includes/SearchEngine.php

   1 <?php
   2 # See search.doc
   3
   4 class SearchEngine {
   5         /* private */ var $mUsertext, $mSearchterms;
   6         /* private */ var $mTitlecond, $mTextcond;
   7
   8         var $doSearchRedirects = true;
   9         var $addtoquery = array();
  10         var $namespacesToSearch = array();
  11         var $alternateTitle;
  12         var $all_titles = false;
  13
  14         function SearchEngine( $text )
  15         {
  16                 # We display the query, so let's strip it for safety
  17                 #
  18                 global $wgDBmysql4;
  19                 $lc = SearchEngine::legalSearchChars() . "()";
  20                 if( $wgDBmysql4 ) $lc .= "\"~<>*+-";
  21                 $this->mUsertext = trim( preg_replace( "/[^{$lc}]/", " ", $text ) );
  22                 $this->mSearchterms = array();
  23                 $this->mStrictMatching = true; # Google-style, add '+' on all terms
  24         }
  25
  26         function queryNamespaces()
  27         {
  28                 $namespaces = implode( ",", $this->namespacesToSearch );
  29                 if ($namespaces == "") {
  30                         $namespaces = "0";
  31                 }
  32                 return "AND cur_namespace IN (" . $namespaces . ")";
  33         }
  34
  35         function searchRedirects()
  36         {
  37                 if ( $this->doSearchRedirects ) {
  38                         return "";
  39                 } else {
  40                         return "AND cur_is_redirect=0 ";
  41                 }
  42         }
  43
  44         /* private */ function initNamespaceCheckbox( $i )
  45         {
  46                 global $wgUser, $wgNamespacesToBeSearchedDefault;
  47
  48                 if ($wgUser->getID()) {
  49                         // User is logged in so we retrieve his default namespaces
  50                         return $wgUser->getOption( "searchNs".$i );
  51                 } else {
  52                         // User is not logged in so we give him the global default namespaces
  53                         return !empty($wgNamespacesToBeSearchedDefault[ $i ]);
  54                 }
  55         }
  56
  57         # Display the "power search" footer. Does not actually perform the search,
  58         # that is done by showResults()
  59         function powersearch()
  60         {
  61                 global $wgUser, $wgOut, $wgLang, $wgTitle, $wgRequest;
  62                 $sk =& $wgUser->getSkin();
  63
  64                 $search                 = $wgRequest->getText( 'search' );
  65                 $searchx                = $wgRequest->getVal( 'searchx' );
  66                 $listredirs             = $wgRequest->getVal( 'redirs' );
  67
  68                 $ret = wfMsg("powersearchtext"); # Text to be returned
  69                 $tempText = ""; # Temporary text, for substitution into $ret
  70
  71                 if( isset( $_REQUEST["searchx"] ) ) {
  72                         $this->addtoquery["searchx"] = "1";
  73                 }
  74
  75                 # Do namespace checkboxes
  76                 $namespaces = $wgLang->getNamespaces();
  77                 foreach ( $namespaces as $i => $namespace ) {
  78                         # Skip virtual namespaces
  79                         if ( $i < 0 ) {
  80                                 continue;
  81                         }
  82
  83                         $formVar = "ns$i";
  84
  85                         # Initialise checkboxValues, either from defaults or from
  86                         # a previous invocation
  87                         if ( !isset( $searchx ) ) {
  88                                 $checkboxValue = $this->initNamespaceCheckbox( $i );
  89                         } else {
  90                                 $checkboxValue = $wgRequest->getVal( $formVar );
  91                         }
  92
  93                         $checked = "";
  94                         if ( $checkboxValue == 1 ) {
  95                                 $checked = " checked='checked'";
  96                                 $this->addtoquery["ns{$i}"] = 1;
  97                                 array_push( $this->namespacesToSearch, $i );
  98                         }
  99                         $name = str_replace( "_", " ", $namespaces[$i] );
 100                         if ( "" == $name ) {
 101                                 $name = wfMsg( "blanknamespace" );
 102                         }
 103
 104                         if ( $tempText !== "" ) {
 105                                 $tempText .= " ";
 106                         }
 107                         $tempText .= "<input type='checkbox' value=\"1\" name=\"" .
