*gasp*
[lhc/web/wiklou.git] / includes / SearchEngine.php
index ee38899..e1de0bb 100644 (file)
 <?php
-# See search.doc
-
+/**
+ * Contain a class for special pages
+ * @package MediaWiki
+ */
+
+/**
+ * @package MediaWiki
+ */
 class SearchEngine {
-       /* private */ var $mUsertext, $mSearchterms;
-       /* private */ var $mTitlecond, $mTextcond;
-
-       var $doSearchRedirects = true;
-       var $addtoquery = array();
-       var $namespacesToSearch = array();
-       var $alternateTitle;
-       var $all_titles = false;
-
-       function SearchEngine( $text )
-       {
-               # We display the query, so let's strip it for safety
-               #
-               global $wgDBmysql4;
-               $lc = SearchEngine::legalSearchChars() . "()";
-               if( $wgDBmysql4 ) $lc .= "\"~<>*+-";
-               $this->mUsertext = trim( preg_replace( "/[^{$lc}]/", " ", $text ) );
-               $this->mSearchterms = array();
-               $this->mStrictMatching = true; # Google-style, add '+' on all terms
+       var $limit = 10;
+       var $offset = 0;
+       var $searchTerms = array();
+       var $namespaces = array( 0 );
+       var $showRedirects = false;
+       
+       /**
+        * Perform a full text search query and return a result set.
+        *
+        * @param string $term - Raw search term
+        * @param array $namespaces - List of namespaces to search
+        * @return ResultWrapper
+        * @access public
+        */
+       function searchText( $term ) {
+               return $this->db->resultObject( $this->db->query( $this->getQuery( $this->filter( $term ), true ) ) );
        }
 
-       function queryNamespaces()
-       {
-               $namespaces = implode( ",", $this->namespacesToSearch );
-               if ($namespaces == "") {
-                       $namespaces = "0";
-               }
-               return "AND cur_namespace IN (" . $namespaces . ")";
+       /**
+        * Perform a title-only search query and return a result set.
+        *
+        * @param string $term - Raw search term
+        * @param array $namespaces - List of namespaces to search
+        * @return ResultWrapper
+        * @access public
+        */
+       function searchTitle( $term ) {
+               return $this->db->resultObject( $this->db->query( $this->getQuery( $this->filter( $term ), false ) ) );
        }
-
-       function searchRedirects()
-       {
-               if ( $this->doSearchRedirects ) {
-                       return "";
-               } else {
-                       return "AND cur_is_redirect=0 ";
+       
+       /**
+        * If an exact title match can be find, or a very slightly close match,
+        * return the title. If no match, returns NULL.
+        *
+        * @static
+        * @param string $term
+        * @return Title
+        * @access private
+        */
+       function getNearMatch( $term ) {
+               # Exact match? No need to look further.
+               $title = Title::newFromText( $term );
+               if ( $title->getNamespace() == NS_SPECIAL || 0 != $title->getArticleID() ) {
+                       return $title;
                }
-       }
 
-       /* private */ function initNamespaceCheckbox( $i )
-       {
-               global $wgUser, $wgNamespacesToBeSearchedDefault;
-               
-               if ($wgUser->getID()) {
-                       // User is logged in so we retrieve his default namespaces
-                       return $wgUser->getOption( "searchNs".$i );
-               } else {
-                       // User is not logged in so we give him the global default namespaces
-                       return $wgNamespacesToBeSearchedDefault[ $i ];
+               # Now try all lower case (i.e. first letter capitalized)
+               #
+               $title = Title::newFromText( strtolower( $term ) );
+               if ( 0 != $title->getArticleID() ) {
+                       return $title;
                }
-       }
-
-       # Display the "power search" footer. Does not actually perform the search, 
-       # that is done by showResults()
-       function powersearch()
-       {
-               global $wgUser, $wgOut, $wgLang, $wgTitle;
-
-               $search                 = $_REQUEST['search'];
-               $searchx                = $_REQUEST['searchx'];
-               $listredirs             = $_REQUEST['redirs'];
-               
-               $ret = wfMsg("powersearchtext"); # Text to be returned
-               $tempText = ""; # Temporary text, for substitution into $ret    
 
