includes/Revision.php

   1 <?php
   2
   3 /**
   4  * @todo document
   5  */
   6 class Revision {
   7         const DELETED_TEXT = 1;
   8         const DELETED_COMMENT = 2;
   9         const DELETED_USER = 4;
  10         const DELETED_RESTRICTED = 8;
  11         // Convenience field
  12         const SUPPRESSED_USER = 12;
  13         // Audience options for Revision::getText()
  14         const FOR_PUBLIC = 1;
  15         const FOR_THIS_USER = 2;
  16         const RAW = 3;
  17
  18         /**
  19          * Load a page revision from a given revision ID number.
  20          * Returns null if no such revision can be found.
  21          *
  22          * @param $id Integer
  23          * @return Revision or null
  24          */
  25         public static function newFromId( $id ) {
  26                 return Revision::newFromConds(
  27                         array( 'page_id=rev_page',
  28                                    'rev_id' => intval( $id ) ) );
  29         }
  30
  31         /**
  32          * Load either the current, or a specified, revision
  33          * that's attached to a given title. If not attached
  34          * to that title, will return null.
  35          *
  36          * @param $title Title
  37          * @param $id Integer (optional)
  38          * @return Revision or null
  39          */
  40         public static function newFromTitle( $title, $id = 0 ) {
  41                 $conds = array(
  42                         'page_namespace' => $title->getNamespace(),
  43                         'page_title'     => $title->getDBkey()
  44                 );
  45                 if ( $id ) {
  46                         // Use the specified ID
  47                         $conds['rev_id'] = $id;
  48                 } elseif ( wfGetLB()->getServerCount() > 1 ) {
  49                         // Get the latest revision ID from the master
  50                         $dbw = wfGetDB( DB_MASTER );
  51                         $latest = $dbw->selectField( 'page', 'page_latest', $conds, __METHOD__ );
  52                         if ( $latest === false ) {
  53                                 return null; // page does not exist
  54                         }
  55                         $conds['rev_id'] = $latest;
  56                 } else {
  57                         // Use a join to get the latest revision
  58                         $conds[] = 'rev_id=page_latest';
  59                 }
  60                 $conds[] = 'page_id=rev_page';
  61                 return Revision::newFromConds( $conds );
  62         }
  63
  64         /**
  65          * Load either the current, or a specified, revision
  66          * that's attached to a given page ID.
  67          * Returns null if no such revision can be found.
  68          *
  69          * @param $revId Integer
  70          * @param $pageId Integer (optional)
  71          * @return Revision or null
  72          */
  73         public static function newFromPageId( $pageId, $revId = 0 ) {
  74                 $conds = array( 'page_id' => $pageId );
  75                 if ( $revId ) {
  76                         $conds['rev_id'] = $revId;
  77                 } elseif ( wfGetLB()->getServerCount() > 1 ) {
  78                         // Get the latest revision ID from the master
  79                         $dbw = wfGetDB( DB_MASTER );
  80                         $latest = $dbw->selectField( 'page', 'page_latest', $conds, __METHOD__ );
  81                         if ( $latest === false ) {
  82                                 return null; // page does not exist
  83                         }
  84                         $conds['rev_id'] = $latest;
  85                 } else {
  86                         $conds[] = 'rev_id = page_latest';
  87                 }
  88                 $conds[] = 'page_id=rev_page';
  89                 return Revision::newFromConds( $conds );
  90         }
  91
  92         /**
  93          * Make a fake revision object from an archive table row. This is queried
  94          * for permissions or even inserted (as in Special:Undelete)
  95          * @todo FIXME: Should be a subclass for RevisionDelete. [TS]
  96          *
  97          * @param $row
  98          * @param $overrides array
  99          *
 100          * @return Revision
 101          */
 102         public static function newFromArchiveRow( $row, $overrides = array() ) {
 103                 $attribs = $overrides + array(
 104                         'page'       => isset( $row->ar_page_id ) ? $row->ar_page_id : null,
 105                         'id'         => isset( $row->ar_rev_id ) ? $row->ar_rev_id : null,
 106                         'comment'    => $row->ar_comment,
 107                         'user'       => $row->ar_user,
 108                         'user_text'  => $row->ar_user_text,
 109                         'timestamp'  => $row->ar_timestamp,
 110                         'minor_edit' => $row->ar_minor_edit,
 111                         'text_id'    => isset( $row->ar_text_id ) ? $row->ar_text_id : null,
 112                         'deleted'    => $row->ar_deleted,
 113                         'len'        => $row->ar_len);
 114                 if ( isset( $row->ar_text ) && !$row->ar_text_id ) {
 115                         // Pre-1.5 ar_text row
 116                         $attribs['text'] = self::getRevisionText( $row, 'ar_' );
 117                         if ( $attribs['text'] === false ) {
 118                                 throw new MWException( 'Unable to load text from archive row (possibly bug 22624)' );
 119                         }
 120                 }
 121                 return new self( $attribs );
 122         }
 123
 124         /**
 125          * @since 1.19
 126          *
 127          * @param $row
 128          * @return Revision
 129          */
 130         public static function newFromRow( $row ) {
 131                 return new self( $row );
 132         }
 133
 134         /**
 135          * Load a page revision from a given revision ID number.
