Added release notes for 'ContentHandler::runLegacyHooks' removal

[mediawiki.git] / includes / libs / rdbms / database / DatabaseSqlite.php

<?php
/**
 * This is the SQLite database abstraction layer.
 * See maintenance/sqlite/README for development notes and other specific information
 *
 * 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 Database
 */

/**
 * @ingroup Database
 */
class DatabaseSqlite extends Database {
        /** @var bool Whether full text is enabled */
        private static $fulltextEnabled = null;

        /** @var string Directory */
        protected $dbDir;
        /** @var string File name for SQLite database file */
        protected $dbPath;
        /** @var string Transaction mode */
        protected $trxMode;

        /** @var int The number of rows affected as an integer */
        protected $mAffectedRows;
        /** @var resource */
        protected $mLastResult;

        /** @var PDO */
        protected $mConn;

        /** @var FSLockManager (hopefully on the same server as the DB) */
        protected $lockMgr;

        /**
         * Additional params include:
         *   - dbDirectory : directory containing the DB and the lock file directory
         *                   [defaults to $wgSQLiteDataDir]
         *   - dbFilePath  : use this to force the path of the DB file
         *   - trxMode     : one of (deferred, immediate, exclusive)
         * @param array $p
         */
        function __construct( array $p ) {
                if ( isset( $p['dbFilePath'] ) ) {
                        parent::__construct( $p );
                        // Standalone .sqlite file mode.
                        // Super doesn't open when $user is false, but we can work with $dbName,
                        // which is derived from the file path in this case.
                        $this->openFile( $p['dbFilePath'] );
                        $lockDomain = md5( $p['dbFilePath'] );
                } elseif ( !isset( $p['dbDirectory'] ) ) {
                        throw new InvalidArgumentException( "Need 'dbDirectory' or 'dbFilePath' parameter." );
                } else {
                        $this->dbDir = $p['dbDirectory'];
                        $this->mDBname = $p['dbname'];
                        $lockDomain = $this->mDBname;
                        // Stock wiki mode using standard file names per DB.
                        parent::__construct( $p );
                        // Super doesn't open when $user is false, but we can work with $dbName
                        if ( $p['dbname'] && !$this->isOpen() ) {
                                if ( $this->open( $p['host'], $p['user'], $p['password'], $p['dbname'] ) ) {
                                        $done = [];
                                        foreach ( $this->tableAliases as $params ) {
                                                if ( isset( $done[$params['dbname']] ) ) {
                                                        continue;
                                                }
                                                $this->attachDatabase( $params['dbname'] );
                                                $done[$params['dbname']] = 1;
                                        }
                                }
                        }
                }

                $this->trxMode = isset( $p['trxMode'] ) ? strtoupper( $p['trxMode'] ) : null;
                if ( $this->trxMode &&
                        !in_array( $this->trxMode, [ 'DEFERRED', 'IMMEDIATE', 'EXCLUSIVE' ] )
                ) {
                        $this->trxMode = null;
                        $this->queryLogger->warning( "Invalid SQLite transaction mode provided." );
                }

                $this->lockMgr = new FSLockManager( [
                        'domain' => $lockDomain,
                        'lockDirectory' => "{$this->dbDir}/locks"
                ] );
        }

        /**
         * @param string $filename
         * @param array $p Options map; supports:
         *   - flags       : (same as __construct counterpart)
         *   - trxMode     : (same as __construct counterpart)
         *   - dbDirectory : (same as __construct counterpart)
         * @return DatabaseSqlite
         * @since 1.25
         */
        public static function newStandaloneInstance( $filename, array $p = [] ) {
                $p['dbFilePath'] = $filename;
                $p['schema'] = false;
                $p['tablePrefix'] = '';

                return Database::factory( 'sqlite', $p );
        }

        /**
         * @return string
         */
        function getType() {
                return 'sqlite';
        }

        /**
         * @todo Check if it should be true like parent class
         *
         * @return bool
         */
        function implicitGroupby() {
                return false;
        }