 108                           "ns{$i}\"{$checked} />{$name}\n";
 109                 }
 110                 $ret = str_replace ( "$1", $tempText, $ret );
 111
 112                 # List redirects checkbox
 113
 114                 $checked = "";
 115                 if ( $listredirs == 1 ) {
 116                         $this->addtoquery["redirs"] = 1;
 117                         $checked = " checked='checked'";
 118                 }
 119                 $tempText = "<input type='checkbox' value='1' name=\"redirs\"{$checked} />\n";
 120                 $ret = str_replace( "$2", $tempText, $ret );
 121
 122                 # Search field
 123
 124                 $tempText = "<input type='text' name=\"search\" value=\"" .
 125                         htmlspecialchars( $search ) ."\" width='80' />\n";
 126         $ret = str_replace( "$3", $tempText, $ret );
 127
 128                 # Searchx button
 129
 130                 $tempText = "<input type='submit' name=\"searchx\" value=\"" .
 131                   wfMsg("powersearch") . "\" />\n";
 132                 $ret = str_replace( "$9", $tempText, $ret );
 133
 134                 $action = $sk->escapeSearchLink();
 135                 $ret = "<br /><br />\n<form id=\"powersearch\" method=\"get\" " .
 136                   "action=\"$action\">\n{$ret}\n</form>\n";
 137
 138                 if ( isset ( $searchx ) ) {
 139                         if ( ! $listredirs ) {
 140                                 $this->doSearchRedirects = false;
 141                         }
 142                 }
 143                 return $ret;
 144         }
 145
 146         function setupPage() {
 147                 global $wgOut;
 148                 $wgOut->setPageTitle( wfMsg( "searchresults" ) );
 149                 $q = wfMsg( "searchquery", htmlspecialchars( $this->mUsertext ) );
 150                 $wgOut->setSubtitle( $q );
 151                 $wgOut->setArticleRelated( false );
 152                 $wgOut->setRobotpolicy( "noindex,nofollow" );
 153         }
 154
 155         # Perform the search and construct the results page
 156         function showResults()
 157         {
 158                 global $wgUser, $wgTitle, $wgOut, $wgLang, $wgRequest;
 159                 global $wgDisableTextSearch, $wgInputEncoding;
 160                 global $wgLoadBalancer;
 161
 162                 $wgLoadBalancer->force(-1);
 163
 164                 $fname = "SearchEngine::showResults";
 165
 166                 $search = $wgRequest->getText( 'search' );
 167
 168                 $powersearch = $this->powersearch(); /* Need side-effects here? */
 169
 170                 $this->setupPage();
 171
 172                 $sk = $wgUser->getSkin();
 173                 $header = wfMsg( "searchresulttext", $sk->makeKnownLink(
 174                   wfMsg( "searchhelppage" ), wfMsg( "searchingwikipedia" ) ) );
 175                 $wgOut->addHTML( $header );
 176
 177                 $this->parseQuery();
 178                 if ( "" == $this->mTitlecond || "" == $this->mTextcond ) {
 179                         $wgOut->addHTML( "<h2>" . wfMsg( "badquery" ) . "</h2>\n" .
 180                           "<p>" . wfMsg( "badquerytext" ) . "</p>\n" );
 181                         return;
 182                 }
 183                 list( $limit, $offset ) = wfCheckLimits( 20, "searchlimit" );
 184
 185                 $searchnamespaces = $this->queryNamespaces();
 186                 $redircond = $this->searchRedirects();
 187
 188                 if ( $wgDisableTextSearch ) {
 189                         $wgOut->addHTML( wfMsg( "searchdisabled" ) );
 190                         $wgOut->addHTML( wfMsg( "googlesearch", htmlspecialchars( $search ), $GLOBALS['wgInputEncoding'] ) );
 191                 } else {
 192                         $sql = "SELECT cur_id,cur_namespace,cur_title," .
