includes/pager/IndexPager.php

   1 <?php
   2 /**
   3  * Efficient paging for SQL queries.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Pager
  22  */
  23
  24 use Wikimedia\Rdbms\IResultWrapper;
  25 use Wikimedia\Rdbms\IDatabase;
  26
  27 /**
  28  * IndexPager is an efficient pager which uses a (roughly unique) index in the
  29  * data set to implement paging, rather than a "LIMIT offset,limit" clause.
  30  * In MySQL, such a limit/offset clause requires counting through the
  31  * specified number of offset rows to find the desired data, which can be
  32  * expensive for large offsets.
  33  *
  34  * ReverseChronologicalPager is a child class of the abstract IndexPager, and
  35  * contains  some formatting and display code which is specific to the use of
  36  * timestamps as  indexes. Here is a synopsis of its operation:
  37  *
  38  *    * The query is specified by the offset, limit and direction (dir)
  39  *      parameters, in addition to any subclass-specific parameters.
  40  *    * The offset is the non-inclusive start of the DB query. A row with an
  41  *      index value equal to the offset will never be shown.
  42  *    * The query may either be done backwards, where the rows are returned by
  43  *      the database in the opposite order to which they are displayed to the
  44  *      user, or forwards. This is specified by the "dir" parameter, dir=prev
  45  *      means backwards, anything else means forwards. The offset value
  46  *      specifies the start of the database result set, which may be either
  47  *      the start or end of the displayed data set. This allows "previous"
  48  *      links to be implemented without knowledge of the index value at the
  49  *      start of the previous page.
  50  *    * An additional row beyond the user-specified limit is always requested.
  51  *      This allows us to tell whether we should display a "next" link in the
  52  *      case of forwards mode, or a "previous" link in the case of backwards
  53  *      mode. Determining whether to display the other link (the one for the
  54  *      page before the start of the database result set) can be done
  55  *      heuristically by examining the offset.
  56  *
  57  *    * An empty offset indicates that the offset condition should be omitted
  58  *      from the query. This naturally produces either the first page or the
  59  *      last page depending on the dir parameter.
  60  *
  61  *  Subclassing the pager to implement concrete functionality should be fairly
  62  *  simple, please see the examples in HistoryAction.php and
  63  *  SpecialBlockList.php. You just need to override formatRow(),
  64  *  getQueryInfo() and getIndexField(). Don't forget to call the parent
  65  *  constructor if you override it.
  66  *
  67  * @ingroup Pager
  68  */
  69 abstract class IndexPager extends ContextSource implements Pager {
  70         /** Backwards-compatible constant for $mDefaultDirection field (do not change) */
  71         const DIR_ASCENDING = false;
  72         /** Backwards-compatible constant for $mDefaultDirection field (do not change) */
  73         const DIR_DESCENDING = true;
  74
  75         /** Backwards-compatible constant for reallyDoQuery() (do not change) */
  76         const QUERY_ASCENDING = true;
  77         /** Backwards-compatible constant for reallyDoQuery() (do not change) */
  78         const QUERY_DESCENDING = false;
  79
  80         /** @var WebRequest */
  81         public $mRequest;
  82         /** @var int[] List of default entry limit options to be presented to clients */
  83         public $mLimitsShown = [ 20, 50, 100, 250, 500 ];
  84         /** @var int The default entry limit choosen for clients */
  85         public $mDefaultLimit = 50;
  86         /** @var mixed The starting point to enumerate entries */
  87         public $mOffset;
  88         /** @var int The maximum number of entries to show */
  89         public $mLimit;
  90         /** @var bool Whether the listing query completed */
  91         public $mQueryDone = false;
  92         /** @var IDatabase */
  93         public $mDb;
  94         /** @var stdClass|bool|null Extra row fetched at the end to see if the end was reached */
  95         public $mPastTheEndRow;
  96
  97         /**
  98          * The index to actually be used for ordering. This is a single column,
  99          * for one ordering, even if multiple orderings are supported.
 100          * @var string
 101          */
 102         protected $mIndexField;
 103         /**
 104          * An array of secondary columns to order by. These fields are not part of the offset.
 105          * This is a column list for one ordering, even if multiple orderings are supported.