        /** Open an SQLite database and return a resource handle to it
         *  NOTE: only $dbName is used, the other parameters are irrelevant for SQLite databases
         *
         * @param string $server
         * @param string $user
         * @param string $pass
         * @param string $dbName
         *
         * @throws DBConnectionError
         * @return bool
         */
        function open( $server, $user, $pass, $dbName ) {
                $this->close();
                $fileName = self::generateFileName( $this->dbDir, $dbName );
                if ( !is_readable( $fileName ) ) {
                        $this->mConn = false;
                        throw new DBConnectionError( $this, "SQLite database not accessible" );
                }
                $this->openFile( $fileName );

                return (bool)$this->mConn;
        }

        /**
         * Opens a database file
         *
         * @param string $fileName
         * @throws DBConnectionError
         * @return PDO|bool SQL connection or false if failed
         */
        protected function openFile( $fileName ) {
                $err = false;

                $this->dbPath = $fileName;
                try {
                        if ( $this->mFlags & self::DBO_PERSISTENT ) {
                                $this->mConn = new PDO( "sqlite:$fileName", '', '',
                                        [ PDO::ATTR_PERSISTENT => true ] );
                        } else {
                                $this->mConn = new PDO( "sqlite:$fileName", '', '' );
                        }
                } catch ( PDOException $e ) {
                        $err = $e->getMessage();
                }

                if ( !$this->mConn ) {
                        $this->queryLogger->debug( "DB connection error: $err\n" );
                        throw new DBConnectionError( $this, $err );
                }

                $this->mOpened = !!$this->mConn;
                if ( $this->mOpened ) {
                        # Set error codes only, don't raise exceptions
                        $this->mConn->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_SILENT );
                        # Enforce LIKE to be case sensitive, just like MySQL
                        $this->query( 'PRAGMA case_sensitive_like = 1' );

                        return $this->mConn;
                }

                return false;
        }

        public function selectDB( $db ) {
                return false; // doesn't make sense
        }

        /**
         * @return string SQLite DB file path
         * @since 1.25
         */
        public function getDbFilePath() {
                return $this->dbPath;
        }

        /**
         * Does not actually close the connection, just destroys the reference for GC to do its work
         * @return bool
         */
        protected function closeConnection() {
                $this->mConn = null;

                return true;
        }

        /**
         * Generates a database file name. Explicitly public for installer.
         * @param string $dir Directory where database resides
         * @param string $dbName Database name
         * @return string
         */
        public static function generateFileName( $dir, $dbName ) {
                return "$dir/$dbName.sqlite";
        }

        /**
         * Check if the searchindext table is FTS enabled.
         * @return bool False if not enabled.
         */
        function checkForEnabledSearch() {
                if ( self::$fulltextEnabled === null ) {
                        self::$fulltextEnabled = false;
                        $table = $this->tableName( 'searchindex' );
                        $res = $this->query( "SELECT sql FROM sqlite_master WHERE tbl_name = '$table'", __METHOD__ );
                        if ( $res ) {
                                $row = $res->fetchRow();
                                self::$fulltextEnabled = stristr( $row['sql'], 'fts' ) !== false;
                        }
                }

                return self::$fulltextEnabled;
        }

        /**
         * Returns version of currently supported SQLite fulltext search module or false if none present.
         * @return string
         */
        static function getFulltextSearchModule() {
                static $cachedResult = null;
                if ( $cachedResult !== null ) {
                        return $cachedResult;
                }
                $cachedResult = false;
                $table = 'dummy_search_test';

                $db = self::newStandaloneInstance( ':memory:' );
                if ( $db->query( "CREATE VIRTUAL TABLE $table USING FTS3(dummy_field)", __METHOD__, true ) ) {
                        $cachedResult = 'FTS3';
                }
                $db->close();

                return $cachedResult;
        }

        /**
         * Attaches external database to our connection, see https://sqlite.org/lang_attach.html
         * for details.
         *
         * @param string $name Database name to be used in queries like
         *   SELECT foo FROM dbname.table
         * @param bool|string $file Database file name. If omitted, will be generated
         *   using $name and configured data directory
         * @param string $fname Calling function name
         * @return ResultWrapper
         */
        function attachDatabase( $name, $file = false, $fname = __METHOD__ ) {
                if ( !$file ) {
                        $file = self::generateFileName( $this->dbDir, $name );
                }
                $file = $this->addQuotes( $file );

                return $this->query( "ATTACH DATABASE $file AS $name", $fname );
        }

        function isWriteQuery( $sql ) {
                return parent::isWriteQuery( $sql ) && !preg_match( '/^(ATTACH|PRAGMA)\b/i', $sql );
        }

