includes/search/SearchEngine.php

   1 <?php
   2 /**
   3  * Basic search engine
   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 Search
  22  */
  23
  24 /**
  25  * @defgroup Search Search
  26  */
  27
  28 use MediaWiki\MediaWikiServices;
  29
  30 /**
  31  * Contain a class for special pages
  32  * @ingroup Search
  33  */
  34 abstract class SearchEngine {
  35         const DEFAULT_SORT = 'relevance';
  36
  37         /** @var string */
  38         public $prefix = '';
  39
  40         /** @var int[]|null */
  41         public $namespaces = [ NS_MAIN ];
  42
  43         /** @var int */
  44         protected $limit = 10;
  45
  46         /** @var int */
  47         protected $offset = 0;
  48
  49         /** @var array|string */
  50         protected $searchTerms = [];
  51
  52         /** @var bool */
  53         protected $showSuggestion = true;
  54         private $sort = self::DEFAULT_SORT;
  55
  56         /** @var array Feature values */
  57         protected $features = [];
  58
  59         /** @const string profile type for completionSearch */
  60         const COMPLETION_PROFILE_TYPE = 'completionSearchProfile';
  61
  62         /** @const string profile type for query independent ranking features */
  63         const FT_QUERY_INDEP_PROFILE_TYPE = 'fulltextQueryIndepProfile';
  64
  65         /** @const int flag for legalSearchChars: includes all chars allowed in a search query */
  66         const CHARS_ALL = 1;
  67
  68         /** @const int flag for legalSearchChars: includes all chars allowed in a search term */
  69         const CHARS_NO_SYNTAX = 2;
  70
  71         /**
  72          * Perform a full text search query and return a result set.
  73          * If full text searches are not supported or disabled, return null.
  74          *
  75          * As of 1.32 overriding this function is deprecated. It will
  76          * be converted to final in 1.34. Override self::doSearchText().
  77          *
  78          * @param string $term Raw search term
  79          * @return SearchResultSet|Status|null
  80          */
  81         public function searchText( $term ) {
  82                 return $this->maybePaginate( function () use ( $term ) {
  83                         return $this->doSearchText( $term );
  84                 } );
  85         }
  86
  87         /**
  88          * Perform a full text search query and return a result set.
  89          *
  90          * @param string $term Raw search term
  91          * @return SearchResultSet|Status|null
  92          * @since 1.32
  93          */
  94         protected function doSearchText( $term ) {
  95                 return null;
  96         }
  97
  98         /**
  99          * Perform a title search in the article archive.
 100          * NOTE: these results still should be filtered by
 101          * matching against PageArchive, permissions checks etc
 102          * The results returned by this methods are only sugegstions and
 103          * may not end up being shown to the user.
 104          *
 105          * As of 1.32 overriding this function is deprecated. It will
 106          * be converted to final in 1.34. Override self::doSearchArchiveTitle().
 107          *
 108          * @param string $term Raw search term
 109          * @return Status<Title[]>
 110          * @since 1.29
 111          */
 112         public function searchArchiveTitle( $term ) {
 113                 return $this->doSearchArchiveTitle( $term );
 114         }
 115
 116         /**
 117          * Perform a title search in the article archive.
 118          *
 119          * @param string $term Raw search term
 120          * @return Status<Title[]>
 121          * @since 1.32
 122          */
 123         protected function doSearchArchiveTitle( $term ) {
 124                 return Status::newGood( [] );
 125         }
 126
 127         /**
 128          * Perform a title-only search query and return a result set.
 129          * If title searches are not supported or disabled, return null.
 130          * STUB
 131          *
 132          * As of 1.32 overriding this function is deprecated. It will
 133          * be converted to final in 1.34. Override self::doSearchTitle().
 134          *
 135          * @param string $term Raw search term
 136          * @return SearchResultSet|null
 137          */
 138         public function searchTitle( $term ) {
 139                 return $this->maybePaginate( function () use ( $term ) {
 140                         return $this->doSearchTitle( $term );
 141                 } );
 142         }
 143
 144         /**
 145          * Perform a title-only search query and return a result set.