 106          * @var string[]
 107          */
 108         protected $mExtraSortFields;
 109         /** For pages that support multiple types of ordering, which one to use.
 110          * @var string|null
 111          */
 112         protected $mOrderType;
 113         /**
 114          * $mDefaultDirection gives the direction to use when sorting results:
 115          * DIR_ASCENDING or DIR_DESCENDING. If $mIsBackwards is set, we start from
 116          * the opposite end, but we still sort the page itself according to
 117          * $mDefaultDirection. For example, if $mDefaultDirection is DIR_ASCENDING
 118          * but we're going backwards, we'll display the last page of results, but
 119          * the last result will be at the bottom, not the top.
 120          *
 121          * Like $mIndexField, $mDefaultDirection will be a single value even if the
 122          * class supports multiple default directions for different order types.
 123          * @var bool
 124          */
 125         public $mDefaultDirection;
 126         /** @var bool */
 127         public $mIsBackwards;
 128
 129         /** @var bool True if the current result set is the first one */
 130         public $mIsFirst;
 131         /** @var bool */
 132         public $mIsLast;
 133
 134         /** @var mixed */
 135         protected $mLastShown;
 136         /** @var mixed */
 137         protected $mFirstShown;
 138         /** @var mixed */
 139         protected $mPastTheEndIndex;
 140         /** @var array */
 141         protected $mDefaultQuery;
 142         /** @var string */
 143         protected $mNavigationBar;
 144
 145         /**
 146          * Whether to include the offset in the query
 147          * @var bool
 148          */
 149         protected $mIncludeOffset = false;
 150
 151         /**
 152          * Result object for the query. Warning: seek before use.
 153          *
 154          * @var IResultWrapper
 155          */
 156         public $mResult;
 157
 158         public function __construct( IContextSource $context = null ) {
 159                 if ( $context ) {
 160                         $this->setContext( $context );
 161                 }
 162
 163                 $this->mRequest = $this->getRequest();
 164
 165                 # NB: the offset is quoted, not validated. It is treated as an
 166                 # arbitrary string to support the widest variety of index types. Be
 167                 # careful outputting it into HTML!
 168                 $this->mOffset = $this->mRequest->getText( 'offset' );
 169
 170                 # Use consistent behavior for the limit options
 171                 $this->mDefaultLimit = $this->getUser()->getIntOption( 'rclimit' );
 172                 if ( !$this->mLimit ) {
 173                         // Don't override if a subclass calls $this->setLimit() in its constructor.
 174                         list( $this->mLimit, /* $offset */ ) = $this->mRequest->getLimitOffset();
 175                 }
 176
 177                 $this->mIsBackwards = ( $this->mRequest->getVal( 'dir' ) == 'prev' );
 178                 # Let the subclass set the DB here; otherwise use a replica DB for the current wiki
 179                 $this->mDb = $this->mDb ?: wfGetDB( DB_REPLICA );
 180
 181                 $index = $this->getIndexField(); // column to sort on
 182                 $extraSort = $this->getExtraSortFields(); // extra columns to sort on for query planning
 183                 $order = $this->mRequest->getVal( 'order' );
 184                 if ( is_array( $index ) && isset( $index[$order] ) ) {
 185                         $this->mOrderType = $order;
 186                         $this->mIndexField = $index[$order];
 187                         $this->mExtraSortFields = isset( $extraSort[$order] )
 188                                 ? (array)$extraSort[$order]
 189                                 : [];
 190                 } elseif ( is_array( $index ) ) {
 191                         # First element is the default
 192                         $this->mIndexField = reset( $index );
 193                         $this->mOrderType = key( $index );
 194                         $this->mExtraSortFields = isset( $extraSort[$this->mOrderType] )
 195                                 ? (array)$extraSort[$this->mOrderType]
 196                                 : [];
 197                 } else {
 198                         # $index is not an array
 199                         $this->mOrderType = null;
 200                         $this->mIndexField = $index;
 201                         $this->mExtraSortFields = (array)$extraSort;
 202                 }
 203
 204                 if ( !isset( $this->mDefaultDirection ) ) {
 205                         $dir = $this->getDefaultDirections();
 206                         $this->mDefaultDirection = is_array( $dir )
 207                                 ? $dir[$this->mOrderType]
 208                                 : $dir;
 209                 }
 210         }
 211
 212         /**
 213          * Get the Database object in use
 214          *
 215          * @return IDatabase
 216          */
 217         public function getDatabase() {
 218                 return $this->mDb;
 219         }
 220
 221         /**
 222          * Do the query, using information from the object context. This function
 223          * has been kept minimal to make it overridable if necessary, to allow for
 224          * result sets formed from multiple DB queries.
