* Some enhancements to live preview
[lhc/web/wiklou.git] / includes / Revision.php
index e7b6864..f5a84ca 100644 (file)
@@ -1,33 +1,32 @@
 <?php
 /**
- * @package MediaWiki
  * @todo document
  */
 
-/** */
-require_once( 'Database.php' );
-require_once( 'Article.php' );
-
 /**
- * @package MediaWiki
  * @todo document
  */
 class Revision {
+       const DELETED_TEXT = 1;
+       const DELETED_COMMENT = 2;
+       const DELETED_USER = 4;
+    const DELETED_RESTRICTED = 8;
+    const DELETED_NAME = 16;
+       
        /**
         * Load a page revision from a given revision ID number.
         * Returns null if no such revision can be found.
         *
         * @param int $id
-        * @static
         * @access public
+        * @static
         */
-       function &newFromId( $id ) {
+       public static function newFromId( $id ) {
                return Revision::newFromConds(
                        array( 'page_id=rev_page',
-                              'rev_id' => IntVal( $id ),
-                              'rev_id=old_id' ) );
+                              'rev_id' => intval( $id ) ) );
        }
-       
+
        /**
         * Load either the current, or a specified, revision
         * that's attached to a given title. If not attached
@@ -37,10 +36,11 @@ class Revision {
         * @param int $id
         * @return Revision
         * @access public
+        * @static
         */
-       function &newFromTitle( &$title, $id = 0 ) {
+       public static function newFromTitle( &$title, $id = 0 ) {
                if( $id ) {
-                       $matchId = IntVal( $id );
+                       $matchId = intval( $id );
                } else {
                        $matchId = 'page_latest';
                }
@@ -48,30 +48,135 @@ class Revision {
                        array( "rev_id=$matchId",
                               'page_id=rev_page',
                               'page_namespace' => $title->getNamespace(),
-                              'page_title'     => $title->getDbkey(),
-                              'rev_id=old_id' ) );
+                              'page_title'     => $title->getDbkey() ) );
        }
-       
+
+       /**
+        * 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
+        */
+       private static function newFromConds( $conditions ) {
+               $db = wfGetDB( DB_SLAVE );
+               $row = Revision::loadFromConds( $db, $conditions );
+               if( is_null( $row ) ) {
+                       $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
         */
-       function &newFromConds( $conditions ) {
-               $res =& Revision::fetchFromConds( $conditions );
+       private static function loadFromConds( $db, $conditions ) {
+               $res = Revision::fetchFromConds( $db, $conditions );
                if( $res ) {
                        $row = $res->fetchObject();
                        $res->free();
                        if( $row ) {
-                               return new Revision( $row );
+                               $ret = new Revision( $row );
+                               return $ret;
                        }
                }
-               return null;
+               $ret = null;
+               return $ret;
        }
-       
+
        /**
         * Return a wrapper for a series of database rows to
         * fetch all of a given page's revisions in turn.
@@ -79,17 +184,17 @@ class Revision {
         *
         * @param Title $title
         * @return ResultWrapper
-        * @static
         * @access public
+        * @static
         */
-       function &fetchAllRevisions( &$title ) {
+       public static function fetchAllRevisions( &$title ) {
                return Revision::fetchFromConds(
+                       wfGetDB( DB_SLAVE ),
                        array( 'page_namespace' => $title->getNamespace(),
                               'page_title'     => $title->getDbkey(),
-                              'page_id=rev_page',
-                              'rev_id=old_id' ) );             
+                              'page_id=rev_page' ) );
        }
-       
+
        /**
         * Return a wrapper for a series of database rows to
         * fetch all of a given page's revisions in turn.
@@ -97,163 +202,311 @@ class Revision {
         *
         * @param Title $title
         * @return ResultWrapper
-        * @static
         * @access public
+        * @static
         */
-       function &fetchRevision( &$title ) {
+       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',
-                              'rev_id=old_id' ) );             
+                              '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
-        * @static
         * @access private
+        * @static
         */
-       function &fetchFromConds( $conditions ) {
-               $dbr =& wfGetDB( DB_SLAVE );
-               $res = $dbr->select(
-                       array( 'page', 'revision', 'text' ),
+       private static function fetchFromConds( $db, $conditions ) {
+               $res = $db->select(
+                       array( 'page', 'revision' ),
                        array( 'page_namespace',
                               'page_title',
                               'page_latest',
                               'rev_id',
                               'rev_page',
+                              'rev_text_id',
                               'rev_comment',
                               'rev_user_text',
                               'rev_user',
                               'rev_minor_edit',
                               'rev_timestamp',
-                              'old_flags',
-                              'old_text' ),
+                              'rev_deleted' ),
                        $conditions,
-                       'Revision::fetchRow' );
-               return $dbr->resultObject( $res );
+                       'Revision::fetchRow',
+                       array( 'LIMIT' => 1 ) );
+               $ret = $db->resultObject( $res );
+               return $ret;
        }
-       
+
        /**
         * @param object $row
         * @access private
         */
        function Revision( $row ) {
-               $this->mId        = IntVal( $row->rev_id );
-               $this->mPage      = IntVal( $row->rev_page );
-               $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->mCurrent   = ( $row->rev_id == $row->page_latest );
-               $this->mTitle     = Title::makeTitle( $row->page_namespace,
-                                                     $row->page_title );
-               $this->mText      = $this->getRevisionText( $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->page_latest ) ) {
+                               $this->mCurrent   = ( $row->rev_id == $row->page_latest );
+                               $this->mTitle     = Title::makeTitle( $row->page_namespace,
+                                                                     $row->page_title );
+                       } 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;
+
+                       // 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;
+               } else {
+                       throw new MWException( 'Revision constructor passed invalid row format.' );
+               }
        }
-       
+
        /**#@+
         * @access public
         */
-       
+
        /**
         * @return int
         */
        function getId() {
                return $this->mId;
        }
-       
+
+       /**
+        * @return int
+        */
+       function getTextId() {
+               return $this->mTextId;
+       }
+
        /**
         * Returns the title of the page associated with this entry.
         * @return Title
         */
-       function &getTitle() {
+       function getTitle() {
                if( isset( $this->mTitle ) ) {
                        return $this->mTitle;
                }
-               $dbr =& wfGetDB( DB_SLAVE );
+               $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' );
+                       'Revision::getTitle' );
                if( $row ) {
-                       $this->mTitle =& Title::makeTitle( $row->page_namespace,
+                       $this->mTitle = Title::makeTitle( $row->page_namespace,
                                                           $row->page_title );
                }
                return $this->mTitle;
        }
-       
+
+       /**
+        * Set the title of the revision
+        * @param Title $title
+        */
+       function setTitle( $title ) {
+               $this->mTitle = $title;
+       }
+
+       /**
+        * @return int
+        */
+       function getPage() {
+               return $this->mPage;
+       }
+
        /**
+        * Fetch revision's user id if it's available to all users
         * @return int
         */
        function getUser() {
+               if( $this->isDeleted( self::DELETED_USER ) ) {
+                       return 0;
+               } else {
+                       return $this->mUser;
+               }
+       }
+
+       /**
+        * Fetch revision's user id without regard for the current user's permissions
+        * @return string
+        */
+       function getRawUser() {
                return $this->mUser;
        }
-       
+
        /**
+        * Fetch revision's username if it's available to all users
         * @return string
         */
        function getUserText() {
+               if( $this->isDeleted( self::DELETED_USER ) ) {
+                       return "";
+               } else {
+                       return $this->mUserText;
+               }
+       }
+
+       /**
+        * Fetch revision's username without regard for view restrictions
+        * @return string
+        */
+       function getRawUserText() {
                return $this->mUserText;
        }
        
