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          * @return bool
 108          */
 109         public function setFeatureData( $feature, $data ) {
 110                 $this->features[$feature] = $data;
 111         }
 112
 113         /**
 114          * When overridden in derived class, performs database-specific conversions
 115          * on text to be used for searching or updating search index.
 116          * Default implementation does nothing (simply returns $string).
 117          *
 118          * @param string $string String to process
 119          * @return string
 120          */
 121         public function normalizeText( $string ) {
 122                 global $wgContLang;
 123
 124                 // Some languages such as Chinese require word segmentation
 125                 return $wgContLang->segmentByWord( $string );
 126         }
 127
 128         /**
 129          * Transform search term in cases when parts of the query came as different
 130          * GET params (when supported), e.g. for prefix queries:
 131          * search=test&prefix=Main_Page/Archive -> test prefix:Main Page/Archive
 132          * @param string $term
 133          * @return string
 134          */
 135         public function transformSearchTerm( $term ) {
 136                 return $term;
 137         }
 138
 139         /**
 140          * Get service class to finding near matches.
 141          * @param Config $config Configuration to use for the matcher.
 142          * @return SearchNearMatcher
 143          */
 144         public function getNearMatcher( Config $config ) {
 145                 global $wgContLang;
 146                 return new SearchNearMatcher( $config, $wgContLang );
 147         }
 148
 149         /**
 150          * Get near matcher for default SearchEngine.
 151          * @return SearchNearMatcher
 152          */
 153         protected static function defaultNearMatcher() {
 154                 $config = MediaWikiServices::getInstance()->getMainConfig();
 155                 return MediaWikiServices::getInstance()->newSearchEngine()->getNearMatcher( $config );
 156         }
 157
 158         /**
 159          * If an exact title match can be found, or a very slightly close match,
 160          * return the title. If no match, returns NULL.
 161          * @deprecated since 1.27; Use SearchEngine::getNearMatcher()
 162          * @param string $searchterm
 163          * @return Title
 164          */
 165         public static function getNearMatch( $searchterm ) {
 166                 return static::defaultNearMatcher()->getNearMatch( $searchterm );
 167         }
 168
 169         /**
 170          * Do a near match (see SearchEngine::getNearMatch) and wrap it into a
 171          * SearchResultSet.
 172          * @deprecated since 1.27; Use SearchEngine::getNearMatcher()
 173          * @param string $searchterm
 174          * @return SearchResultSet
 175          */
 176         public static function getNearMatchResultSet( $searchterm ) {
 177                 return static::defaultNearMatcher()->getNearMatchResultSet( $searchterm );
 178         }
 179
 180         /**
 181          * Get chars legal for search.
 182          * NOTE: usage as static is deprecated and preserved only as BC measure
 183          * @return string
 184          */
 185         public static function legalSearchChars() {
 186                 return "A-Za-z_'.0-9\\x80-\\xFF\\-";
 187         }
 188
 189         /**
 190          * Set the maximum number of results to return
 191          * and how many to skip before returning the first.
 192          *
 193          * @param int $limit
 194          * @param int $offset
 195          */
 196         function setLimitOffset( $limit, $offset = 0 ) {
 197                 $this->limit = intval( $limit );
 198                 $this->offset = intval( $offset );
 199         }
 200
 201         /**
 202          * Set which namespaces the search should include.
 203          * Give an array of namespace index numbers.
 204          *
 205          * @param int[]|null $namespaces
 206          */
 207         function setNamespaces( $namespaces ) {
 208                 if ( $namespaces ) {
 209                         // Filter namespaces to only keep valid ones
 210                         $validNs = $this->searchableNamespaces();
 211                         $namespaces = array_filter( $namespaces, function( $ns ) use( $validNs ) {
 212                                 return $ns < 0 || isset( $validNs[$ns] );
 213                         } );
 214                 } else {
 215                         $namespaces = [];
 216                 }
 217                 $this->namespaces = $namespaces;
 218         }
 219
 220         /**
 221          * Set whether the searcher should try to build a suggestion.  Note: some searchers
 222          * don't support building a suggestion in the first place and others don't respect
 223          * this flag.