 193                           "cur_text FROM cur,searchindex " .
 194                           "WHERE cur_id=si_page AND {$this->mTitlecond} " .
 195                           "{$searchnamespaces} {$redircond}" .
 196                           "LIMIT {$offset}, {$limit}";
 197                         $res1 = wfQuery( $sql, DB_READ, $fname );
 198                         $num = wfNumRows($res1);
 199
 200                         $sk = $wgUser->getSkin();
 201                         $text = "";
 202
 203                         $this->parseQuery();
 204                         if ( "" == $this->mTitlecond || "" == $this->mTextcond ) {
 205                                 $wgOut->addHTML( "<h2>" . wfMsg( "badquery" ) . "</h2>\n" .
 206                                   "<p>" . wfMsg( "badquerytext" ) . "</p>\n" );
 207                                 return;
 208                         }
 209                         list( $limit, $offset ) = wfCheckLimits( 20, "searchlimit" );
 210
 211                         $searchnamespaces = $this->queryNamespaces();
 212                         $redircond = $this->searchRedirects();
 213
 214                         $sql = "SELECT cur_id,cur_namespace,cur_title," .
 215                           "cur_text FROM cur,searchindex " .
 216                           "WHERE cur_id=si_page AND {$this->mTitlecond} " .
 217                           "{$searchnamespaces} {$redircond}" .
 218                           "LIMIT {$offset}, {$limit}";
 219                         $res1 = wfQuery( $sql, DB_READ, $fname );
 220                         $num = wfNumRows($res1);
 221
 222                         $sql = "SELECT cur_id,cur_namespace,cur_title," .
 223                           "cur_text FROM cur,searchindex " .
 224                           "WHERE cur_id=si_page AND {$this->mTextcond} " .
 225                           "{$searchnamespaces} {$redircond} " .
 226                           "LIMIT {$offset}, {$limit}";
 227                         $res2 = wfQuery( $sql, DB_READ, $fname );
 228                         $num = $num + wfNumRows($res2);
 229
 230                         if ( $num == $limit ) {
 231                           $top = wfShowingResults( $offset, $limit);
 232                         } else {
 233                           $top = wfShowingResultsNum( $offset, $limit, $num );
 234                         }
 235                         $wgOut->addHTML( "<p>{$top}</p>\n" );
 236
 237                         # For powersearch
 238
 239                         $a2l = "" ;
 240                         $akk = array_keys( $this->addtoquery ) ;
 241                         foreach ( $akk AS $ak ) {
 242                                 $a2l .= "&{$ak}={$this->addtoquery[$ak]}" ;
 243                         }
 244
 245                         $sl = wfViewPrevNext( $offset, $limit, "",
 246                           "search=" . wfUrlencode( $this->mUsertext ) . $a2l );
 247                         $wgOut->addHTML( "<br />{$sl}\n" );
 248
 249                         $foundsome = false;
 250
 251                         if ( 0 == wfNumRows( $res1 ) ) {
 252                                 $wgOut->addHTML( "<h2>" . wfMsg( "notitlematches" ) .
 253                                   "</h2>\n" );
 254                         } else {
 255                                 $foundsome = true;
 256                                 $off = $offset + 1;
 257                                 $wgOut->addHTML( "<h2>" . wfMsg( "titlematches" ) .
 258                                   "</h2>\n<ol start='{$off}'>" );
 259
 260                                 while ( $row = wfFetchObject( $res1 ) ) {
 261                                         $this->showHit( $row );
 262                                 }
 263                                 wfFreeResult( $res1 );
 264                                 $wgOut->addHTML( "</ol>\n" );
 265                         }
 266
 267                         if ( 0 == wfNumRows( $res2 ) ) {
 268                                 $wgOut->addHTML( "<h2>" . wfMsg( "notextmatches" ) .