 136          * Returns null if no such revision can be found.
 137          *
 138          * @param $db DatabaseBase
 139          * @param $id Integer
 140          * @return Revision or null
 141          */
 142         public static function loadFromId( $db, $id ) {
 143                 return Revision::loadFromConds( $db,
 144                         array( 'page_id=rev_page',
 145                                    'rev_id' => intval( $id ) ) );
 146         }
 147
 148         /**
 149          * Load either the current, or a specified, revision
 150          * that's attached to a given page. If not attached
 151          * to that page, will return null.
 152          *
 153          * @param $db DatabaseBase
 154          * @param $pageid Integer
 155          * @param $id Integer
 156          * @return Revision or null
 157          */
 158         public static function loadFromPageId( $db, $pageid, $id = 0 ) {
 159                 $conds = array( 'page_id=rev_page','rev_page' => intval( $pageid ), 'page_id'=>intval( $pageid ) );
 160                 if( $id ) {
 161                         $conds['rev_id'] = intval( $id );
 162                 } else {
 163                         $conds[] = 'rev_id=page_latest';
 164                 }
 165                 return Revision::loadFromConds( $db, $conds );
 166         }
 167
 168         /**
 169          * Load either the current, or a specified, revision
 170          * that's attached to a given page. If not attached
 171          * to that page, will return null.
 172          *
 173          * @param $db DatabaseBase
 174          * @param $title Title
 175          * @param $id Integer
 176          * @return Revision or null
 177          */
 178         public static function loadFromTitle( $db, $title, $id = 0 ) {
 179                 if( $id ) {
 180                         $matchId = intval( $id );
 181                 } else {
 182                         $matchId = 'page_latest';
 183                 }
 184                 return Revision::loadFromConds(
 185                         $db,
 186                         array( "rev_id=$matchId",
 187                                    'page_id=rev_page',
 188                                    'page_namespace' => $title->getNamespace(),
 189                                    'page_title'     => $title->getDBkey() ) );
 190         }
 191
 192         /**
 193          * Load the revision for the given title with the given timestamp.
 194          * WARNING: Timestamps may in some circumstances not be unique,
 195          * so this isn't the best key to use.
 196          *
 197          * @param $db DatabaseBase
 198          * @param $title Title
 199          * @param $timestamp String
 200          * @return Revision or null
 201          */
 202         public static function loadFromTimestamp( $db, $title, $timestamp ) {
 203                 return Revision::loadFromConds(
 204                         $db,
 205                         array( 'rev_timestamp'  => $db->timestamp( $timestamp ),
 206                                    'page_id=rev_page',
 207                                    'page_namespace' => $title->getNamespace(),
 208                                    'page_title'     => $title->getDBkey() ) );
 209         }
 210
 211         /**
 212          * Given a set of conditions, fetch a revision.
 213          *
 214          * @param $conditions Array
 215          * @return Revision or null
 216          */
 217         public static function newFromConds( $conditions ) {
 218                 $db = wfGetDB( DB_SLAVE );
 219                 $row = Revision::loadFromConds( $db, $conditions );
 220                 if( is_null( $row ) && wfGetLB()->getServerCount() > 1 ) {
 221                         $dbw = wfGetDB( DB_MASTER );
 222                         $row = Revision::loadFromConds( $dbw, $conditions );
 223                 }
 224                 return $row;
 225         }
 226
 227         /**
 228          * Given a set of conditions, fetch a revision from
 229          * the given database connection.
 230          *
 231          * @param $db DatabaseBase
 232          * @param $conditions Array
 233          * @return Revision or null
 234          */
 235         private static function loadFromConds( $db, $conditions ) {
 236                 $res = Revision::fetchFromConds( $db, $conditions );
 237                 if( $res ) {
 238                         $row = $res->fetchObject();
 239                         $res->free();
 240                         if( $row ) {
 241                                 $ret = new Revision( $row );
 242                                 return $ret;
 243                         }
 244                 }
 245                 $ret = null;
 246                 return $ret;
 247         }
 248
 249         /**
 250          * Return a wrapper for a series of database rows to
 251          * fetch all of a given page's revisions in turn.
 252          * Each row can be fed to the constructor to get objects.
 253          *
 254          * @param $title Title
 255          * @return ResultWrapper
 256          */
 257         public static function fetchRevision( $title ) {
 258                 return Revision::fetchFromConds(
 259                         wfGetDB( DB_SLAVE ),
 260                         array( 'rev_id=page_latest',
 261                                    'page_namespace' => $title->getNamespace(),
 262                                    'page_title'     => $title->getDBkey(),
 263                                    'page_id=rev_page' ) );
 264         }
 265
 266         /**
 267          * Given a set of conditions, return a ResultWrapper
 268          * which will return matching database rows with the
 269          * fields necessary to build Revision objects.
