Fix for r47482: put the RELEASE-NOTES entry in the "bug fixes" section and not the...

[mediawiki.git] / includes / db / DatabaseMssql.php

<?php
/**
 * This script is the MSSQL Server database abstraction layer
 *
 * See maintenance/mssql/README for development notes and other specific information
 * @ingroup Database
 * @file
 */

/**
 * @ingroup Database
 */
class DatabaseMssql extends Database {

        var $mAffectedRows;
        var $mLastResult;
        var $mLastError;
        var $mLastErrorNo;
        var $mDatabaseFile;

        /**
         * Constructor
         */
        function __construct($server = false, $user = false, $password = false, $dbName = false,
                        $failFunction = false, $flags = 0, $tablePrefix = 'get from global') {

                global $wgOut, $wgDBprefix, $wgCommandLineMode;
                if (!isset($wgOut)) $wgOut = NULL; # Can't get a reference if it hasn't been set yet
                $this->mOut =& $wgOut;
                $this->mFailFunction = $failFunction;
                $this->mFlags = $flags;

                if ( $this->mFlags & DBO_DEFAULT ) {
                        if ( $wgCommandLineMode ) {
                                $this->mFlags &= ~DBO_TRX;
                        } else {
                                $this->mFlags |= DBO_TRX;
                        }
                }

                /** Get the default table prefix*/
                $this->mTablePrefix = $tablePrefix == 'get from global' ? $wgDBprefix : $tablePrefix;

                if ($server) $this->open($server, $user, $password, $dbName);

        }

        /**
         * todo: check if these should be true like parent class
         */
        function implicitGroupby()   { return false; }
        function implicitOrderby()   { return false; }

        static function newFromParams($server, $user, $password, $dbName, $failFunction = false, $flags = 0) {
                return new DatabaseMssql($server, $user, $password, $dbName, $failFunction, $flags);
        }

        /** Open an MSSQL database and return a resource handle to it
         *  NOTE: only $dbName is used, the other parameters are irrelevant for MSSQL databases
         */
        function open($server,$user,$password,$dbName) {
                wfProfileIn(__METHOD__);

                # Test for missing mysql.so
                # First try to load it
                if (!@extension_loaded('mssql')) {
                        @dl('mssql.so');
                }

                # Fail now
                # Otherwise we get a suppressed fatal error, which is very hard to track down
                if (!function_exists( 'mssql_connect')) {
                        throw new DBConnectionError( $this, "MSSQL functions missing, have you compiled PHP with the --with-mssql option?\n" );
                }

                $this->close();
                $this->mServer   = $server;
                $this->mUser     = $user;
                $this->mPassword = $password;
                $this->mDBname   = $dbName;

                wfProfileIn("dbconnect-$server");

                # Try to connect up to three times
                # The kernel's default SYN retransmission period is far too slow for us,
                # so we use a short timeout plus a manual retry.
                $this->mConn = false;
                $max = 3;
                for ( $i = 0; $i < $max && !$this->mConn; $i++ ) {
                        if ( $i > 1 ) {
                                usleep( 1000 );
                        }
                        if ($this->mFlags & DBO_PERSISTENT) {
                                @/**/$this->mConn = mssql_pconnect($server, $user, $password);
                        } else {
                                # Create a new connection...
                                @/**/$this->mConn = mssql_connect($server, $user, $password, true);
                        }
                }
                
                wfProfileOut("dbconnect-$server");

                if ($dbName != '') {
                        if ($this->mConn !== false) {
                                $success = @/**/mssql_select_db($dbName, $this->mConn);
                                if (!$success) {
                                        $error = "Error selecting database $dbName on server {$this->mServer} " .
                                                "from client host " . wfHostname() . "\n";
                                        wfLogDBError(" Error selecting database $dbName on server {$this->mServer} \n");
                                        wfDebug( $error );
                                }
                        } else {
                                wfDebug("DB connection error\n");
                                wfDebug("Server: $server, User: $user, Password: ".substr($password, 0, 3)."...\n");
                                $success = false;
                        }
                } else {
                        # Delay USE query
                        $success = (bool)$this->mConn;
                }

                if (!$success) $this->reportConnectionError();
                $this->mOpened = $success;
                wfProfileOut(__METHOD__);
                return $success;
        }

        /**
         * Close an MSSQL database
         */
        function close() {
                $this->mOpened = false;
                if ($this->mConn) {
                        if ($this->trxLevel()) $this->immediateCommit();
                        return mssql_close($this->mConn);
                } else return true;
        }