 269                                   "</h2>\n" );
 270                         } else {
 271                                 $foundsome = true;
 272                                 $off = $offset + 1;
 273                                 $wgOut->addHTML( "<h2>" . wfMsg( "textmatches" ) . "</h2>\n" .
 274                                   "<ol start='{$off}'>" );
 275                                 while ( $row = wfFetchObject( $res2 ) ) {
 276                                         $this->showHit( $row );
 277                                 }
 278                                 wfFreeResult( $res2 );
 279                                 $wgOut->addHTML( "</ol>\n" );
 280                         }
 281                         if ( ! $foundsome ) {
 282                                 $wgOut->addHTML( "<p>" . wfMsg( "nonefound" ) . "</p>\n" );
 283                         }
 284                         $wgOut->addHTML( "<p>{$sl}</p>\n" );
 285                         $wgOut->addHTML( $powersearch );
 286                 }
 287                 $wgLoadBalancer->force(0);
 288         }
 289
 290         function legalSearchChars()
 291         {
 292                 $lc = "A-Za-z_'0-9\\x80-\\xFF\\-";
 293                 return $lc;
 294         }
 295
 296         function parseQuery()
 297         {
 298                 global $wgDBminWordLen, $wgLang, $wgDBmysql4;
 299
 300                 if( $wgDBmysql4 ) {
 301                         # Use cleaner boolean search if available
 302                         return $this->parseQuery4();
 303                 }
 304                 # on non mysql4 database: get list of words we don't want to search for
 305                 require_once( "FulltextStoplist.php" );
 306
 307                 $lc = SearchEngine::legalSearchChars() . "()";
 308                 $q = preg_replace( "/([()])/", " \\1 ", $this->mUsertext );
 309                 $q = preg_replace( "/\\s+/", " ", $q );
 310                 $w = explode( " ", strtolower( trim( $q ) ) );
 311
 312                 $last = $cond = "";
 313                 foreach ( $w as $word ) {
 314                         $word = $wgLang->stripForSearch( $word );
 315                         if ( "and" == $word || "or" == $word || "not" == $word
 316                           || "(" == $word || ")" == $word ) {
 317                                 $cond .= " " . strtoupper( $word );
 318                                 $last = "";
 319                         } else if ( strlen( $word ) < $wgDBminWordLen ) {
 320                                 continue;
 321                         } else if ( FulltextStoplist::inList( $word ) ) {
 322                                 continue;
 323                         } else {
 324                                 if ( "" != $last ) { $cond .= " AND"; }
 325                                 $cond .= " (MATCH (##field##) AGAINST ('" .
 326                                   wfStrencode( $word ). "'))";
 327                                 $last = $word;
 328                                 array_push( $this->mSearchterms, "\\b" . $word . "\\b" );
 329                         }
 330                 }
 331                 if ( 0 == count( $this->mSearchterms ) ) { return; }
 332
 333                 $this->mTitlecond = "(" . str_replace( "##field##",
 334                   "si_title", $cond ) . " )";
 335
 336                 $this->mTextcond = "(" . str_replace( "##field##",
 337                   "si_text", $cond ) . " AND (cur_is_redirect=0) )";
 338         }
 339
 340         function parseQuery4()
 341         {
 342                 global $wgLang;
 343                 $lc = SearchEngine::legalSearchChars();
 344                 $searchon = "";
 345                 $this->mSearchterms = array();
 346
 347                 # FIXME: This doesn't handle parenthetical expressions.
