* changed display function for length to Linker::formatRevisionSize

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

<?php
/**
 * This is the MS SQL Server Native database abstraction layer.
 *
 * @file
 * @ingroup Database
 * @author Joel Penner <a-joelpe at microsoft dot com>
 * @author Chris Pucci <a-cpucci at microsoft dot com>
 * @author Ryan Biesemeyer <v-ryanbi at microsoft dot com>
 */

/**
 * @ingroup Database
 */
class DatabaseMssql extends DatabaseBase {
        var $mInsertId = NULL;
        var $mLastResult = NULL;
        var $mAffectedRows = NULL;

        var $mPort;

        function cascadingDeletes() {
                return true;
        }
        function cleanupTriggers() {
                return true;
        }
        function strictIPs() {
                return true;
        }
        function realTimestamps() {
                return true;
        }
        function implicitGroupby() {
                return false;
        }
        function implicitOrderby() {
                return false;
        }
        function functionalIndexes() {
                return true;
        }
        function unionSupportsOrderAndLimit() {
                return false;
        }

        /**
         * Usually aborts on failure
         */
        function open( $server, $user, $password, $dbName ) {
                # Test for driver support, to avoid suppressed fatal error
                if ( !function_exists( 'sqlsrv_connect' ) ) {
                        throw new DBConnectionError( $this, "MS Sql Server Native (sqlsrv) functions missing. You can download the driver from: http://go.microsoft.com/fwlink/?LinkId=123470\n" );
                }

                global $wgDBport;

                if ( !strlen( $user ) ) { # e.g. the class is being loaded
                        return;
                }

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

                $connectionInfo = array();

                if( $dbName ) {
                        $connectionInfo['Database'] = $dbName;
                }

                // Start NT Auth Hack
                // Quick and dirty work around to provide NT Auth designation support.
                // Current solution requires installer to know to input 'ntauth' for both username and password
                // to trigger connection via NT Auth. - ugly, ugly, ugly
                // TO-DO: Make this better and add NT Auth choice to MW installer when SQL Server option is chosen.
                $ntAuthUserTest = strtolower( $user );
                $ntAuthPassTest = strtolower( $password );

                // Decide which auth scenerio to use
                if( $ntAuthPassTest == 'ntauth' && $ntAuthUserTest == 'ntauth' ){
                        // Don't add credentials to $connectionInfo
                } else {
                        $connectionInfo['UID'] = $user;
                        $connectionInfo['PWD'] = $password;
                }
                // End NT Auth Hack

                wfSuppressWarnings();
                $this->mConn = sqlsrv_connect( $server, $connectionInfo );
                wfRestoreWarnings();

                if ( $this->mConn === false ) {
                        wfDebug( "DB connection error\n" );
                        wfDebug( "Server: $server, Database: $dbName, User: $user, Password: " . substr( $password, 0, 3 ) . "...\n" );
                        wfDebug( $this->lastError() . "\n" );
                        return false;
                }

                $this->mOpened = true;
                return $this->mConn;
        }

        /**
         * Closes a database connection, if it is open
         * Returns success, true if already closed
         */
        function close() {
                $this->mOpened = false;
                if ( $this->mConn ) {
                        return sqlsrv_close( $this->mConn );
                } else {
                        return true;
                }
        }

        function doQuery( $sql ) {
                wfDebug( "SQL: [$sql]\n" );
                $this->offset = 0;

                // several extensions seem to think that all databases support limits via LIMIT N after the WHERE clause
                // well, MSSQL uses SELECT TOP N, so to catch any of those extensions we'll do a quick check for a LIMIT
                // clause and pass $sql through $this->LimitToTopN() which parses the limit clause and passes the result to
                // $this->limitResult();
                if ( preg_match( '/\bLIMIT\s*/i', $sql ) ) {
                        // massage LIMIT -> TopN
                        $sql = $this->LimitToTopN( $sql ) ;
                }

                // MSSQL doesn't have EXTRACT(epoch FROM XXX)
                if ( preg_match('#\bEXTRACT\s*?\(\s*?EPOCH\s+FROM\b#i', $sql, $matches ) ) {
                        // This is same as UNIX_TIMESTAMP, we need to calc # of seconds from 1970
                        $sql = str_replace( $matches[0], "DATEDIFF(s,CONVERT(datetime,'1/1/1970'),", $sql );
                }

                // perform query
                $stmt = sqlsrv_query( $this->mConn, $sql );
                if ( $stmt == false ) {
                        $message = "A database error has occurred.  Did you forget to run maintenance/update.php after upgrading?  See: http://www.mediawiki.org/wiki/Manual:Upgrading#Run_the_update_script\n" .
                                "Query: " . htmlentities( $sql ) . "\n" .
                                "Function: " . __METHOD__ . "\n";
                        // process each error (our driver will give us an array of errors unlike other providers)
                        foreach ( sqlsrv_errors() as $error ) {
                                $message .= $message . "ERROR[" . $error['code'] . "] " . $error['message'] . "\n";
                        }

                        throw new DBUnexpectedError( $this, $message );
                }
                // remember number of rows affected
                $this->mAffectedRows = sqlsrv_rows_affected( $stmt );