        /**
         * - MSSQL doesn't seem to do buffered results
         * - the trasnaction syntax is modified here to avoid having to replicate
         *   Database::query which uses BEGIN, COMMIT, ROLLBACK
         */
        function doQuery($sql) {
                if ($sql == 'BEGIN' || $sql == 'COMMIT' || $sql == 'ROLLBACK') return true; # $sql .= ' TRANSACTION';
                $sql = preg_replace('|[^\x07-\x7e]|','?',$sql); # TODO: need to fix unicode - just removing it here while testing
                $ret = mssql_query($sql, $this->mConn);
                if ($ret === false) {
                        $err = mssql_get_last_message();
                        if ($err) $this->mlastError = $err;
                        $row = mssql_fetch_row(mssql_query('select @@ERROR'));
                        if ($row[0]) $this->mlastErrorNo = $row[0];
                } else $this->mlastErrorNo = false;
                return $ret;
        }

        /**
         * Free a result object
         */
        function freeResult( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                if ( !@/**/mssql_free_result( $res ) ) {
                        throw new DBUnexpectedError( $this, "Unable to free MSSQL result" );
                }
        }

        /**
         * Fetch the next row from the given result object, in object form.
         * Fields can be retrieved with $row->fieldname, with fields acting like
         * member variables.
         *
         * @param $res SQL result object as returned from Database::query(), etc.
         * @return MySQL row object
         * @throws DBUnexpectedError Thrown if the database returns an error
         */
        function fetchObject( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                @/**/$row = mssql_fetch_object( $res );
                if ( $this->lastErrno() ) {
                        throw new DBUnexpectedError( $this, 'Error in fetchObject(): ' . htmlspecialchars( $this->lastError() ) );
                }
                return $row;
        }

        /**
         * Fetch the next row from the given result object, in associative array
         * form.  Fields are retrieved with $row['fieldname'].
         *
         * @param $res SQL result object as returned from Database::query(), etc.
         * @return MySQL row object
         * @throws DBUnexpectedError Thrown if the database returns an error
         */
        function fetchRow( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                @/**/$row = mssql_fetch_array( $res );
                if ( $this->lastErrno() ) {
                        throw new DBUnexpectedError( $this, 'Error in fetchRow(): ' . htmlspecialchars( $this->lastError() ) );
                }
                return $row;
        }

        /**
         * Get the number of rows in a result object
         */
        function numRows( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                @/**/$n = mssql_num_rows( $res );
                if ( $this->lastErrno() ) {
                        throw new DBUnexpectedError( $this, 'Error in numRows(): ' . htmlspecialchars( $this->lastError() ) );
                }
                return $n;
        }

        /**
         * Get the number of fields in a result object
         * See documentation for mysql_num_fields()
         * @param $res SQL result object as returned from Database::query(), etc.
         */
        function numFields( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return mssql_num_fields( $res );
        }

        /**
         * Get a field name in a result object
         * See documentation for mysql_field_name():
         * http://www.php.net/mysql_field_name
         * @param $res SQL result object as returned from Database::query(), etc.
         * @param $n Int
         */
        function fieldName( $res, $n ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return mssql_field_name( $res, $n );
        }

        /**
         * Get the inserted value of an auto-increment row
         *
         * The value inserted should be fetched from nextSequenceValue()
         *
         * Example:
         * $id = $dbw->nextSequenceValue('page_page_id_seq');
         * $dbw->insert('page',array('page_id' => $id));
         * $id = $dbw->insertId();
         */
        function insertId() {
                $row = mssql_fetch_row(mssql_query('select @@IDENTITY'));
                return $row[0];
        }

        /**
         * Change the position of the cursor in a result object
         * See mysql_data_seek()
         * @param $res SQL result object as returned from Database::query(), etc.
         * @param $row Database row
         */
        function dataSeek( $res, $row ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return mssql_data_seek( $res, $row );
        }

        /**
         * Get the last error number
         */
        function lastErrno() {
                return $this->mlastErrorNo;
        }

        /**
         * Get a description of the last error
         */
        function lastError() {
                return $this->mlastError;
        }

        /**
         * Get the number of rows affected by the last write query
         */
        function affectedRows() {
                return mssql_rows_affected( $this->mConn );
        }