-               if( isset( $_REQUEST["searchx"] ) ) {
-                       $this->addtoquery["searchx"] = "1";
+               # Now try capitalized string
+               #
+               $title = Title::newFromText( ucwords( strtolower( $term ) ) );
+               if ( 0 != $title->getArticleID() ) {
+                       return $title;
                }
-               
-               # Do namespace checkboxes
-               $namespaces = $wgLang->getNamespaces();
-               foreach ( $namespaces as $i => $namespace ) {
-                       # Skip virtual namespaces
-                       if ( $i < 0 ) {
-                               continue;
-                       }
-
-                       $formVar = "ns$i";
 
-                       # Initialise checkboxValues, either from defaults or from 
-                       # a previous invocation
-                       if ( !isset( $searchx ) ) {
-                               $checkboxValue = $this->initNamespaceCheckbox( $i );
-                       } else {
-                               $checkboxValue = $_REQUEST[$formVar];
-                       }
-
-                       $checked = "";
-                       if ( $checkboxValue == 1 ) {
-                               $checked = " checked";
-                               $this->addtoquery["ns{$i}"] = 1;
-                               array_push( $this->namespacesToSearch, $i );
-                       }
-                       $name = str_replace( "_", " ", $namespaces[$i] );
-                       if ( "" == $name ) { 
-                               $name = wfMsg( "blanknamespace" ); 
-                       }
-
-                       if ( $tempText !== "" ) { 
-                               $tempText .= " "; 
-                       }
-                       $tempText .= "<input type=checkbox value=\"1\" name=\"" .
-                         "ns{$i}\"{$checked}>{$name}\n";
+               # Now try all upper case
+               #
+               $title = Title::newFromText( strtoupper( $term ) );
+               if ( 0 != $title->getArticleID() ) {
+                       return $title;
                }
-               $ret = str_replace ( "$1", $tempText, $ret );
 
-               # List redirects checkbox
+               $title = Title::newFromText( $term );
 
-               $checked = "";
-               if ( $listredirs == 1 ) {
-                       $this->addtoquery["redirs"] = 1;
-                       $checked = " checked";
+               # Entering an IP address goes to the contributions page
+               if ( ( $title->getNamespace() == NS_USER && User::isIP($title->getText() ) )
+                       || User::isIP( trim( $term ) ) ) {
+                       return Title::makeTitle( NS_SPECIAL, "Contributions/" . $title->getDbkey() );
                }
-               $tempText = "<input type=checkbox value=1 name=\"redirs\"{$checked}>\n";
-               $ret = str_replace( "$2", $tempText, $ret );
 
-               # Search field
 
-               $tempText = "<input type=text name=\"search\" value=\"" .
-                       htmlspecialchars( $search ) ."\" width=80>\n";
-        $ret = str_replace( "$3", $tempText, $ret );
-
-               # Searchx button
-
-               $tempText = "<input type=submit name=\"searchx\" value=\"" .
-                 wfMsg("powersearch") . "\">\n";
-               $ret = str_replace( "$9", $tempText, $ret );
-
-               $titleObj = NULL; # this does tricky stuff
+               # Entering a user goes to the user page whether it's there or not
+               if ( $title->getNamespace() == NS_USER ) {
+                       return $title;
+               }
                