                // if it is a SELECT statement, or an insert with a request to output something we want to return a row.
                if ( ( preg_match( '#\bSELECT\s#i', $sql ) ) ||
                        ( preg_match( '#\bINSERT\s#i', $sql ) && preg_match( '#\bOUTPUT\s+INSERTED\b#i', $sql ) ) ) {
                        // this is essentially a rowset, but Mediawiki calls these 'result'
                        // the rowset owns freeing the statement
                        $res = new MssqlResult( $stmt );
                } else {
                        // otherwise we simply return it was successful, failure throws an exception
                        $res = true;
                }
                return $res;
        }

        function freeResult( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                $res->free();
        }

        function fetchObject( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                $row = $res->fetch( 'OBJECT' );
                return $row;
        }

        function getErrors() {
                $strRet = '';
                $retErrors = sqlsrv_errors( SQLSRV_ERR_ALL );
                if ( $retErrors != null ) {
                        foreach ( $retErrors as $arrError ) {
                                $strRet .= "SQLState: " . $arrError[ 'SQLSTATE'] . "\n";
                                $strRet .= "Error Code: " . $arrError[ 'code'] . "\n";
                                $strRet .= "Message: " . $arrError[ 'message'] . "\n";
                        }
                } else {
                        $strRet = "No errors found";
                }
                return $strRet;
        }

        function fetchRow( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                $row = $res->fetch( SQLSRV_FETCH_BOTH );
                return $row;
        }

        function numRows( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return ( $res ) ? $res->numrows() : 0;
        }

        function numFields( $res ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return ( $res ) ? $res->numfields() : 0;
        }

        function fieldName( $res, $n ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return ( $res ) ? $res->fieldname( $n ) : 0;
        }

        /**
         * This must be called after nextSequenceVal
         */
        function insertId() {
                return $this->mInsertId;
        }

        function dataSeek( $res, $row ) {
                if ( $res instanceof ResultWrapper ) {
                        $res = $res->result;
                }
                return ( $res ) ? $res->seek( $row ) : false;
        }

        function lastError() {
                if ( $this->mConn ) {
                        return $this->getErrors();
                } else {
                        return "No database connection";
                }
        }

        function lastErrno() {
                $err = sqlsrv_errors( SQLSRV_ERR_ALL );
                if ( $err[0] ) {
                        return $err[0]['code'];
                } else {
                        return 0;
                }
        }

        function affectedRows() {
                return $this->mAffectedRows;
        }

        /**
         * 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
         * @param $join_conds Array: Associative array of table join conditions (optional)
         *                                                 (e.g. array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
         * @return Mixed: database result resource (feed to Database::fetchObject or whatever), or false on failure
         */
        function select( $table, $vars, $conds = '', $fname = 'DatabaseMssql::select', $options = array(), $join_conds = array() )
        {
                $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
                if ( isset( $options['EXPLAIN'] ) ) {
                        sqlsrv_query( $this->mConn, "SET SHOWPLAN_ALL ON;" );
                        $ret = $this->query( $sql, $fname );
                        sqlsrv_query( $this->mConn, "SET SHOWPLAN_ALL OFF;" );
                        return $ret;
                }
                return $this->query( $sql, $fname );
        }

        /**
         * 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
         * @param $join_conds Array: Associative array of table join conditions (optional)
         *                    (e.g. array( 'page' => array('LEFT JOIN','page_latest=rev_id') )
         * @return string, the SQL text
         */
        function selectSQLText( $table, $vars, $conds = '', $fname = 'DatabaseMssql::select', $options = array(), $join_conds = array() ) {
                if ( isset( $options['EXPLAIN'] ) ) {
                        unset( $options['EXPLAIN'] );
                }
                return parent::selectSQLText(  $table, $vars, $conds, $fname, $options, $join_conds );
        }

        /**
         * Estimate rows in dataset
         * Returns estimated count, based on SHOWPLAN_ALL output
         * This is not necessarily an accurate estimate, so use sparingly
         * Returns -1 if count cannot be found
         * Takes same arguments as Database::select()
         */
        function estimateRowCount( $table, $vars = '*', $conds = '', $fname = 'DatabaseMssql::estimateRowCount', $options = array() ) {
                $options['EXPLAIN'] = true;// http://msdn2.microsoft.com/en-us/library/aa259203.aspx
                $res = $this->select( $table, $vars, $conds, $fname, $options );

                $rows = -1;
                if ( $res ) {
                        $row = $this->fetchRow( $res );
                        if ( isset( $row['EstimateRows'] ) ) $rows = $row['EstimateRows'];
                }
                return $rows;
        }

        /**
         * Returns information about an index
         * If errors are explicitly ignored, returns NULL on failure
         */
        function indexInfo( $table, $index, $fname = 'DatabaseMssql::indexExists' ) {
                # This does not return the same info as MYSQL would, but that's OK because MediaWiki never uses the
                # returned value except to check for the existance of indexes.
                $sql = "sp_helpindex '" . $table . "'";
                $res = $this->query( $sql, $fname );
                if ( !$res ) {
                        return NULL;
                }