        /**
         * Simple UPDATE wrapper
         * Usually aborts on failure
         * If errors are explicitly ignored, returns success
         *
         * This function exists for historical reasons, Database::update() has a more standard
         * calling convention and feature set
         */
        function set( $table, $var, $value, $cond, $fname = 'Database::set' )
        {
                if ($value == "NULL") $value = "''"; # see comments in makeListWithoutNulls()
                $table = $this->tableName( $table );
                $sql = "UPDATE $table SET $var = '" .
                  $this->strencode( $value ) . "' WHERE ($cond)";
                return (bool)$this->query( $sql, $fname );
        }

        /**
         * Simple SELECT wrapper, returns a single field, input must be encoded
         * Usually aborts on failure
         * If errors are explicitly ignored, returns FALSE on failure
         */
        function selectField( $table, $var, $cond='', $fname = 'Database::selectField', $options = array() ) {
                if ( !is_array( $options ) ) {
                        $options = array( $options );
                }
                $options['LIMIT'] = 1;

                $res = $this->select( $table, $var, $cond, $fname, $options );
                if ( $res === false || !$this->numRows( $res ) ) {
                        return false;
                }
                $row = $this->fetchRow( $res );
                if ( $row !== false ) {
                        $this->freeResult( $res );
                        return $row[0];
                } else {
                        return false;
                }
        }

        /**
         * Returns an optional USE INDEX clause to go after the table, and a
         * string to go at the end of the query
         *
         * @private
         *
         * @param $options Array: an associative array of options to be turned into
         *              an SQL query, valid keys are listed in the function.
         * @return array
         */
        function makeSelectOptions( $options ) {
                $preLimitTail = $postLimitTail = '';
                $startOpts = '';

                $noKeyOptions = array();
                foreach ( $options as $key => $option ) {
                        if ( is_numeric( $key ) ) {
                                $noKeyOptions[$option] = true;
                        }
                }

                if ( isset( $options['GROUP BY'] ) ) $preLimitTail .= " GROUP BY {$options['GROUP BY']}";
                if ( isset( $options['HAVING'] ) ) $preLimitTail .= " HAVING {$options['HAVING']}";
                if ( isset( $options['ORDER BY'] ) ) $preLimitTail .= " ORDER BY {$options['ORDER BY']}";
                
                //if (isset($options['LIMIT'])) {
                //      $tailOpts .= $this->limitResult('', $options['LIMIT'],
                //              isset($options['OFFSET']) ? $options['OFFSET'] 
                //              : false);
                //}

                if ( isset( $noKeyOptions['FOR UPDATE'] ) ) $postLimitTail .= ' FOR UPDATE';
                if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) $postLimitTail .= ' LOCK IN SHARE MODE';
                if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) $startOpts .= 'DISTINCT';

                # Various MySQL extensions
                if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) $startOpts .= ' /*! STRAIGHT_JOIN */';
                if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) $startOpts .= ' HIGH_PRIORITY';
                if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) $startOpts .= ' SQL_BIG_RESULT';
                if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) $startOpts .= ' SQL_BUFFER_RESULT';
                if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) $startOpts .= ' SQL_SMALL_RESULT';
                if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) $startOpts .= ' SQL_CALC_FOUND_ROWS';
                if ( isset( $noKeyOptions['SQL_CACHE'] ) ) $startOpts .= ' SQL_CACHE';
                if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) $startOpts .= ' SQL_NO_CACHE';

                if ( isset( $options['USE INDEX'] ) && ! is_array( $options['USE INDEX'] ) ) {
                        $useIndex = $this->useIndexClause( $options['USE INDEX'] );
                } else {
                        $useIndex = '';
                }
                
                return array( $startOpts, $useIndex, $preLimitTail, $postLimitTail );
        }

        /**
         * SELECT wrapper
         *
         * @param $table   Mixed: Array or string, table name(s) (prefix auto-added)
         * @param $vars    Mixed: Array or string, field name(s) to be retrieved
         * @param $conds   Mixed: Array or string, condition(s) for WHERE
         * @param $fname   String: Calling function name (use __METHOD__) for logs/profiling
         * @param $options Array: Associative array of options (e.g. array('GROUP BY' => 'page_title')),
         *                        see Database::makeSelectOptions code for list of supported stuff
         * @return mixed Database result resource (feed to Database::fetchObject or whatever), or false on failure
         */
        function select( $table, $vars, $conds='', $fname = 'Database::select', $options = array() )
        {
                if( is_array( $vars ) ) {
                        $vars = implode( ',', $vars );
                }
                if( !is_array( $options ) ) {
                        $options = array( $options );
                }
                if( is_array( $table ) ) {
                        if ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
                                $from = ' FROM ' . $this->tableNamesWithUseIndex( $table, $options['USE INDEX'] );
                        else
                                $from = ' FROM ' . implode( ',', array_map( array( &$this, 'tableName' ), $table ) );
                } elseif ($table!='') {
                        if ($table{0}==' ') {
                                $from = ' FROM ' . $table;
                        } else {
                                $from = ' FROM ' . $this->tableName( $table );
                        }
                } else {
                        $from = '';
                }