 146          *
 147          * @param string $term Raw search term
 148          * @return SearchResultSet|null
 149          * @since 1.32
 150          */
 151         protected function doSearchTitle( $term ) {
 152                 return null;
 153         }
 154
 155         /**
 156          * Performs an overfetch and shrink operation to determine if
 157          * the next page is available for search engines that do not
 158          * explicitly implement their own pagination.
 159          *
 160          * @param Closure $fn Takes no arguments
 161          * @return SearchResultSet|Status<SearchResultSet>|null Result of calling $fn
 162          */
 163         private function maybePaginate( Closure $fn ) {
 164                 if ( $this instanceof PaginatingSearchEngine ) {
 165                         return $fn();
 166                 }
 167                 $this->limit++;
 168                 try {
 169                         $resultSetOrStatus = $fn();
 170                 } finally {
 171                         $this->limit--;
 172                 }
 173
 174                 $resultSet = null;
 175                 if ( $resultSetOrStatus instanceof SearchResultSet ) {
 176                         $resultSet = $resultSetOrStatus;
 177                 } elseif ( $resultSetOrStatus instanceof Status &&
 178                         $resultSetOrStatus->getValue() instanceof SearchResultSet
 179                 ) {
 180                         $resultSet = $resultSetOrStatus->getValue();
 181                 }
 182                 if ( $resultSet ) {
 183                         $resultSet->shrink( $this->limit );
 184                 }
 185
 186                 return $resultSetOrStatus;
 187         }
 188
 189         /**
 190          * @since 1.18
 191          * @param string $feature
 192          * @return bool
 193          */
 194         public function supports( $feature ) {
 195                 switch ( $feature ) {
 196                         case 'search-update':
 197                                 return true;
 198                         case 'title-suffix-filter':
 199                         default:
 200                                 return false;
 201                 }
 202         }
 203
 204         /**
 205          * Way to pass custom data for engines
 206          * @since 1.18
 207          * @param string $feature
 208          * @param mixed $data
 209          */
 210         public function setFeatureData( $feature, $data ) {
 211                 $this->features[$feature] = $data;
 212         }
 213
 214         /**
 215          * Way to retrieve custom data set by setFeatureData
 216          * or by the engine itself.
 217          * @since 1.29
 218          * @param string $feature feature name
 219          * @return mixed the feature value or null if unset
 220          */
 221         public function getFeatureData( $feature ) {
 222                 if ( isset( $this->features[$feature] ) ) {
 223                         return $this->features[$feature];
 224                 }
 225                 return null;
 226         }
 227
 228         /**
 229          * When overridden in derived class, performs database-specific conversions
 230          * on text to be used for searching or updating search index.
 231          * Default implementation does nothing (simply returns $string).
 232          *
 233          * @param string $string String to process
 234          * @return string
 235          */
 236         public function normalizeText( $string ) {
 237                 global $wgContLang;
 238
 239                 // Some languages such as Chinese require word segmentation
 240                 return $wgContLang->segmentByWord( $string );
 241         }
 242
 243         /**
 244          * Transform search term in cases when parts of the query came as different
 245          * GET params (when supported), e.g. for prefix queries:
 246          * search=test&prefix=Main_Page/Archive -> test prefix:Main Page/Archive
 247          * @param string $term
 248          * @return string
 249          * @deprecated since 1.32 this should now be handled internally by the
 250          * search engine
 251          */
 252         public function transformSearchTerm( $term ) {
 253                 return $term;
 254         }
 255
 256         /**
 257          * Get service class to finding near matches.
 258          * @param Config $config Configuration to use for the matcher.
 259          * @return SearchNearMatcher
 260          */
 261         public function getNearMatcher( Config $config ) {
 262                 global $wgContLang;
 263                 return new SearchNearMatcher( $config, $wgContLang );
 264         }
 265
 266         /**
 267          * Get near matcher for default SearchEngine.