                $result = array();
                foreach ( $res as $row ) {
                        if ( $row->index_name == $index ) {
                                $row->Non_unique = !stristr( $row->index_description, "unique" );
                                $cols = explode( ", ", $row->index_keys );
                                foreach ( $cols as $col ) {
                                        $row->Column_name = trim( $col );
                                        $result[] = clone $row;
                                }
                        } else if ( $index == 'PRIMARY' && stristr( $row->index_description, 'PRIMARY' ) ) {
                                $row->Non_unique = 0;
                                $cols = explode( ", ", $row->index_keys );
                                foreach ( $cols as $col ) {
                                        $row->Column_name = trim( $col );
                                        $result[] = clone $row;
                                }
                        }
                }
                return empty( $result ) ? false : $result;
        }

        /**
         * INSERT wrapper, inserts an array into a table
         *
         * $arrToInsert 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
         */
        function insert( $table, $arrToInsert, $fname = 'DatabaseMssql::insert', $options = array() ) {
                # No rows to insert, easy just return now
                if ( !count( $arrToInsert ) ) {
                        return true;
                }

                if ( !is_array( $options ) ) {
                        $options = array( $options );
                }

                $table = $this->tableName( $table );

                if ( !( isset( $arrToInsert[0] ) && is_array( $arrToInsert[0] ) ) ) {// Not multi row
                        $arrToInsert = array( 0 => $arrToInsert );// make everything multi row compatible
                }

                $allOk = true;

                // We know the table we're inserting into, get its identity column
                $identity = null;
                $tableRaw = preg_replace( '#\[([^\]]*)\]#', '$1', $table ); // strip matching square brackets from table name
                $res = $this->doQuery( "SELECT NAME AS idColumn FROM SYS.IDENTITY_COLUMNS WHERE OBJECT_NAME(OBJECT_ID)='{$tableRaw}'" );
                if( $res && $res->numrows() ){
                        // There is an identity for this table.
                        $identity = array_pop( $res->fetch( SQLSRV_FETCH_ASSOC ) );
                }
                unset( $res );

                foreach ( $arrToInsert as $a ) {
                        // start out with empty identity column, this is so we can return it as a result of the insert logic
                        $sqlPre = '';
                        $sqlPost = '';
                        $identityClause = '';

                        // if we have an identity column
                        if( $identity ) {
                                // iterate through
                                foreach ($a as $k => $v ) {
                                        if ( $k == $identity ) {
                                                if( !is_null($v) ){
                                                        // there is a value being passed to us, we need to turn on and off inserted identity
                                                        $sqlPre = "SET IDENTITY_INSERT $table ON;" ;
                                                        $sqlPost = ";SET IDENTITY_INSERT $table OFF;";

                                                } else {
                                                        // we can't insert NULL into an identity column, so remove the column from the insert.
                                                        unset( $a[$k] );
                                                }
                                        }
                                }
                                $identityClause = "OUTPUT INSERTED.$identity "; // we want to output an identity column as result
                        }

                        $keys = array_keys( $a );

                        // INSERT IGNORE is not supported by SQL Server
                        // remove IGNORE from options list and set ignore flag to true
                        $ignoreClause = false;
                        foreach ( $options as $k => $v ) {
                                if ( strtoupper( $v ) == "IGNORE" ) {
                                        unset( $options[$k] );
                                        $ignoreClause = true;
                                }
                        }

                        // translate MySQL INSERT IGNORE to something SQL Server can use
                        // 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')
                        if ( $ignoreClause ) {
                                $prival = $a[$keys[0]];
                                $sqlPre .= "IF NOT EXISTS (SELECT * FROM $table WHERE $keys[0] = '$prival')";
                        }

                        // Build the actual query
                        $sql = $sqlPre . 'INSERT ' . implode( ' ', $options ) .
                                " INTO $table (" . implode( ',', $keys ) . ") $identityClause VALUES (";

                        $first = true;
                        foreach ( $a as $value ) {
                                if ( $first ) {
                                        $first = false;
                                } else {
                                        $sql .= ',';
                                }
                                if ( is_string( $value ) ) {
                                        $sql .= $this->addQuotes( $value );
                                } elseif ( is_null( $value ) ) {
                                        $sql .= 'null';
                                } elseif ( is_array( $value ) || is_object( $value ) ) {
                                        if ( is_object( $value ) && strtolower( get_class( $value ) ) == 'blob' ) {
                                                $sql .= $this->addQuotes( $value );
                                        }  else {
                                                $sql .= $this->addQuotes( serialize( $value ) );
                                        }
                                } else {
                                        $sql .= $value;
                                }
                        }
                        $sql .= ')' . $sqlPost;

                        // Run the query
                        $ret = sqlsrv_query( $this->mConn, $sql );

                        if ( $ret === false ) {
                                throw new DBQueryError( $this, $this->getErrors(), $this->lastErrno(), $sql, $fname );
                        } elseif ( $ret != NULL ) {
                                // remember number of rows affected
                                $this->mAffectedRows = sqlsrv_rows_affected( $ret );
                                if ( !is_null($identity) ) {
                                        // then we want to get the identity column value we were assigned and save it off
                                        $row = sqlsrv_fetch_object( $ret );
                                        $this->mInsertId = $row->$identity;
                                }
                                sqlsrv_free_stmt( $ret );
                                continue;
                        }
                        $allOk = false;
                }
                return $allOk;
        }