                list( $startOpts, $useIndex, $preLimitTail, $postLimitTail ) = $this->makeSelectOptions( $options );

                if( !empty( $conds ) ) {
                        if ( is_array( $conds ) ) {
                                $conds = $this->makeList( $conds, LIST_AND );
                        }
                        $sql = "SELECT $startOpts $vars $from $useIndex WHERE $conds $preLimitTail";
                } else {
                        $sql = "SELECT $startOpts $vars $from $useIndex $preLimitTail";
                }

                if (isset($options['LIMIT']))
                        $sql = $this->limitResult($sql, $options['LIMIT'],
                                isset($options['OFFSET']) ? $options['OFFSET'] : false);
                $sql = "$sql $postLimitTail";
                
                if (isset($options['EXPLAIN'])) {
                        $sql = 'EXPLAIN ' . $sql;
                }
                return $this->query( $sql, $fname );
        }

        /**
         * Estimate rows in dataset
         * Returns estimated count, based on EXPLAIN output
         * Takes same arguments as Database::select()
         */
        function estimateRowCount( $table, $vars='*', $conds='', $fname = 'Database::estimateRowCount', $options = array() ) {
                $rows = 0;
                $res = $this->select ($table, 'COUNT(*)', $conds, $fname, $options );
                if ($res) {
                        $row = $this->fetchObject($res);
                        $rows = $row[0];
                }
                $this->freeResult($res);
                return $rows;
        }
        
        /**
         * Determines whether a field exists in a table
         * Usually aborts on failure
         * If errors are explicitly ignored, returns NULL on failure
         */
        function fieldExists( $table, $field, $fname = 'Database::fieldExists' ) {
                $table = $this->tableName( $table );
                $sql = "SELECT TOP 1 * FROM $table";
                $res = $this->query( $sql, 'Database::fieldExists' );

                $found = false;
                while ( $row = $this->fetchArray( $res ) ) {
                        if ( isset($row[$field]) ) {
                                $found = true;
                                break;
                        }
                }

                $this->freeResult( $res );
                return $found;
        }

        /**
         * Get information about an index into an object
         * Returns false if the index does not exist
         */
        function indexInfo( $table, $index, $fname = 'Database::indexInfo' ) {

                throw new DBUnexpectedError( $this, 'Database::indexInfo called which is not supported yet' );
                return NULL;

                $table = $this->tableName( $table );
                $sql = 'SHOW INDEX FROM '.$table;
                $res = $this->query( $sql, $fname );
                if ( !$res ) {
                        return NULL;
                }

                $result = array();
                while ( $row = $this->fetchObject( $res ) ) {
                        if ( $row->Key_name == $index ) {
                                $result[] = $row;
                        }
                }
                $this->freeResult($res);
                
                return empty($result) ? false : $result;
        }

        /**
         * Query whether a given table exists
         */
        function tableExists( $table ) {
                $table = $this->tableName( $table );
                $res = $this->query( "SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = '$table'" );
                $exist = ($res->numRows() > 0);
                $this->freeResult($res);
                return $exist;
        }

        /**
         * mysql_fetch_field() wrapper
         * Returns false if the field doesn't exist
         *
         * @param $table
         * @param $field
         */
        function fieldInfo( $table, $field ) {
                $table = $this->tableName( $table );
                $res = $this->query( "SELECT TOP 1 * FROM $table" );
                $n = mssql_num_fields( $res->result );
                for( $i = 0; $i < $n; $i++ ) {
                        $meta = mssql_fetch_field( $res->result, $i );
                        if( $field == $meta->name ) {
                                return new MSSQLField($meta);
                        }
                }
                return false;
        }

        /**
         * mysql_field_type() wrapper
         */
        function fieldType( $res, $index ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return mssql_field_type( $res, $index );
        }