        /**
         * SQLite doesn't allow buffered results or data seeking etc, so we'll use fetchAll as the result
         *
         * @param string $sql
         * @return bool|ResultWrapper
         */
        protected function doQuery( $sql ) {
                $res = $this->mConn->query( $sql );
                if ( $res === false ) {
                        return false;
                }

                $r = $res instanceof ResultWrapper ? $res->result : $res;
                $this->mAffectedRows = $r->rowCount();
                $res = new ResultWrapper( $this, $r->fetchAll() );

                return $res;
        }

        /**
         * @param ResultWrapper|mixed $res
         */
        function freeResult( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res->result = null;
                } else {
                        $res = null;
                }
        }

        /**
         * @param ResultWrapper|array $res
         * @return stdClass|bool
         */
        function fetchObject( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $r =& $res->result;
                } else {
                        $r =& $res;
                }

                $cur = current( $r );
                if ( is_array( $cur ) ) {
                        next( $r );
                        $obj = new stdClass;
                        foreach ( $cur as $k => $v ) {
                                if ( !is_numeric( $k ) ) {
                                        $obj->$k = $v;
                                }
                        }

                        return $obj;
                }

                return false;
        }

        /**
         * @param ResultWrapper|mixed $res
         * @return array|bool
         */
        function fetchRow( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $r =& $res->result;
                } else {
                        $r =& $res;
                }
                $cur = current( $r );
                if ( is_array( $cur ) ) {
                        next( $r );

                        return $cur;
                }

                return false;
        }

        /**
         * The PDO::Statement class implements the array interface so count() will work
         *
         * @param ResultWrapper|array $res
         * @return int
         */
        function numRows( $res ) {
                $r = $res instanceof ResultWrapper ? $res->result : $res;

                return count( $r );
        }

        /**
         * @param ResultWrapper $res
         * @return int
         */
        function numFields( $res ) {
                $r = $res instanceof ResultWrapper ? $res->result : $res;
                if ( is_array( $r ) && count( $r ) > 0 ) {
                        // The size of the result array is twice the number of fields. (Bug: 65578)
                        return count( $r[0] ) / 2;
                } else {
                        // If the result is empty return 0
                        return 0;
                }
        }

        /**
         * @param ResultWrapper $res
         * @param int $n
         * @return bool
         */
        function fieldName( $res, $n ) {
                $r = $res instanceof ResultWrapper ? $res->result : $res;
                if ( is_array( $r ) ) {
                        $keys = array_keys( $r[0] );

                        return $keys[$n];
                }

                return false;
        }

        /**
         * Use MySQL's naming (accounts for prefix etc) but remove surrounding backticks
         *
         * @param string $name
         * @param string $format
         * @return string
         */
        function tableName( $name, $format = 'quoted' ) {
                // table names starting with sqlite_ are reserved
                if ( strpos( $name, 'sqlite_' ) === 0 ) {
                        return $name;
                }

                return str_replace( '"', '', parent::tableName( $name, $format ) );
        }

        /**
         * This must be called after nextSequenceVal
         *
         * @return int
         */
        function insertId() {
                // PDO::lastInsertId yields a string :(
                return intval( $this->mConn->lastInsertId() );
        }

        /**
         * @param ResultWrapper|array $res
         * @param int $row
         */
        function dataSeek( $res, $row ) {
                if ( $res instanceof ResultWrapper ) {
                        $r =& $res->result;
                } else {
                        $r =& $res;
                }
                reset( $r );
                if ( $row > 0 ) {
                        for ( $i = 0; $i < $row; $i++ ) {
                                next( $r );
                        }
                }
        }

        /**
         * @return string
         */
        function lastError() {
                if ( !is_object( $this->mConn ) ) {
                        return "Cannot return last error, no db connection";
                }
                $e = $this->mConn->errorInfo();

                return isset( $e[2] ) ? $e[2] : '';
        }

        /**
         * @return string
         */
        function lastErrno() {
                if ( !is_object( $this->mConn ) ) {
                        return "Cannot return last error, no db connection";
                } else {
                        $info = $this->mConn->errorInfo();

                        return $info[1];
                }
        }

        /**
         * @return int
         */
        function affectedRows() {
                return $this->mAffectedRows;
        }

