includes/libs/rdbms/database/DatabaseMssql.php

   1 <?php
   2 /**
   3  * This is the MS SQL Server Native database abstraction layer.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Database
  22  * @author Joel Penner <a-joelpe at microsoft dot com>
  23  * @author Chris Pucci <a-cpucci at microsoft dot com>
  24  * @author Ryan Biesemeyer <v-ryanbi at microsoft dot com>
  25  * @author Ryan Schmidt <skizzerz at gmail dot com>
  26  */
  27 use Wikimedia\Rdbms\Blob;
  28 use Wikimedia\Rdbms\MssqlBlob;
  29 use Wikimedia\Rdbms\MssqlField;
  30
  31 /**
  32  * @ingroup Database
  33  */
  34 class DatabaseMssql extends Database {
  35         protected $mPort;
  36         protected $mUseWindowsAuth = false;
  37
  38         protected $mInsertId = null;
  39         protected $mLastResult = null;
  40         protected $mAffectedRows = null;
  41         protected $mSubqueryId = 0;
  42         protected $mScrollableCursor = true;
  43         protected $mPrepareStatements = true;
  44         protected $mBinaryColumnCache = null;
  45         protected $mBitColumnCache = null;
  46         protected $mIgnoreDupKeyErrors = false;
  47         protected $mIgnoreErrors = [];
  48
  49         public function implicitGroupby() {
  50                 return false;
  51         }
  52
  53         public function implicitOrderby() {
  54                 return false;
  55         }
  56
  57         public function unionSupportsOrderAndLimit() {
  58                 return false;
  59         }
  60
  61         public function __construct( array $params ) {
  62                 $this->mPort = $params['port'];
  63                 $this->mUseWindowsAuth = $params['UseWindowsAuth'];
  64
  65                 parent::__construct( $params );
  66         }
  67
  68         /**
  69          * Usually aborts on failure
  70          * @param string $server
  71          * @param string $user
  72          * @param string $password
  73          * @param string $dbName
  74          * @throws DBConnectionError
  75          * @return bool|resource|null
  76          */
  77         public function open( $server, $user, $password, $dbName ) {
  78                 # Test for driver support, to avoid suppressed fatal error
  79                 if ( !function_exists( 'sqlsrv_connect' ) ) {
  80                         throw new DBConnectionError(
  81                                 $this,
  82                                 "Microsoft SQL Server Native (sqlsrv) functions missing.
  83                                 You can download the driver from: http://go.microsoft.com/fwlink/?LinkId=123470\n"
  84                         );
  85                 }
  86
  87                 # e.g. the class is being loaded
  88                 if ( !strlen( $user ) ) {
  89                         return null;
  90                 }
  91
  92                 $this->close();
  93                 $this->mServer = $server;
  94                 $this->mUser = $user;
  95                 $this->mPassword = $password;
  96                 $this->mDBname = $dbName;
  97
  98                 $connectionInfo = [];
  99
 100                 if ( $dbName ) {
 101                         $connectionInfo['Database'] = $dbName;
 102                 }
 103
 104                 // Decide which auth scenerio to use
 105                 // if we are using Windows auth, then don't add credentials to $connectionInfo
 106                 if ( !$this->mUseWindowsAuth ) {
 107                         $connectionInfo['UID'] = $user;
 108                         $connectionInfo['PWD'] = $password;
 109                 }
 110
 111                 MediaWiki\suppressWarnings();
 112                 $this->mConn = sqlsrv_connect( $server, $connectionInfo );
 113                 MediaWiki\restoreWarnings();
 114
 115                 if ( $this->mConn === false ) {
 116                         throw new DBConnectionError( $this, $this->lastError() );
 117                 }
 118
 119                 $this->mOpened = true;
 120
 121                 return $this->mConn;
 122         }
 123
 124         /**
 125          * Closes a database connection, if it is open
 126          * Returns success, true if already closed
 127          * @return bool
 128          */
 129         protected function closeConnection() {
 130                 return sqlsrv_close( $this->mConn );
 131         }
 132
 133         /**
 134          * @param bool|MssqlResultWrapper|resource $result
 135          * @return bool|MssqlResultWrapper
 136          */
 137         protected function resultObject( $result ) {
