Support offsets in prefix searching

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

<?php
/**
 * MySQL search engine
 *
 * Copyright (C) 2004 Brion Vibber <brion@pobox.com>
 * https://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 SearchDatabase {
        protected $strictMatching = true;

        private static $mMinSearchLength;

        /**
         * Parse the user's query and transform it into an SQL fragment which will
         * become part of a WHERE clause
         *
         * @param string $filteredText
         * @param string $fulltext
         *
         * @return string
         */
        function parseQuery( $filteredText, $fulltext ) {
                global $wgContLang;

                $lc = $this->legalSearchChars(); // Minus format chars
                $searchon = '';
                $this->searchTerms = array();

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

                                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->addQuotes( $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 string $term Raw search term
         * @return SqlSearchResultSet
         */
        function searchText( $term ) {
                return $this->searchInternal( $term, true );
        }

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

        protected function searchInternal( $term, $fulltext ) {
                // This seems out of place, why is this called with empty term?
                if ( trim( $term ) === '' ) {
                        return null;
                }

                $filteredTerm = $this->filter( $term );
                $query = $this->getQuery( $filteredTerm, $fulltext );
                $resultSet = $this->db->select(
                        $query['tables'], $query['fields'], $query['conds'],
                        __METHOD__, $query['options'], $query['joins']
                );

                $total = null;
                $query = $this->getCountQuery( $filteredTerm, $fulltext );
                $totalResult = $this->db->select(
                        $query['tables'], $query['fields'], $query['conds'],
                        __METHOD__, $query['options'], $query['joins']
                );

                $row = $totalResult->fetchObject();
                if ( $row ) {
                        $total = intval( $row->c );
                }
                $totalResult->free();

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

        public function supports( $feature ) {
                switch ( $feature ) {
                case 'title-suffix-filter':
                        return true;
                default:
                        return parent::supports( $feature );
                }
        }

        /**
         * Add special conditions
         * @param array $query
         * @since 1.18
         */
        protected function queryFeatures( &$query ) {
                foreach ( $this->features as $feature => $value ) {
                        if ( $feature === 'title-suffix-filter' && $value ) {
                                $query['conds'][] = 'page_title' . $this->db->buildLike( $this->db->anyString(), $value );
                        }
                }
        }

        /**
         * Add namespace conditions
         * @param array $query
         * @since 1.18 (changed)
         */
        function queryNamespaces( &$query ) {
                if ( is_array( $this->namespaces ) ) {
                        if ( count( $this->namespaces ) === 0 ) {
                                $this->namespaces[] = '0';
                        }
                        $query['conds']['page_namespace'] = $this->namespaces;
                }
        }

        /**
         * Add limit options
         * @param array $query
         * @since 1.18
         */
        protected function limitResult( &$query ) {
                $query['options']['LIMIT'] = $this->limit;
                $query['options']['OFFSET'] = $this->offset;
        }

        /**
         * Construct the SQL query to do the search.
         * The guts shoulds be constructed in queryMain()
         * @param string $filteredTerm
         * @param bool $fulltext
         * @return array
         * @since 1.18 (changed)
         */
        function getQuery( $filteredTerm, $fulltext ) {
                $query = array(
                        'tables' => array(),
                        'fields' => array(),
                        'conds' => array(),
                        'options' => array(),
                        'joins' => array(),
                );

                $this->queryMain( $query, $filteredTerm, $fulltext );
                $this->queryFeatures( $query );
                $this->queryNamespaces( $query );
                $this->limitResult( $query );

                return $query;
        }

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

        /**
         * Get the base part of the search query.
         *
         * @param array &$query Search query array
         * @param string $filteredTerm
         * @param bool $fulltext
         * @since 1.18 (changed)
         */
        function queryMain( &$query, $filteredTerm, $fulltext ) {
                $match = $this->parseQuery( $filteredTerm, $fulltext );
                $query['tables'][] = 'page';
                $query['tables'][] = 'searchindex';
                $query['fields'][] = 'page_id';
                $query['fields'][] = 'page_namespace';
                $query['fields'][] = 'page_title';
                $query['conds'][] = 'page_id=si_page';
                $query['conds'][] = $match;
        }

        /**
         * @since 1.18 (changed)
         * @param string $filteredTerm
         * @param bool $fulltext
         * @return array
         */
        function getCountQuery( $filteredTerm, $fulltext ) {
                $match = $this->parseQuery( $filteredTerm, $fulltext );

                $query = array(
                        'tables' => array( 'page', 'searchindex' ),
                        'fields' => array( 'COUNT(*) as c' ),
                        'conds' => array( 'page_id=si_page', $match ),
                        'options' => array(),
                        'joins' => array(),
                );

                $this->queryFeatures( $query );
                $this->queryNamespaces( $query );

                return $query;
        }

        /**
         * Create or update the search index record for the given page.
         * Title and text should be pre-processed.
         *
         * @param int $id
         * @param string $title
         * @param string $text
         */
        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 int $id
         * @param string $title
         */
        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() ) );
        }

        /**
         * Delete an indexed page
         * Title should be pre-processed.
         *
         * @param int $id Page id that was deleted
         * @param string $title Title of page that was deleted
         */
        function delete( $id, $title ) {
                $dbw = wfGetDB( DB_MASTER );

                $dbw->delete( 'searchindex', array( 'si_page' => $id ), __METHOD__ );
        }

        /**
         * Converts some characters for MySQL's indexing to grok it correctly,
         * and pads short words to overcome limitations.
         * @param string $string
         * @return mixed|string
         */
        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.
         * @param array $matches
         * @return string
         */
        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;
        }
}