 348                 if( preg_match_all( '/([-+<>~]?)(([' . $lc . ']+)(\*?)|"[^"]*")/',
 349                           $this->mUsertext, $m, PREG_SET_ORDER ) ) {
 350                         foreach( $m as $terms ) {
 351                                 if( $searchon !== "" ) $searchon .= " ";
 352                                 if( $this->mStrictMatching && ($terms[1] == "") ) {
 353                                         $terms[1] = "+";
 354                                 }
 355                                 $searchon .= $terms[1] . $wgLang->stripForSearch( $terms[2] );
 356                                 if( $terms[3] ) {
 357                                         $regexp = preg_quote( $terms[3] );
 358                                         if( $terms[4] ) $regexp .= "[0-9A-Za-z_]+";
 359                                 } else {
 360                                         $regexp = preg_quote( str_replace( '"', '', $terms[2] ) );
 361                                 }
 362                                 $this->mSearchterms[] = $regexp;
 363                         }
 364                         wfDebug( "Would search with '$searchon'\n" );
 365                         wfDebug( "Match with /\b" . implode( '\b|\b', $this->mSearchterms ) . "\b/\n" );
 366                 } else {
 367                         wfDebug( "Can't understand search query '$this->mUsertext'\n" );
 368                 }
 369
 370                 $searchon = wfStrencode( $searchon );
 371                 $this->mTitlecond = " MATCH(si_title) AGAINST('$searchon' IN BOOLEAN MODE)";
 372                 $this->mTextcond = " (MATCH(si_text) AGAINST('$searchon' IN BOOLEAN MODE) AND cur_is_redirect=0)";
 373         }
 374
 375         function showHit( $row )
 376         {
 377                 global $wgUser, $wgOut;
 378
 379                 $t = Title::makeName( $row->cur_namespace, $row->cur_title );
 380                 $sk = $wgUser->getSkin();
 381
 382                 $contextlines = $wgUser->getOption( "contextlines" );
 383                 if ( "" == $contextlines ) { $contextlines = 5; }
 384                 $contextchars = $wgUser->getOption( "contextchars" );
 385                 if ( "" == $contextchars ) { $contextchars = 50; }
 386
 387                 $link = $sk->makeKnownLink( $t, "" );
 388                 $size = wfMsg( "nbytes", strlen( $row->cur_text ) );
 389                 $wgOut->addHTML( "<li>{$link} ({$size})" );
 390
 391                 $lines = explode( "\n", $row->cur_text );
 392                 $pat1 = "/(.*)(" . implode( "|", $this->mSearchterms ) . ")(.*)/i";
 393                 $lineno = 0;
 394
 395                 foreach ( $lines as $line ) {
 396                         if ( 0 == $contextlines ) { break; }
 397                         --$contextlines;
 398                         ++$lineno;
 399                         if ( ! preg_match( $pat1, $line, $m ) ) { continue; }
 400
 401                         $pre = $m[1];
 402                         if ( 0 == $contextchars ) { $pre = "..."; }
 403                         else {
 404                                 if ( strlen( $pre ) > $contextchars ) {
 405                                         $pre = "..." . substr( $pre, -$contextchars );
 406                                 }
 407                         }
 408                         $pre = wfEscapeHTML( $pre );
 409
 410                         if ( count( $m ) < 3 ) { $post = ""; }
 411                         else { $post = $m[3]; }
 412
 413                         if ( 0 == $contextchars ) { $post = "..."; }
 414                         else {
 415                                 if ( strlen( $post ) > $contextchars ) {
 416                                         $post = substr( $post, 0, $contextchars ) . "...";
 417                                 }
 418                         }
 419                         $post = wfEscapeHTML( $post );
 420                         $found = wfEscapeHTML( $m[2] );
 421
 422                         $line = "{$pre}{$found}{$post}";
 423                         $pat2 = "/(" . implode( "|", $this->mSearchterms ) . ")/i";
 424                         $line = preg_replace( $pat2,
 425                           "<font color='red'>\\1</font>", $line );
 426
 427                         $wgOut->addHTML( "<br /><small>{$lineno}: {$line}</small>\n" );
 428                 }
 429                 $wgOut->addHTML( "</li>\n" );
 430         }
 431
 432         function goResult()
 433         {
 434                 global $wgOut, $wgRequest, $wgGoToEdit;
 435                 global $wgDisableTextSearch;
 436                 $fname = "SearchEngine::goResult";
 437
 438                 $search = trim( $wgRequest->getText( "search" ) );
 439
 440                 # Try to go to page as entered.
