
         *
         * @param integer $audience One of:
         *      Revision::FOR_PUBLIC       to be displayed to all users
         *      Revision::FOR_THIS_USER    to be displayed to $wgUser
         *      Revision::RAW              get the text regardless of permissions
         *
         *
         * @return string
         */
        public function getText( $audience = self::FOR_PUBLIC ) {
                if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_TEXT ) ) {
                        return "";
                } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_TEXT ) ) {
                        return "";
                } else {
                        return $this->getRawText();
                }
        }

        /**
         * Alias for getText(Revision::FOR_THIS_USER)
         */
        public function revText() {
                return $this->getText( self::FOR_THIS_USER );
        }

        /**
         * Fetch revision text without regard for view restrictions
         * @return string
         */
        public function getRawText() {
                if( is_null( $this->mText ) ) {
                        // Revision text is immutable. Load on demand:
                        $this->mText = $this->loadText();
                }
                return $this->mText;
        }

        /**
         * @return string
         */
        public function getTimestamp() {
                return wfTimestamp(TS_MW, $this->mTimestamp);
        }

        /**
         * @return bool
         */
        public function isCurrent() {
                return $this->mCurrent;
        }

        /**
         * Get previous revision for this title
         * @return Revision
         */
        public function getPrevious() {
                if( $this->getTitle() ) {
                        $prev = $this->getTitle()->getPreviousRevisionID( $this->getId() );
                        if( $prev ) {
                                return Revision::newFromTitle( $this->getTitle(), $prev );
                        }
                }
                return null;
        }

        /**
         * @return Revision
         */
        public function getNext() {
                if( $this->getTitle() ) {
                        $next = $this->getTitle()->getNextRevisionID( $this->getId() );
                        if ( $next ) {
                                return Revision::newFromTitle( $this->getTitle(), $next );
                        }
                }
                return null;
        }

        /**
         * Get previous revision Id for this page_id
         * This is used to populate rev_parent_id on save
         * @param Database $db
         * @return int
         */
        private function getPreviousRevisionId( $db ) {
                if( is_null($this->mPage) ) {
                        return 0;
                }
                # Use page_latest if ID is not given
                if( !$this->mId ) {
                        $prevId = $db->selectField( 'page', 'page_latest',
                                array( 'page_id' => $this->mPage ),
                                __METHOD__ );
                } else {
                        $prevId = $db->selectField( 'revision', 'rev_id',
                                array( 'rev_page' => $this->mPage, 'rev_id < ' . $this->mId ),
                                __METHOD__,
                                array( 'ORDER BY' => 'rev_id DESC' ) );
                }
                return intval($prevId);
        }

        /**
          * Get revision text associated with an old or archive row
          * $row is usually an object from wfFetchRow(), both the flags and the text
          * field must be included
          *
          * @param object $row The text data
          * @param string $prefix table prefix (default 'old_')
          * @return string $text|false the text requested
          */
        public static function getRevisionText( $row, $prefix = 'old_' ) {
                wfProfileIn( __METHOD__ );

                # Get data
                $textField = $prefix . 'text';
                $flagsField = $prefix . 'flags';

                if( isset( $row->$flagsField ) ) {
                        $flags = explode( ',', $row->$flagsField );
                } else {
                        $flags = array();
                }

                if( isset( $row->$textField ) ) {
                        $text = $row->$textField;
                } else {
                        wfProfileOut( __METHOD__ );
                        return false;
                }

                # Use external methods for external objects, text in table is URL-only then
                if ( in_array( 'external', $flags ) ) {
                        $url=$text;
                        @list(/* $proto */,$path)=explode('://',$url,2);
                        if ($path=="") {
                                wfProfileOut( __METHOD__ );
                                return false;
                        }
                        $text=ExternalStore::fetchFromURL($url);
                }

                // If the text was fetched without an error, convert it
                if ( $text !== false ) {
                        if( in_array( 'gzip', $flags ) ) {
                                # Deal with optional compression of archived pages.
                                # This can be done periodically via maintenance/compressOld.php, and
                                # as pages are saved if $wgCompressRevisions is set.
                                $text = gzinflate( $text );
                        }

                        if( in_array( 'object', $flags ) ) {
                                # Generic compressed storage
                                $obj = unserialize( $text );
                                if ( !is_object( $obj ) ) {
                                        // Invalid object
                                        wfProfileOut( __METHOD__ );
                                        return false;
                                }
                                $text = $obj->getText();
                        }

                        global $wgLegacyEncoding;
                        if( $wgLegacyEncoding && !in_array( 'utf-8', $flags ) && !in_array( 'utf8', $flags ) ) {
                                # Old revisions kept around in a legacy encoding?
                                # Upconvert on demand.
                                # ("utf8" checked for compatibility with some broken
                                #  conversion scripts 2008-12-30)
                                global $wgInputEncoding, $wgContLang;
                                $text = $wgContLang->iconv( $wgLegacyEncoding, $wgInputEncoding, $text );
                        }
                }
                wfProfileOut( __METHOD__ );
                return $text;
        }