 270          *
 271          * @param $db DatabaseBase
 272          * @param $conditions Array
 273          * @return ResultWrapper
 274          */
 275         private static function fetchFromConds( $db, $conditions ) {
 276                 $fields = self::selectFields();
 277                 $fields[] = 'page_namespace';
 278                 $fields[] = 'page_title';
 279                 $fields[] = 'page_latest';
 280                 return $db->select(
 281                         array( 'page', 'revision' ),
 282                         $fields,
 283                         $conditions,
 284                         __METHOD__,
 285                         array( 'LIMIT' => 1 ) );
 286         }
 287
 288         /**
 289          * Return the list of revision fields that should be selected to create
 290          * a new revision.
 291          */
 292         public static function selectFields() {
 293                 return array(
 294                         'rev_id',
 295                         'rev_page',
 296                         'rev_text_id',
 297                         'rev_timestamp',
 298                         'rev_comment',
 299                         'rev_user_text,'.
 300                         'rev_user',
 301                         'rev_minor_edit',
 302                         'rev_deleted',
 303                         'rev_len',
 304                         'rev_parent_id'
 305                 );
 306         }
 307
 308         /**
 309          * Return the list of text fields that should be selected to read the
 310          * revision text
 311          */
 312         static function selectTextFields() {
 313                 return array(
 314                         'old_text',
 315                         'old_flags'
 316                 );
 317         }
 318
 319         /**
 320          * Return the list of page fields that should be selected from page table
 321          */
 322         static function selectPageFields() {
 323                 return array(
 324                         'page_namespace',
 325                         'page_title',
 326                         'page_latest'
 327                 );
 328         }
 329
 330         /**
 331          * Constructor
 332          *
 333          * @param $row Mixed: either a database row or an array
 334          * @access private
 335          */
 336         function __construct( $row ) {
 337                 if( is_object( $row ) ) {
 338                         $this->mId        = intval( $row->rev_id );
 339                         $this->mPage      = intval( $row->rev_page );
 340                         $this->mTextId    = intval( $row->rev_text_id );
 341                         $this->mComment   =         $row->rev_comment;
 342                         $this->mUserText  =         $row->rev_user_text;
 343                         $this->mUser      = intval( $row->rev_user );
 344                         $this->mMinorEdit = intval( $row->rev_minor_edit );
 345                         $this->mTimestamp =         $row->rev_timestamp;
 346                         $this->mDeleted   = intval( $row->rev_deleted );
 347
 348                         if( !isset( $row->rev_parent_id ) ) {
 349                                 $this->mParentId = is_null($row->rev_parent_id) ? null : 0;
 350                         } else {
 351                                 $this->mParentId  = intval( $row->rev_parent_id );
 352                         }
 353
 354                         if( !isset( $row->rev_len ) || is_null( $row->rev_len ) ) {
 355                                 $this->mSize = null;
 356                         } else {
 357                                 $this->mSize = intval( $row->rev_len );
 358                         }
 359
 360                         if( isset( $row->page_latest ) ) {
 361                                 $this->mCurrent = ( $row->rev_id == $row->page_latest );
 362                                 $this->mTitle = Title::newFromRow( $row );
 363                         } else {
 364                                 $this->mCurrent = false;
 365                                 $this->mTitle = null;
 366                         }
 367
 368                         // Lazy extraction...
 369                         $this->mText      = null;
 370                         if( isset( $row->old_text ) ) {
 371                                 $this->mTextRow = $row;
 372                         } else {
 373                                 // 'text' table row entry will be lazy-loaded
 374                                 $this->mTextRow = null;
 375                         }
 376                 } elseif( is_array( $row ) ) {
 377                         // Build a new revision to be saved...
 378                         global $wgUser;
 379
 380                         $this->mId        = isset( $row['id']         ) ? intval( $row['id']         ) : null;
 381                         $this->mPage      = isset( $row['page']       ) ? intval( $row['page']       ) : null;
 382                         $this->mTextId    = isset( $row['text_id']    ) ? intval( $row['text_id']    ) : null;
 383                         $this->mUserText  = isset( $row['user_text']  ) ? strval( $row['user_text']  ) : $wgUser->getName();
 384                         $this->mUser      = isset( $row['user']       ) ? intval( $row['user']       ) : $wgUser->getId();
 385                         $this->mMinorEdit = isset( $row['minor_edit'] ) ? intval( $row['minor_edit'] ) : 0;
 386                         $this->mTimestamp = isset( $row['timestamp']  ) ? strval( $row['timestamp']  ) : wfTimestamp( TS_MW );
 387                         $this->mDeleted   = isset( $row['deleted']    ) ? intval( $row['deleted']    ) : 0;
 388                         $this->mSize      = isset( $row['len']        ) ? intval( $row['len']        ) : null;
 389                         $this->mParentId  = isset( $row['parent_id']  ) ? intval( $row['parent_id']  ) : null;
 390
 391                         // Enforce spacing trimming on supplied text
 392                         $this->mComment   = isset( $row['comment']    ) ?  trim( strval( $row['comment'] ) ) : null;
 393                         $this->mText      = isset( $row['text']       ) ? rtrim( strval( $row['text']    ) ) : null;
 394                         $this->mTextRow   = null;
 395
 396                         $this->mTitle     = null; # Load on demand if needed
 397                         $this->mCurrent   = false;
 398                         # If we still have no len_size, see it we have the text to figure it out
 399                         if ( !$this->mSize )
 400                                 $this->mSize      = is_null( $this->mText ) ? null : strlen( $this->mText );
 401                 } else {
 402                         throw new MWException( 'Revision constructor passed invalid row format.' );
 403                 }
 404                 $this->mUnpatrolled = null;
 405         }
 406
 407         /**
 408          * Get revision ID
 409          *
 410          * @return Integer
 411          */
 412         public function getId() {
 413                 return $this->mId;
 414         }
 415
 416         /**
 417          * Get text row ID
 418          *
 419          * @return Integer
 420          */
 421         public function getTextId() {
 422                 return $this->mTextId;
 423         }
 424
 425         /**
 426          * Get parent revision ID (the original previous page revision)
 427          *
 428          * @return Integer
 429          */
 430         public function getParentId() {
 431                 return $this->mParentId;
 432         }
 433
 434         /**
 435          * Returns the length of the text in this revision, or null if unknown.