 138                 if ( !$result ) {
 139                         return false;
 140                 } elseif ( $result instanceof MssqlResultWrapper ) {
 141                         return $result;
 142                 } elseif ( $result === true ) {
 143                         // Successful write query
 144                         return $result;
 145                 } else {
 146                         return new MssqlResultWrapper( $this, $result );
 147                 }
 148         }
 149
 150         /**
 151          * @param string $sql
 152          * @return bool|MssqlResultWrapper|resource
 153          * @throws DBUnexpectedError
 154          */
 155         protected function doQuery( $sql ) {
 156                 // several extensions seem to think that all databases support limits
 157                 // via LIMIT N after the WHERE clause, but  MSSQL uses SELECT TOP N,
 158                 // so to catch any of those extensions we'll do a quick check for a
 159                 // LIMIT clause and pass $sql through $this->LimitToTopN() which parses
 160                 // the LIMIT clause and passes the result to $this->limitResult();
 161                 if ( preg_match( '/\bLIMIT\s*/i', $sql ) ) {
 162                         // massage LIMIT -> TopN
 163                         $sql = $this->LimitToTopN( $sql );
 164                 }
 165
 166                 // MSSQL doesn't have EXTRACT(epoch FROM XXX)
 167                 if ( preg_match( '#\bEXTRACT\s*?\(\s*?EPOCH\s+FROM\b#i', $sql, $matches ) ) {
 168                         // This is same as UNIX_TIMESTAMP, we need to calc # of seconds from 1970
 169                         $sql = str_replace( $matches[0], "DATEDIFF(s,CONVERT(datetime,'1/1/1970'),", $sql );
 170                 }
 171
 172                 // perform query
 173
 174                 // SQLSRV_CURSOR_STATIC is slower than SQLSRV_CURSOR_CLIENT_BUFFERED (one of the two is
 175                 // needed if we want to be able to seek around the result set), however CLIENT_BUFFERED
 176                 // has a bug in the sqlsrv driver where wchar_t types (such as nvarchar) that are empty
 177                 // strings make php throw a fatal error "Severe error translating Unicode"
 178                 if ( $this->mScrollableCursor ) {
 179                         $scrollArr = [ 'Scrollable' => SQLSRV_CURSOR_STATIC ];
 180                 } else {
 181                         $scrollArr = [];
 182                 }
 183
 184                 if ( $this->mPrepareStatements ) {
 185                         // we do prepare + execute so we can get its field metadata for later usage if desired
 186                         $stmt = sqlsrv_prepare( $this->mConn, $sql, [], $scrollArr );
 187                         $success = sqlsrv_execute( $stmt );
 188                 } else {
 189                         $stmt = sqlsrv_query( $this->mConn, $sql, [], $scrollArr );
 190                         $success = (bool)$stmt;
 191                 }
 192
 193                 // Make a copy to ensure what we add below does not get reflected in future queries
 194                 $ignoreErrors = $this->mIgnoreErrors;
 195
 196                 if ( $this->mIgnoreDupKeyErrors ) {
 197                         // ignore duplicate key errors
 198                         // this emulates INSERT IGNORE in MySQL
 199                         $ignoreErrors[] = '2601'; // duplicate key error caused by unique index
 200                         $ignoreErrors[] = '2627'; // duplicate key error caused by primary key
 201                         $ignoreErrors[] = '3621'; // generic "the statement has been terminated" error
 202                 }
 203
 204                 if ( $success === false ) {
 205                         $errors = sqlsrv_errors();
 206                         $success = true;
 207
 208                         foreach ( $errors as $err ) {
 209                                 if ( !in_array( $err['code'], $ignoreErrors ) ) {
 210                                         $success = false;
 211                                         break;
 212                                 }
 213                         }
 214
 215                         if ( $success === false ) {
 216                                 return false;
 217                         }
 218                 }
 219                 // remember number of rows affected
 220                 $this->mAffectedRows = sqlsrv_rows_affected( $stmt );
 221
 222                 return $stmt;
 223         }
 224
 225         public function freeResult( $res ) {
 226                 if ( $res instanceof ResultWrapper ) {