 224          *
 225          * @param bool $showSuggestion Should the searcher try to build suggestions
 226          */
 227         function setShowSuggestion( $showSuggestion ) {
 228                 $this->showSuggestion = $showSuggestion;
 229         }
 230
 231         /**
 232          * Get the valid sort directions.  All search engines support 'relevance' but others
 233          * might support more. The default in all implementations should be 'relevance.'
 234          *
 235          * @since 1.25
 236          * @return array(string) the valid sort directions for setSort
 237          */
 238         public function getValidSorts() {
 239                 return [ 'relevance' ];
 240         }
 241
 242         /**
 243          * Set the sort direction of the search results. Must be one returned by
 244          * SearchEngine::getValidSorts()
 245          *
 246          * @since 1.25
 247          * @throws InvalidArgumentException
 248          * @param string $sort sort direction for query result
 249          */
 250         public function setSort( $sort ) {
 251                 if ( !in_array( $sort, $this->getValidSorts() ) ) {
 252                         throw new InvalidArgumentException( "Invalid sort: $sort. " .
 253                                 "Must be one of: " . implode( ', ', $this->getValidSorts() ) );
 254                 }
 255                 $this->sort = $sort;
 256         }
 257
 258         /**
 259          * Get the sort direction of the search results
 260          *
 261          * @since 1.25
 262          * @return string
 263          */
 264         public function getSort() {
 265                 return $this->sort;
 266         }
 267
 268         /**
 269          * Parse some common prefixes: all (search everything)
 270          * or namespace names and set the list of namespaces
 271          * of this class accordingly.
 272          *
 273          * @param string $query
 274          * @return string
 275          */
 276         function replacePrefixes( $query ) {
 277                 $queryAndNs = self::parseNamespacePrefixes( $query );
 278                 if ( $queryAndNs === false ) {
 279                         return $query;
 280                 }
 281                 $this->namespaces = $queryAndNs[1];
 282                 return $queryAndNs[0];
 283         }
 284
 285         /**
 286          * Parse some common prefixes: all (search everything)
 287          * or namespace names
 288          *
 289          * @param string $query
 290          * @return false|array false if no namespace was extracted, an array
 291          * with the parsed query at index 0 and an array of namespaces at index
 292          * 1 (or null for all namespaces).
 293          */
 294         public static function parseNamespacePrefixes( $query ) {
 295                 global $wgContLang;
 296
 297                 $parsed = $query;
 298                 if ( strpos( $query, ':' ) === false ) { // nothing to do
 299                         return false;
 300                 }
 301                 $extractedNamespace = null;
 302
 303                 $allkeyword = wfMessage( 'searchall' )->inContentLanguage()->text() . ":";
 304                 if ( strncmp( $query, $allkeyword, strlen( $allkeyword ) ) == 0 ) {
 305                         $extractedNamespace = null;
 306                         $parsed = substr( $query, strlen( $allkeyword ) );
 307                 } elseif ( strpos( $query, ':' ) !== false ) {
 308                         // TODO: should we unify with PrefixSearch::extractNamespace ?
 309                         $prefix = str_replace( ' ', '_', substr( $query, 0, strpos( $query, ':' ) ) );
 310                         $index = $wgContLang->getNsIndex( $prefix );
 311                         if ( $index !== false ) {
 312                                 $extractedNamespace = [ $index ];
 313                                 $parsed = substr( $query, strlen( $prefix ) + 1 );
 314                         } else {
 315                                 return false;
 316                         }
 317                 }
 318
 319                 if ( trim( $parsed ) == '' ) {
 320                         $parsed = $query; // prefix was the whole query
 321                 }
 322
 323                 return [ $parsed, $extractedNamespace ];
 324         }
 325
 326         /**
 327          * Find snippet highlight settings for all users
 328          * @return array Contextlines, contextchars
 329          */
 330         public static function userHighlightPrefs() {
 331                 $contextlines = 2; // Hardcode this. Old defaults sucked. :)
 332                 $contextchars = 75; // same as above.... :P
 333                 return [ $contextlines, $contextchars ];
 334         }
 335
 336         /**
 337          * Create or update the search index record for the given page.