-               $ret = "<br><br>\n<form id=\"powersearch\" method=\"get\" " .
-                 "action=\"" . $titleObj->getUrl() . "\">\n{$ret}\n</form>\n";
-
-               if ( isset ( $searchx ) ) {
-                       if ( ! $listredirs ) { 
-                               $this->doSearchRedirects = false; 
-                       }
+               # Quoted term? Try without the quotes...
+               if( preg_match( '/^"([^"]+)"$/', $term, $matches ) ) {
+                       return SearchEngine::getNearMatch( $matches[1] );
                }
-               return $ret;
+               
+               return NULL;
        }
-
-       # Perform the search and construct the results page
-       function showResults()
-       {
-               global $wgUser, $wgTitle, $wgOut, $wgLang, $wgDisableTextSearch;
-               global $wgInputEncoding;
-               $fname = "SearchEngine::showResults";
-
-               $search = $_REQUEST['search'];
-
-               $powersearch = $this->powersearch(); /* Need side-effects here? */
-
-               $wgOut->setPageTitle( wfMsg( "searchresults" ) );
-               $q = wfMsg( "searchquery", htmlspecialchars( $this->mUsertext ) );
-               $wgOut->setSubtitle( $q );
-               $wgOut->setArticleRelated( false );
-               $wgOut->setRobotpolicy( "noindex,nofollow" );
-
-               $sk = $wgUser->getSkin();
-               $header = wfMsg( "searchresulttext", $sk->makeKnownLink(
-                 wfMsg( "searchhelppage" ), wfMsg( "searchingwikipedia" ) ) );
-               $wgOut->addHTML( $header );
-
-               $this->parseQuery();
-               if ( "" == $this->mTitlecond || "" == $this->mTextcond ) {
-                       $wgOut->addHTML( "<h2>" . wfMsg( "badquery" ) . "</h2>\n" .
-                         "<p>" . wfMsg( "badquerytext" ) );
-                       return;
-               }
-               list( $limit, $offset ) = wfCheckLimits( 20, "searchlimit" );
-
-               $searchnamespaces = $this->queryNamespaces();
-               $redircond = $this->searchRedirects();
-
-               if ( $wgDisableTextSearch ) {
-                       $wgOut->addHTML( wfMsg( "searchdisabled" ) );
-                       $wgOut->addHTML( wfMsg( "googlesearch", htmlspecialchars( $search ), $GLOBALS['wgInputEncoding'] ) );
-               } else {
-                       $sql = "SELECT cur_id,cur_namespace,cur_title," .
-                         "cur_text FROM cur,searchindex " .
-                         "WHERE cur_id=si_page AND {$this->mTitlecond} " .
-                         "{$searchnamespaces} {$redircond}" .
-                         "LIMIT {$offset}, {$limit}";
-                       $res1 = wfQuery( $sql, DB_READ, $fname );
-                       $num = wfNumRows($res1);
-
-                       $sk = $wgUser->getSkin();
-                       $text = "";
-
-                       $this->parseQuery();
-                       if ( "" == $this->mTitlecond || "" == $this->mTextcond ) {
-                               $wgOut->addHTML( "<h2>" . wfMsg( "badquery" ) . "</h2>\n" .
-                                 "<p>" . wfMsg( "badquerytext" ) );
-                               return;
-                       }
-                       list( $limit, $offset ) = wfCheckLimits( 20, "searchlimit" );
-       
-                       $searchnamespaces = $this->queryNamespaces();
-                       $redircond = $this->searchRedirects();
        
-                       $sql = "SELECT cur_id,cur_namespace,cur_title," .
-                         "cur_text FROM cur,searchindex " .
-                         "WHERE cur_id=si_page AND {$this->mTitlecond} " .
-                         "{$searchnamespaces} {$redircond}" .
-                         "LIMIT {$offset}, {$limit}";
-                       $res1 = wfQuery( $sql, DB_READ, $fname );
-                       $num = wfNumRows($res1);
-       
-                       $sql = "SELECT cur_id,cur_namespace,cur_title," .
-                         "cur_text FROM cur,searchindex " .
-                         "WHERE cur_id=si_page AND {$this->mTextcond} " .
-                         "{$searchnamespaces} {$redircond} " .
-                         "LIMIT {$offset}, {$limit}";
-                       $res2 = wfQuery( $sql, DB_READ, $fname );
-                       $num = $num + wfNumRows($res2);
+       function legalSearchChars() {
+               return "A-Za-z_'0-9\\x80-\\xFF\\-";
+       }
 
