Tweak doc comment per bug 28340

[mediawiki.git] / includes / search / SearchMySQL.php

<?php
/**
 * MySQL search engine
 *
 * Copyright (C) 2004 Brion Vibber <brion@pobox.com>
 * http://www.mediawiki.org/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Search
 */

/**
 * Search engine hook for MySQL 4+
 * @ingroup Search
 */
class SearchMySQL extends SearchEngine {
        var $strictMatching = true;
        static $mMinSearchLength;

        /**
         * Creates an instance of this class
         * @param $db DatabaseMysql: database object
         */
        function __construct( $db ) {
                parent::__construct( $db );
        }

        /** 
         * Parse the user's query and transform it into an SQL fragment which will 
         * become part of a WHERE clause
         */
        function parseQuery( $filteredText, $fulltext ) {
                global $wgContLang;
                $lc = SearchEngine::legalSearchChars(); // Minus format chars
                $searchon = '';
                $this->searchTerms = array();

                # FIXME: This doesn't handle parenthetical expressions.
                $m = array();
                if( preg_match_all( '/([-+<>~]?)(([' . $lc . ']+)(\*?)|"[^"]*")/',
                          $filteredText, $m, PREG_SET_ORDER ) ) {
                        foreach( $m as $bits ) {
                                @list( /* all */, $modifier, $term, $nonQuoted, $wildcard ) = $bits;

                                if( $nonQuoted != '' ) {
                                        $term = $nonQuoted;
                                        $quote = '';
                                } else {
                                        $term = str_replace( '"', '', $term );
                                        $quote = '"';
                                }

                                if( $searchon !== '' ) $searchon .= ' ';
                                if( $this->strictMatching && ($modifier == '') ) {
                                        // If we leave this out, boolean op defaults to OR which is rarely helpful.
                                        $modifier = '+';
                                }

                                // Some languages such as Serbian store the input form in the search index,
                                // so we may need to search for matches in multiple writing system variants.
                                $convertedVariants = $wgContLang->autoConvertToAllVariants( $term );
                                if( is_array( $convertedVariants ) ) {
                                        $variants = array_unique( array_values( $convertedVariants ) );
                                } else {
                                        $variants = array( $term );
                                }

                                // The low-level search index does some processing on input to work
                                // around problems with minimum lengths and encoding in MySQL's
                                // fulltext engine.
                                // For Chinese this also inserts spaces between adjacent Han characters.
                                $strippedVariants = array_map(
                                        array( $wgContLang, 'normalizeForSearch' ),
                                        $variants );

                                // Some languages such as Chinese force all variants to a canonical
                                // form when stripping to the low-level search index, so to be sure
                                // let's check our variants list for unique items after stripping.
                                $strippedVariants = array_unique( $strippedVariants );

                                $searchon .= $modifier;
                                if( count( $strippedVariants) > 1 )
                                        $searchon .= '(';
                                foreach( $strippedVariants as $stripped ) {
                                        $stripped = $this->normalizeText( $stripped );
                                        if( $nonQuoted && strpos( $stripped, ' ' ) !== false ) {
                                                // Hack for Chinese: we need to toss in quotes for
                                                // multiple-character phrases since normalizeForSearch()
                                                // added spaces between them to make word breaks.
                                                $stripped = '"' . trim( $stripped ) . '"';
                                        }
                                        $searchon .= "$quote$stripped$quote$wildcard ";
                                }
                                if( count( $strippedVariants) > 1 )
                                        $searchon .= ')';

                                // Match individual terms or quoted phrase in result highlighting...
                                // Note that variants will be introduced in a later stage for highlighting!
                                $regexp = $this->regexTerm( $term, $wildcard );
                                $this->searchTerms[] = $regexp;
                        }
                        wfDebug( __METHOD__ . ": Would search with '$searchon'\n" );
                        wfDebug( __METHOD__ . ': Match with /' . implode( '|', $this->searchTerms ) . "/\n" );
                } else {
                        wfDebug( __METHOD__ . ": Can't understand search query '{$filteredText}'\n" );
                }

                $searchon = $this->db->strencode( $searchon );
                $field = $this->getIndexField( $fulltext );
                return " MATCH($field) AGAINST('$searchon' IN BOOLEAN MODE) ";
        }

        function regexTerm( $string, $wildcard ) {
                global $wgContLang;