 268          * @return SearchNearMatcher
 269          */
 270         protected static function defaultNearMatcher() {
 271                 $config = MediaWikiServices::getInstance()->getMainConfig();
 272                 return MediaWikiServices::getInstance()->newSearchEngine()->getNearMatcher( $config );
 273         }
 274
 275         /**
 276          * If an exact title match can be found, or a very slightly close match,
 277          * return the title. If no match, returns NULL.
 278          * @deprecated since 1.27; Use SearchEngine::getNearMatcher()
 279          * @param string $searchterm
 280          * @return Title
 281          */
 282         public static function getNearMatch( $searchterm ) {
 283                 return static::defaultNearMatcher()->getNearMatch( $searchterm );
 284         }
 285
 286         /**
 287          * Do a near match (see SearchEngine::getNearMatch) and wrap it into a
 288          * SearchResultSet.
 289          * @deprecated since 1.27; Use SearchEngine::getNearMatcher()
 290          * @param string $searchterm
 291          * @return SearchResultSet
 292          */
 293         public static function getNearMatchResultSet( $searchterm ) {
 294                 return static::defaultNearMatcher()->getNearMatchResultSet( $searchterm );
 295         }
 296
 297         /**
 298          * Get chars legal for search
 299          * NOTE: usage as static is deprecated and preserved only as BC measure
 300          * @param int $type type of search chars (see self::CHARS_ALL
 301          * and self::CHARS_NO_SYNTAX). Defaults to CHARS_ALL
 302          * @return string
 303          */
 304         public static function legalSearchChars( $type = self::CHARS_ALL ) {
 305                 return "A-Za-z_'.0-9\\x80-\\xFF\\-";
 306         }
 307
 308         /**
 309          * Set the maximum number of results to return
 310          * and how many to skip before returning the first.
 311          *
 312          * @param int $limit
 313          * @param int $offset
 314          */
 315         function setLimitOffset( $limit, $offset = 0 ) {
 316                 $this->limit = intval( $limit );
 317                 $this->offset = intval( $offset );
 318         }
 319
 320         /**
 321          * Set which namespaces the search should include.
 322          * Give an array of namespace index numbers.
 323          *
 324          * @param int[]|null $namespaces
 325          */
 326         function setNamespaces( $namespaces ) {
 327                 if ( $namespaces ) {
 328                         // Filter namespaces to only keep valid ones
 329                         $validNs = $this->searchableNamespaces();
 330                         $namespaces = array_filter( $namespaces, function ( $ns ) use( $validNs ) {
 331                                 return $ns < 0 || isset( $validNs[$ns] );
 332                         } );
 333                 } else {
 334                         $namespaces = [];
 335                 }
 336                 $this->namespaces = $namespaces;
 337         }
 338
 339         /**
 340          * Set whether the searcher should try to build a suggestion.  Note: some searchers
 341          * don't support building a suggestion in the first place and others don't respect
 342          * this flag.
 343          *
 344          * @param bool $showSuggestion Should the searcher try to build suggestions
 345          */
 346         function setShowSuggestion( $showSuggestion ) {
 347                 $this->showSuggestion = $showSuggestion;
 348         }
 349
 350         /**
 351          * Get the valid sort directions.  All search engines support 'relevance' but others
 352          * might support more. The default in all implementations must be 'relevance.'
 353          *
 354          * @since 1.25
 355          * @return string[] the valid sort directions for setSort
 356          */
 357         public function getValidSorts() {
 358                 return [ self::DEFAULT_SORT ];
 359         }
 360
 361         /**
 362          * Set the sort direction of the search results. Must be one returned by
 363          * SearchEngine::getValidSorts()
 364          *
 365          * @since 1.25
 366          * @throws InvalidArgumentException
 367          * @param string $sort sort direction for query result
 368          */
 369         public function setSort( $sort ) {
 370                 if ( !in_array( $sort, $this->getValidSorts() ) ) {
 371                         throw new InvalidArgumentException( "Invalid sort: $sort. " .
 372                                 "Must be one of: " . implode( ', ', $this->getValidSorts() ) );
 373                 }
 374                 $this->sort = $sort;
 375         }
 376
 377         /**
 378          * Get the sort direction of the search results
 379          *
 380          * @since 1.25
 381          * @return string
 382          */
 383         public function getSort() {
 384                 return $this->sort;
 385         }
 386
 387         /**
 388          * Parse some common prefixes: all (search everything)
 389          * or namespace names and set the list of namespaces
 390          * of this class accordingly.