        /**
         * INSERT wrapper, inserts an array into a table
         *
         * $a may be a single associative array, or an array of these with numeric keys, for
         * multi-row insert.
         *
         * Usually aborts on failure
         * If errors are explicitly ignored, returns success
         * 
         * Same as parent class implementation except that it removes primary key from column lists
         * because MSSQL doesn't support writing nulls to IDENTITY (AUTO_INCREMENT) columns
         */
        function insert( $table, $a, $fname = 'Database::insert', $options = array() ) {
                # No rows to insert, easy just return now
                if ( !count( $a ) ) {
                        return true;
                }
                $table = $this->tableName( $table );
                if ( !is_array( $options ) ) {
                        $options = array( $options );
                }
                
                # todo: need to record primary keys at table create time, and remove NULL assignments to them
                if ( isset( $a[0] ) && is_array( $a[0] ) ) {
                        $multi = true;
                        $keys = array_keys( $a[0] );
#                       if (ereg('_id$',$keys[0])) {
                                foreach ($a as $i) {
                                        if (is_null($i[$keys[0]])) unset($i[$keys[0]]); # remove primary-key column from multiple insert lists if empty value
                                }
#                       }
                        $keys = array_keys( $a[0] );
                } else {
                        $multi = false;
                        $keys = array_keys( $a );
#                       if (ereg('_id$',$keys[0]) && empty($a[$keys[0]])) unset($a[$keys[0]]); # remove primary-key column from insert list if empty value
                        if (is_null($a[$keys[0]])) unset($a[$keys[0]]); # remove primary-key column from insert list if empty value
                        $keys = array_keys( $a );
                }

                # handle IGNORE option
                # example:
                #   MySQL: INSERT IGNORE INTO user_groups (ug_user,ug_group) VALUES ('1','sysop')
                #   MSSQL: IF NOT EXISTS (SELECT * FROM user_groups WHERE ug_user = '1') INSERT INTO user_groups (ug_user,ug_group) VALUES ('1','sysop')
                $ignore = in_array('IGNORE',$options);

                # remove IGNORE from options list
                if ($ignore) {
                        $oldoptions = $options;
                        $options = array();
                        foreach ($oldoptions as $o) if ($o != 'IGNORE') $options[] = $o;
                }

                $keylist = implode(',', $keys);
                $sql = 'INSERT '.implode(' ', $options)." INTO $table (".implode(',', $keys).') VALUES ';
                if ($multi) {
                        if ($ignore) {
                                # If multiple and ignore, then do each row as a separate conditional insert
                                foreach ($a as $row) {
                                        $prival = $row[$keys[0]];
                                        $sql = "IF NOT EXISTS (SELECT * FROM $table WHERE $keys[0] = '$prival') $sql";
                                        if (!$this->query("$sql (".$this->makeListWithoutNulls($row).')', $fname)) return false;
                                }
                                return true;
                        } else {
                                $first = true;
                                foreach ($a as $row) {
                                        if ($first) $first = false; else $sql .= ',';
                                        $sql .= '('.$this->makeListWithoutNulls($row).')';
                                }
                        }
                } else {
                        if ($ignore) {
                                $prival = $a[$keys[0]];
                                $sql = "IF NOT EXISTS (SELECT * FROM $table WHERE $keys[0] = '$prival') $sql";
                        }
                        $sql .= '('.$this->makeListWithoutNulls($a).')';
                }
                return (bool)$this->query( $sql, $fname );
        }

        /**
         * MSSQL doesn't allow implicit casting of NULL's into non-null values for NOT NULL columns
         *   for now I've just converted the NULL's in the lists for updates and inserts into empty strings
         *   which get implicitly casted to 0 for numeric columns
         * NOTE: the set() method above converts NULL to empty string as well but not via this method
         */
        function makeListWithoutNulls($a, $mode = LIST_COMMA) {
                return str_replace("NULL","''",$this->makeList($a,$mode));
        }

        /**
         * UPDATE wrapper, takes a condition array and a SET array
         *
         * @param $table   String: The table to UPDATE
         * @param $values  Array: An array of values to SET
         * @param $conds   Array: An array of conditions (WHERE). Use '*' to update all rows.
         * @param $fname   String: The Class::Function calling this function
         *                        (for the log)
         * @param $options Array: An array of UPDATE options, can be one or
         *                        more of IGNORE, LOW_PRIORITY
         * @return bool
         */
        function update( $table, $values, $conds, $fname = 'Database::update', $options = array() ) {
                $table = $this->tableName( $table );
                $opts = $this->makeUpdateOptions( $options );
                $sql = "UPDATE $opts $table SET " . $this->makeListWithoutNulls( $values, LIST_SET );
                if ( $conds != '*' ) {
                        $sql .= " WHERE " . $this->makeList( $conds, LIST_AND );
                }
                return $this->query( $sql, $fname );
        }