 436          *
 437          * @return Integer
 438          */
 439         public function getSize() {
 440                 return $this->mSize;
 441         }
 442
 443         /**
 444          * Returns the title of the page associated with this entry.
 445          *
 446          * @return Title
 447          */
 448         public function getTitle() {
 449                 if( isset( $this->mTitle ) ) {
 450                         return $this->mTitle;
 451                 }
 452                 $dbr = wfGetDB( DB_SLAVE );
 453                 $row = $dbr->selectRow(
 454                         array( 'page', 'revision' ),
 455                         array( 'page_namespace', 'page_title' ),
 456                         array( 'page_id=rev_page',
 457                                    'rev_id' => $this->mId ),
 458                         'Revision::getTitle' );
 459                 if( $row ) {
 460                         $this->mTitle = Title::makeTitle( $row->page_namespace, $row->page_title );
 461                 }
 462                 return $this->mTitle;
 463         }
 464
 465         /**
 466          * Set the title of the revision
 467          *
 468          * @param $title Title
 469          */
 470         public function setTitle( $title ) {
 471                 $this->mTitle = $title;
 472         }
 473
 474         /**
 475          * Get the page ID
 476          *
 477          * @return Integer
 478          */
 479         public function getPage() {
 480                 return $this->mPage;
 481         }
 482
 483         /**
 484          * Fetch revision's user id if it's available to the specified audience.
 485          * If the specified audience does not have access to it, zero will be
 486          * returned.
 487          *
 488          * @param $audience Integer: one of:
 489          *      Revision::FOR_PUBLIC       to be displayed to all users
 490          *      Revision::FOR_THIS_USER    to be displayed to $wgUser
 491          *      Revision::RAW              get the ID regardless of permissions
 492          *
 493          *
 494          * @return Integer
 495          */
 496         public function getUser( $audience = self::FOR_PUBLIC ) {
 497                 if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_USER ) ) {
 498                         return 0;
 499                 } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_USER ) ) {
 500                         return 0;
 501                 } else {
 502                         return $this->mUser;
 503                 }
 504         }
 505
 506         /**
 507          * Fetch revision's user id without regard for the current user's permissions
 508          *
 509          * @return String
 510          */
 511         public function getRawUser() {
 512                 return $this->mUser;
 513         }
 514
 515         /**
 516          * Fetch revision's username if it's available to the specified audience.
 517          * If the specified audience does not have access to the username, an
 518          * empty string will be returned.
 519          *
 520          * @param $audience Integer: one of:
 521          *      Revision::FOR_PUBLIC       to be displayed to all users
 522          *      Revision::FOR_THIS_USER    to be displayed to $wgUser
 523          *      Revision::RAW              get the text regardless of permissions
 524          *
 525          * @return string
 526          */
 527         public function getUserText( $audience = self::FOR_PUBLIC ) {
 528                 if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_USER ) ) {
 529                         return '';
 530                 } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_USER ) ) {
 531                         return '';
 532                 } else {
 533                         return $this->mUserText;
 534                 }
 535         }
 536
 537         /**
 538          * Fetch revision's username without regard for view restrictions
 539          *
 540          * @return String
 541          */
 542         public function getRawUserText() {
 543                 return $this->mUserText;
 544         }
 545
 546         /**
 547          * Fetch revision comment if it's available to the specified audience.
 548          * If the specified audience does not have access to the comment, an
 549          * empty string will be returned.