        /**
         * Returns information about an index
         * Returns false if the index does not exist
         * - if errors are explicitly ignored, returns NULL on failure
         *
         * @param string $table
         * @param string $index
         * @param string $fname
         * @return array|false
         */
        function indexInfo( $table, $index, $fname = __METHOD__ ) {
                $sql = 'PRAGMA index_info(' . $this->addQuotes( $this->indexName( $index ) ) . ')';
                $res = $this->query( $sql, $fname );
                if ( !$res || $res->numRows() == 0 ) {
                        return false;
                }
                $info = [];
                foreach ( $res as $row ) {
                        $info[] = $row->name;
                }

                return $info;
        }

        /**
         * @param string $table
         * @param string $index
         * @param string $fname
         * @return bool|null
         */
        function indexUnique( $table, $index, $fname = __METHOD__ ) {
                $row = $this->selectRow( 'sqlite_master', '*',
                        [
                                'type' => 'index',
                                'name' => $this->indexName( $index ),
                        ], $fname );
                if ( !$row || !isset( $row->sql ) ) {
                        return null;
                }

                // $row->sql will be of the form CREATE [UNIQUE] INDEX ...
                $indexPos = strpos( $row->sql, 'INDEX' );
                if ( $indexPos === false ) {
                        return null;
                }
                $firstPart = substr( $row->sql, 0, $indexPos );
                $options = explode( ' ', $firstPart );

                return in_array( 'UNIQUE', $options );
        }

        /**
         * Filter the options used in SELECT statements
         *
         * @param array $options
         * @return array
         */
        function makeSelectOptions( $options ) {
                foreach ( $options as $k => $v ) {
                        if ( is_numeric( $k ) && ( $v == 'FOR UPDATE' || $v == 'LOCK IN SHARE MODE' ) ) {
                                $options[$k] = '';
                        }
                }

                return parent::makeSelectOptions( $options );
        }

        /**
         * @param array $options
         * @return string
         */
        protected function makeUpdateOptionsArray( $options ) {
                $options = parent::makeUpdateOptionsArray( $options );
                $options = self::fixIgnore( $options );

                return $options;
        }

        /**
         * @param array $options
         * @return array
         */
        static function fixIgnore( $options ) {
                # SQLite uses OR IGNORE not just IGNORE
                foreach ( $options as $k => $v ) {
                        if ( $v == 'IGNORE' ) {
                                $options[$k] = 'OR IGNORE';
                        }
                }

                return $options;
        }

        /**
         * @param array $options
         * @return string
         */
        function makeInsertOptions( $options ) {
                $options = self::fixIgnore( $options );

                return parent::makeInsertOptions( $options );
        }

        /**
         * Based on generic method (parent) with some prior SQLite-sepcific adjustments
         * @param string $table
         * @param array $a
         * @param string $fname
         * @param array $options
         * @return bool
         */
        function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
                if ( !count( $a ) ) {
                        return true;
                }

                # SQLite can't handle multi-row inserts, so divide up into multiple single-row inserts
                if ( isset( $a[0] ) && is_array( $a[0] ) ) {
                        $ret = true;
                        foreach ( $a as $v ) {
                                if ( !parent::insert( $table, $v, "$fname/multi-row", $options ) ) {
                                        $ret = false;
                                }
                        }
                } else {
                        $ret = parent::insert( $table, $a, "$fname/single-row", $options );
                }

                return $ret;
        }

        /**
         * @param string $table
         * @param array $uniqueIndexes Unused
         * @param string|array $rows
         * @param string $fname
         * @return bool|ResultWrapper
         */
        function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
                if ( !count( $rows ) ) {
                        return true;
                }

                # SQLite can't handle multi-row replaces, so divide up into multiple single-row queries
                if ( isset( $rows[0] ) && is_array( $rows[0] ) ) {
                        $ret = true;
                        foreach ( $rows as $v ) {
                                if ( !$this->nativeReplace( $table, $v, "$fname/multi-row" ) ) {
                                        $ret = false;
                                }
                        }
                } else {
                        $ret = $this->nativeReplace( $table, $rows, "$fname/single-row" );
                }

                return $ret;
        }

        /**
         * Returns the size of a text field, or -1 for "unlimited"
         * In SQLite this is SQLITE_MAX_LENGTH, by default 1GB. No way to query it though.
         *
         * @param string $table
         * @param string $field
         * @return int
         */
        function textFieldSize( $table, $field ) {
                return -1;
        }