        /**
         * If $wgCompressRevisions is enabled, we will compress data.
         * The input string is modified in place.
         * Return value is the flags field: contains 'gzip' if the
         * data is compressed, and 'utf-8' if we're saving in UTF-8
         * mode.
         *
         * @param mixed $text reference to a text
         * @return string
         */
        public static function compressRevisionText( &$text ) {
                global $wgCompressRevisions;
                $flags = array();

                # Revisions not marked this way will be converted
                # on load if $wgLegacyCharset is set in the future.
                $flags[] = 'utf-8';

                if( $wgCompressRevisions ) {
                        if( function_exists( 'gzdeflate' ) ) {
                                $text = gzdeflate( $text );
                                $flags[] = 'gzip';
                        } else {
                                wfDebug( "Revision::compressRevisionText() -- no zlib support, not compressing\n" );
                        }
                }
                return implode( ',', $flags );
        }

        /**
         * Insert a new revision into the database, returning the new revision ID
         * number on success and dies horribly on failure.
         *
         * @param Database $dbw
         * @return int
         */
        public function insertOn( $dbw ) {
                global $wgDefaultExternalStore;

                wfProfileIn( __METHOD__ );

                $data = $this->mText;
                $flags = Revision::compressRevisionText( $data );

                # Write to external storage if required
                if( $wgDefaultExternalStore ) {
                        // Store and get the URL
                        $data = ExternalStore::insertToDefault( $data );
                        if( !$data ) {
                                throw new MWException( "Unable to store text to external storage" );
                        }
                        if( $flags ) {
                                $flags .= ',';
                        }
                        $flags .= 'external';
                }

                # Record the text (or external storage URL) to the text table
                if( !isset( $this->mTextId ) ) {
                        $old_id = $dbw->nextSequenceValue( 'text_old_id_val' );
                        $dbw->insert( 'text',
                                array(
                                        'old_id'    => $old_id,
                                        'old_text'  => $data,
                                        'old_flags' => $flags,
                                ), __METHOD__
                        );
                        $this->mTextId = $dbw->insertId();
                }

                # Record the edit in revisions
                $rev_id = isset( $this->mId )
                        ? $this->mId
                        : $dbw->nextSequenceValue( 'rev_rev_id_val' );
                $dbw->insert( 'revision',
                        array(
                                'rev_id'         => $rev_id,
                                'rev_page'       => $this->mPage,
                                'rev_text_id'    => $this->mTextId,
                                'rev_comment'    => $this->mComment,
                                'rev_minor_edit' => $this->mMinorEdit ? 1 : 0,
                                'rev_user'       => $this->mUser,
                                'rev_user_text'  => $this->mUserText,
                                'rev_timestamp'  => $dbw->timestamp( $this->mTimestamp ),
                                'rev_deleted'    => $this->mDeleted,
                                'rev_len'            => $this->mSize,
                                'rev_parent_id'  => is_null($this->mParentId) ?
                                        $this->getPreviousRevisionId( $dbw ) : $this->mParentId
                        ), __METHOD__
                );

                $this->mId = !is_null($rev_id) ? $rev_id : $dbw->insertId();
                
                wfRunHooks( 'RevisionInsertComplete', array( &$this, $data, $flags ) );
                
                wfProfileOut( __METHOD__ );
                return $this->mId;
        }

        /**
         * Lazy-load the revision's text.
         * Currently hardcoded to the 'text' table storage engine.
         *
         * @return string
         */
        protected function loadText() {
                wfProfileIn( __METHOD__ );

                // Caching may be beneficial for massive use of external storage
                global $wgRevisionCacheExpiry, $wgMemc;
                $textId = $this->getTextId();
                $key = wfMemcKey( 'revisiontext', 'textid', $textId );
                if( $wgRevisionCacheExpiry ) {
                        $text = $wgMemc->get( $key );
                        if( is_string( $text ) ) {
                                wfDebug( __METHOD__. ": got id $textId from cache\n" );
                                wfProfileOut( __METHOD__ );
                                return $text;
                        }
                }

                // If we kept data for lazy extraction, use it now...
                if ( isset( $this->mTextRow ) ) {
                        $row = $this->mTextRow;
                        $this->mTextRow = null;
                } else {
                        $row = null;
                }

                if( !$row ) {
                        // Text data is immutable; check slaves first.
                        $dbr = wfGetDB( DB_SLAVE );
                        $row = $dbr->selectRow( 'text',
                                array( 'old_text', 'old_flags' ),
                                array( 'old_id' => $this->getTextId() ),
                                __METHOD__ );
                }

                if( !$row && wfGetLB()->getServerCount() > 1 ) {
                        // Possible slave lag!
                        $dbw = wfGetDB( DB_MASTER );
                        $row = $dbw->selectRow( 'text',
                                array( 'old_text', 'old_flags' ),
                                array( 'old_id' => $this->getTextId() ),
                                __METHOD__ );
                }