 225          */
 226         public function doQuery() {
 227                 # Use the child class name for profiling
 228                 $fname = __METHOD__ . ' (' . static::class . ')';
 229                 /** @noinspection PhpUnusedLocalVariableInspection */
 230                 $section = Profiler::instance()->scopedProfileIn( $fname );
 231
 232                 $defaultOrder = ( $this->mDefaultDirection === self::DIR_ASCENDING )
 233                         ? self::QUERY_ASCENDING
 234                         : self::QUERY_DESCENDING;
 235                 $order = $this->mIsBackwards ? self::oppositeOrder( $defaultOrder ) : $defaultOrder;
 236
 237                 # Plus an extra row so that we can tell the "next" link should be shown
 238                 $queryLimit = $this->mLimit + 1;
 239
 240                 if ( $this->mOffset == '' ) {
 241                         $isFirst = true;
 242                 } else {
 243                         // If there's an offset, we may or may not be at the first entry.
 244                         // The only way to tell is to run the query in the opposite
 245                         // direction see if we get a row.
 246                         $oldIncludeOffset = $this->mIncludeOffset;
 247                         $this->mIncludeOffset = !$this->mIncludeOffset;
 248                         $oppositeOrder = self::oppositeOrder( $order );
 249                         $isFirst = !$this->reallyDoQuery( $this->mOffset, 1, $oppositeOrder )->numRows();
 250                         $this->mIncludeOffset = $oldIncludeOffset;
 251                 }
 252
 253                 $this->mResult = $this->reallyDoQuery(
 254                         $this->mOffset,
 255                         $queryLimit,
 256                         $order
 257                 );
 258
 259                 $this->extractResultInfo( $isFirst, $queryLimit, $this->mResult );
 260                 $this->mQueryDone = true;
 261
 262                 $this->preprocessResults( $this->mResult );
 263                 $this->mResult->rewind(); // Paranoia
 264         }
 265
 266         /**
 267          * @param bool $order One of the IndexPager::QUERY_* class constants
 268          * @return bool The opposite query order as an IndexPager::QUERY_ constant
 269          */
 270         final protected static function oppositeOrder( $order ) {
 271                 return ( $order === self::QUERY_ASCENDING )
 272                         ? self::QUERY_DESCENDING
 273                         : self::QUERY_ASCENDING;
 274         }
 275
 276         /**
 277          * @return IResultWrapper The result wrapper.
 278          */
 279         function getResult() {
 280                 return $this->mResult;
 281         }
 282
 283         /**
 284          * Set the offset from an other source than the request
 285          *
 286          * @param int|string $offset
 287          */
 288         function setOffset( $offset ) {
 289                 $this->mOffset = $offset;
 290         }
 291
 292         /**
 293          * Set the limit from an other source than the request
 294          *
 295          * Verifies limit is between 1 and 5000
 296          *
 297          * @param int|string $limit
 298          */
 299         function setLimit( $limit ) {
 300                 $limit = (int)$limit;
 301                 // WebRequest::getLimitOffset() puts a cap of 5000, so do same here.
 302                 if ( $limit > 5000 ) {
 303                         $limit = 5000;
 304                 }
 305                 if ( $limit > 0 ) {
 306                         $this->mLimit = $limit;
 307                 }
 308         }
 309
 310         /**
 311          * Get the current limit
 312          *
 313          * @return int
 314          */
 315         function getLimit() {
 316                 return $this->mLimit;
 317         }
 318
 319         /**
 320          * Set whether a row matching exactly the offset should be also included
 321          * in the result or not. By default this is not the case, but when the
 322          * offset is user-supplied this might be wanted.
 323          *
 324          * @param bool $include
 325          */
 326         public function setIncludeOffset( $include ) {
 327                 $this->mIncludeOffset = $include;
 328         }
 329
 330         /**
 331          * Extract some useful data from the result object for use by
 332          * the navigation bar, put it into $this
 333          *
 334          * @param bool $isFirst False if there are rows before those fetched (i.e.