        /**
         * 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 = 'DatabaseMssql::insertSelect',
                $insertOptions = array(), $selectOptions = array() ) {
                $ret = parent::insertSelect( $destTable, $srcTable, $varMap, $conds, $fname, $insertOptions, $selectOptions );

                if ( $ret === false ) {
                        throw new DBQueryError( $this, $this->getErrors(), $this->lastErrno(), /*$sql*/ '', $fname );
                } elseif ( $ret != NULL ) {
                        // remember number of rows affected
                        $this->mAffectedRows = sqlsrv_rows_affected( $ret );
                        return $ret;
                }
                return NULL;
        }

        /**
         * Return the next in a sequence, save the value for retrieval via insertId()
         */
        function nextSequenceValue( $seqName ) {
                if ( !$this->tableExists( 'sequence_' . $seqName ) ) {
                        sqlsrv_query( $this->mConn, "CREATE TABLE [sequence_$seqName] (id INT NOT NULL IDENTITY PRIMARY KEY, junk varchar(10) NULL)" );
                }
                sqlsrv_query( $this->mConn, "INSERT INTO [sequence_$seqName] (junk) VALUES ('')" );
                $ret = sqlsrv_query( $this->mConn, "SELECT TOP 1 id FROM [sequence_$seqName] ORDER BY id DESC" );
                $row = sqlsrv_fetch_array( $ret, SQLSRV_FETCH_ASSOC );// KEEP ASSOC THERE, weird weird bug dealing with the return value if you don't

                sqlsrv_free_stmt( $ret );
                $this->mInsertId = $row['id'];
                return $row['id'];
        }

        /**
         * Return the current value of a sequence. Assumes it has ben nextval'ed in this session.
         */
        function currentSequenceValue( $seqName ) {
                $ret = sqlsrv_query( $this->mConn, "SELECT TOP 1 id FROM [sequence_$seqName] ORDER BY id DESC" );
                if ( $ret !== false ) {
                        $row = sqlsrv_fetch_array( $ret );
                        sqlsrv_free_stmt( $ret );
                        return $row['id'];
                } else {
                        return $this->nextSequenceValue( $seqName );
                }
        }


        # REPLACE query wrapper
        # MSSQL 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
        function replace( $table, $uniqueIndexes, $rows, $fname = 'DatabaseMssql::replace' ) {
                $table = $this->tableName( $table );

                if ( count( $rows ) == 0 ) {
                        return;
                }

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

                foreach ( $rows as $row ) {
                        # Delete rows which collide
                        if ( $uniqueIndexes ) {
                                $sql = "DELETE FROM $table WHERE ";
                                $first = true;
                                foreach ( $uniqueIndexes as $index ) {
                                        if ( $first ) {
                                                $first = false;
                                                $sql .= "(";
                                        } else {
                                                $sql .= ') OR (';
                                        }
                                        if ( is_array( $index ) ) {
                                                $first2 = true;
                                                foreach ( $index as $col ) {
                                                        if ( $first2 ) {
                                                                $first2 = false;
                                                        } else {
                                                                $sql .= ' AND ';
                                                        }
                                                        $sql .= $col . '=' . $this->addQuotes( $row[$col] );
                                                }
                                        } else {
                                                $sql .= $index . '=' . $this->addQuotes( $row[$index] );
                                        }
                                }
                                $sql .= ')';
                                $this->query( $sql, $fname );
                        }

                        # Now insert the row
                        $sql = "INSERT INTO $table (" . $this->makeList( array_keys( $row ), LIST_NAMES ) . ') VALUES (' .
                                $this->makeList( $row, LIST_COMMA ) . ')';
                        $this->query( $sql, $fname );
                }
        }

        # DELETE where the condition is a join
        function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds, $fname = "DatabaseMssql::deleteJoin" ) {
                if ( !$conds ) {
                        throw new DBUnexpectedError( $this, 'DatabaseMssql::deleteJoin() called with empty $conds' );
                }

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

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

        # Returns the size of a text field, or -1 for "unlimited"
        function textFieldSize( $table, $field ) {
                $table = $this->tableName( $table );
                $sql = "SELECT CHARACTER_MAXIMUM_LENGTH,DATA_TYPE FROM INFORMATION_SCHEMA.Columns
                        WHERE TABLE_NAME = '$table' AND COLUMN_NAME = '$field'";
                $res = $this->query( $sql );
                $row = $this->fetchRow( $res );
                $size = -1;
                if ( strtolower( $row['DATA_TYPE'] ) != 'text' ) {
                        $size = $row['CHARACTER_MAXIMUM_LENGTH'];
                }
                return $size;
        }

        /**
         * Construct a LIMIT query with optional offset
         * This is used for query pages
         * $sql string SQL query we will append the limit too
         * $limit integer the SQL limit
         * $offset integer the SQL offset (default false)
         */
        function limitResult( $sql, $limit, $offset = false ) {
                if ( $offset === false || $offset == 0 ) {
                        if ( strpos( $sql, "SELECT" ) === false ) {
                                return "TOP {$limit} " . $sql;
                        } else {
                                return preg_replace( '/\bSELECT(\s*DISTINCT)?\b/Dsi', 'SELECT$1 TOP ' . $limit, $sql, 1 );
                        }
                } else {
                        $sql = '
                                SELECT * FROM (
                                  SELECT sub2.*, ROW_NUMBER() OVER(ORDER BY sub2.line2) AS line3 FROM (
                                        SELECT 1 AS line2, sub1.* FROM (' . $sql . ') AS sub1
                                  ) as sub2
                                ) AS sub3
                                WHERE line3 BETWEEN ' . ( $offset + 1 ) . ' AND ' . ( $offset + $limit );
                        return $sql;
                }
        }