 550          *
 551          * @param $audience Integer: one of:
 552          *      Revision::FOR_PUBLIC       to be displayed to all users
 553          *      Revision::FOR_THIS_USER    to be displayed to $wgUser
 554          *      Revision::RAW              get the text regardless of permissions
 555          *
 556          * @return String
 557          */
 558         function getComment( $audience = self::FOR_PUBLIC ) {
 559                 if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_COMMENT ) ) {
 560                         return '';
 561                 } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_COMMENT ) ) {
 562                         return '';
 563                 } else {
 564                         return $this->mComment;
 565                 }
 566         }
 567
 568         /**
 569          * Fetch revision comment without regard for the current user's permissions
 570          *
 571          * @return String
 572          */
 573         public function getRawComment() {
 574                 return $this->mComment;
 575         }
 576
 577         /**
 578          * @return Boolean
 579          */
 580         public function isMinor() {
 581                 return (bool)$this->mMinorEdit;
 582         }
 583
 584         /**
 585          * @return Integer rcid of the unpatrolled row, zero if there isn't one
 586          */
 587         public function isUnpatrolled() {
 588                 if( $this->mUnpatrolled !== null ) {
 589                         return $this->mUnpatrolled;
 590                 }
 591                 $dbr = wfGetDB( DB_SLAVE );
 592                 $this->mUnpatrolled = $dbr->selectField( 'recentchanges',
 593                         'rc_id',
 594                         array( // Add redundant user,timestamp condition so we can use the existing index
 595                                 'rc_user_text'  => $this->getRawUserText(),
 596                                 'rc_timestamp'  => $dbr->timestamp( $this->getTimestamp() ),
 597                                 'rc_this_oldid' => $this->getId(),
 598                                 'rc_patrolled'  => 0
 599                         ),
 600                         __METHOD__
 601                 );
 602                 return (int)$this->mUnpatrolled;
 603         }
 604
 605         /**
 606          * @param $field int one of DELETED_* bitfield constants
 607          *
 608          * @return Boolean
 609          */
 610         public function isDeleted( $field ) {
 611                 return ( $this->mDeleted & $field ) == $field;
 612         }
 613
 614         /**
 615          * Get the deletion bitfield of the revision
 616          *
 617          * @return int
 618          */
 619         public function getVisibility() {
 620                 return (int)$this->mDeleted;
 621         }
 622
 623         /**
 624          * Fetch revision text if it's available to the specified audience.
 625          * If the specified audience does not have the ability to view this
 626          * revision, an empty string will be returned.
 627          *
 628          * @param $audience Integer: one of:
 629          *      Revision::FOR_PUBLIC       to be displayed to all users
 630          *      Revision::FOR_THIS_USER    to be displayed to $wgUser
 631          *      Revision::RAW              get the text regardless of permissions
 632          *
 633          * @return String
 634          */
 635         public function getText( $audience = self::FOR_PUBLIC ) {
 636                 if( $audience == self::FOR_PUBLIC && $this->isDeleted( self::DELETED_TEXT ) ) {
 637                         return '';
 638                 } elseif( $audience == self::FOR_THIS_USER && !$this->userCan( self::DELETED_TEXT ) ) {
 639                         return '';
 640                 } else {
 641                         return $this->getRawText();
 642                 }
 643         }
 644
 645         /**
 646          * Alias for getText(Revision::FOR_THIS_USER)
 647          *
 648          * @deprecated since 1.17
 649          * @return String
 650          */
 651         public function revText() {
 652                 wfDeprecated( __METHOD__ );
 653                 return $this->getText( self::FOR_THIS_USER );
 654         }
 655
 656         /**
 657          * Fetch revision text without regard for view restrictions
 658          *
 659          * @return String
 660          */
 661         public function getRawText() {
 662                 if( is_null( $this->mText ) ) {
 663                         // Revision text is immutable. Load on demand:
 664                         $this->mText = $this->loadText();
 665                 }
 666                 return $this->mText;
 667         }
 668
 669         /**
 670          * @return String
 671          */
 672         public function getTimestamp() {
 673                 return wfTimestamp( TS_MW, $this->mTimestamp );
 674         }
 675
 676         /**
 677          * @return Boolean
 678          */
 679         public function isCurrent() {
 680                 return $this->mCurrent;
 681         }
 682
 683         /**
 684          * Get previous revision for this title
 685          *
 686          * @return Revision or null
 687          */
 688         public function getPrevious() {
 689                 if( $this->getTitle() ) {
 690                         $prev = $this->getTitle()->getPreviousRevisionID( $this->getId() );
 691                         if( $prev ) {
 692                                 return Revision::newFromTitle( $this->getTitle(), $prev );
 693                         }
 694                 }
 695                 return null;
 696         }
 697
 698         /**
 699          * Get next revision for this title
 700          *
 701          * @return Revision or null
 702          */
 703         public function getNext() {
 704                 if( $this->getTitle() ) {
 705                         $next = $this->getTitle()->getNextRevisionID( $this->getId() );
 706                         if ( $next ) {
 707                                 return Revision::newFromTitle( $this->getTitle(), $next );
 708                         }
 709                 }
 710                 return null;
 711         }
 712
 713         /**
 714          * Get previous revision Id for this page_id