 391          *
 392          * @deprecated since 1.32; should be handled internally by the search engine
 393          * @param string $query
 394          * @return string
 395          */
 396         function replacePrefixes( $query ) {
 397                 return $query;
 398         }
 399
 400         /**
 401          * Parse some common prefixes: all (search everything)
 402          * or namespace names
 403          *
 404          * @param string $query
 405          * @param bool $withAllKeyword activate support of the "all:" keyword and its
 406          * translations to activate searching on all namespaces.
 407          * @param bool $withPrefixSearchExtractNamespaceHook call the PrefixSearchExtractNamespace hook
 408          *  if classic namespace identification did not match.
 409          * @return false|array false if no namespace was extracted, an array
 410          * with the parsed query at index 0 and an array of namespaces at index
 411          * 1 (or null for all namespaces).
 412          * @throws FatalError
 413          * @throws MWException
 414          */
 415         public static function parseNamespacePrefixes(
 416                 $query,
 417                 $withAllKeyword = true,
 418                 $withPrefixSearchExtractNamespaceHook = false
 419         ) {
 420                 global $wgContLang;
 421
 422                 $parsed = $query;
 423                 if ( strpos( $query, ':' ) === false ) { // nothing to do
 424                         return false;
 425                 }
 426                 $extractedNamespace = null;
 427
 428                 $allQuery = false;
 429                 if ( $withAllKeyword ) {
 430                         $allkeywords = [];
 431
 432                         $allkeywords[] = wfMessage( 'searchall' )->inContentLanguage()->text() . ":";
 433                         // force all: so that we have a common syntax for all the wikis
 434                         if ( !in_array( 'all:', $allkeywords ) ) {
 435                                 $allkeywords[] = 'all:';
 436                         }
 437
 438                         foreach ( $allkeywords as $kw ) {
 439                                 if ( strncmp( $query, $kw, strlen( $kw ) ) == 0 ) {
 440                                         $extractedNamespace = null;
 441                                         $parsed = substr( $query, strlen( $kw ) );
 442                                         $allQuery = true;
 443                                         break;
 444                                 }
 445                         }
 446                 }
 447
 448                 if ( !$allQuery && strpos( $query, ':' ) !== false ) {
 449                         $prefix = str_replace( ' ', '_', substr( $query, 0, strpos( $query, ':' ) ) );
 450                         $index = $wgContLang->getNsIndex( $prefix );
 451                         if ( $index !== false ) {
 452                                 $extractedNamespace = [ $index ];
 453                                 $parsed = substr( $query, strlen( $prefix ) + 1 );
 454                         } elseif ( $withPrefixSearchExtractNamespaceHook ) {
 455                                 $hookNamespaces = [ NS_MAIN ];
 456                                 $hookQuery = $query;
 457                                 Hooks::run( 'PrefixSearchExtractNamespace', [ &$hookNamespaces, &$hookQuery ] );
 458                                 if ( $hookQuery !== $query ) {
 459                                         $parsed = $hookQuery;
 460                                         $extractedNamespace = $hookNamespaces;
 461                                 } else {
 462                                         return false;
 463                                 }
 464                         } else {
 465                                 return false;
 466                         }
 467                 }
 468
 469                 return [ $parsed, $extractedNamespace ];
 470         }
 471
 472         /**
 473          * Find snippet highlight settings for all users
 474          * @return array Contextlines, contextchars
 475          */
 476         public static function userHighlightPrefs() {
 477                 $contextlines = 2; // Hardcode this. Old defaults sucked. :)
 478                 $contextchars = 75; // same as above.... :P
 479                 return [ $contextlines, $contextchars ];
 480         }
 481
 482         /**
 483          * Create or update the search index record for the given page.
 484          * Title and text should be pre-processed.