        // If there is a limit clause, parse it, strip it, and pass the remaining sql through limitResult()
        // with the appropriate parameters. Not the prettiest solution, but better than building a whole new parser.
        // This exists becase there are still too many extensions that don't use dynamic sql generation.
        function LimitToTopN( $sql ) {
                // Matches: LIMIT {[offset,] row_count | row_count OFFSET offset}
                $pattern = '/\bLIMIT\s+((([0-9]+)\s*,\s*)?([0-9]+)(\s+OFFSET\s+([0-9]+))?)/i';
                if ( preg_match( $pattern, $sql, $matches ) ) {
                        // row_count = $matches[4]
                        $row_count = $matches[4];
                        // offset = $matches[3] OR $matches[6]
                        $offset = $matches[3] or
                                $offset = $matches[6] or
                                $offset = false;

                        // strip the matching LIMIT clause out
                        $sql = str_replace( $matches[0], '', $sql );
                        return $this->limitResult( $sql, $row_count, $offset );
                }
                return $sql;
        }

        // MSSQL does support this, but documentation is too thin to make a generalized
        // function for this. Apparently UPDATE TOP (N) works, but the sort order
        // may not be what we're expecting so the top n results may be a random selection.
        // TODO: Implement properly.
        function limitResultForUpdate( $sql, $num ) {
                return $sql;
        }

        function timestamp( $ts = 0 ) {
                return wfTimestamp( TS_ISO_8601, $ts );
        }

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

        /**
         * @return string Version information from the database
         */
        function getServerVersion() {
                $server_info = sqlsrv_server_info( $this->mConn );
                $version = 'Error';
                if ( isset( $server_info['SQLServerVersion'] ) ) {
                        $version = $server_info['SQLServerVersion'];
                }
                return $version;
        }

        function tableExists ( $table, $schema = false ) {
                $res = sqlsrv_query( $this->mConn, "SELECT * FROM information_schema.tables
                        WHERE table_type='BASE TABLE' AND table_name = '$table'" );
                if ( $res === false ) {
                        print( "Error in tableExists query: " . $this->getErrors() );
                        return false;
                }
                if ( sqlsrv_fetch( $res ) ) {
                        return true;
                } else {
                        return false;
                }
        }

        /**
         * Query whether a given column exists in the mediawiki schema
         */
        function fieldExists( $table, $field, $fname = 'DatabaseMssql::fieldExists' ) {
                $table = $this->tableName( $table );
                $res = sqlsrv_query( $this->mConn, "SELECT DATA_TYPE FROM INFORMATION_SCHEMA.Columns
                        WHERE TABLE_NAME = '$table' AND COLUMN_NAME = '$field'" );
                if ( $res === false ) {
                        print( "Error in fieldExists query: " . $this->getErrors() );
                        return false;
                }
                if ( sqlsrv_fetch( $res ) ) {
                        return true;
                } else {
                        return false;
                }
        }

        function fieldInfo( $table, $field ) {
                $table = $this->tableName( $table );
                $res = sqlsrv_query( $this->mConn, "SELECT * FROM INFORMATION_SCHEMA.Columns
                        WHERE TABLE_NAME = '$table' AND COLUMN_NAME = '$field'" );
                if ( $res === false ) {
                        print( "Error in fieldInfo query: " . $this->getErrors() );
                        return false;
                }
                $meta = $this->fetchRow( $res );
                if ( $meta ) {
                        return new MssqlField( $meta );
                }
                return false;
        }

        /**
         * Begin a transaction, committing any previously open transaction
         */
        function begin( $fname = 'DatabaseMssql::begin' ) {
                sqlsrv_begin_transaction( $this->mConn );
                $this->mTrxLevel = 1;
        }

        /**
         * End a transaction
         */
        function commit( $fname = 'DatabaseMssql::commit' ) {
                sqlsrv_commit( $this->mConn );
                $this->mTrxLevel = 0;
        }

        /**
         * Rollback a transaction.
         * No-op on non-transactional databases.
         */
        function rollback( $fname = 'DatabaseMssql::rollback' ) {
                sqlsrv_rollback( $this->mConn );
                $this->mTrxLevel = 0;
        }

        function setup_database() {
                global $wgDBuser;

                // Make sure that we can write to the correct schema
                $ctest = "mediawiki_test_table";
                if ( $this->tableExists( $ctest ) ) {
                        $this->doQuery( "DROP TABLE $ctest" );
                }
                $SQL = "CREATE TABLE $ctest (a int)";
                $res = $this->doQuery( $SQL );
                if ( !$res ) {
                        print "<b>FAILED</b>. Make sure that the user " . htmlspecialchars( $wgDBuser ) . " can write to the database</li>\n";
                        die();
                }
                $this->doQuery( "DROP TABLE $ctest" );