 715          * This is used to populate rev_parent_id on save
 716          *
 717          * @param $db DatabaseBase
 718          * @return Integer
 719          */
 720         private function getPreviousRevisionId( $db ) {
 721                 if( is_null( $this->mPage ) ) {
 722                         return 0;
 723                 }
 724                 # Use page_latest if ID is not given
 725                 if( !$this->mId ) {
 726                         $prevId = $db->selectField( 'page', 'page_latest',
 727                                 array( 'page_id' => $this->mPage ),
 728                                 __METHOD__ );
 729                 } else {
 730                         $prevId = $db->selectField( 'revision', 'rev_id',
 731                                 array( 'rev_page' => $this->mPage, 'rev_id < ' . $this->mId ),
 732                                 __METHOD__,
 733                                 array( 'ORDER BY' => 'rev_id DESC' ) );
 734                 }
 735                 return intval( $prevId );
 736         }
 737
 738         /**
 739           * Get revision text associated with an old or archive row
 740           * $row is usually an object from wfFetchRow(), both the flags and the text
 741           * field must be included
 742           *
 743           * @param $row Object: the text data
 744           * @param $prefix String: table prefix (default 'old_')
 745           * @return String: text the text requested or false on failure
 746           */
 747         public static function getRevisionText( $row, $prefix = 'old_' ) {
 748                 wfProfileIn( __METHOD__ );
 749
 750                 # Get data
 751                 $textField = $prefix . 'text';
 752                 $flagsField = $prefix . 'flags';
 753
 754                 if( isset( $row->$flagsField ) ) {
 755                         $flags = explode( ',', $row->$flagsField );
 756                 } else {
 757                         $flags = array();
 758                 }
 759
 760                 if( isset( $row->$textField ) ) {
 761                         $text = $row->$textField;
 762                 } else {
 763                         wfProfileOut( __METHOD__ );
 764                         return false;
 765                 }
 766
 767                 # Use external methods for external objects, text in table is URL-only then
 768                 if ( in_array( 'external', $flags ) ) {
 769                         $url = $text;
 770                         $parts = explode( '://', $url, 2 );
 771                         if( count( $parts ) == 1 || $parts[1] == '' ) {
 772                                 wfProfileOut( __METHOD__ );
 773                                 return false;
 774                         }
 775                         $text = ExternalStore::fetchFromURL( $url );
 776                 }
 777
 778                 // If the text was fetched without an error, convert it
 779                 if ( $text !== false ) {
 780                         if( in_array( 'gzip', $flags ) ) {
 781                                 # Deal with optional compression of archived pages.
 782                                 # This can be done periodically via maintenance/compressOld.php, and
 783                                 # as pages are saved if $wgCompressRevisions is set.
 784                                 $text = gzinflate( $text );
 785                         }
 786
 787                         if( in_array( 'object', $flags ) ) {
 788                                 # Generic compressed storage
 789                                 $obj = unserialize( $text );
 790                                 if ( !is_object( $obj ) ) {
 791                                         // Invalid object
 792                                         wfProfileOut( __METHOD__ );
 793                                         return false;
 794                                 }
 795                                 $text = $obj->getText();
 796                         }
 797
 798                         global $wgLegacyEncoding;
 799                         if( $text !== false && $wgLegacyEncoding
 800                                 && !in_array( 'utf-8', $flags ) && !in_array( 'utf8', $flags ) )
 801                         {
 802                                 # Old revisions kept around in a legacy encoding?
 803                                 # Upconvert on demand.
 804                                 # ("utf8" checked for compatibility with some broken
 805                                 #  conversion scripts 2008-12-30)
 806                                 global $wgContLang;
 807                                 $text = $wgContLang->iconv( $wgLegacyEncoding, 'UTF-8', $text );
 808                         }
 809                 }
 810                 wfProfileOut( __METHOD__ );
 811                 return $text;
 812         }
 813
 814         /**
 815          * If $wgCompressRevisions is enabled, we will compress data.
 816          * The input string is modified in place.
 817          * Return value is the flags field: contains 'gzip' if the
 818          * data is compressed, and 'utf-8' if we're saving in UTF-8
 819          * mode.
 820          *
 821          * @param $text Mixed: reference to a text
 822          * @return String
 823          */
 824         public static function compressRevisionText( &$text ) {
 825                 global $wgCompressRevisions;
 826                 $flags = array();
 827
 828                 # Revisions not marked this way will be converted
 829                 # on load if $wgLegacyCharset is set in the future.
 830                 $flags[] = 'utf-8';
 831
 832                 if( $wgCompressRevisions ) {
 833                         if( function_exists( 'gzdeflate' ) ) {
 834                                 $text = gzdeflate( $text );
 835                                 $flags[] = 'gzip';
 836                         } else {
 837                                 wfDebug( "Revision::compressRevisionText() -- no zlib support, not compressing\n" );
 838                         }
 839                 }
 840                 return implode( ',', $flags );
 841         }
 842
 843         /**
 844          * Insert a new revision into the database, returning the new revision ID
 845          * number on success and dies horribly on failure.