        /**
         * Make UPDATE options for the Database::update function
         *
         * @private
         * @param $options Array: The options passed to Database::update
         * @return string
         */
        function makeUpdateOptions( $options ) {
                if( !is_array( $options ) ) {
                        $options = array( $options );
                }
                $opts = array();
                if ( in_array( 'LOW_PRIORITY', $options ) )
                        $opts[] = $this->lowPriorityOption();
                if ( in_array( 'IGNORE', $options ) )
                        $opts[] = 'IGNORE';
                return implode(' ', $opts);
        }

        /**
         * Change the current database
         */
        function selectDB( $db ) {
                $this->mDBname = $db;
                return mssql_select_db( $db, $this->mConn );
        }

        /**
         * MSSQL has a problem with the backtick quoting, so all this does is ensure the prefix is added exactly once
         */
        function tableName($name) {
                return strpos($name, $this->mTablePrefix) === 0 ? $name : "{$this->mTablePrefix}$name";
        }

        /**
         * MSSQL doubles quotes instead of escaping them
         * @param $s String to be slashed.
         * @return string slashed string.
         */
        function strencode($s) {
                return str_replace("'","''",$s);
        }

        /**
         * USE INDEX clause
         */
        function useIndexClause( $index ) {
                return "";
        }

        /**
         * REPLACE query wrapper
         * PostgreSQL simulates this with a DELETE followed by INSERT
         * $row is the row to insert, an associative array
         * $uniqueIndexes is an array of indexes. Each element may be either a
         * field name or an array of field names
         *
         * It may be more efficient to leave off unique indexes which are unlikely to collide.
         * However if you do this, you run the risk of encountering errors which wouldn't have
         * occurred in MySQL
         *
         * @todo migrate comment to phodocumentor format
         */
        function replace( $table, $uniqueIndexes, $rows, $fname = 'Database::replace' ) {
                $table = $this->tableName( $table );

                # Single row case
                if ( !is_array( reset( $rows ) ) ) {
                        $rows = array( $rows );
                }

                $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) .') VALUES ';
                $first = true;
                foreach ( $rows as $row ) {
                        if ( $first ) {
                                $first = false;
                        } else {
                                $sql .= ',';
                        }
                        $sql .= '(' . $this->makeList( $row ) . ')';
                }
                return $this->query( $sql, $fname );
        }

        /**
         * DELETE where the condition is a join
         * MySQL does this with a multi-table DELETE syntax, PostgreSQL does it with sub-selects
         *
         * For safety, an empty $conds will not delete everything. If you want to delete all rows where the
         * join condition matches, set $conds='*'
         *
         * DO NOT put the join condition in $conds
         *
         * @param $delTable String: The table to delete from.
         * @param $joinTable String: The other table.
         * @param $delVar String: The variable to join on, in the first table.
         * @param $joinVar String: The variable to join on, in the second table.
         * @param $conds Array: Condition array of field names mapped to variables, ANDed together in the WHERE clause
         * @param $fname String: Calling function name
         */
        function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds, $fname = 'Database::deleteJoin' ) {
                if ( !$conds ) {
                        throw new DBUnexpectedError( $this, 'Database::deleteJoin() called with empty $conds' );
                }

                $delTable = $this->tableName( $delTable );
                $joinTable = $this->tableName( $joinTable );
                $sql = "DELETE $delTable FROM $delTable, $joinTable WHERE $delVar=$joinVar ";
                if ( $conds != '*' ) {
                        $sql .= ' AND ' . $this->makeList( $conds, LIST_AND );
                }

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

        /**
         * Returns the size of a text field, or -1 for "unlimited"
         */
        function textFieldSize( $table, $field ) {
                $table = $this->tableName( $table );
                $sql = "SELECT TOP 1 * FROM $table;";
                $res = $this->query( $sql, 'Database::textFieldSize' );
                $row = $this->fetchObject( $res );
                $this->freeResult( $res );

                $m = array();
                if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
                        $size = $m[1];
                } else {
                        $size = -1;
                }
                return $size;
        }

        /**
         * @return string Returns the text of the low priority option if it is supported, or a blank string otherwise
         */
        function lowPriorityOption() {
                return 'LOW_PRIORITY';
        }