                $res = $this->sourceFile( "../maintenance/mssql/tables.sql" );
                if ( $res !== true ) {
                        echo " <b>FAILED</b></li>";
                        die( htmlspecialchars( $res ) );
                }

                # Avoid the non-standard "REPLACE INTO" syntax
                $f = fopen( "../maintenance/interwiki.sql", 'r' );
                if ( $f == false ) {
                        die( "<li>Could not find the interwiki.sql file" );
                }
                # We simply assume it is already empty as we have just created it
                $SQL = "INSERT INTO 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])" );
                }
                print " (table interwiki successfully populated)...\n";

                $this->commit();
        }

        /**
         * Escapes a identifier for use inm SQL.
         * Throws an exception if it is invalid.
         * Reference: http://msdn.microsoft.com/en-us/library/aa224033%28v=SQL.80%29.aspx
         */
        private function escapeIdentifier( $identifier ) {
                if ( strlen( $identifier ) == 0 ) {
                        throw new MWException( "An identifier must not be empty" );
                }
                if ( strlen( $identifier ) > 128 ) {
                        throw new MWException( "The identifier '$identifier' is too long (max. 128)" );
                }
                if ( ( strpos( $identifier, '[' ) !== false ) || ( strpos( $identifier, ']' ) !== false ) ) {
                        // It may be allowed if you quoted with double quotation marks, but that would break if QUOTED_IDENTIFIER is OFF
                        throw new MWException( "You can't use square brackers in the identifier '$identifier'" );
                }
                return "[$identifier]";
        }

        /**
         * Initial setup.
         * Precondition: This object is connected as the superuser.
         * Creates the database, schema, user and login.
         */
        function initial_setup( $dbName, $newUser, $loginPassword ) {
                $dbName = $this->escapeIdentifier( $dbName );

                // It is not clear what can be used as a login,
                // From http://msdn.microsoft.com/en-us/library/ms173463.aspx
                // a sysname may be the same as an identifier.
                $newUser = $this->escapeIdentifier( $newUser );
                $loginPassword = $this->addQuotes( $loginPassword );

                $this->doQuery("CREATE DATABASE $dbName;");
                $this->doQuery("USE $dbName;");
                $this->doQuery("CREATE SCHEMA $dbName;");
                $this->doQuery("
                                                CREATE
                                                        LOGIN $newUser
                                                WITH
                                                        PASSWORD=$loginPassword
                                                ;
                                        ");
                $this->doQuery("
                                                CREATE
                                                        USER $newUser
                                                FOR
                                                        LOGIN $newUser
                                                WITH
                                                        DEFAULT_SCHEMA=$dbName
                                                ;
                                        ");
                $this->doQuery("
                                                GRANT
                                                        BACKUP DATABASE,
                                                        BACKUP LOG,
                                                        CREATE DEFAULT,
                                                        CREATE FUNCTION,
                                                        CREATE PROCEDURE,
                                                        CREATE RULE,
                                                        CREATE TABLE,
                                                        CREATE VIEW,
                                                        CREATE FULLTEXT CATALOG
                                                ON
                                                        DATABASE::$dbName
                                                TO $newUser
                                                ;
                                        ");
                $this->doQuery("
                                                GRANT
                                                        CONTROL
                                                ON
                                                        SCHEMA::$dbName
                                                TO $newUser
                                                ;
                                        ");


        }

        function encodeBlob( $b ) {
        // we can't have zero's and such, this is a simple encoding to make sure we don't barf
                return base64_encode( $b );
        }

        function decodeBlob( $b ) {
        // we can't have zero's and such, this is a simple encoding to make sure we don't barf
        return base64_decode( $b );
        }

        /**
         * @private
         */
        function tableNamesWithUseIndexOrJOIN( $tables, $use_index = array(), $join_conds = array() ) {
                $ret = array();
                $retJOIN = array();
                $use_index_safe = is_array( $use_index ) ? $use_index : array();
                $join_conds_safe = is_array( $join_conds ) ? $join_conds : array();
                foreach ( $tables as $table ) {
                        // Is there a JOIN and INDEX clause for this table?
                        if ( isset( $join_conds_safe[$table] ) && isset( $use_index_safe[$table] ) ) {
                                $tableClause = $join_conds_safe[$table][0] . ' ' . $this->tableName( $table );
                                $tableClause .= ' ' . $this->useIndexClause( implode( ',', (array)$use_index_safe[$table] ) );
                                $tableClause .= ' ON (' . $this->makeList( (array)$join_conds_safe[$table][1], LIST_AND ) . ')';
                                $retJOIN[] = $tableClause;
                        // Is there an INDEX clause?
                        } else if ( isset( $use_index_safe[$table] ) ) {
                                $tableClause = $this->tableName( $table );
                                $tableClause .= ' ' . $this->useIndexClause( implode( ',', (array)$use_index_safe[$table] ) );
                                $ret[] = $tableClause;
                        // Is there a JOIN clause?
                        } else if ( isset( $join_conds_safe[$table] ) ) {
                                $tableClause = $join_conds_safe[$table][0] . ' ' . $this->tableName( $table );
                                $tableClause .= ' ON (' . $this->makeList( (array)$join_conds_safe[$table][1], LIST_AND ) . ')';
                                $retJOIN[] = $tableClause;
                        } else {
                                $tableClause = $this->tableName( $table );
                                $ret[] = $tableClause;
                        }
                }
                // We can't separate explicit JOIN clauses with ',', use ' ' for those
                $straightJoins = !empty( $ret ) ? implode( ',', $ret ) : "";
                $otherJoins = !empty( $retJOIN ) ? implode( ' ', $retJOIN ) : "";
                // Compile our final table clause
                return implode( ' ', array( $straightJoins, $otherJoins ) );
        }