-                       if ( $num == $limit ) {
-                         $top = wfShowingResults( $offset, $limit);
-                       } else {
-                         $top = wfShowingResultsNum( $offset, $limit, $num );
-                       }
-                       $wgOut->addHTML( "<p>{$top}\n" );
-       
-                       # For powersearch
-       
-                       $a2l = "" ;
-                       $akk = array_keys( $this->addtoquery ) ;
-                       foreach ( $akk AS $ak ) {
-                               $a2l .= "&{$ak}={$this->addtoquery[$ak]}" ;
-                       }
-       
-                       $sl = wfViewPrevNext( $offset, $limit, "",
-                         "search=" . wfUrlencode( $this->mUsertext ) . $a2l );
-                       $wgOut->addHTML( "<br>{$sl}\n" );
-       
-                       $foundsome = false;
+       /**
+        * Set the maximum number of results to return
+        * and how many to skip before returning the first.
+        *
+        * @param int $limit
+        * @param int $offset
+        * @access public
+        */
+       function setLimitOffset( $limit, $offset = 0 ) {
+               $this->limit = IntVal( $limit );
+               $this->offset = IntVal( $offset );
+       }
        
-                       if ( 0 == wfNumRows( $res1 ) ) {
-                               $wgOut->addHTML( "<h2>" . wfMsg( "notitlematches" ) .
-                                 "</h2>\n" );
-                       } else {
-                               $foundsome = true;
-                               $off = $offset + 1;
-                               $wgOut->addHTML( "<h2>" . wfMsg( "titlematches" ) .
-                                 "</h2>\n<ol start='{$off}'>" );
+       /**
+        * Set which namespaces the search should include.
+        * Give an array of namespace index numbers.
+        *
+        * @param array $namespaces
+        * @access public
+        */
+       function setNamespaces( $namespaces ) {
+               $this->namespaces = $namespaces;
+       }
        