        /**
+        * Fetch revision comment if it's available to all users
         * @return string
         */
        function getComment() {
+               if( $this->isDeleted( self::DELETED_COMMENT ) ) {
+                       return "";
+               } else {
+                       return $this->mComment;
+               }
+       }
+
+       /**
+        * Fetch revision comment without regard for the current user's permissions
+        * @return string
+        */
+       function getRawComment() {
                return $this->mComment;
        }
-       
+
        /**
         * @return bool
         */
        function isMinor() {
                return (bool)$this->mMinorEdit;
        }
-       
+
+       /**
+        * int $field one of DELETED_* bitfield constants
+        * @return bool
+        */
+       function isDeleted( $field ) {
+               return ($this->mDeleted & $field) == $field;
+       }
+
        /**
+        * Fetch revision text if it's available to all users
         * @return string
         */
        function getText() {
+               if( $this->isDeleted( self::DELETED_TEXT ) ) {
+                       return "";
+               } else {
+                       return $this->getRawText();
+               }
+       }
+       
+       /**
+        * Fetch revision text without regard for view restrictions
+        * @return string
+        */
+       function getRawText() {
+               if( is_null( $this->mText ) ) {
+                       // Revision text is immutable. Load on demand:
+                       $this->mText = $this->loadText();
+               }
                return $this->mText;
        }
        