        function strencode( $s ) { # Should not be called by us
                return str_replace( "'", "''", $s );
        }

        function addQuotes( $s ) {
                if ( $s instanceof Blob ) {
                        return "'" . $s->fetch( $s ) . "'";
                } else {
                        return parent::addQuotes( $s );
                }
        }

        public function addIdentifierQuotes( $s ) {
                // http://msdn.microsoft.com/en-us/library/aa223962.aspx
                return '[' . $s . ']';
        }

        public function isQuotedIdentifier( $name ) {
                return $name[0] == '[' && substr( $name, -1, 1 ) == ']';
        }

        function selectDB( $db ) {
                return ( $this->query( "SET DATABASE $db" ) !== false );
        }

        /**
         * @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 ) {
                $tailOpts = '';
                $startOpts = '';

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

                if ( isset( $options['GROUP BY'] ) ) {
                        $tailOpts .= " GROUP BY {$options['GROUP BY']}";
                }
                if ( isset( $options['HAVING'] ) ) {
                        $tailOpts .= " HAVING {$options['GROUP BY']}";
                }
                if ( isset( $options['ORDER BY'] ) ) {
                        $tailOpts .= " ORDER BY {$options['ORDER BY']}";
                }

                if ( isset( $noKeyOptions['DISTINCT'] ) && isset( $noKeyOptions['DISTINCTROW'] ) ) {
                        $startOpts .= 'DISTINCT';
                }

                // we want this to be compatible with the output of parent::makeSelectOptions()
                return array( $startOpts, '' , $tailOpts, '' );
        }

        /**
         * Get the type of the DBMS, as it appears in $wgDBtype.
         */
        function getType(){
                return 'mssql';
        }

        function buildConcat( $stringList ) {
                return implode( ' + ', $stringList );
        }

        public function getSearchEngine() {
                return "SearchMssql";
        }

        /**
         * Since MSSQL doesn't recognize the infinity keyword, set date manually.
         * @todo Remove magic date
         */
        public function getInfinity() {
                return '3000-01-31 00:00:00.000';
        }

} // end DatabaseMssql class

/**
 * Utility class.
 *
 * @ingroup Database
 */
class MssqlField implements Field {
        private $name, $tablename, $default, $max_length, $nullable, $type;
        function __construct ( $info ) {
                $this->name = $info['COLUMN_NAME'];
                $this->tablename = $info['TABLE_NAME'];
                $this->default = $info['COLUMN_DEFAULT'];
                $this->max_length = $info['CHARACTER_MAXIMUM_LENGTH'];
                $this->nullable = !( strtolower( $info['IS_NULLABLE'] ) == 'no' );
                $this->type = $info['DATA_TYPE'];
        }

        function name() {
                return $this->name;
        }

        function tableName() {
                return $this->tableName;
        }

        function defaultValue() {
                return $this->default;
        }

        function maxLength() {
                return $this->max_length;
        }

        function isNullable() {
                return $this->nullable;
        }

        function type() {
                return $this->type;
        }
}

/**
 * The MSSQL PHP driver doesn't support sqlsrv_num_rows, so we recall all rows into an array and maintain our
 * own cursor index into that array...This is similar to the way the Oracle driver handles this same issue
 *
 * @ingroup Database
 */
class MssqlResult {

        public function __construct( $queryresult = false ) {
                $this->mCursor = 0;
                $this->mRows = array();
                $this->mNumFields = sqlsrv_num_fields( $queryresult );
                $this->mFieldMeta = sqlsrv_field_metadata( $queryresult );

                $rows = sqlsrv_fetch_array( $queryresult, SQLSRV_FETCH_ASSOC );

                foreach( $rows as $row ) {
                        if ( $row !== null ) {
                                foreach ( $row as $k => $v ) {
                                        if ( is_object( $v ) && method_exists( $v, 'format' ) ) {// DateTime Object
                                                $row[$k] = $v->format( "Y-m-d\TH:i:s\Z" );
                                        }
                                }
                                $this->mRows[] = $row;// read results into memory, cursors are not supported
                        }
                }
                $this->mRowCount = count( $this->mRows );
                sqlsrv_free_stmt( $queryresult );
        }

        private function array_to_obj( $array, &$obj ) {
                foreach ( $array as $key => $value ) {
                        if ( is_array( $value ) ) {
                                $obj->$key = new stdClass();
                                $this->array_to_obj( $value, $obj->$key );
                        } else {
                                if ( !empty( $key ) ) {
                                        $obj->$key = $value;
                                }
                        }
                }
                return $obj;
        }