        /**
         * INSERT SELECT wrapper
         * $varMap must be an associative array of the form array( 'dest1' => 'source1', ...)
         * Source items may be literals rather than field names, but strings should be quoted with Database::addQuotes()
         * $conds may be "*" to copy the whole table
         * srcTable may be an array of tables.
         */
        function insertSelect( $destTable, $srcTable, $varMap, $conds, $fname = 'Database::insertSelect',
                $insertOptions = array(), $selectOptions = array() )
        {
                $destTable = $this->tableName( $destTable );
                if ( is_array( $insertOptions ) ) {
                        $insertOptions = implode( ' ', $insertOptions );
                }
                if( !is_array( $selectOptions ) ) {
                        $selectOptions = array( $selectOptions );
                }
                list( $startOpts, $useIndex, $tailOpts ) = $this->makeSelectOptions( $selectOptions );
                if( is_array( $srcTable ) ) {
                        $srcTable =  implode( ',', array_map( array( &$this, 'tableName' ), $srcTable ) );
                } else {
                        $srcTable = $this->tableName( $srcTable );
                }
                $sql = "INSERT $insertOptions INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ')' .
                        " SELECT $startOpts " . implode( ',', $varMap ) .
                        " FROM $srcTable $useIndex ";
                if ( $conds != '*' ) {
                        $sql .= ' WHERE ' . $this->makeList( $conds, LIST_AND );
                }
                $sql .= " $tailOpts";
                return $this->query( $sql, $fname );
        }

        /**
         * Construct a LIMIT query with optional offset
         * This is used for query pages
         * $sql string SQL query we will append the limit to
         * $limit integer the SQL limit
         * $offset integer the SQL offset (default false)
         */
        function limitResult($sql, $limit, $offset=false) {
                if( !is_numeric($limit) ) {
                        throw new DBUnexpectedError( $this, "Invalid non-numeric limit passed to limitResult()\n" );
                }
                if ($offset) {
                        throw new DBUnexpectedError( $this, 'Database::limitResult called with non-zero offset which is not supported yet' );
                } else {
                        $sql = ereg_replace("^SELECT", "SELECT TOP $limit", $sql);
                }
                return $sql;
        }

        /**
         * Returns an SQL expression for a simple conditional.
         *
         * @param $cond String: SQL expression which will result in a boolean value
         * @param $trueVal String: SQL expression to return if true
         * @param $falseVal String: SQL expression to return if false
         * @return string SQL fragment
         */
        function conditional( $cond, $trueVal, $falseVal ) {
                return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
        }

        /**
         * Should determine if the last failure was due to a deadlock
         * @return bool
         */
        function wasDeadlock() {
                return $this->lastErrno() == 1205;
        }

        /**
         * Begin a transaction, committing any previously open transaction
         * @deprecated use begin()
         */
        function immediateBegin( $fname = 'Database::immediateBegin' ) {
                $this->begin();
        }

        /**
         * Commit transaction, if one is open
         * @deprecated use commit()
         */
        function immediateCommit( $fname = 'Database::immediateCommit' ) {
                $this->commit();
        }

        /**
         * Return MW-style timestamp used for MySQL schema
         */
        function timestamp( $ts=0 ) {
                return wfTimestamp(TS_MW,$ts);
        }

        /**
         * Local database timestamp format or null
         */
        function timestampOrNull( $ts = null ) {
                if( is_null( $ts ) ) {
                        return null;
                } else {
                        return $this->timestamp( $ts );
                }
        }

        /**
         * @return string wikitext of a link to the server software's web site
         */
        function getSoftwareLink() {
                return "[http://www.microsoft.com/sql/default.mspx Microsoft SQL Server 2005 Home]";
        }

        /**
         * @return string Version information from the database
         */
        function getServerVersion() {
                $row = mssql_fetch_row(mssql_query('select @@VERSION'));
                return ereg("^(.+[0-9]+\\.[0-9]+\\.[0-9]+) ",$row[0],$m) ? $m[1] : $row[0];
        }

        function limitResultForUpdate($sql, $num) {
                return $sql;
        }

        /**
         * not done
         */
        public function setTimeout($timeout) { return; }

        function ping() {
                wfDebug("Function ping() not written for MSSQL yet");
                return true;
        }

        /**
         * How lagged is this slave?
         */
        public function getLag() {
                return 0;
        }