                $text = self::getRevisionText( $row );

                # No negative caching -- negative hits on text rows may be due to corrupted slave servers
                if( $wgRevisionCacheExpiry && $text !== false ) {
                        $wgMemc->set( $key, $text, $wgRevisionCacheExpiry );
                }

                wfProfileOut( __METHOD__ );

                return $text;
        }

        /**
         * Create a new null-revision for insertion into a page's
         * history. This will not re-save the text, but simply refer
         * to the text from the previous version.
         *
         * Such revisions can for instance identify page rename
         * operations and other such meta-modifications.
         *
         * @param Database $dbw
         * @param int      $pageId ID number of the page to read from
         * @param string   $summary
         * @param bool     $minor
         * @return mixed Revision, or null on error
         */
        public static function newNullRevision( $dbw, $pageId, $summary, $minor ) {
                wfProfileIn( __METHOD__ );

                $current = $dbw->selectRow(
                        array( 'page', 'revision' ),
                        array( 'page_latest', 'rev_text_id', 'rev_len' ),
                        array(
                                'page_id' => $pageId,
                                'page_latest=rev_id',
                                ),
                        __METHOD__ );

                if( $current ) {
                        $revision = new Revision( array(
                                'page'       => $pageId,
                                'comment'    => $summary,
                                'minor_edit' => $minor,
                                'text_id'    => $current->rev_text_id,
                                'parent_id'  => $current->page_latest,
                                'len'        => $current->rev_len
                                ) );
                } else {
                        $revision = null;
                }

                wfProfileOut( __METHOD__ );
                return $revision;
        }

        /**
         * Determine if the current user is allowed to view a particular
         * field of this revision, if it's marked as deleted.
         * @param int $field one of self::DELETED_TEXT,
         *                          self::DELETED_COMMENT,
         *                          self::DELETED_USER
         * @return bool
         */
        public function userCan( $field ) {
                if( ( $this->mDeleted & $field ) == $field ) {
                        global $wgUser;
                        $permission = ( $this->mDeleted & self::DELETED_RESTRICTED ) == self::DELETED_RESTRICTED
                                ? 'suppressrevision'
                                : 'deleterevision';
                        wfDebug( "Checking for $permission due to $field match on $this->mDeleted\n" );
                        return $wgUser->isAllowed( $permission );
                } else {
                        return true;
                }
        }


        /**
         * Get rev_timestamp from rev_id, without loading the rest of the row
         * @param Title $title
         * @param integer $id
         */
        static function getTimestampFromId( $title, $id ) {
                $dbr = wfGetDB( DB_SLAVE );
                // Casting fix for DB2
                if ($id == '') {
                        $id = 0;
                }
                $conds = array( 'rev_id' => $id );
                $conds['rev_page'] = $title->getArticleId();
                $timestamp = $dbr->selectField( 'revision', 'rev_timestamp', $conds, __METHOD__ );
                if ( $timestamp === false && wfGetLB()->getServerCount() > 1 ) {
                        # Not in slave, try master
                        $dbw = wfGetDB( DB_MASTER );
                        $timestamp = $dbw->selectField( 'revision', 'rev_timestamp', $conds, __METHOD__ );
                }
                return wfTimestamp( TS_MW, $timestamp );
        }

        /**
         * Get count of revisions per page...not very efficient
         * @param Database $db
         * @param int $id, page id
         */
        static function countByPageId( $db, $id ) {
                $row = $db->selectRow( 'revision', 'COUNT(*) AS revCount',
                        array( 'rev_page' => $id ), __METHOD__ );
                if( $row ) {
                        return $row->revCount;
                }
                return 0;
        }

        /**
         * Get count of revisions per page...not very efficient
         * @param Database $db
         * @param Title $title
         */
        static function countByTitle( $db, $title ) {
                $id = $title->getArticleId();
                if( $id ) {
                        return Revision::countByPageId( $db, $id );
                }
                return 0;
        }
}

/**
 * Aliases for backwards compatibility with 1.6
 */
define( 'MW_REV_DELETED_TEXT', Revision::DELETED_TEXT );
define( 'MW_REV_DELETED_COMMENT', Revision::DELETED_COMMENT );
define( 'MW_REV_DELETED_USER', Revision::DELETED_USER );
define( 'MW_REV_DELETED_RESTRICTED', Revision::DELETED_RESTRICTED );