 846          *
 847          * @param $dbw DatabaseBase: (master connection)
 848          * @return Integer
 849          */
 850         public function insertOn( $dbw ) {
 851                 global $wgDefaultExternalStore;
 852
 853                 wfProfileIn( __METHOD__ );
 854
 855                 $data = $this->mText;
 856                 $flags = Revision::compressRevisionText( $data );
 857
 858                 # Write to external storage if required
 859                 if( $wgDefaultExternalStore ) {
 860                         // Store and get the URL
 861                         $data = ExternalStore::insertToDefault( $data );
 862                         if( !$data ) {
 863                                 throw new MWException( "Unable to store text to external storage" );
 864                         }
 865                         if( $flags ) {
 866                                 $flags .= ',';
 867                         }
 868                         $flags .= 'external';
 869                 }
 870
 871                 # Record the text (or external storage URL) to the text table
 872                 if( !isset( $this->mTextId ) ) {
 873                         $old_id = $dbw->nextSequenceValue( 'text_old_id_seq' );
 874                         $dbw->insert( 'text',
 875                                 array(
 876                                         'old_id'    => $old_id,
 877                                         'old_text'  => $data,
 878                                         'old_flags' => $flags,
 879                                 ), __METHOD__
 880                         );
 881                         $this->mTextId = $dbw->insertId();
 882                 }
 883
 884                 if ( $this->mComment === null ) $this->mComment = "";
 885
 886                 # Record the edit in revisions
 887                 $rev_id = isset( $this->mId )
 888                         ? $this->mId
 889                         : $dbw->nextSequenceValue( 'revision_rev_id_seq' );
 890                 $dbw->insert( 'revision',
 891                         array(
 892                                 'rev_id'         => $rev_id,
 893                                 'rev_page'       => $this->mPage,
 894                                 'rev_text_id'    => $this->mTextId,
 895                                 'rev_comment'    => $this->mComment,
 896                                 'rev_minor_edit' => $this->mMinorEdit ? 1 : 0,
 897                                 'rev_user'       => $this->mUser,
 898                                 'rev_user_text'  => $this->mUserText,
 899                                 'rev_timestamp'  => $dbw->timestamp( $this->mTimestamp ),
 900                                 'rev_deleted'    => $this->mDeleted,
 901                                 'rev_len'        => $this->mSize,
 902                                 'rev_parent_id'  => is_null($this->mParentId) ?
 903                                         $this->getPreviousRevisionId( $dbw ) : $this->mParentId
 904                         ), __METHOD__
 905                 );
 906
 907                 $this->mId = !is_null( $rev_id ) ? $rev_id : $dbw->insertId();
 908
 909                 wfRunHooks( 'RevisionInsertComplete', array( &$this, $data, $flags ) );
 910
 911                 wfProfileOut( __METHOD__ );
 912                 return $this->mId;
 913         }
 914
 915         /**
 916          * Lazy-load the revision's text.
 917          * Currently hardcoded to the 'text' table storage engine.
 918          *
 919          * @return String
 920          */
 921         protected function loadText() {
 922                 wfProfileIn( __METHOD__ );
 923
 924                 // Caching may be beneficial for massive use of external storage
 925                 global $wgRevisionCacheExpiry, $wgMemc;
 926                 $textId = $this->getTextId();
 927                 $key = wfMemcKey( 'revisiontext', 'textid', $textId );
 928                 if( $wgRevisionCacheExpiry ) {
 929                         $text = $wgMemc->get( $key );
 930                         if( is_string( $text ) ) {
 931                                 wfDebug( __METHOD__ . ": got id $textId from cache\n" );
 932                                 wfProfileOut( __METHOD__ );
 933                                 return $text;
 934                         }
 935                 }
 936
 937                 // If we kept data for lazy extraction, use it now...
 938                 if ( isset( $this->mTextRow ) ) {
 939                         $row = $this->mTextRow;
 940                         $this->mTextRow = null;
 941                 } else {
 942                         $row = null;
 943                 }
 944
 945                 if( !$row ) {
 946                         // Text data is immutable; check slaves first.
 947                         $dbr = wfGetDB( DB_SLAVE );
 948                         $row = $dbr->selectRow( 'text',
 949                                 array( 'old_text', 'old_flags' ),
 950                                 array( 'old_id' => $this->getTextId() ),
 951                                 __METHOD__ );
 952                 }
 953
 954                 if( !$row && wfGetLB()->getServerCount() > 1 ) {
 955                         // Possible slave lag!
 956                         $dbw = wfGetDB( DB_MASTER );
 957                         $row = $dbw->selectRow( 'text',
 958                                 array( 'old_text', 'old_flags' ),
 959                                 array( 'old_id' => $this->getTextId() ),
 960                                 __METHOD__ );
 961                 }
 962
 963                 $text = self::getRevisionText( $row );
 964
 965                 # No negative caching -- negative hits on text rows may be due to corrupted slave servers
 966                 if( $wgRevisionCacheExpiry && $text !== false ) {
 967                         $wgMemc->set( $key, $text, $wgRevisionCacheExpiry );
 968                 }
 969
 970                 wfProfileOut( __METHOD__ );
 971
 972                 return $text;
 973         }
 974
 975         /**
 976          * Create a new null-revision for insertion into a page's
 977          * history. This will not re-save the text, but simply refer
 978          * to the text from the previous version.