-                               while ( $row = wfFetchObject( $res1 ) ) {
-                                       $this->showHit( $row );
-                               }
-                               wfFreeResult( $res1 );
-                               $wgOut->addHTML( "</ol>\n" );
-                       }
-
-                       if ( 0 == wfNumRows( $res2 ) ) {
-                               $wgOut->addHTML( "<h2>" . wfMsg( "notextmatches" ) .
-                                 "</h2>\n" );
-                       } else {
-                               $foundsome = true;
-                               $off = $offset + 1;
-                               $wgOut->addHTML( "<h2>" . wfMsg( "textmatches" ) . "</h2>\n" .
-                                 "<ol start='{$off}'>" );
-                               while ( $row = wfFetchObject( $res2 ) ) {
-                                       $this->showHit( $row );
-                               }
-                               wfFreeResult( $res2 );
-                               $wgOut->addHTML( "</ol>\n" );
-                       }
-                       if ( ! $foundsome ) {
-                               $wgOut->addHTML( "<p>" . wfMsg( "nonefound" ) . "\n" );
+       /**
+        * Make a list of searchable namespaces and their canonical names.
+        * @return array
+        * @access public
+        */
+       function searchableNamespaces() {
+               global $wgContLang;
+               $arr = array();
+               foreach( $wgContLang->getNamespaces() as $ns => $name ) {
+                       if( $ns >= NS_MAIN ) {
+                               $arr[$ns] = $name;
                        }
-                       $wgOut->addHTML( "<p>{$sl}\n" );
-                       $wgOut->addHTML( $powersearch );
                }
+               return $arr;
        }
-
-       function legalSearchChars()
-       {
-               $lc = "A-Za-z_'0-9\\x80-\\xFF\\-";
-               return $lc;
+       
+       /**
+        * Fetch an array of regular expression fragments for matching
+        * the search terms as parsed by this engine in a text extract.
+        *
+        * @return array
+        * @access public
+        */
+       function termMatches() {
+               return $this->searchTerms;
        }
-
-       function parseQuery()
-       {
-               global $wgDBminWordLen, $wgLang, $wgDBmysql4;
-
-               if( $wgDBmysql4 ) {
-                       # Use cleaner boolean search if available
-                       return $this->parseQuery4();
-               }
-
-               $lc = SearchEngine::legalSearchChars() . "()";
-               $q = preg_replace( "/([()])/", " \\1 ", $this->mUsertext );
-               $q = preg_replace( "/\\s+/", " ", $q );
-               $w = explode( " ", strtolower( trim( $q ) ) );
-
-               $last = $cond = "";
-               foreach ( $w as $word ) {
-                       $word = $wgLang->stripForSearch( $word );
-                       if ( "and" == $word || "or" == $word || "not" == $word
-                         || "(" == $word || ")" == $word ) {
-                               $cond .= " " . strtoupper( $word );
-                               $last = "";
-                       } else if ( strlen( $word ) < $wgDBminWordLen ) {
-                               continue;
-                       } else if ( FulltextStoplist::inList( $word ) ) {
-                               continue;
-                       } else {
-                               if ( "" != $last ) { $cond .= " AND"; }
-                               $cond .= " (MATCH (##field##) AGAINST ('" .
-                                 wfStrencode( $word ). "'))";
-                               $last = $word;
-                               array_push( $this->mSearchterms, "\\b" . $word . "\\b" );
-                       }
-               }
-               if ( 0 == count( $this->mSearchterms ) ) { return; }
-
-               $this->mTitlecond = "(" . str_replace( "##field##",
-                 "si_title", $cond ) . " )";
-
-               $this->mTextcond = "(" . str_replace( "##field##",
-                 "si_text", $cond ) . " AND (cur_is_redirect=0) )";
+       
+       /**
+        * Return a 'cleaned up' search string
+        *
+        * @return string
+        * @access public
+        */
+       function filter( $text ) {
+               $lc = $this->legalSearchChars();
+               return trim( preg_replace( "/[^{$lc}]/", " ", $text ) );
        }
        