 338          * Title and text should be pre-processed.
 339          * STUB
 340          *
 341          * @param int $id
 342          * @param string $title
 343          * @param string $text
 344          */
 345         function update( $id, $title, $text ) {
 346                 // no-op
 347         }
 348
 349         /**
 350          * Update a search index record's title only.
 351          * Title should be pre-processed.
 352          * STUB
 353          *
 354          * @param int $id
 355          * @param string $title
 356          */
 357         function updateTitle( $id, $title ) {
 358                 // no-op
 359         }
 360
 361         /**
 362          * Delete an indexed page
 363          * Title should be pre-processed.
 364          * STUB
 365          *
 366          * @param int $id Page id that was deleted
 367          * @param string $title Title of page that was deleted
 368          */
 369         function delete( $id, $title ) {
 370                 // no-op
 371         }
 372
 373         /**
 374          * Get OpenSearch suggestion template
 375          *
 376          * @deprecated since 1.25
 377          * @return string
 378          */
 379         public static function getOpenSearchTemplate() {
 380                 wfDeprecated( __METHOD__, '1.25' );
 381                 return ApiOpenSearch::getOpenSearchTemplate( 'application/x-suggestions+json' );
 382         }
 383
 384         /**
 385          * Get the raw text for updating the index from a content object
 386          * Nicer search backends could possibly do something cooler than
 387          * just returning raw text
 388          *
 389          * @todo This isn't ideal, we'd really like to have content-specific handling here
 390          * @param Title $t Title we're indexing
 391          * @param Content $c Content of the page to index
 392          * @return string
 393          */
 394         public function getTextFromContent( Title $t, Content $c = null ) {
 395                 return $c ? $c->getTextForSearchIndex() : '';
 396         }
 397
 398         /**
 399          * If an implementation of SearchEngine handles all of its own text processing
 400          * in getTextFromContent() and doesn't require SearchUpdate::updateText()'s
 401          * rather silly handling, it should return true here instead.
 402          *
 403          * @return bool
 404          */
 405         public function textAlreadyUpdatedForIndex() {
 406                 return false;
 407         }
 408
 409         /**
 410          * Makes search simple string if it was namespaced.
 411          * Sets namespaces of the search to namespaces extracted from string.
 412          * @param string $search
 413          * @return string Simplified search string
 414          */
 415         protected function normalizeNamespaces( $search ) {
 416                 // Find a Title which is not an interwiki and is in NS_MAIN
 417                 $title = Title::newFromText( $search );
 418                 $ns = $this->namespaces;
 419                 if ( $title && !$title->isExternal() ) {
 420                         $ns = [ $title->getNamespace() ];
 421                         $search = $title->getText();
 422                         if ( $ns[0] == NS_MAIN ) {
 423                                 $ns = $this->namespaces; // no explicit prefix, use default namespaces
 424                                 Hooks::run( 'PrefixSearchExtractNamespace', [ &$ns, &$search ] );
 425                         }
 426                 } else {
 427                         $title = Title::newFromText( $search . 'Dummy' );
 428                         if ( $title && $title->getText() == 'Dummy'
 429                                         && $title->getNamespace() != NS_MAIN
 430                                         && !$title->isExternal() )
 431                         {
 432                                 $ns = [ $title->getNamespace() ];
 433                                 $search = '';
 434                         } else {
 435                                 Hooks::run( 'PrefixSearchExtractNamespace', [ &$ns, &$search ] );
 436                         }
 437                 }
 438
 439                 $ns = array_map( function( $space ) {
 440                         return $space == NS_MEDIA ? NS_FILE : $space;
 441                 }, $ns );
 442
 443                 $this->setNamespaces( $ns );
 444                 return $search;
 445         }
 446
 447         /**
 448          * Perform a completion search.
 449          * Does not resolve namespaces and does not check variants.
 450          * Search engine implementations may want to override this function.