 227                         $res = $res->result;
 228                 }
 229
 230                 sqlsrv_free_stmt( $res );
 231         }
 232
 233         /**
 234          * @param MssqlResultWrapper $res
 235          * @return stdClass
 236          */
 237         public function fetchObject( $res ) {
 238                 // $res is expected to be an instance of MssqlResultWrapper here
 239                 return $res->fetchObject();
 240         }
 241
 242         /**
 243          * @param MssqlResultWrapper $res
 244          * @return array
 245          */
 246         public function fetchRow( $res ) {
 247                 return $res->fetchRow();
 248         }
 249
 250         /**
 251          * @param mixed $res
 252          * @return int
 253          */
 254         public function numRows( $res ) {
 255                 if ( $res instanceof ResultWrapper ) {
 256                         $res = $res->result;
 257                 }
 258
 259                 $ret = sqlsrv_num_rows( $res );
 260
 261                 if ( $ret === false ) {
 262                         // we cannot get an amount of rows from this cursor type
 263                         // has_rows returns bool true/false if the result has rows
 264                         $ret = (int)sqlsrv_has_rows( $res );
 265                 }
 266
 267                 return $ret;
 268         }
 269
 270         /**
 271          * @param mixed $res
 272          * @return int
 273          */
 274         public function numFields( $res ) {
 275                 if ( $res instanceof ResultWrapper ) {
 276                         $res = $res->result;
 277                 }
 278
 279                 return sqlsrv_num_fields( $res );
 280         }
 281
 282         /**
 283          * @param mixed $res
 284          * @param int $n
 285          * @return int
 286          */
 287         public function fieldName( $res, $n ) {
 288                 if ( $res instanceof ResultWrapper ) {
 289                         $res = $res->result;
 290                 }
 291
 292                 return sqlsrv_field_metadata( $res )[$n]['Name'];
 293         }
 294
 295         /**
 296          * This must be called after nextSequenceVal
 297          * @return int|null
 298          */
 299         public function insertId() {
 300                 return $this->mInsertId;
 301         }
 302
 303         /**
 304          * @param MssqlResultWrapper $res
 305          * @param int $row
 306          * @return bool
 307          */
 308         public function dataSeek( $res, $row ) {
 309                 return $res->seek( $row );
 310         }
 311
 312         /**
 313          * @return string
 314          */
 315         public function lastError() {
 316                 $strRet = '';
 317                 $retErrors = sqlsrv_errors( SQLSRV_ERR_ALL );
 318                 if ( $retErrors != null ) {
 319                         foreach ( $retErrors as $arrError ) {
 320                                 $strRet .= $this->formatError( $arrError ) . "\n";
 321                         }
 322                 } else {
 323                         $strRet = "No errors found";
 324                 }
 325
 326                 return $strRet;
 327         }
 328
 329         /**
 330          * @param array $err
 331          * @return string
 332          */
 333         private function formatError( $err ) {
 334                 return '[SQLSTATE ' .
 335                         $err['SQLSTATE'] . '][Error Code ' . $err['code'] . ']' . $err['message'];
 336         }
 337
 338         /**
 339          * @return string|int
 340          */
 341         public function lastErrno() {
 342                 $err = sqlsrv_errors( SQLSRV_ERR_ALL );
 343                 if ( $err !== null && isset( $err[0] ) ) {
 344                         return $err[0]['code'];
 345                 } else {
 346                         return 0;
 347                 }
 348         }
 349
 350         /**
 351          * @return int
 352          */
 353         public function affectedRows() {
 354                 return $this->mAffectedRows;
 355         }
 356
 357         /**
 358          * SELECT wrapper
 359          *
 360          * @param mixed $table Array or string, table name(s) (prefix auto-added)
 361          * @param mixed $vars Array or string, field name(s) to be retrieved
 362          * @param mixed $conds Array or string, condition(s) for WHERE
 363          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
 364          * @param array $options Associative array of options (e.g.