+       /**
+        * Fetch revision text if it's available to THIS user
+        * @return string
+        */
+       function revText() {
+               if( !$this->userCan( self::DELETED_TEXT ) ) {
+                       return "";
+               } else {
+                       return $this->getRawText();
+               }
+       }
+
        /**
         * @return string
         */
        function getTimestamp() {
-               return $this->mTimestamp;
+               return wfTimestamp(TS_MW, $this->mTimestamp);
        }
-       
+
        /**
         * @return bool
         */
        function isCurrent() {
                return $this->mCurrent;
        }
-       
+
        /**
         * @return Revision
         */
-       function &getPrevious() {
+       function getPrevious() {
                $prev = $this->mTitle->getPreviousRevisionID( $this->mId );
-               return Revision::newFromTitle( $this->mTitle, $prev );
+               if ( $prev ) {
+                       return Revision::newFromTitle( $this->mTitle, $prev );
+               } else {
+                       return null;
+               }
        }
 
        /**
         * @return Revision
         */
-       function &getNext() {
+       function getNext() {
                $next = $this->mTitle->getNextRevisionID( $this->mId );
-               return Revision::newFromTitle( $this->mTitle, $next );
+               if ( $next ) {
+                       return Revision::newFromTitle( $this->mTitle, $next );
+               } else {
+                       return null;
+               }
        }
        /**#@-*/
 
@@ -266,10 +519,10 @@ class Revision {
          * @param string $prefix table prefix (default 'old_')
          * @return string $text|false the text requested
          */
-       function getRevisionText( $row, $prefix = 'old_' ) {
+       public static function getRevisionText( $row, $prefix = 'old_' ) {
                $fname = 'Revision::getRevisionText';
                wfProfileIn( $fname );
-               
+
                # Get data
                $textField = $prefix . 'text';
                $flagsField = $prefix . 'flags';
@@ -287,31 +540,44 @@ class Revision {
                        return 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 );
+               # 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( $fname );
+                               return false;
+                       }
+                       $text=ExternalStore::fetchFromURL($url);
                }
-                       
-               if( in_array( 'object', $flags ) ) {
-                       # Generic compressed storage
-                       $obj = unserialize( $text );
 
-                       # Bugger, corrupted my test database by double-serializing
-                       if ( !is_object( $obj ) ) {
-                               $obj = unserialize( $obj );
+               // 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 );
                        }
 
