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