 979          *
 980          * Such revisions can for instance identify page rename
 981          * operations and other such meta-modifications.
 982          *
 983          * @param $dbw DatabaseBase
 984          * @param $pageId Integer: ID number of the page to read from
 985          * @param $summary String: revision's summary
 986          * @param $minor Boolean: whether the revision should be considered as minor
 987          * @return Revision|null on error
 988          */
 989         public static function newNullRevision( $dbw, $pageId, $summary, $minor ) {
 990                 wfProfileIn( __METHOD__ );
 991
 992                 $current = $dbw->selectRow(
 993                         array( 'page', 'revision' ),
 994                         array( 'page_latest', 'rev_text_id', 'rev_len' ),
 995                         array(
 996                                 'page_id' => $pageId,
 997                                 'page_latest=rev_id',
 998                                 ),
 999                         __METHOD__ );
1000
1001                 if( $current ) {
1002                         $revision = new Revision( array(
1003                                 'page'       => $pageId,
1004                                 'comment'    => $summary,
1005                                 'minor_edit' => $minor,
1006                                 'text_id'    => $current->rev_text_id,
1007                                 'parent_id'  => $current->page_latest,
1008                                 'len'        => $current->rev_len
1009                                 ) );
1010                 } else {
1011                         $revision = null;
1012                 }
1013
1014                 wfProfileOut( __METHOD__ );
1015                 return $revision;
1016         }
1017
1018         /**
1019          * Determine if the current user is allowed to view a particular
1020          * field of this revision, if it's marked as deleted.
1021          *
1022          * @param $field Integer:one of self::DELETED_TEXT,
1023          *                              self::DELETED_COMMENT,
1024          *                              self::DELETED_USER
1025          * @return Boolean
1026          */
1027         public function userCan( $field ) {
1028                 return self::userCanBitfield( $this->mDeleted, $field );
1029         }
1030
1031         /**
1032          * Determine if the current user is allowed to view a particular
1033          * field of this revision, if it's marked as deleted. This is used
1034          * by various classes to avoid duplication.
1035          *
1036          * @param $bitfield Integer: current field
1037          * @param $field Integer: one of self::DELETED_TEXT = File::DELETED_FILE,
1038          *                               self::DELETED_COMMENT = File::DELETED_COMMENT,
1039          *                               self::DELETED_USER = File::DELETED_USER
1040          * @return Boolean
1041          */
1042         public static function userCanBitfield( $bitfield, $field ) {
1043                 if( $bitfield & $field ) { // aspect is deleted
1044                         global $wgUser;
1045                         if ( $bitfield & self::DELETED_RESTRICTED ) {
1046                                 $permission = 'suppressrevision';
1047                         } elseif ( $field & self::DELETED_TEXT ) {
1048                                 $permission = 'deletedtext';
1049                         } else {
1050                                 $permission = 'deletedhistory';
1051                         }
1052                         wfDebug( "Checking for $permission due to $field match on $bitfield\n" );
1053                         return $wgUser->isAllowed( $permission );
1054                 } else {
1055                         return true;
1056                 }
1057         }
1058
1059         /**
1060          * Get rev_timestamp from rev_id, without loading the rest of the row
1061          *
1062          * @param $title Title
1063          * @param $id Integer
1064          * @return String
1065          */
1066         static function getTimestampFromId( $title, $id ) {
1067                 $dbr = wfGetDB( DB_SLAVE );
1068                 // Casting fix for DB2
1069                 if ( $id == '' ) {
1070                         $id = 0;
1071                 }
1072                 $conds = array( 'rev_id' => $id );
1073                 $conds['rev_page'] = $title->getArticleId();
1074                 $timestamp = $dbr->selectField( 'revision', 'rev_timestamp', $conds, __METHOD__ );
1075                 if ( $timestamp === false && wfGetLB()->getServerCount() > 1 ) {
1076                         # Not in slave, try master
1077                         $dbw = wfGetDB( DB_MASTER );
1078                         $timestamp = $dbw->selectField( 'revision', 'rev_timestamp', $conds, __METHOD__ );
1079                 }
1080                 return wfTimestamp( TS_MW, $timestamp );
1081         }
1082
1083         /**
1084          * Get count of revisions per page...not very efficient
1085          *
1086          * @param $db DatabaseBase
1087          * @param $id Integer: page id
1088          * @return Integer
1089          */
1090         static function countByPageId( $db, $id ) {
1091                 $row = $db->selectRow( 'revision', 'COUNT(*) AS revCount',
1092                         array( 'rev_page' => $id ), __METHOD__ );
1093                 if( $row ) {
1094                         return $row->revCount;
1095                 }
1096                 return 0;
1097         }
1098
1099         /**
1100          * Get count of revisions per page...not very efficient
1101          *
1102          * @param $db DatabaseBase
1103          * @param $title Title
1104          * @return Integer
1105          */
1106         static function countByTitle( $db, $title ) {
1107                 $id = $title->getArticleId();
1108                 if( $id ) {
1109                         return Revision::countByPageId( $db, $id );
1110                 }
1111                 return 0;
1112         }
1113 }