 451          * @param string $search
 452          * @return SearchSuggestionSet
 453          */
 454         protected function completionSearchBackend( $search ) {
 455                 $results = [];
 456
 457                 $search = trim( $search );
 458
 459                 if ( !in_array( NS_SPECIAL, $this->namespaces ) && // We do not run hook on Special: search
 460                          !Hooks::run( 'PrefixSearchBackend',
 461                                 [ $this->namespaces, $search, $this->limit, &$results, $this->offset ]
 462                 ) ) {
 463                         // False means hook worked.
 464                         // FIXME: Yes, the API is weird. That's why it is going to be deprecated.
 465
 466                         return SearchSuggestionSet::fromStrings( $results );
 467                 } else {
 468                         // Hook did not do the job, use default simple search
 469                         $results = $this->simplePrefixSearch( $search );
 470                         return SearchSuggestionSet::fromTitles( $results );
 471                 }
 472         }
 473
 474         /**
 475          * Perform a completion search.
 476          * @param string $search
 477          * @return SearchSuggestionSet
 478          */
 479         public function completionSearch( $search ) {
 480                 if ( trim( $search ) === '' ) {
 481                         return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
 482                 }
 483                 $search = $this->normalizeNamespaces( $search );
 484                 return $this->processCompletionResults( $search, $this->completionSearchBackend( $search ) );
 485         }
 486
 487         /**
 488          * Perform a completion search with variants.
 489          * @param string $search
 490          * @return SearchSuggestionSet
 491          */
 492         public function completionSearchWithVariants( $search ) {
 493                 if ( trim( $search ) === '' ) {
 494                         return SearchSuggestionSet::emptySuggestionSet(); // Return empty result
 495                 }
 496                 $search = $this->normalizeNamespaces( $search );
 497
 498                 $results = $this->completionSearchBackend( $search );
 499                 $fallbackLimit = $this->limit - $results->getSize();
 500                 if ( $fallbackLimit > 0 ) {
 501                         global $wgContLang;
 502
 503                         $fallbackSearches = $wgContLang->autoConvertToAllVariants( $search );
 504                         $fallbackSearches = array_diff( array_unique( $fallbackSearches ), [ $search ] );
 505
 506                         foreach ( $fallbackSearches as $fbs ) {
 507                                 $this->setLimitOffset( $fallbackLimit );
 508                                 $fallbackSearchResult = $this->completionSearch( $fbs );
 509                                 $results->appendAll( $fallbackSearchResult );
 510                                 $fallbackLimit -= count( $fallbackSearchResult );
 511                                 if ( $fallbackLimit <= 0 ) {
 512                                         break;
 513                                 }
 514                         }
 515                 }
 516                 return $this->processCompletionResults( $search, $results );
 517         }
 518
 519         /**
 520          * Extract titles from completion results
 521          * @param SearchSuggestionSet $completionResults
 522          * @return Title[]
 523          */
 524         public function extractTitles( SearchSuggestionSet $completionResults ) {
 525                 return $completionResults->map( function( SearchSuggestion $sugg ) {
 526                         return $sugg->getSuggestedTitle();
 527                 } );
 528         }
 529
 530         /**
 531          * Process completion search results.
 532          * Resolves the titles and rescores.
 533          * @param SearchSuggestionSet $suggestions
 534          * @return SearchSuggestionSet
 535          */
 536         protected function processCompletionResults( $search, SearchSuggestionSet $suggestions ) {
 537                 $search = trim( $search );
 538                 // preload the titles with LinkBatch
 539                 $titles = $suggestions->map( function( SearchSuggestion $sugg ) {
 540                         return $sugg->getSuggestedTitle();
 541                 } );
 542                 $lb = new LinkBatch( $titles );
 543                 $lb->setCaller( __METHOD__ );
 544                 $lb->execute();
 545
 546                 $results = $suggestions->map( function( SearchSuggestion $sugg ) {
 547                         return $sugg->getSuggestedTitle()->getPrefixedText();
 548                 } );
 549
 550                 if ( $this->offset === 0 ) {
 551                         // Rescore results with an exact title match
 552                         // NOTE: in some cases like cross-namespace redirects
 553                         // (frequently used as shortcuts e.g. WP:WP on huwiki) some
 554                         // backends like Cirrus will return no results. We should still
 555                         // try an exact title match to workaround this limitation
 556                         $rescorer = new SearchExactMatchRescorer();
 557                         $rescoredResults = $rescorer->rescore( $search, $this->namespaces, $results, $this->limit );
 558                 } else {
 559                         // No need to rescore if offset is not 0
 560                         // The exact match must have been returned at position 0
 561                         // if it existed.