-       function parseQuery4()
-       {
-               global $wgLang;
-               $lc = SearchEngine::legalSearchChars();
-               $searchon = "";
-               $this->mSearchterms = array();
-
-               # FIXME: This doesn't handle parenthetical expressions.
-               if( preg_match_all( '/([-+<>~]?)(([' . $lc . ']+)(\*?)|"[^"]*")/',
-                         $this->mUsertext, $m, PREG_SET_ORDER ) ) {
-                       foreach( $m as $terms ) {
-                               if( $searchon !== "" ) $searchon .= " ";
-                               if( $this->mStrictMatching && ($terms[1] == "") ) {
-                                       $terms[1] = "+";
-                               }
-                               $searchon .= $terms[1] . $wgLang->stripForSearch( $terms[2] );
-                               if( $terms[3] ) {
-                                       $regexp = preg_quote( $terms[3] );
-                                       if( $terms[4] ) $regexp .= "[0-9A-Za-z_]+";
-                               } else {
-                                       $regexp = preg_quote( str_replace( '"', '', $terms[2] ) );
-                               }
-                               $this->mSearchterms[] = $regexp;
-                       }
-                       wfDebug( "Would search with '$searchon'\n" );
-                       wfDebug( "Match with /\b" . implode( '\b|\b', $this->mSearchterms ) . "\b/\n" );
+       /**
+        * Return a partial WHERE clause to exclude redirects, if so set
+        * @return string
+        * @access private
+        */
+       function queryRedirect() {
+               if( $this->showRedirects ) {
+                       return 'AND cur_is_redirect=0';
                } else {
-                       wfDebug( "Can't understand search query '$this->mUsertext'\n" );
+                       return '';
                }
-               
-               $searchon = wfStrencode( $searchon );
-               $this->mTitlecond = " MATCH(si_title) AGAINST('$searchon' IN BOOLEAN MODE)";
-               $this->mTextcond = " (MATCH(si_text) AGAINST('$searchon' IN BOOLEAN MODE) AND cur_is_redirect=0)";
        }
-
-       function showHit( $row )
-       {
-               global $wgUser, $wgOut;
-
-               $t = Title::makeName( $row->cur_namespace, $row->cur_title );
-               $sk = $wgUser->getSkin();
-
-               $contextlines = $wgUser->getOption( "contextlines" );
-               if ( "" == $contextlines ) { $contextlines = 5; }
-               $contextchars = $wgUser->getOption( "contextchars" );
-               if ( "" == $contextchars ) { $contextchars = 50; }
-
-               $link = $sk->makeKnownLink( $t, "" );
-               $size = wfMsg( "nbytes", strlen( $row->cur_text ) );
-               $wgOut->addHTML( "<li>{$link} ({$size})" );
-
-               $lines = explode( "\n", $row->cur_text );
-               $pat1 = "/(.*)(" . implode( "|", $this->mSearchterms ) . ")(.*)/i";
-               $lineno = 0;
-
-               foreach ( $lines as $line ) {
-                       if ( 0 == $contextlines ) { break; }
-                       --$contextlines;
-                       ++$lineno;
-                       if ( ! preg_match( $pat1, $line, $m ) ) { continue; }
-
-                       $pre = $m[1];
-                       if ( 0 == $contextchars ) { $pre = "..."; }
-                       else {
-                               if ( strlen( $pre ) > $contextchars ) {
-                                       $pre = "..." . substr( $pre, -$contextchars );
-                               }
-                       }
-                       $pre = wfEscapeHTML( $pre );
-
-                       if ( count( $m ) < 3 ) { $post = ""; }
-                       else { $post = $m[3]; }
-
-                       if ( 0 == $contextchars ) { $post = "..."; }
-                       else {
-                               if ( strlen( $post ) > $contextchars ) {
-                                       $post = substr( $post, 0, $contextchars ) . "...";
-                               }
-                       }
-                       $post = wfEscapeHTML( $post );
-                       $found = wfEscapeHTML( $m[2] );
-
-                       $line = "{$pre}{$found}{$post}";
-                       $pat2 = "/(" . implode( "|", $this->mSearchterms ) . ")/i";
-                       $line = preg_replace( $pat2,
-                         "<font color='red'>\\1</font>", $line );
-
-                       $wgOut->addHTML( "<br><small>{$lineno}: {$line}</small>\n" );
+       
+       /**
+        * Return a partial WHERE clause to limit the search to the given namespaces
+        * @return string
+        * @access private
+        */
+       function queryNamespaces() {
+               $namespaces = implode( ',', $this->namespaces );
+               if ($namespaces == '') {
+                       $namespaces = '0';
                }
-               $wgOut->addHTML( "</li>\n" );
+               return 'AND page_namespace IN (' . $namespaces . ')';
        }
-
-       function goResult()
-       {
-               global $wgOut, $wgDisableTextSearch;
-               $fname = "SearchEngine::goResult";
-               
-               $search         = $_REQUEST['search'];
-
-               # First try to go to page as entered.
-               #
-               $t = Title::newFromText( $search );
-
-               # If the string cannot be used to create a title
-               if( false == $t ){ 
-                       $this->showResults();
-                       return;
-               }
-
-               if ( 0 != $t->getArticleID() ) {
-                       $wgOut->redirect( $t->getURL() );
-                       return;
-               }
-
-               # Now try all lower case (i.e. first letter capitalized)
-               #
-               $t = Title::newFromText( strtolower( $search ) );
-               if ( 0 != $t->getArticleID() ) {
-                       $wgOut->redirect( $t->getURL() );
-                       return;
-               }
-
-               # Now try capitalized string
-               #
-               $t = Title::newFromText( ucwords( strtolower( $search ) ) );
-               if ( 0 != $t->getArticleID() ) {
-                       $wgOut->redirect( $t->getURL() );
-                       return;
-               }
-
-               # Now try all upper case
-               #
-               $t = Title::newFromText( strtoupper( $search ) );
-               if ( 0 != $t->getArticleID() ) {
-                       $wgOut->redirect( $t->getURL() );
-                       return;
-               }
-
-               # No match, generate an edit URL
-               $t = Title::newFromText( $this->mUsertext );
-               $wgOut->addHTML( wfMsg("nogomatch", $t->getURL( "action=edit", true ) ) . "\n<p>" );
-
-               # Try a fuzzy title search
-               $anyhit = false;
-               global $wgDisableFuzzySearch;
-               if(! $wgDisableFuzzySearch ){
-                       foreach( array(NS_MAIN, NS_WP, NS_USER, NS_IMAGE, NS_MEDIAWIKI) as $namespace){
-                               $anyhit |= SearchEngine::doFuzzyTitleSearch( $search, $namespace );
-                       }
-               }
-               
-               if( ! $anyhit ){
-                       return $this->showResults();
-               }
+       
+       /**
+        * Return a LIMIT clause to limit results on the query.
+        * @return string
+        * @access private
+        */
+       function queryLimit() {
+               return $this->db->limitResult( $this->limit, $this->offset );
        }
 