 485          * STUB
 486          *
 487          * @param int $id
 488          * @param string $title
 489          * @param string $text
 490          */
 491         function update( $id, $title, $text ) {
 492                 // no-op
 493         }
 494
 495         /**
 496          * Update a search index record's title only.
 497          * Title should be pre-processed.
 498          * STUB
 499          *
 500          * @param int $id
 501          * @param string $title
 502          */
 503         function updateTitle( $id, $title ) {
 504                 // no-op
 505         }
 506
 507         /**
 508          * Delete an indexed page
 509          * Title should be pre-processed.
 510          * STUB
 511          *
 512          * @param int $id Page id that was deleted
 513          * @param string $title Title of page that was deleted
 514          */
 515         function delete( $id, $title ) {
 516                 // no-op
 517         }
 518
 519         /**
 520          * Get the raw text for updating the index from a content object
 521          * Nicer search backends could possibly do something cooler than
 522          * just returning raw text
 523          *
 524          * @todo This isn't ideal, we'd really like to have content-specific handling here
 525          * @param Title $t Title we're indexing
 526          * @param Content|null $c Content of the page to index
 527          * @return string
 528          */
 529         public function getTextFromContent( Title $t, Content $c = null ) {
 530                 return $c ? $c->getTextForSearchIndex() : '';
 531         }
 532
 533         /**
 534          * If an implementation of SearchEngine handles all of its own text processing
 535          * in getTextFromContent() and doesn't require SearchUpdate::updateText()'s
 536          * rather silly handling, it should return true here instead.
 537          *
 538          * @return bool
 539          */
 540         public function textAlreadyUpdatedForIndex() {
 541                 return false;
 542         }
 543
 544         /**
 545          * Makes search simple string if it was namespaced.
 546          * Sets namespaces of the search to namespaces extracted from string.
 547          * @param string $search
 548          * @return string Simplified search string
 549          */
 550         protected function normalizeNamespaces( $search ) {
 551                 $queryAndNs = self::parseNamespacePrefixes( $search, false, true );
 552                 if ( $queryAndNs !== false ) {
 553                         $this->setNamespaces( $queryAndNs[1] );
 554                         return $queryAndNs[0];
 555                 }
 556                 return $search;
 557         }
 558
 559         /**
 560          * Perform an overfetch of completion search results. This allows
 561          * determining if another page of results is available.
 562          *
 563          * @param string $search
 564          * @return SearchSuggestionSet
 565          */
 566         protected function completionSearchBackendOverfetch( $search ) {
 567                 $this->limit++;
 568                 try {
 569                         return $this->completionSearchBackend( $search );
 570                 } finally {
 571                         $this->limit--;
 572                 }
 573         }
 574
 575         /**
 576          * Perform a completion search.
 577          * Does not resolve namespaces and does not check variants.
 578          * Search engine implementations may want to override this function.
 579          * @param string $search
 580          * @return SearchSuggestionSet
 581          */
 582         protected function completionSearchBackend( $search ) {
 583                 $results = [];
 584
 585                 $search = trim( $search );
 586
 587                 if ( !in_array( NS_SPECIAL, $this->namespaces ) && // We do not run hook on Special: search
 588                          !Hooks::run( 'PrefixSearchBackend',
 589                                 [ $this->namespaces, $search, $this->limit, &$results, $this->offset ]
 590                 ) ) {
 591                         // False means hook worked.
 592                         // FIXME: Yes, the API is weird. That's why it is going to be deprecated.
 593
 594                         return SearchSuggestionSet::fromStrings( $results );
 595                 } else {
 596                         // Hook did not do the job, use default simple search
 597                         $results = $this->simplePrefixSearch( $search );
 598                         return SearchSuggestionSet::fromTitles( $results );
 599                 }
 600         }
 601
 602         /**
 603          * Perform a completion search.
 604          * @param string $search
 605          * @return SearchSuggestionSet
 606          */
 607         public function completionSearch( $search ) {
 608                 if ( trim( $search ) === '' ) {
 609                         return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
 610                 }
 611                 $search = $this->normalizeNamespaces( $search );
 612                 $suggestions = $this->completionSearchBackendOverfetch( $search );
 613                 return $this->processCompletionResults( $search, $suggestions );
 614         }
 615
 616         /**
 617          * Perform a completion search with variants.