        /**
         * @return bool
         */
        function unionSupportsOrderAndLimit() {
                return false;
        }

        /**
         * @param string[] $sqls
         * @param bool $all Whether to "UNION ALL" or not
         * @return string
         */
        function unionQueries( $sqls, $all ) {
                $glue = $all ? ' UNION ALL ' : ' UNION ';

                return implode( $glue, $sqls );
        }

        /**
         * @return bool
         */
        function wasDeadlock() {
                return $this->lastErrno() == 5; // SQLITE_BUSY
        }

        /**
         * @return bool
         */
        function wasErrorReissuable() {
                return $this->lastErrno() == 17; // SQLITE_SCHEMA;
        }

        /**
         * @return bool
         */
        function wasReadOnlyError() {
                return $this->lastErrno() == 8; // SQLITE_READONLY;
        }

        /**
         * @return string Wikitext of a link to the server software's web site
         */
        public function getSoftwareLink() {
                return "[{{int:version-db-sqlite-url}} SQLite]";
        }

        /**
         * @return string Version information from the database
         */
        function getServerVersion() {
                $ver = $this->mConn->getAttribute( PDO::ATTR_SERVER_VERSION );

                return $ver;
        }

        /**
         * Get information about a given field
         * Returns false if the field does not exist.
         *
         * @param string $table
         * @param string $field
         * @return SQLiteField|bool False on failure
         */
        function fieldInfo( $table, $field ) {
                $tableName = $this->tableName( $table );
                $sql = 'PRAGMA table_info(' . $this->addQuotes( $tableName ) . ')';
                $res = $this->query( $sql, __METHOD__ );
                foreach ( $res as $row ) {
                        if ( $row->name == $field ) {
                                return new SQLiteField( $row, $tableName );
                        }
                }

                return false;
        }

        protected function doBegin( $fname = '' ) {
                if ( $this->trxMode ) {
                        $this->query( "BEGIN {$this->trxMode}", $fname );
                } else {
                        $this->query( 'BEGIN', $fname );
                }
                $this->mTrxLevel = 1;
        }

        /**
         * @param string $s
         * @return string
         */
        function strencode( $s ) {
                return substr( $this->addQuotes( $s ), 1, -1 );
        }

        /**
         * @param string $b
         * @return Blob
         */
        function encodeBlob( $b ) {
                return new Blob( $b );
        }

        /**
         * @param Blob|string $b
         * @return string
         */
        function decodeBlob( $b ) {
                if ( $b instanceof Blob ) {
                        $b = $b->fetch();
                }

                return $b;
        }

        /**
         * @param string|int|null|bool|Blob $s
         * @return string|int
         */
        function addQuotes( $s ) {
                if ( $s instanceof Blob ) {
                        return "x'" . bin2hex( $s->fetch() ) . "'";
                } elseif ( is_bool( $s ) ) {
                        return (int)$s;
                } elseif ( strpos( $s, "\0" ) !== false ) {
                        // SQLite doesn't support \0 in strings, so use the hex representation as a workaround.
                        // This is a known limitation of SQLite's mprintf function which PDO
                        // should work around, but doesn't. I have reported this to php.net as bug #63419:
                        // https://bugs.php.net/bug.php?id=63419
                        // There was already a similar report for SQLite3::escapeString, bug #62361:
                        // https://bugs.php.net/bug.php?id=62361
                        // There is an additional bug regarding sorting this data after insert
                        // on older versions of sqlite shipped with ubuntu 12.04
                        // https://phabricator.wikimedia.org/T74367
                        $this->queryLogger->debug(
                                __FUNCTION__ .
                                ': Quoting value containing null byte. ' .
                                'For consistency all binary data should have been ' .
                                'first processed with self::encodeBlob()'
                        );
                        return "x'" . bin2hex( $s ) . "'";
                } else {
                        return $this->mConn->quote( $s );
                }
        }

        /**
         * @return string
         */
        function buildLike() {
                $params = func_get_args();
                if ( count( $params ) > 0 && is_array( $params[0] ) ) {
                        $params = $params[0];
                }

                return parent::buildLike( $params ) . "ESCAPE '\' ";
        }

        /**
         * @param string $field Field or column to cast
         * @return string
         * @since 1.28
         */
        public function buildStringCast( $field ) {
                return 'CAST ( ' . $field . ' AS TEXT )';
        }