 562                         $rescoredResults = $results;
 563                 }
 564
 565                 if ( count( $rescoredResults ) > 0 ) {
 566                         $found = array_search( $rescoredResults[0], $results );
 567                         if ( $found === false ) {
 568                                 // If the first result is not in the previous array it
 569                                 // means that we found a new exact match
 570                                 $exactMatch = SearchSuggestion::fromTitle( 0, Title::newFromText( $rescoredResults[0] ) );
 571                                 $suggestions->prepend( $exactMatch );
 572                                 $suggestions->shrink( $this->limit );
 573                         } else {
 574                                 // if the first result is not the same we need to rescore
 575                                 if ( $found > 0 ) {
 576                                         $suggestions->rescore( $found );
 577                                 }
 578                         }
 579                 }
 580
 581                 return $suggestions;
 582         }
 583
 584         /**
 585          * Simple prefix search for subpages.
 586          * @param string $search
 587          * @return Title[]
 588          */
 589         public function defaultPrefixSearch( $search ) {
 590                 if ( trim( $search ) === '' ) {
 591                         return [];
 592                 }
 593
 594                 $search = $this->normalizeNamespaces( $search );
 595                 return $this->simplePrefixSearch( $search );
 596         }
 597
 598         /**
 599          * Call out to simple search backend.
 600          * Defaults to TitlePrefixSearch.
 601          * @param string $search
 602          * @return Title[]
 603          */
 604         protected function simplePrefixSearch( $search ) {
 605                 // Use default database prefix search
 606                 $backend = new TitlePrefixSearch;
 607                 return $backend->defaultSearchBackend( $this->namespaces, $search, $this->limit, $this->offset );
 608         }
 609
 610         /**
 611          * Make a list of searchable namespaces and their canonical names.
 612          * @deprecated since 1.27; use SearchEngineConfig::searchableNamespaces()
 613          * @return array
 614          */
 615         public static function searchableNamespaces() {
 616                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->searchableNamespaces();
 617         }
 618
 619         /**
 620          * Extract default namespaces to search from the given user's
 621          * settings, returning a list of index numbers.
 622          * @deprecated since 1.27; use SearchEngineConfig::userNamespaces()
 623          * @param user $user
 624          * @return array
 625          */
 626         public static function userNamespaces( $user ) {
 627                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->userNamespaces( $user );
 628         }
 629
 630         /**
 631          * An array of namespaces indexes to be searched by default
 632          * @deprecated since 1.27; use SearchEngineConfig::defaultNamespaces()
 633          * @return array
 634          */
 635         public static function defaultNamespaces() {
 636                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->defaultNamespaces();
 637         }
 638
 639         /**
 640          * Get a list of namespace names useful for showing in tooltips
 641          * and preferences
 642          * @deprecated since 1.27; use SearchEngineConfig::namespacesAsText()
 643          * @param array $namespaces
 644          * @return array
 645          */
 646         public static function namespacesAsText( $namespaces ) {
 647                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->namespacesAsText( $namespaces );
 648         }
 649
 650         /**
 651          * Load up the appropriate search engine class for the currently
 652          * active database backend, and return a configured instance.
 653          * @deprecated since 1.27; Use SearchEngineFactory::create
 654          * @param string $type Type of search backend, if not the default
 655          * @return SearchEngine
 656          */
 657         public static function create( $type = null ) {
 658                 return MediaWikiServices::getInstance()->getSearchEngineFactory()->create( $type );
 659         }
 660
 661         /**
 662          * Return the search engines we support. If only $wgSearchType
 663          * is set, it'll be an array of just that one item.
 664          * @deprecated since 1.27; use SearchEngineConfig::getSearchTypes()
 665          * @return array
 666          */
 667         public static function getSearchTypes() {
 668                 return MediaWikiServices::getInstance()->getSearchEngineConfig()->getSearchTypes();
 669         }
 670
 671         /**
 672          * Get a list of supported profiles.