 618          * @param string $search
 619          * @return SearchSuggestionSet
 620          */
 621         public function completionSearchWithVariants( $search ) {
 622                 if ( trim( $search ) === '' ) {
 623                         return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
 624                 }
 625                 $search = $this->normalizeNamespaces( $search );
 626
 627                 $results = $this->completionSearchBackendOverfetch( $search );
 628                 $fallbackLimit = 1 + $this->limit - $results->getSize();
 629                 if ( $fallbackLimit > 0 ) {
 630                         global $wgContLang;
 631
 632                         $fallbackSearches = $wgContLang->autoConvertToAllVariants( $search );
 633                         $fallbackSearches = array_diff( array_unique( $fallbackSearches ), [ $search ] );
 634
 635                         foreach ( $fallbackSearches as $fbs ) {
 636                                 $this->setLimitOffset( $fallbackLimit );
 637                                 $fallbackSearchResult = $this->completionSearch( $fbs );
 638                                 $results->appendAll( $fallbackSearchResult );
 639                                 $fallbackLimit -= $fallbackSearchResult->getSize();
 640                                 if ( $fallbackLimit <= 0 ) {
 641                                         break;
 642                                 }
 643                         }
 644                 }
 645                 return $this->processCompletionResults( $search, $results );
 646         }
 647
 648         /**
 649          * Extract titles from completion results
 650          * @param SearchSuggestionSet $completionResults
 651          * @return Title[]
 652          */
 653         public function extractTitles( SearchSuggestionSet $completionResults ) {
 654                 return $completionResults->map( function ( SearchSuggestion $sugg ) {
 655                         return $sugg->getSuggestedTitle();
 656                 } );
 657         }
 658
 659         /**
 660          * Process completion search results.
 661          * Resolves the titles and rescores.
 662          * @param string $search
 663          * @param SearchSuggestionSet $suggestions
 664          * @return SearchSuggestionSet
 665          */
 666         protected function processCompletionResults( $search, SearchSuggestionSet $suggestions ) {
 667                 // We over-fetched to determine pagination. Shrink back down if we have extra results
 668                 // and mark if pagination is possible
 669                 $suggestions->shrink( $this->limit );
 670
 671                 $search = trim( $search );
 672                 // preload the titles with LinkBatch
 673                 $lb = new LinkBatch( $suggestions->map( function ( SearchSuggestion $sugg ) {
 674                         return $sugg->getSuggestedTitle();
 675                 } ) );
 676                 $lb->setCaller( __METHOD__ );
 677                 $lb->execute();
 678
 679                 $diff = $suggestions->filter( function ( SearchSuggestion $sugg ) {
 680                         return $sugg->getSuggestedTitle()->isKnown();
 681                 } );
 682                 if ( $diff > 0 ) {
 683                         MediaWikiServices::getInstance()->getStatsdDataFactory()
 684                                 ->updateCount( 'search.completion.missing', $diff );
 685                 }
 686
 687                 $results = $suggestions->map( function ( SearchSuggestion $sugg ) {
 688                         return $sugg->getSuggestedTitle()->getPrefixedText();
 689                 } );
 690
 691                 if ( $this->offset === 0 ) {
 692                         // Rescore results with an exact title match
 693                         // NOTE: in some cases like cross-namespace redirects
 694                         // (frequently used as shortcuts e.g. WP:WP on huwiki) some
 695                         // backends like Cirrus will return no results. We should still
 696                         // try an exact title match to workaround this limitation
 697                         $rescorer = new SearchExactMatchRescorer();
 698                         $rescoredResults = $rescorer->rescore( $search, $this->namespaces, $results, $this->limit );
 699                 } else {
 700                         // No need to rescore if offset is not 0
 701                         // The exact match must have been returned at position 0
 702                         // if it existed.