        /**
         * No-op version of deadlockLoop
         *
         * @return mixed
         */
        public function deadlockLoop( /*...*/ ) {
                $args = func_get_args();
                $function = array_shift( $args );

                return call_user_func_array( $function, $args );
        }

        /**
         * @param string $s
         * @return string
         */
        protected function replaceVars( $s ) {
                $s = parent::replaceVars( $s );
                if ( preg_match( '/^\s*(CREATE|ALTER) TABLE/i', $s ) ) {
                        // CREATE TABLE hacks to allow schema file sharing with MySQL

                        // binary/varbinary column type -> blob
                        $s = preg_replace( '/\b(var)?binary(\(\d+\))/i', 'BLOB', $s );
                        // no such thing as unsigned
                        $s = preg_replace( '/\b(un)?signed\b/i', '', $s );
                        // INT -> INTEGER
                        $s = preg_replace( '/\b(tiny|small|medium|big|)int(\s*\(\s*\d+\s*\)|\b)/i', 'INTEGER', $s );
                        // floating point types -> REAL
                        $s = preg_replace(
                                '/\b(float|double(\s+precision)?)(\s*\(\s*\d+\s*(,\s*\d+\s*)?\)|\b)/i',
                                'REAL',
                                $s
                        );
                        // varchar -> TEXT
                        $s = preg_replace( '/\b(var)?char\s*\(.*?\)/i', 'TEXT', $s );
                        // TEXT normalization
                        $s = preg_replace( '/\b(tiny|medium|long)text\b/i', 'TEXT', $s );
                        // BLOB normalization
                        $s = preg_replace( '/\b(tiny|small|medium|long|)blob\b/i', 'BLOB', $s );
                        // BOOL -> INTEGER
                        $s = preg_replace( '/\bbool(ean)?\b/i', 'INTEGER', $s );
                        // DATETIME -> TEXT
                        $s = preg_replace( '/\b(datetime|timestamp)\b/i', 'TEXT', $s );
                        // No ENUM type
                        $s = preg_replace( '/\benum\s*\([^)]*\)/i', 'TEXT', $s );
                        // binary collation type -> nothing
                        $s = preg_replace( '/\bbinary\b/i', '', $s );
                        // auto_increment -> autoincrement
                        $s = preg_replace( '/\bauto_increment\b/i', 'AUTOINCREMENT', $s );
                        // No explicit options
                        $s = preg_replace( '/\)[^);]*(;?)\s*$/', ')\1', $s );
                        // AUTOINCREMENT should immedidately follow PRIMARY KEY
                        $s = preg_replace( '/primary key (.*?) autoincrement/i', 'PRIMARY KEY AUTOINCREMENT $1', $s );
                } elseif ( preg_match( '/^\s*CREATE (\s*(?:UNIQUE|FULLTEXT)\s+)?INDEX/i', $s ) ) {
                        // No truncated indexes
                        $s = preg_replace( '/\(\d+\)/', '', $s );
                        // No FULLTEXT
                        $s = preg_replace( '/\bfulltext\b/i', '', $s );
                } elseif ( preg_match( '/^\s*DROP INDEX/i', $s ) ) {
                        // DROP INDEX is database-wide, not table-specific, so no ON <table> clause.
                        $s = preg_replace( '/\sON\s+[^\s]*/i', '', $s );
                } elseif ( preg_match( '/^\s*INSERT IGNORE\b/i', $s ) ) {
                        // INSERT IGNORE --> INSERT OR IGNORE
                        $s = preg_replace( '/^\s*INSERT IGNORE\b/i', 'INSERT OR IGNORE', $s );
                }

                return $s;
        }

        public function lock( $lockName, $method, $timeout = 5 ) {
                if ( !is_dir( "{$this->dbDir}/locks" ) ) { // create dir as needed
                        if ( !is_writable( $this->dbDir ) || !mkdir( "{$this->dbDir}/locks" ) ) {
                                throw new DBError( $this, "Cannot create directory \"{$this->dbDir}/locks\"." );
                        }
                }

                return $this->lockMgr->lock( [ $lockName ], LockManager::LOCK_EX, $timeout )->isOK();
        }

        public function unlock( $lockName, $method ) {
                return $this->lockMgr->unlock( [ $lockName ], LockManager::LOCK_EX )->isOK();
        }