 335          *     if a "previous" link would make sense)
 336          * @param int $limit Exact query limit
 337          * @param IResultWrapper $res
 338          */
 339         function extractResultInfo( $isFirst, $limit, IResultWrapper $res ) {
 340                 $numRows = $res->numRows();
 341                 if ( $numRows ) {
 342                         # Remove any table prefix from index field
 343                         $parts = explode( '.', $this->mIndexField );
 344                         $indexColumn = end( $parts );
 345
 346                         $row = $res->fetchRow();
 347                         $firstIndex = $row[$indexColumn];
 348
 349                         # Discard the extra result row if there is one
 350                         if ( $numRows > $this->mLimit && $numRows > 1 ) {
 351                                 $res->seek( $numRows - 1 );
 352                                 $this->mPastTheEndRow = $res->fetchObject();
 353                                 $this->mPastTheEndIndex = $this->mPastTheEndRow->$indexColumn;
 354                                 $res->seek( $numRows - 2 );
 355                                 $row = $res->fetchRow();
 356                                 $lastIndex = $row[$indexColumn];
 357                         } else {
 358                                 $this->mPastTheEndRow = null;
 359                                 # Setting indexes to an empty string means that they will be
 360                                 # omitted if they would otherwise appear in URLs. It just so
 361                                 # happens that this  is the right thing to do in the standard
 362                                 # UI, in all the relevant cases.
 363                                 $this->mPastTheEndIndex = '';
 364                                 $res->seek( $numRows - 1 );
 365                                 $row = $res->fetchRow();
 366                                 $lastIndex = $row[$indexColumn];
 367                         }
 368                 } else {
 369                         $firstIndex = '';
 370                         $lastIndex = '';
 371                         $this->mPastTheEndRow = null;
 372                         $this->mPastTheEndIndex = '';
 373                 }
 374
 375                 if ( $this->mIsBackwards ) {
 376                         $this->mIsFirst = ( $numRows < $limit );
 377                         $this->mIsLast = $isFirst;
 378                         $this->mLastShown = $firstIndex;
 379                         $this->mFirstShown = $lastIndex;
 380                 } else {
 381                         $this->mIsFirst = $isFirst;
 382                         $this->mIsLast = ( $numRows < $limit );
 383                         $this->mLastShown = $lastIndex;
 384                         $this->mFirstShown = $firstIndex;
 385                 }
 386         }
 387
 388         /**
 389          * Get some text to go in brackets in the "function name" part of the SQL comment
 390          *
 391          * @return string
 392          */
 393         function getSqlComment() {
 394                 return static::class;
 395         }
 396
 397         /**
 398          * Do a query with specified parameters, rather than using the object context
 399          *
 400          * @note For b/c, query direction is true for ascending and false for descending
 401          *
 402          * @param string $offset Index offset, inclusive
 403          * @param int $limit Exact query limit
 404          * @param bool $order IndexPager::QUERY_ASCENDING or IndexPager::QUERY_DESCENDING
 405          * @return IResultWrapper
 406          */
 407         public function reallyDoQuery( $offset, $limit, $order ) {
 408                 list( $tables, $fields, $conds, $fname, $options, $join_conds ) =
 409                         $this->buildQueryInfo( $offset, $limit, $order );
 410
 411                 return $this->mDb->select( $tables, $fields, $conds, $fname, $options, $join_conds );
 412         }
 413
 414         /**
 415          * Build variables to use by the database wrapper.