-                       $text = $obj->getText();
-               }
-       
-               global $wgLegacyEncoding;
-               if( $wgLegacyEncoding && !in_array( 'utf-8', $flags ) ) {
-                       # Old revisions kept around in a legacy encoding?
-                       # Upconvert on demand.
-                       global $wgInputEncoding, $wgContLang;
-                       $text = $wgContLang->iconv( $wgLegacyEncoding, $wgInputEncoding, $text );
+                       if( in_array( 'object', $flags ) ) {
+                               # Generic compressed storage
+                               $obj = unserialize( $text );
+                               if ( !is_object( $obj ) ) {
+                                       // Invalid object
+                                       wfProfileOut( $fname );
+                                       return false;
+                               }
+                               $text = $obj->getText();
+                       }
+
+                       global $wgLegacyEncoding;
+                       if( $wgLegacyEncoding && !in_array( 'utf-8', $flags ) ) {
+                               # Old revisions kept around in a legacy encoding?
+                               # Upconvert on demand.
+                               global $wgInputEncoding, $wgContLang;
+                               $text = $wgContLang->iconv( $wgLegacyEncoding, $wgInputEncoding . '//IGNORE', $text );
+                       }
                }
                wfProfileOut( $fname );
                return $text;
@@ -329,13 +595,13 @@ class Revision {
         * @return string
         */
        function compressRevisionText( &$text ) {
-               global $wgCompressRevisions, $wgUseLatin1;
+               global $wgCompressRevisions;
                $flags = array();
-               if( !$wgUseLatin1 ) {
-                       # Revisions not marked this way will be converted
-                       # on load if $wgLegacyCharset is set in the future.
-                       $flags[] = 'utf-8';
-               }
+
+               # 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 );
@@ -346,5 +612,244 @@ class Revision {
                }
                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 $dbw
+        * @return int
+        */
+       function insertOn( &$dbw ) {
+               global $wgDefaultExternalStore;
+               
+               $fname = 'Revision::insertOn';
+               wfProfileIn( $fname );
+
+               $data = $this->mText;
+               $flags = Revision::compressRevisionText( $data );
+
+               # Write to external storage if required
+               if ( $wgDefaultExternalStore ) {
+                       if ( is_array( $wgDefaultExternalStore ) ) {
+                               // Distribute storage across multiple clusters
+                               $store = $wgDefaultExternalStore[mt_rand(0, count( $wgDefaultExternalStore ) - 1)];
+                       } else {
+                               $store = $wgDefaultExternalStore;
+                       }
+                       // Store and get the URL
+                       $data = ExternalStore::insert( $store, $data );
+                       if ( !$data ) {
+                               # This should only happen in the case of a configuration error, where the external store is not valid
+                               throw new MWException( "Unable to store text to external storage $store" );
+                       }
+                       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,
+                               ), $fname
+                       );
+                       $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,
+                       ), $fname
+               );
+
+               $this->mId = !is_null($rev_id) ? $rev_id : $dbw->insertId();
+               wfProfileOut( $fname );
+               return $this->mId;
+       }
+
+       /**
+        * Lazy-load the revision's text.
+        * Currently hardcoded to the 'text' table storage engine.
+        *
+        * @return string
+        * @access private
+        */
+       function loadText() {
+               $fname = 'Revision::loadText';
+               wfProfileIn( $fname );
+               
+               // Caching may be beneficial for massive use of external storage
+               global $wgRevisionCacheExpiry, $wgMemc;
+               $key = wfMemcKey( 'revisiontext', 'textid', $this->getTextId() );
+               if( $wgRevisionCacheExpiry ) {
+                       $text = $wgMemc->get( $key );
+                       if( is_string( $text ) ) {
+                               wfProfileOut( $fname );
+                               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() ),
+                               $fname);
+               }
+
+               if( !$row ) {
+                       // Possible slave lag!
+                       $dbw = wfGetDB( DB_MASTER );
+                       $row = $dbw->selectRow( 'text',
+                               array( 'old_text', 'old_flags' ),
+                               array( 'old_id' => $this->getTextId() ),
+                               $fname);
+               }
+
+               $text = Revision::getRevisionText( $row );
+               
+               if( $wgRevisionCacheExpiry ) {
+                       $wgMemc->set( $key, $text, $wgRevisionCacheExpiry );
+               }
+               
+               wfProfileOut( $fname );
+
+               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     $minor
+        * @return Revision
+        */
+       function newNullRevision( &$dbw, $pageId, $summary, $minor ) {
+               $fname = 'Revision::newNullRevision';
+               wfProfileIn( $fname );
+
+               $current = $dbw->selectRow(
+                       array( 'page', 'revision' ),
+                       array( 'page_latest', 'rev_text_id' ),
+                       array(
+                               'page_id' => $pageId,
+                               'page_latest=rev_id',
+                               ),
+                       $fname );
+
+               if( $current ) {
+                       $revision = new Revision( array(
+                               'page'       => $pageId,
+                               'comment'    => $summary,
+                               'minor_edit' => $minor,
+                               'text_id'    => $current->rev_text_id,
+                               ) );
+               } else {
+                       $revision = null;
+               }
+
+               wfProfileOut( $fname );
+               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
+        */
+       function userCan( $field ) {
+               if( ( $this->mDeleted & $field ) == $field ) {
+                       global $wgUser;
+                       $permission = ( $this->mDeleted & self::DELETED_RESTRICTED ) == self::DELETED_RESTRICTED
+                               ? 'hiderevision'
+                               : '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 integer $id
+        */
+       static function getTimestampFromID( $id ) {
+               $dbr = wfGetDB( DB_SLAVE );
+               $timestamp = $dbr->selectField( 'revision', 'rev_timestamp', 
+                       array( 'rev_id' => $id ), __METHOD__ );
+               if ( $timestamp === false ) {
+                       # Not in slave, try master
+                       $dbw = wfGetDB( DB_MASTER );
+                       $timestamp = $dbw->selectField( 'revision', 'rev_timestamp', 
+                               array( 'rev_id' => $id ), __METHOD__ );
+               }
+               return $timestamp;
+       }
+       
+       static function countByPageId( $db, $id ) {
+               $row = $db->selectRow( 'revision', 'COUNT(*) AS revCount',
+                       array( 'rev_page' => $id ), __METHOD__ );
+               if( $row ) {
+                       return $row->revCount;
+               }
+               return 0;
+       }
+       
+       static function countByTitle( $db, $title ) {
+               $id = $title->getArticleId();
+               if( $id ) {
+                       return Revision::countByPageId( $db, $id );
+               }
+               return 0;
+       }
 }
-?>
\ No newline at end of file
+
+/**
+ * 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 );
+
+
+?>