 703                         $rescoredResults = $results;
 704                 }
 705
 706                 if ( count( $rescoredResults ) > 0 ) {
 707                         $found = array_search( $rescoredResults[0], $results );
 708                         if ( $found === false ) {
 709                                 // If the first result is not in the previous array it
 710                                 // means that we found a new exact match
 711                                 $exactMatch = SearchSuggestion::fromTitle( 0, Title::newFromText( $rescoredResults[0] ) );
 712                                 $suggestions->prepend( $exactMatch );
 713                                 $suggestions->shrink( $this->limit );
 714                         } else {
 715                                 // if the first result is not the same we need to rescore
 716                                 if ( $found > 0 ) {
 717                                         $suggestions->rescore( $found );
 718                                 }
 719                         }
 720                 }
 721
 722                 return $suggestions;
 723         }
 724
 725         /**
 726          * Simple prefix search for subpages.
 727          * @param string $search
 728          * @return Title[]
 729          */
 730         public function defaultPrefixSearch( $search ) {
 731                 if ( trim( $search ) === '' ) {
 732                         return [];
 733                 }
 734
 735                 $search = $this->normalizeNamespaces( $search );
 736                 return $this->simplePrefixSearch( $search );
 737         }
 738
 739         /**
 740          * Call out to simple search backend.
 741          * Defaults to TitlePrefixSearch.
 742          * @param string $search
 743          * @return Title[]
 744          */
 745         protected function simplePrefixSearch( $search ) {
 746                 // Use default database prefix search
 747                 $backend = new TitlePrefixSearch;
 748                 return $backend->defaultSearchBackend( $this->namespaces, $search, $this->limit, $this->offset );
 749         }
 750
 751         /**
 752          * Make a list of searchable namespaces and their canonical names.
 753          * @deprecated since 1.27; use SearchEngineConfig::searchableNamespaces()
 754          * @return array
 755          */
 756         public static function searchableNamespaces() {
 757                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->searchableNamespaces();
 758         }
 759
 760         /**
 761          * Extract default namespaces to search from the given user's
 762          * settings, returning a list of index numbers.
 763          * @deprecated since 1.27; use SearchEngineConfig::userNamespaces()
 764          * @param user $user
 765          * @return array
 766          */
 767         public static function userNamespaces( $user ) {
 768                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->userNamespaces( $user );
 769         }
 770
 771         /**
 772          * An array of namespaces indexes to be searched by default
 773          * @deprecated since 1.27; use SearchEngineConfig::defaultNamespaces()
 774          * @return array
 775          */
 776         public static function defaultNamespaces() {
 777                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->defaultNamespaces();
 778         }
 779
 780         /**
 781          * Get a list of namespace names useful for showing in tooltips
 782          * and preferences
 783          * @deprecated since 1.27; use SearchEngineConfig::namespacesAsText()
 784          * @param array $namespaces
 785          * @return array
 786          */
 787         public static function namespacesAsText( $namespaces ) {
 788                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->namespacesAsText( $namespaces );
 789         }
 790
 791         /**
 792          * Load up the appropriate search engine class for the currently
 793          * active database backend, and return a configured instance.
 794          * @deprecated since 1.27; Use SearchEngineFactory::create
 795          * @param string $type Type of search backend, if not the default
 796          * @return SearchEngine
 797          */
 798         public static function create( $type = null ) {
 799                 return MediaWikiServices::getInstance()->getSearchEngineFactory()->create( $type );
 800         }
 801
 802         /**
 803          * Return the search engines we support. If only $wgSearchType
 804          * is set, it'll be an array of just that one item.
 805          * @deprecated since 1.27; use SearchEngineConfig::getSearchTypes()
 806          * @return array
 807          */
 808         public static function getSearchTypes() {
 809                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->getSearchTypes();
 810         }
 811
 812         /**
 813          * Get a list of supported profiles.
 814          * Some search engine implementations may expose specific profiles to fine-tune
 815          * its behaviors.