 416          *
 417          * @note For b/c, query direction is true for ascending and false for descending
 418          *
 419          * @param string $offset Index offset, inclusive
 420          * @param int $limit Exact query limit
 421          * @param bool $order IndexPager::QUERY_ASCENDING or IndexPager::QUERY_DESCENDING
 422          * @return array
 423          */
 424         protected function buildQueryInfo( $offset, $limit, $order ) {
 425                 $fname = __METHOD__ . ' (' . $this->getSqlComment() . ')';
 426                 $info = $this->getQueryInfo();
 427                 $tables = $info['tables'];
 428                 $fields = $info['fields'];
 429                 $conds = $info['conds'] ?? [];
 430                 $options = $info['options'] ?? [];
 431                 $join_conds = $info['join_conds'] ?? [];
 432                 $sortColumns = array_merge( [ $this->mIndexField ], $this->mExtraSortFields );
 433                 if ( $order === self::QUERY_ASCENDING ) {
 434                         $options['ORDER BY'] = $sortColumns;
 435                         $operator = $this->mIncludeOffset ? '>=' : '>';
 436                 } else {
 437                         $orderBy = [];
 438                         foreach ( $sortColumns as $col ) {
 439                                 $orderBy[] = $col . ' DESC';
 440                         }
 441                         $options['ORDER BY'] = $orderBy;
 442                         $operator = $this->mIncludeOffset ? '<=' : '<';
 443                 }
 444                 if ( $offset != '' ) {
 445                         $conds[] = $this->mIndexField . $operator . $this->mDb->addQuotes( $offset );
 446                 }
 447                 $options['LIMIT'] = intval( $limit );
 448                 return [ $tables, $fields, $conds, $fname, $options, $join_conds ];
 449         }
 450
 451         /**
 452          * Pre-process results; useful for performing batch existence checks, etc.
 453          *
 454          * @param IResultWrapper $result
 455          */
 456         protected function preprocessResults( $result ) {
 457         }
 458
 459         /**
 460          * Get the formatted result list. Calls getStartBody(), formatRow() and
 461          * getEndBody(), concatenates the results and returns them.
 462          *
 463          * @return string
 464          */
 465         public function getBody() {
 466                 if ( !$this->mQueryDone ) {
 467                         $this->doQuery();
 468                 }
 469
 470                 if ( $this->mResult->numRows() ) {
 471                         # Do any special query batches before display
 472                         $this->doBatchLookups();
 473                 }
 474
 475                 # Don't use any extra rows returned by the query
 476                 $numRows = min( $this->mResult->numRows(), $this->mLimit );
 477
 478                 $s = $this->getStartBody();
 479                 if ( $numRows ) {
 480                         if ( $this->mIsBackwards ) {
 481                                 for ( $i = $numRows - 1; $i >= 0; $i-- ) {
 482                                         $this->mResult->seek( $i );
 483                                         $row = $this->mResult->fetchObject();
 484                                         $s .= $this->formatRow( $row );
 485                                 }
 486                         } else {
 487                                 $this->mResult->seek( 0 );
 488                                 for ( $i = 0; $i < $numRows; $i++ ) {
 489                                         $row = $this->mResult->fetchObject();
 490                                         $s .= $this->formatRow( $row );
 491                                 }
 492                         }
 493                 } else {
 494                         $s .= $this->getEmptyBody();
 495                 }
 496                 $s .= $this->getEndBody();
 497                 return $s;
 498         }
 499
 500         /**
 501          * Make a self-link
 502          *
 503          * @param string $text Text displayed on the link
 504          * @param array|null $query Associative array of parameter to be in the query string
 505          * @param string|null $type Link type used to create additional attributes, like "rel", "class" or
 506          *  "title". Valid values (non-exhaustive list): 'first', 'last', 'prev', 'next', 'asc', 'desc'.
 507          * @return string HTML fragment
 508          */
 509         function makeLink( $text, array $query = null, $type = null ) {
 510                 if ( $query === null ) {
 511                         return $text;
 512                 }
 513
 514                 $attrs = [];
 515                 if ( in_array( $type, [ 'prev', 'next' ] ) ) {
 516                         $attrs['rel'] = $type;
 517                 }
 518
 519                 if ( in_array( $type, [ 'asc', 'desc' ] ) ) {
 520                         $attrs['title'] = $this->msg( $type == 'asc' ? 'sort-ascending' : 'sort-descending' )->text();
 521                 }
 522
 523                 if ( $type ) {
 524                         $attrs['class'] = "mw-{$type}link";
 525                 }
 526
 527                 return Linker::linkKnown(
 528                         $this->getTitle(),
 529                         $text,
 530                         $attrs,
 531                         $query + $this->getDefaultQuery()
 532                 );
 533         }
 534
 535         /**
 536          * Called from getBody(), before getStartBody() is called and
 537          * after doQuery() was called. This will be called only if there
 538          * are rows in the result set.