 441                 #
 442                 $t = Title::newFromText( $search );
 443
 444                 # If the string cannot be used to create a title
 445                 if( false == $t ){
 446                         $this->showResults();
 447                         return;
 448                 }
 449
 450                 # Exact match? No need to look further.
 451                 if ( $t->getNamespace() == NS_SPECIAL || 0 != $t->getArticleID() ) {
 452                         $wgOut->redirect( $t->getFullURL() );
 453                         return;
 454                 }
 455
 456                 # Now try all lower case (i.e. first letter capitalized)
 457                 #
 458                 $t = Title::newFromText( strtolower( $search ) );
 459                 if ( 0 != $t->getArticleID() ) {
 460                         $wgOut->redirect( $t->getFullURL() );
 461                         return;
 462                 }
 463
 464                 # Now try capitalized string
 465                 #
 466                 $t = Title::newFromText( ucwords( strtolower( $search ) ) );
 467                 if ( 0 != $t->getArticleID() ) {
 468                         $wgOut->redirect( $t->getFullURL() );
 469                         return;
 470                 }
 471
 472                 # Now try all upper case
 473                 #
 474                 $t = Title::newFromText( strtoupper( $search ) );
 475                 if ( 0 != $t->getArticleID() ) {
 476                         $wgOut->redirect( $t->getFullURL() );
 477                         return;
 478                 }
 479
 480                 # Entering an IP address goes to the contributions page
 481                 if ( preg_match( '/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/', $search ) ) {
 482                         $title = Title::makeTitle( NS_SPECIAL, "Contributions" );
 483                         $wgOut->redirect( $title->getFullUrl( "target=$search" ) );
 484                         return;
 485                 }
 486
 487                 # No match, generate an edit URL
 488                 $t = Title::newFromText( $this->mUsertext );
 489
 490                 # If the feature is enabled, go straight to the edit page
 491                 if ( $wgGoToEdit ) {
 492                         $wgOut->redirect( $t->getFullURL( "action=edit" ) );
 493                         return;
 494                 }
 495
 496                 if( $t ) {
 497                         $editurl = $t->escapeLocalURL( "action=edit" );
 498                 } else {
 499                         $editurl = ""; # ??
 500                 }
 501                 $wgOut->addHTML( "<p>" . wfMsg("nogomatch", $editurl ) . "</p>\n" );
 502
 503                 # Try a fuzzy title search
 504                 $anyhit = false;
 505                 global $wgDisableFuzzySearch;
 506                 if(! $wgDisableFuzzySearch ){
 507                         foreach( array(NS_MAIN, NS_WP, NS_USER, NS_IMAGE, NS_MEDIAWIKI) as $namespace){
 508                                 $anyhit |= SearchEngine::doFuzzyTitleSearch( $search, $namespace );
 509                         }
 510                 }
 511
 512                 if( ! $anyhit ){
 513                         return $this->showResults();
 514                 }
 515         }
 516
 517         /* static */ function doFuzzyTitleSearch( $search, $namespace ){
 518                 global $wgLang, $wgOut;
 519
 520                 $this->setupPage();
 521
 522                 $sstr = ucfirst($search);
 523                 $sstr = str_replace(" ", "_", $sstr);
 524                 $fuzzymatches = SearchEngine::fuzzyTitles( $sstr, $namespace );
 525                 $fuzzymatches = array_slice($fuzzymatches, 0, 10);
 526                 $slen = strlen( $search );
 527                 $wikitext = "";
 528                 foreach($fuzzymatches as $res){
 529                         $t = str_replace("_", " ", $res[1]);
 530                         $tfull = $wgLang->getNsText( $namespace ) . ":$t|$t";
 531                         if( $namespace == NS_MAIN )
 532                                 $tfull = "$t";
 533                         $distance = $res[0];
 534                         $closeness = (strlen( $search ) - $distance) / strlen( $search );
 535                         $percent = intval( $closeness * 100 ) . "%";
 536                         $stars = str_repeat("*", ceil(5 * $closeness) );
 537                         $wikitext .= "* [[$tfull]] $percent ($stars)\n";
 538                 }
 539                 if( $wikitext ){
 540                         if( $namespace != NS_MAIN )
 541                                 $wikitext = "=== " . $wgLang->getNsText( $namespace ) . " ===\n" . $wikitext;
 542                         $wgOut->addWikiText( $wikitext );
 543                         return true;
 544                 }
 545                 return false;
 546         }
 547
 548         /* static */ function fuzzyTitles( $sstr, $namespace = NS_MAIN ){
 549                 $span = 0.10; // weed on title length before doing levenshtein.