                $regex = preg_quote( $string, '/' );
                if( $wgContLang->hasWordBreaks() ) {
                        if( $wildcard ) {
                                // Don't cut off the final bit!
                                $regex = "\b$regex";
                        } else {
                                $regex = "\b$regex\b";
                        }
                } else {
                        // For Chinese, words may legitimately abut other words in the text literal.
                        // Don't add \b boundary checks... note this could cause false positives
                        // for latin chars.
                }
                return $regex;
        }

        public static function legalSearchChars() {
                return "\"*" . parent::legalSearchChars();
        }

        /**
         * Perform a full text search query and return a result set.
         *
         * @param $term String: raw search term
         * @return MySQLSearchResultSet
         */
        function searchText( $term ) {
                return $this->searchInternal( $term, true );
        }

        /**
         * Perform a title-only search query and return a result set.
         *
         * @param $term String: raw search term
         * @return MySQLSearchResultSet
         */
        function searchTitle( $term ) {
                return $this->searchInternal( $term, false );
        }

        protected function searchInternal( $term, $fulltext ) {
                global $wgCountTotalSearchHits;

                $filteredTerm = $this->filter( $term );
                $resultSet = $this->db->query( $this->getQuery( $filteredTerm, $fulltext ) );

                $total = null;
                if( $wgCountTotalSearchHits ) {
                        $totalResult = $this->db->query( $this->getCountQuery( $filteredTerm, $fulltext ) );
                        $row = $totalResult->fetchObject();
                        if( $row ) {
                                $total = intval( $row->c );
                        }
                        $totalResult->free();
                }

                return new MySQLSearchResultSet( $resultSet, $this->searchTerms, $total );
        }


        /**
         * Return a partial WHERE clause to exclude redirects, if so set
         * @return String
         */
        function queryRedirect() {
                if( $this->showRedirects ) {
                        return '';
                } else {
                        return 'page_is_redirect=0';
                }
        }

        /**
         * Return a partial WHERE clause to limit the search to the given namespaces
         * @return String
         */
        function queryNamespaces() {
                if( is_null($this->namespaces) )
                        return '';  # search all
                if ( !count( $this->namespaces ) ) {
                        $namespaces = '0';
                } else {
                        $namespaces = $this->db->makeList( $this->namespaces );
                }
                return 'page_namespace IN (' . $namespaces . ')';
        }

        /**
         * Return a LIMIT clause to limit results on the query.
         * @return String
         */
        function queryLimit() {
                return $this->db->limitResult( '', $this->limit, $this->offset );
        }

        /**
         * Does not do anything for generic search engine
         * subclasses may define this though
         * @return String
         */
        function queryRanking( $filteredTerm, $fulltext ) {
                return '';
        }

        /**
         * Construct the full SQL query to do the search.
         * The guts shoulds be constructed in queryMain()
         * @param $filteredTerm String
         * @param $fulltext Boolean
         */
        function getQuery( $filteredTerm, $fulltext ) {
                $query = $this->queryMain( $filteredTerm, $fulltext ) . ' ';

                $redir = $this->queryRedirect();

                if ( $redir ) {
                        $query .= 'AND ' . $redir . ' ';
                }

                $namespace = $this->queryNamespaces();

                if ( $namespace ) {
                        $query .= 'AND ' . $namespace . ' ';
                }

                $query .= $this->queryRanking( $filteredTerm, $fulltext ) . ' ' .
                        $this->queryLimit();

                return $query;
        }

        /**
         * Picks which field to index on, depending on what type of query.
         * @param $fulltext Boolean
         * @return String
         */
        function getIndexField( $fulltext ) {
                return $fulltext ? 'si_text' : 'si_title';
        }

        /**
         * Get the base part of the search query.
         * The actual match syntax will depend on the server
         * version; MySQL 3 and MySQL 4 have different capabilities
         * in their fulltext search indexes.
         *
         * @param $filteredTerm String
         * @param $fulltext Boolean
         * @return String
         */
        function queryMain( $filteredTerm, $fulltext ) {
                $match = $this->parseQuery( $filteredTerm, $fulltext );
                $page        = $this->db->tableName( 'page' );
                $searchindex = $this->db->tableName( 'searchindex' );
                return 'SELECT page_id, page_namespace, page_title ' .
                        "FROM $page,$searchindex " .
                        'WHERE page_id=si_page AND ' . $match;
        }

        function getCountQuery( $filteredTerm, $fulltext ) {
                $match = $this->parseQuery( $filteredTerm, $fulltext );

                return $this->db->selectSQLText( array( 'page', 'searchindex' ),
                        'COUNT(*) AS c',
                        array(
                                'page_id=si_page',
                                $match,
                                $this->queryRedirect(),
                                $this->queryNamespaces()
                        ),
                        __METHOD__
                );
        }