 539          *
 540          * @return void
 541          */
 542         protected function doBatchLookups() {
 543         }
 544
 545         /**
 546          * Hook into getBody(), allows text to be inserted at the start. This
 547          * will be called even if there are no rows in the result set.
 548          *
 549          * @return string
 550          */
 551         protected function getStartBody() {
 552                 return '';
 553         }
 554
 555         /**
 556          * Hook into getBody() for the end of the list
 557          *
 558          * @return string
 559          */
 560         protected function getEndBody() {
 561                 return '';
 562         }
 563
 564         /**
 565          * Hook into getBody(), for the bit between the start and the
 566          * end when there are no rows
 567          *
 568          * @return string
 569          */
 570         protected function getEmptyBody() {
 571                 return '';
 572         }
 573
 574         /**
 575          * Get an array of query parameters that should be put into self-links.
 576          * By default, all parameters passed in the URL are used, except for a
 577          * short blacklist.
 578          *
 579          * @return array Associative array
 580          */
 581         function getDefaultQuery() {
 582                 if ( !isset( $this->mDefaultQuery ) ) {
 583                         $this->mDefaultQuery = $this->getRequest()->getQueryValues();
 584                         unset( $this->mDefaultQuery['title'] );
 585                         unset( $this->mDefaultQuery['dir'] );
 586                         unset( $this->mDefaultQuery['offset'] );
 587                         unset( $this->mDefaultQuery['limit'] );
 588                         unset( $this->mDefaultQuery['order'] );
 589                         unset( $this->mDefaultQuery['month'] );
 590                         unset( $this->mDefaultQuery['year'] );
 591                 }
 592                 return $this->mDefaultQuery;
 593         }
 594
 595         /**
 596          * Get the number of rows in the result set
 597          *
 598          * @return int
 599          */
 600         function getNumRows() {
 601                 if ( !$this->mQueryDone ) {
 602                         $this->doQuery();
 603                 }
 604                 return $this->mResult->numRows();
 605         }
 606
 607         /**
 608          * Get a URL query array for the prev, next, first and last links.
 609          *
 610          * @return array
 611          */
 612         function getPagingQueries() {
 613                 if ( !$this->mQueryDone ) {
 614                         $this->doQuery();
 615                 }
 616
 617                 # Don't announce the limit everywhere if it's the default
 618                 $urlLimit = $this->mLimit == $this->mDefaultLimit ? null : $this->mLimit;
 619
 620                 if ( $this->mIsFirst ) {
 621                         $prev = false;
 622                         $first = false;
 623                 } else {
 624                         $prev = [
 625                                 'dir' => 'prev',
 626                                 'offset' => $this->mFirstShown,
 627                                 'limit' => $urlLimit
 628                         ];
 629                         $first = [ 'limit' => $urlLimit ];
 630                 }
 631                 if ( $this->mIsLast ) {
 632                         $next = false;
 633                         $last = false;
 634                 } else {
 635                         $next = [ 'offset' => $this->mLastShown, 'limit' => $urlLimit ];
 636                         $last = [ 'dir' => 'prev', 'limit' => $urlLimit ];
 637                 }
 638                 return [
 639                         'prev' => $prev,
 640                         'next' => $next,
 641                         'first' => $first,
 642                         'last' => $last
 643                 ];
 644         }
 645
 646         /**
 647          * Returns whether to show the "navigation bar"
 648          *
 649          * @return bool
 650          */
 651         function isNavigationBarShown() {
 652                 if ( !$this->mQueryDone ) {
 653                         $this->doQuery();
 654                 }
 655                 // Hide navigation by default if there is nothing to page
 656                 return !( $this->mIsFirst && $this->mIsLast );
 657         }
 658
 659         /**
 660          * Get paging links. If a link is disabled, the item from $disabledTexts
 661          * will be used. If there is no such item, the unlinked text from
 662          * $linkTexts will be used. Both $linkTexts and $disabledTexts are arrays
 663          * of HTML.