 550                 $tolerance = 0.35; // allowed percentage of erronous characters
 551                 $slen = strlen($sstr);
 552                 $tolerance_count = ceil($tolerance * $slen);
 553                 $spanabs = ceil($slen * (1 + $span)) - $slen;
 554                 # print "Word: $sstr, len = $slen, range = [$min, $max], tolerance_count = $tolerance_count<BR>\n";
 555                 $result = array();
 556                 $cnt = 0;
 557                 for( $i=0; $i <= $spanabs; $i++ ){
 558                         $titles = SearchEngine::getTitlesByLength( $slen + $i, $namespace );
 559                         if( $i != 0) {
 560                                 $titles = array_merge($titles, SearchEngine::getTitlesByLength( $slen - $i, $namespace ) );
 561                         }
 562                         foreach($titles as $t){
 563                                 $d = levenshtein($sstr, $t);
 564                                 if($d < $tolerance_count)
 565                                         $result[] = array($d, $t);
 566                                 $cnt++;
 567                         }
 568                 }
 569                 usort($result, "SearchEngine_pcmp");
 570                 return $result;
 571         }
 572
 573         /* static */ function getTitlesByLength($aLength, $aNamespace = 0){
 574                 global $wgMemc, $wgDBname;
 575
 576                 // to avoid multiple costly SELECTs in case of no memcached
 577                 if( $this->all_titles ){
 578                         if( isset( $this->all_titles[$aLength][$aNamespace] ) ){
 579                                 return $this->all_titles[$aLength][$aNamespace];
 580                         } else {
 581                                 return array();
 582                         }
 583                 }
 584
 585                 $mkey = "$wgDBname:titlesbylength:$aLength:$aNamespace";
 586                 $mkeyts = "$wgDBname:titlesbylength:createtime";
 587                 $ts = $wgMemc->get( $mkeyts );
 588                 $result = $wgMemc->get( $mkey );
 589
 590                 if( time() - $ts < 3600 ){
 591                         // note: in case of insufficient memcached space, we return
 592                         // an empty list instead of starting to hit the DB.
 593                         return is_array( $result ) ? $result : array();
 594                 }
 595
 596                 $wgMemc->set( $mkeyts, time() );
 597
 598                 $res = wfQuery("SELECT cur_title, cur_namespace FROM cur", DB_READ);
 599                 $titles = array(); // length, ns, [titles]
 600                 while( $obj = wfFetchObject( $res ) ){
 601                         $title = $obj->cur_title;
 602                         $ns = $obj->cur_namespace;
 603                         $len = strlen( $title );
 604                         $titles[$len][$ns][] = $title;
 605                 }
 606                 foreach($titles as $length => $length_arr){
 607                         foreach($length_arr as $ns => $title_arr){
 608                                 $mkey = "$wgDBname:titlesbylength:$length:$ns";
 609                                 $wgMemc->set( $mkey, $title_arr, 3600 * 24 );
 610                         }
 611                 }
 612                 $this->all_titles = $titles;
 613                 if( isset( $titles[$aLength][$aNamespace] ) )
 614                         return $titles[$aLength][$aNamespace];
 615                 else
 616                         return array();
 617         }
 618 }
 619
 620 /* private static */ function SearchEngine_pcmp($a, $b){ return $a[0] - $b[0]; }
 621
 622 ?>