-       /* static */ function doFuzzyTitleSearch( $search, $namespace ){
-               global $wgLang, $wgOut;
-               $sstr = ucfirst($search);
-               $sstr = str_replace(" ", "_", $sstr);
-               $fuzzymatches = SearchEngine::fuzzyTitles( $sstr, $namespace );
-               $fuzzymatches = array_slice($fuzzymatches, 0, 10);
-               $slen = strlen( $search );
-               $wikitext = "";
-               foreach($fuzzymatches as $res){
-                       $t = str_replace("_", " ", $res[1]);
-                       $tfull = $wgLang->getNsText( $namespace ) . ":$t|$t";
-                       if( $namespace == NS_MAIN )
-                               $tfull = "$t";
-                       $distance = $res[0];
-                       $closeness = (strlen( $search ) - $distance) / strlen( $search );
-                       $percent = intval( $closeness * 100 ) . "%";
-                       $stars = str_repeat("*", ceil(5 * $closeness) );
-                       $wikitext .= "* [[$tfull]] $percent ($stars)\n";        
-               }
-               if( $wikitext ){
-                       if( $namespace != NS_MAIN )
-                               $wikitext = "=== " . $wgLang->getNsText( $namespace ) . " ===\n" . $wikitext;
-                       $wgOut->addWikiText( $wikitext );
-                       return true;
-               }
-               return false;
+       /**
+        * Does not do anything for generic search engine
+        * subclasses may define this though
+        * @return string
+        * @access private
+        */
+       function queryRanking($filteredTerm,$fulltext) {
+               return "";
        }
-
-       /* static */ function fuzzyTitles( $sstr, $namespace = NS_MAIN ){
-               $span = 0.10; // weed on title length before doing levenshtein.
-               $tolerance = 0.35; // allowed percentage of erronous characters
-               $slen = strlen($sstr);
-               $tolerance_count = ceil($tolerance * $slen);
-               $spanabs = ceil($slen * (1 + $span)) - $slen;
-               # print "Word: $sstr, len = $slen, range = [$min, $max], tolerance_count = $tolerance_count<BR>\n";
-               $result = array();
-               for( $i=0; $i <= $spanabs; $i++ ){
-                       $titles = SearchEngine::getTitlesByLength( $slen + $i, $namespace );
-                       if( $i != 0)
-                               $titles = array_merge($titles, SearchEngine::getTitlesByLength( $slen - $i, $namespace ) );
-                       foreach($titles as $t){
-                               $d = levenshtein($sstr, $t);
-                               if($d < $tolerance_count) 
-                                       $result[] = array($d, $t);
-                               $cnt++;
-                       }
-               }
-               usort($result, "SearchEngine_pcmp");
-               return $result;
+       
+       /**
+        * Construct the full SQL query to do the search.
+        * The guts shoulds be constructed in queryMain()
+        * @param string $filteredTerm
+        * @param bool $fulltext
+        * @access private
+        */
+       function getQuery( $filteredTerm, $fulltext ) {
+               return $this->queryMain( $filteredTerm, $fulltext ) . ' ' .
+                       $this->queryRedirect() . ' ' .
+                       $this->queryNamespaces() . ' ' .
+                       $this->queryRanking($filteredTerm, $fulltext) . ' ' .
+                       $this->queryLimit();
        }
 