        public function fetch( $mode = SQLSRV_FETCH_BOTH, $object_class = 'stdClass' ) {
                if ( $this->mCursor >= $this->mRowCount || $this->mRowCount == 0 ) {
                        return false;
                }
                $arrNum = array();
                if ( $mode == SQLSRV_FETCH_NUMERIC || $mode == SQLSRV_FETCH_BOTH ) {
                        foreach ( $this->mRows[$this->mCursor] as $value ) {
                                $arrNum[] = $value;
                        }
                }
                switch( $mode ) {
                        case SQLSRV_FETCH_ASSOC:
                                $ret = $this->mRows[$this->mCursor];
                                break;
                        case SQLSRV_FETCH_NUMERIC:
                                $ret = $arrNum;
                                break;
                        case 'OBJECT':
                                $o = new $object_class;
                                $ret = $this->array_to_obj( $this->mRows[$this->mCursor], $o );
                                break;
                        case SQLSRV_FETCH_BOTH:
                        default:
                                $ret = $this->mRows[$this->mCursor] + $arrNum;
                                break;
                }

                $this->mCursor++;
                return $ret;
        }

        public function get( $pos, $fld ) {
                return $this->mRows[$pos][$fld];
        }

        public function numrows() {
                return $this->mRowCount;
        }

        public function seek( $iRow ) {
                $this->mCursor = min( $iRow, $this->mRowCount );
        }

        public function numfields() {
                return $this->mNumFields;
        }

        public function fieldname( $nr ) {
                $arrKeys = array_keys( $this->mRows[0] );
                return $arrKeys[$nr];
        }

        public function fieldtype( $nr ) {
                $i = 0;
                $intType = -1;
                foreach ( $this->mFieldMeta as $meta ) {
                        if ( $nr == $i ) {
                                $intType = $meta['Type'];
                                break;
                        }
                        $i++;
                }
                // http://msdn.microsoft.com/en-us/library/cc296183.aspx contains type table
                switch( $intType ) {
                        case SQLSRV_SQLTYPE_BIGINT:             $strType = 'bigint'; break;
                        case SQLSRV_SQLTYPE_BINARY:             $strType = 'binary'; break;
                        case SQLSRV_SQLTYPE_BIT:                        $strType = 'bit'; break;
                        case SQLSRV_SQLTYPE_CHAR:                       $strType = 'char'; break;
                        case SQLSRV_SQLTYPE_DATETIME:           $strType = 'datetime'; break;
                        case SQLSRV_SQLTYPE_DECIMAL/*($precision, $scale)*/: $strType = 'decimal'; break;
                        case SQLSRV_SQLTYPE_FLOAT:                      $strType = 'float'; break;
                        case SQLSRV_SQLTYPE_IMAGE:                      $strType = 'image'; break;
                        case SQLSRV_SQLTYPE_INT:                        $strType = 'int'; break;
                        case SQLSRV_SQLTYPE_MONEY:                      $strType = 'money'; break;
                        case SQLSRV_SQLTYPE_NCHAR/*($charCount)*/: $strType = 'nchar'; break;
                        case SQLSRV_SQLTYPE_NUMERIC/*($precision, $scale)*/: $strType = 'numeric'; break;
                        case SQLSRV_SQLTYPE_NVARCHAR/*($charCount)*/: $strType = 'nvarchar'; break;
                        // case SQLSRV_SQLTYPE_NVARCHAR('max'): $strType = 'nvarchar(MAX)'; break;
                        case SQLSRV_SQLTYPE_NTEXT:                      $strType = 'ntext'; break;
                        case SQLSRV_SQLTYPE_REAL:                       $strType = 'real'; break;
                        case SQLSRV_SQLTYPE_SMALLDATETIME:      $strType = 'smalldatetime'; break;
                        case SQLSRV_SQLTYPE_SMALLINT:           $strType = 'smallint'; break;
                        case SQLSRV_SQLTYPE_SMALLMONEY:         $strType = 'smallmoney'; break;
                        case SQLSRV_SQLTYPE_TEXT:                       $strType = 'text'; break;
                        case SQLSRV_SQLTYPE_TIMESTAMP:          $strType = 'timestamp'; break;
                        case SQLSRV_SQLTYPE_TINYINT:            $strType = 'tinyint'; break;
                        case SQLSRV_SQLTYPE_UNIQUEIDENTIFIER: $strType = 'uniqueidentifier'; break;
                        case SQLSRV_SQLTYPE_UDT:                        $strType = 'UDT'; break;
                        case SQLSRV_SQLTYPE_VARBINARY/*($byteCount)*/: $strType = 'varbinary'; break;
                        // case SQLSRV_SQLTYPE_VARBINARY('max'): $strType = 'varbinary(MAX)'; break;
                        case SQLSRV_SQLTYPE_VARCHAR/*($charCount)*/: $strType = 'varchar'; break;
                        // case SQLSRV_SQLTYPE_VARCHAR('max'): $strType = 'varchar(MAX)'; break;
                        case SQLSRV_SQLTYPE_XML:                        $strType = 'xml'; break;
                        default: $strType = $intType;
                }
                return $strType;
        }

        public function free() {
                unset( $this->mRows );
                return;
        }
}