 816          * The profile can be passed as a feature data with setFeatureData( $profileType, $profileName )
 817          * The array returned by this function contains the following keys:
 818          * - name: the profile name to use with setFeatureData
 819          * - desc-message: the i18n description
 820          * - default: set to true if this profile is the default
 821          *
 822          * @since 1.28
 823          * @param string $profileType the type of profiles
 824          * @param User|null $user the user requesting the list of profiles
 825          * @return array|null the list of profiles or null if none available
 826          */
 827         public function getProfiles( $profileType, User $user = null ) {
 828                 return null;
 829         }
 830
 831         /**
 832          * Create a search field definition.
 833          * Specific search engines should override this method to create search fields.
 834          * @param string $name
 835          * @param int $type One of the types in SearchIndexField::INDEX_TYPE_*
 836          * @return SearchIndexField
 837          * @since 1.28
 838          */
 839         public function makeSearchFieldMapping( $name, $type ) {
 840                 return new NullIndexField();
 841         }
 842
 843         /**
 844          * Get fields for search index
 845          * @since 1.28
 846          * @return SearchIndexField[] Index field definitions for all content handlers
 847          */
 848         public function getSearchIndexFields() {
 849                 $models = ContentHandler::getContentModels();
 850                 $fields = [];
 851                 $seenHandlers = new SplObjectStorage();
 852                 foreach ( $models as $model ) {
 853                         try {
 854                                 $handler = ContentHandler::getForModelID( $model );
 855                         }
 856                         catch ( MWUnknownContentModelException $e ) {
 857                                 // If we can find no handler, ignore it
 858                                 continue;
 859                         }
 860                         // Several models can have the same handler, so avoid processing it repeatedly
 861                         if ( $seenHandlers->contains( $handler ) ) {
 862                                 // We already did this one
 863                                 continue;
 864                         }
 865                         $seenHandlers->attach( $handler );
 866                         $handlerFields = $handler->getFieldsForSearchIndex( $this );
 867                         foreach ( $handlerFields as $fieldName => $fieldData ) {
 868                                 if ( empty( $fields[$fieldName] ) ) {
 869                                         $fields[$fieldName] = $fieldData;
 870                                 } else {
 871                                         // TODO: do we allow some clashes with the same type or reject all of them?
 872                                         $mergeDef = $fields[$fieldName]->merge( $fieldData );
 873                                         if ( !$mergeDef ) {
 874                                                 throw new InvalidArgumentException( "Duplicate field $fieldName for model $model" );
 875                                         }
 876                                         $fields[$fieldName] = $mergeDef;
 877                                 }
 878                         }
 879                 }
 880                 // Hook to allow extensions to produce search mapping fields
 881                 Hooks::run( 'SearchIndexFields', [ &$fields, $this ] );
 882                 return $fields;
 883         }
 884
 885         /**
 886          * Augment search results with extra data.
 887          *
 888          * @param SearchResultSet $resultSet
 889          */
 890         public function augmentSearchResults( SearchResultSet $resultSet ) {
 891                 $setAugmentors = [];
 892                 $rowAugmentors = [];
 893                 Hooks::run( "SearchResultsAugment", [ &$setAugmentors, &$rowAugmentors ] );
 894                 if ( !$setAugmentors && !$rowAugmentors ) {
 895                         // We're done here
 896                         return;
 897                 }
 898
 899                 // Convert row augmentors to set augmentor
 900                 foreach ( $rowAugmentors as $name => $row ) {
 901                         if ( isset( $setAugmentors[$name] ) ) {
 902                                 throw new InvalidArgumentException( "Both row and set augmentors are defined for $name" );
 903                         }
 904                         $setAugmentors[$name] = new PerRowAugmentor( $row );
 905                 }
 906
 907                 foreach ( $setAugmentors as $name => $augmentor ) {
 908                         $data = $augmentor->augmentAll( $resultSet );
 909                         if ( $data ) {
 910                                 $resultSet->setAugmentedData( $name, $data );
 911                         }
 912                 }
 913         }
 914 }
 915
 916 /**
 917  * Dummy class to be used when non-supported Database engine is present.
 918  * @todo FIXME: Dummy class should probably try something at least mildly useful,
 919  * such as a LIKE search through titles.
 920  * @ingroup Search
 921  */
 922 class SearchEngineDummy extends SearchEngine {
 923         // no-op
 924 }