        /**
         * Create or update the search index record for the given page.
         * Title and text should be pre-processed.
         *
         * @param $id Integer
         * @param $title String
         * @param $text String
         */
        function update( $id, $title, $text ) {
                $dbw = wfGetDB( DB_MASTER );
                $dbw->replace( 'searchindex',
                        array( 'si_page' ),
                        array(
                                'si_page' => $id,
                                'si_title' => $this->normalizeText( $title ),
                                'si_text' => $this->normalizeText( $text )
                        ), __METHOD__ );
        }

        /**
         * Update a search index record's title only.
         * Title should be pre-processed.
         *
         * @param $id Integer
         * @param $title String
         */
        function updateTitle( $id, $title ) {
                $dbw = wfGetDB( DB_MASTER );

                $dbw->update( 'searchindex',
                        array( 'si_title' => $this->normalizeText( $title ) ),
                        array( 'si_page'  => $id ),
                        __METHOD__,
                        array( $dbw->lowPriorityOption() ) );
        }

        /**
         * Converts some characters for MySQL's indexing to grok it correctly,
         * and pads short words to overcome limitations.
         */
        function normalizeText( $string ) {
                global $wgContLang;

                wfProfileIn( __METHOD__ );

                $out = parent::normalizeText( $string );

                // MySQL fulltext index doesn't grok utf-8, so we
                // need to fold cases and convert to hex
                $out = preg_replace_callback(
                        "/([\\xc0-\\xff][\\x80-\\xbf]*)/",
                        array( $this, 'stripForSearchCallback' ),
                        $wgContLang->lc( $out ) );

                // And to add insult to injury, the default indexing
                // ignores short words... Pad them so we can pass them
                // through without reconfiguring the server...
                $minLength = $this->minSearchLength();
                if( $minLength > 1 ) {
                        $n = $minLength - 1;
                        $out = preg_replace(
                                "/\b(\w{1,$n})\b/",
                                "$1u800",
                                $out );
                }

                // Periods within things like hostnames and IP addresses
                // are also important -- we want a search for "example.com"
                // or "192.168.1.1" to work sanely.
                //
                // MySQL's search seems to ignore them, so you'd match on
                // "example.wikipedia.com" and "192.168.83.1" as well.
                $out = preg_replace(
                        "/(\w)\.(\w|\*)/u",
                        "$1u82e$2",
                        $out );

                wfProfileOut( __METHOD__ );

                return $out;
        }

        /**
         * Armor a case-folded UTF-8 string to get through MySQL's
         * fulltext search without being mucked up by funny charset
         * settings or anything else of the sort.
         */
        protected function stripForSearchCallback( $matches ) {
                return 'u8' . bin2hex( $matches[1] );
        }

        /**
         * Check MySQL server's ft_min_word_len setting so we know
         * if we need to pad short words...
         * 
         * @return int
         */
        protected function minSearchLength() {
                if( is_null( self::$mMinSearchLength ) ) {
                        $sql = "SHOW GLOBAL VARIABLES LIKE 'ft\\_min\\_word\\_len'";

                        $dbr = wfGetDB( DB_SLAVE );
                        $result = $dbr->query( $sql );
                        $row = $result->fetchObject();
                        $result->free();

                        if( $row && $row->Variable_name == 'ft_min_word_len' ) {
                                self::$mMinSearchLength = intval( $row->Value );
                        } else {
                                self::$mMinSearchLength = 0;
                        }
                }
                return self::$mMinSearchLength;
        }
}

/**
 * @ingroup Search
 */
class MySQLSearchResultSet extends SqlSearchResultSet {
        function __construct( $resultSet, $terms, $totalHits=null ) {
                parent::__construct( $resultSet, $terms );
                $this->mTotalHits = $totalHits;
        }

        function getTotalHits() {
                return $this->mTotalHits;
        }
}