 673          * Some search engine implementations may expose specific profiles to fine-tune
 674          * its behaviors.
 675          * The profile can be passed as a feature data with setFeatureData( $profileType, $profileName )
 676          * The array returned by this function contains the following keys:
 677          * - name: the profile name to use with setFeatureData
 678          * - desc-message: the i18n description
 679          * - default: set to true if this profile is the default
 680          *
 681          * @since 1.28
 682          * @param string $profileType the type of profiles
 683          * @param User|null $user the user requesting the list of profiles
 684          * @return array|null the list of profiles or null if none available
 685          */
 686         public function getProfiles( $profileType, User $user = null ) {
 687                 return null;
 688         }
 689
 690         /**
 691          * Create a search field definition.
 692          * Specific search engines should override this method to create search fields.
 693          * @param string $name
 694          * @param int    $type One of the types in SearchIndexField::INDEX_TYPE_*
 695          * @return SearchIndexField
 696          * @since 1.28
 697          */
 698         public function makeSearchFieldMapping( $name, $type ) {
 699                 return new NullIndexField();
 700         }
 701
 702         /**
 703          * Get fields for search index
 704          * @since 1.28
 705          * @return SearchIndexField[] Index field definitions for all content handlers
 706          */
 707         public function getSearchIndexFields() {
 708                 $models = ContentHandler::getContentModels();
 709                 $fields = [];
 710                 foreach ( $models as $model ) {
 711                         $handler = ContentHandler::getForModelID( $model );
 712                         $handlerFields = $handler->getFieldsForSearchIndex( $this );
 713                         foreach ( $handlerFields as $fieldName => $fieldData ) {
 714                                 if ( empty( $fields[$fieldName] ) ) {
 715                                         $fields[$fieldName] = $fieldData;
 716                                 } else {
 717                                         // TODO: do we allow some clashes with the same type or reject all of them?
 718                                         $mergeDef = $fields[$fieldName]->merge( $fieldData );
 719                                         if ( !$mergeDef ) {
 720                                                 throw new InvalidArgumentException( "Duplicate field $fieldName for model $model" );
 721                                         }
 722                                         $fields[$fieldName] = $mergeDef;
 723                                 }
 724                         }
 725                 }
 726                 // Hook to allow extensions to produce search mapping fields
 727                 Hooks::run( 'SearchIndexFields', [ &$fields, $this ] );
 728                 return $fields;
 729         }
 730
 731         /**
 732          * Augment search results with extra data.
 733          *
 734          * @param SearchResultSet $resultSet
 735          */
 736         public function augmentSearchResults( SearchResultSet $resultSet ) {
 737                 $setAugmentors = [];
 738                 $rowAugmentors = [];
 739                 Hooks::run( "SearchResultsAugment", [ &$setAugmentors, &$rowAugmentors ] );
 740
 741                 if ( !$setAugmentors && !$rowAugmentors ) {
 742                         // We're done here
 743                         return;
 744                 }
 745
 746                 // Convert row augmentors to set augmentor
 747                 foreach ( $rowAugmentors as $name => $row ) {
 748                         if ( isset( $setAugmentors[$name] ) ) {
 749                                 throw new InvalidArgumentException( "Both row and set augmentors are defined for $name" );
 750                         }
 751                         $setAugmentors[$name] = new PerRowAugmentor( $row );
 752                 }
 753
 754                 foreach ( $setAugmentors as $name => $augmentor ) {
 755                         $data = $augmentor->augmentAll( $resultSet );
 756                         if ( $data ) {
 757                                 $resultSet->setAugmentedData( $name, $data );
 758                         }
 759                 }
 760         }
 761 }
 762
 763 /**
 764  * Dummy class to be used when non-supported Database engine is present.
 765  * @todo FIXME: Dummy class should probably try something at least mildly useful,
 766  * such as a LIKE search through titles.
 767  * @ingroup Search
 768  */
 769 class SearchEngineDummy extends SearchEngine {
 770         // no-op
 771 }