        /**
         * Build a concatenation list to feed into a SQL query
         *
         * @param string[] $stringList
         * @return string
         */
        function buildConcat( $stringList ) {
                return '(' . implode( ') || (', $stringList ) . ')';
        }

        public function buildGroupConcatField(
                $delim, $table, $field, $conds = '', $join_conds = []
        ) {
                $fld = "group_concat($field," . $this->addQuotes( $delim ) . ')';

                return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
        }

        /**
         * @param string $oldName
         * @param string $newName
         * @param bool $temporary
         * @param string $fname
         * @return bool|ResultWrapper
         * @throws RuntimeException
         */
        function duplicateTableStructure( $oldName, $newName, $temporary = false, $fname = __METHOD__ ) {
                $res = $this->query( "SELECT sql FROM sqlite_master WHERE tbl_name=" .
                        $this->addQuotes( $oldName ) . " AND type='table'", $fname );
                $obj = $this->fetchObject( $res );
                if ( !$obj ) {
                        throw new RuntimeException( "Couldn't retrieve structure for table $oldName" );
                }
                $sql = $obj->sql;
                $sql = preg_replace(
                        '/(?<=\W)"?' . preg_quote( trim( $this->addIdentifierQuotes( $oldName ), '"' ) ) . '"?(?=\W)/',
                        $this->addIdentifierQuotes( $newName ),
                        $sql,
                        1
                );
                if ( $temporary ) {
                        if ( preg_match( '/^\\s*CREATE\\s+VIRTUAL\\s+TABLE\b/i', $sql ) ) {
                                $this->queryLogger->debug(
                                        "Table $oldName is virtual, can't create a temporary duplicate.\n" );
                        } else {
                                $sql = str_replace( 'CREATE TABLE', 'CREATE TEMPORARY TABLE', $sql );
                        }
                }

                $res = $this->query( $sql, $fname );

                // Take over indexes
                $indexList = $this->query( 'PRAGMA INDEX_LIST(' . $this->addQuotes( $oldName ) . ')' );
                foreach ( $indexList as $index ) {
                        if ( strpos( $index->name, 'sqlite_autoindex' ) === 0 ) {
                                continue;
                        }

                        if ( $index->unique ) {
                                $sql = 'CREATE UNIQUE INDEX';
                        } else {
                                $sql = 'CREATE INDEX';
                        }
                        // Try to come up with a new index name, given indexes have database scope in SQLite
                        $indexName = $newName . '_' . $index->name;
                        $sql .= ' ' . $indexName . ' ON ' . $newName;

                        $indexInfo = $this->query( 'PRAGMA INDEX_INFO(' . $this->addQuotes( $index->name ) . ')' );
                        $fields = [];
                        foreach ( $indexInfo as $indexInfoRow ) {
                                $fields[$indexInfoRow->seqno] = $indexInfoRow->name;
                        }

                        $sql .= '(' . implode( ',', $fields ) . ')';

                        $this->query( $sql );
                }

                return $res;
        }

        /**
         * List all tables on the database
         *
         * @param string $prefix Only show tables with this prefix, e.g. mw_
         * @param string $fname Calling function name
         *
         * @return array
         */
        function listTables( $prefix = null, $fname = __METHOD__ ) {
                $result = $this->select(
                        'sqlite_master',
                        'name',
                        "type='table'"
                );

                $endArray = [];

                foreach ( $result as $table ) {
                        $vars = get_object_vars( $table );
                        $table = array_pop( $vars );

                        if ( !$prefix || strpos( $table, $prefix ) === 0 ) {
                                if ( strpos( $table, 'sqlite_' ) !== 0 ) {
                                        $endArray[] = $table;
                                }
                        }
                }

                return $endArray;
        }

        /**
         * Override due to no CASCADE support
         *
         * @param string $tableName
         * @param string $fName
         * @return bool|ResultWrapper
         * @throws DBReadOnlyError
         */
        public function dropTable( $tableName, $fName = __METHOD__ ) {
                if ( !$this->tableExists( $tableName, $fName ) ) {
                        return false;
                }
                $sql = "DROP TABLE " . $this->tableName( $tableName );

                return $this->query( $sql, $fName );
        }

        protected function requiresDatabaseUser() {
                return false; // just a file
        }

        /**
         * @return string
         */
        public function __toString() {
                return 'SQLite ' . (string)$this->mConn->getAttribute( PDO::ATTR_SERVER_VERSION );
        }
}