        /**
         * Called by the installer script
         * - this is the same way as DatabasePostgresql.php, MySQL reads in tables.sql and interwiki.sql using dbsource (which calls db->sourceFile)
         */
        public function setup_database() {
                global $IP,$wgDBTableOptions;
                $wgDBTableOptions = '';
                $mysql_tmpl = "$IP/maintenance/tables.sql";
                $mysql_iw   = "$IP/maintenance/interwiki.sql";
                $mssql_tmpl = "$IP/maintenance/mssql/tables.sql";

                # Make an MSSQL template file if it doesn't exist (based on the same one MySQL uses to create a new wiki db)
                if (!file_exists($mssql_tmpl)) { # todo: make this conditional again
                        $sql = file_get_contents($mysql_tmpl);
                        $sql = preg_replace('/^\s*--.*?$/m','',$sql); # strip comments
                        $sql = preg_replace('/^\s*(UNIQUE )?(INDEX|KEY|FULLTEXT).+?$/m', '', $sql); # These indexes should be created with a CREATE INDEX query
                        $sql = preg_replace('/(\sKEY) [^\(]+\(/is', '$1 (', $sql); # "KEY foo (foo)" should just be "KEY (foo)"
                        $sql = preg_replace('/(varchar\([0-9]+\))\s+binary/i', '$1', $sql); # "varchar(n) binary" cannot be followed by "binary"
                        $sql = preg_replace('/(var)?binary\(([0-9]+)\)/ie', '"varchar(".strlen(pow(2,$2)).")"', $sql); # use varchar(chars) not binary(bits)
                        $sql = preg_replace('/ (var)?binary/i', ' varchar', $sql); # use varchar not binary
                        $sql = preg_replace('/(varchar\([0-9]+\)(?! N))/', '$1 NULL', $sql); # MSSQL complains if NULL is put into a varchar
                        #$sql = preg_replace('/ binary/i',' varchar',$sql); # MSSQL binary's can't be assigned with strings, so use varchar's instead
                        #$sql = preg_replace('/(binary\([0-9]+\) (NOT NULL )?default) [\'"].*?[\'"]/i','$1 0',$sql); # binary default cannot be string
                        $sql = preg_replace('/[a-z]*(blob|text)([ ,])/i', 'text$2', $sql); # no BLOB types in MSSQL
                        $sql = preg_replace('/\).+?;/',');', $sql); # remove all table options
                        $sql = preg_replace('/ (un)?signed/i', '', $sql);
                        $sql = preg_replace('/ENUM\(.+?\)/','TEXT',$sql); # Make ENUM's into TEXT's
                        $sql = str_replace(' bool ', ' bit ', $sql);
                        $sql = str_replace('auto_increment', 'IDENTITY(1,1)', $sql);
                        #$sql = preg_replace('/NOT NULL(?! IDENTITY)/', 'NULL', $sql); # Allow NULL's for non IDENTITY columns

                        # Tidy up and write file
                        $sql = preg_replace('/,\s*\)/s', "\n)", $sql); # Remove spurious commas left after INDEX removals
                        $sql = preg_replace('/^\s*^/m', '', $sql); # Remove empty lines
                        $sql = preg_replace('/;$/m', ";\n", $sql); # Separate each statement with an empty line
                        file_put_contents($mssql_tmpl, $sql);
                }

                # Parse the MSSQL template replacing inline variables such as /*$wgDBprefix*/
                $err = $this->sourceFile($mssql_tmpl);
                if ($err !== true) $this->reportQueryError($err,0,$sql,__FUNCTION__);

                # Use DatabasePostgres's code to populate interwiki from MySQL template
                $f = fopen($mysql_iw,'r');
                if ($f == false) dieout("<li>Could not find the interwiki.sql file");
                $sql = "INSERT INTO {$this->mTablePrefix}interwiki(iw_prefix,iw_url,iw_local) VALUES ";
                while (!feof($f)) {
                        $line = fgets($f,1024);
                        $matches = array();
                        if (!preg_match('/^\s*(\(.+?),(\d)\)/', $line, $matches)) continue;
                        $this->query("$sql $matches[1],$matches[2])");
                }
        }
        
        /** 
         * No-op lock functions
         */
        public function lock( $lockName, $method ) {
                return true;
        }
        public function unlock( $lockName, $method ) {
                return true;
        }
        
        public function getSearchEngine() {
                return "SearchEngineDummy";
        }

}

/**
 * @ingroup Database
 */
class MSSQLField extends MySQLField {

        function __construct() {
        }

        static function fromText($db, $table, $field) {
                $n = new MSSQLField;
                $n->name = $field;
                $n->tablename = $table;
                return $n;
        }

} // end DatabaseMssql class