 664          *
 665          * @param array $linkTexts
 666          * @param array $disabledTexts
 667          * @return array
 668          */
 669         function getPagingLinks( $linkTexts, $disabledTexts = [] ) {
 670                 $queries = $this->getPagingQueries();
 671                 $links = [];
 672
 673                 foreach ( $queries as $type => $query ) {
 674                         if ( $query !== false ) {
 675                                 $links[$type] = $this->makeLink(
 676                                         $linkTexts[$type],
 677                                         $queries[$type],
 678                                         $type
 679                                 );
 680                         } elseif ( isset( $disabledTexts[$type] ) ) {
 681                                 $links[$type] = $disabledTexts[$type];
 682                         } else {
 683                                 $links[$type] = $linkTexts[$type];
 684                         }
 685                 }
 686
 687                 return $links;
 688         }
 689
 690         function getLimitLinks() {
 691                 $links = [];
 692                 if ( $this->mIsBackwards ) {
 693                         $offset = $this->mPastTheEndIndex;
 694                 } else {
 695                         $offset = $this->mOffset;
 696                 }
 697                 foreach ( $this->mLimitsShown as $limit ) {
 698                         $links[] = $this->makeLink(
 699                                 $this->getLanguage()->formatNum( $limit ),
 700                                 [ 'offset' => $offset, 'limit' => $limit ],
 701                                 'num'
 702                         );
 703                 }
 704                 return $links;
 705         }
 706
 707         /**
 708          * Abstract formatting function. This should return an HTML string
 709          * representing the result row $row. Rows will be concatenated and
 710          * returned by getBody()
 711          *
 712          * @param array|stdClass $row Database row
 713          * @return string
 714          */
 715         abstract function formatRow( $row );
 716
 717         /**
 718          * This function should be overridden to provide all parameters
 719          * needed for the main paged query. It returns an associative
 720          * array with the following elements:
 721          *    tables => Table(s) for passing to Database::select()
 722          *    fields => Field(s) for passing to Database::select(), may be *
 723          *    conds => WHERE conditions
 724          *    options => option array
 725          *    join_conds => JOIN conditions
 726          *
 727          * @return array
 728          */
 729         abstract function getQueryInfo();
 730
 731         /**
 732          * This function should be overridden to return the name of the index fi-
 733          * eld.  If the pager supports multiple orders, it may return an array of
 734          * 'querykey' => 'indexfield' pairs, so that a request with &count=querykey
 735          * will use indexfield to sort.  In this case, the first returned key is
 736          * the default.
 737          *
 738          * Needless to say, it's really not a good idea to use a non-unique index
 739          * for this!  That won't page right.
 740          *
 741          * @return string|string[]
 742          */
 743         abstract function getIndexField();
 744
 745         /**
 746          * This function should be overridden to return the names of secondary columns
 747          * to order by in addition to the column in getIndexField(). These fields will
 748          * not be used in the pager offset or in any links for users.
 749          *
 750          * If getIndexField() returns an array of 'querykey' => 'indexfield' pairs then
 751          * this must return a corresponding array of 'querykey' => [ fields... ] pairs
 752          * in order for a request with &count=querykey to use [ fields... ] to sort.
 753          *
 754          * This is useful for pagers that GROUP BY a unique column (say page_id)
 755          * and ORDER BY another (say page_len). Using GROUP BY and ORDER BY both on
 756          * page_len,page_id avoids temp tables (given a page_len index). This would
 757          * also work if page_id was non-unique but we had a page_len,page_id index.
 758          *
 759          * @return string[]|array[]
 760          */
 761         protected function getExtraSortFields() {
 762                 return [];
 763         }
 764
 765         /**
 766          * Return the default sorting direction: DIR_ASCENDING or DIR_DESCENDING.
 767          * You can also have an associative array of ordertype => dir,
 768          * if multiple order types are supported.  In this case getIndexField()
 769          * must return an array, and the keys of that must exactly match the keys
 770          * of this.
 771          *
 772          * For backward compatibility, this method's return value will be ignored
 773          * if $this->mDefaultDirection is already set when the constructor is
 774          * called, for instance if it's statically initialized.  In that case the
 775          * value of that variable (which must be a boolean) will be used.
 776          *
 777          * Note that despite its name, this does not return the value of the
 778          * $this->mDefaultDirection member variable.  That's the default for this
 779          * particular instantiation, which is a single value.  This is the set of
 780          * all defaults for the class.
 781          *
 782          * @return bool
 783          */
 784         protected function getDefaultDirections() {
 785                 return self::DIR_ASCENDING;
 786         }
 787 }