-       /* static */ function getTitlesByLength($aLength, $aNamespace = 0){
-               global $wgMemc, $wgDBname;
-
-               // to avoid multiple costly SELECTs in case of no memcached
-               if( $this->all_titles ){ 
-                       if( isset( $this->all_titles[$aLength][$aNamespace] ) ){
-                               return $this->all_titles[$aLength][$aNamespace];
-                       } else {
-                               return array();
-                       }
-               }
-
-               $mkey = "$wgDBname:titlesbylength:$aLength:$aNamespace";
-               $mkeyts = "$wgDBname:titlesbylength:createtime";
-               $ts = $wgMemc->get( $mkeyts );
-               $result = $wgMemc->get( $mkey );
-
-               if( time() - $ts < 3600 ){
-                       // note: in case of insufficient memcached space, we return
-                       // an empty list instead of starting to hit the DB.
-                       return is_array( $result ) ? $result : array();
-               }
+       /**
+        * Load up the appropriate search engine class for the currently
+          * active database backend, and return a configured instance.
+          *
+          * @return SearchEngine
+          * @access private
+       */
+       function create() {
+                global $wgDBtype, $wgDBmysql4, $wgSearchType;
+                if( $wgDBtype == 'mysql' ) {
+                        if( $wgDBmysql4 ) {
+                                $class = 'SearchMySQL4';
+                                require_once( 'SearchMySQL4.php' );
+                        } else {
+                                $class = 'SearchMysql3';
+                                require_once( 'SearchMySQL3.php' );
+                        }
+                } else if ( $wgDBtype == 'PostgreSQL' ) {
+                        $class = 'SearchTsearch2';
+                        require_once( 'SearchTsearch2.php' );
+                } else {
+                        $class = 'SearchEngineDummy';
+                }
+                $search = new $class( wfGetDB( DB_SLAVE ) );
+                $search->setLimitOffset(0,0);
+                return $search;
+       }
 
-               $wgMemc->set( $mkeyts, time() );
+       
+}
 
-               $res = wfQuery("SELECT cur_title, cur_namespace FROM cur", DB_READ);
-               $titles = array(); // length, ns, [titles]
-               while( $obj = wfFetchObject( $res ) ){
-                       $title = $obj->cur_title;
-                       $ns = $obj->cur_namespace;
-                       $len = strlen( $title );
-                       $titles[$len][$ns][] = $title;
-               } 
-               foreach($titles as $length => $length_arr){
-                       foreach($length_arr as $ns => $title_arr){
-                               $mkey = "$wgDBname:titlesbylength:$length:$ns";
-                               $wgMemc->set( $mkey, $title_arr, 3600 * 24 );
-                       }
-               }
-               $this->all_titles = $titles;
-               if( isset( $titles[$aLength][$aNamespace] ) )
-                       return $titles[$aLength][$aNamespace];
-               else
-                       return array();
+/**
+ * @package MediaWiki
+ */
+class SearchEngineDummy {
+       function search( $term ) {
+               return null;
        }
 }
 
-/* private static */ function SearchEngine_pcmp($a, $b){ return $a[0] - $b[0]; }
-
-?>