 365          *   [ 'GROUP BY' => 'page_title' ]), see Database::makeSelectOptions
 366          *   code for list of supported stuff
 367          * @param array $join_conds Associative array of table join conditions
 368          *   (optional) (e.g. [ 'page' => [ 'LEFT JOIN','page_latest=rev_id' ] ]
 369          * @return mixed Database result resource (feed to Database::fetchObject
 370          *   or whatever), or false on failure
 371          * @throws DBQueryError
 372          * @throws DBUnexpectedError
 373          * @throws Exception
 374          */
 375         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
 376                 $options = [], $join_conds = []
 377         ) {
 378                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
 379                 if ( isset( $options['EXPLAIN'] ) ) {
 380                         try {
 381                                 $this->mScrollableCursor = false;
 382                                 $this->mPrepareStatements = false;
 383                                 $this->query( "SET SHOWPLAN_ALL ON" );
 384                                 $ret = $this->query( $sql, $fname );
 385                                 $this->query( "SET SHOWPLAN_ALL OFF" );
 386                         } catch ( DBQueryError $dqe ) {
 387                                 if ( isset( $options['FOR COUNT'] ) ) {
 388                                         // likely don't have privs for SHOWPLAN, so run a select count instead
 389                                         $this->query( "SET SHOWPLAN_ALL OFF" );
 390                                         unset( $options['EXPLAIN'] );
 391                                         $ret = $this->select(
 392                                                 $table,
 393                                                 'COUNT(*) AS EstimateRows',
 394                                                 $conds,
 395                                                 $fname,
 396                                                 $options,
 397                                                 $join_conds
 398                                         );
 399                                 } else {
 400                                         // someone actually wanted the query plan instead of an est row count
 401                                         // let them know of the error
 402                                         $this->mScrollableCursor = true;
 403                                         $this->mPrepareStatements = true;
 404                                         throw $dqe;
 405                                 }
 406                         }
 407                         $this->mScrollableCursor = true;
 408                         $this->mPrepareStatements = true;
 409                         return $ret;
 410                 }
 411                 return $this->query( $sql, $fname );
 412         }
 413
 414         /**
 415          * SELECT wrapper
 416          *
 417          * @param mixed $table Array or string, table name(s) (prefix auto-added)
 418          * @param mixed $vars Array or string, field name(s) to be retrieved
 419          * @param mixed $conds Array or string, condition(s) for WHERE
 420          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
 421          * @param array $options Associative array of options (e.g. [ 'GROUP BY' => 'page_title' ]),
 422          *   see Database::makeSelectOptions code for list of supported stuff
 423          * @param array $join_conds Associative array of table join conditions (optional)
 424          *    (e.g. [ 'page' => [ 'LEFT JOIN','page_latest=rev_id' ] ]
 425          * @return string The SQL text
 426          */
 427         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
 428                 $options = [], $join_conds = []
 429         ) {
 430                 if ( isset( $options['EXPLAIN'] ) ) {
 431                         unset( $options['EXPLAIN'] );
 432                 }
 433
 434                 $sql = parent::selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
 435
 436                 // try to rewrite aggregations of bit columns (currently MAX and MIN)
 437                 if ( strpos( $sql, 'MAX(' ) !== false || strpos( $sql, 'MIN(' ) !== false ) {
 438                         $bitColumns = [];
 439                         if ( is_array( $table ) ) {
 440                                 foreach ( $table as $t ) {
 441                                         $bitColumns += $this->getBitColumns( $this->tableName( $t ) );
 442                                 }
 443                         } else {
 444                                 $bitColumns = $this->getBitColumns( $this->tableName( $table ) );
 445                         }
 446
 447                         foreach ( $bitColumns as $col => $info ) {
 448                                 $replace = [
 449                                         "MAX({$col})" => "MAX(CAST({$col} AS tinyint))",
 450                                         "MIN({$col})" => "MIN(CAST({$col} AS tinyint))",
 451                                 ];
 452                                 $sql = str_replace( array_keys( $replace ), array_values( $replace ), $sql );
 453                         }
 454                 }
 455
 456                 return $sql;
 457         }
 458
 459         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
 460                 $fname = __METHOD__
 461         ) {
 462                 $this->mScrollableCursor = false;
 463                 try {
 464                         parent::deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds, $fname );
 465                 } catch ( Exception $e ) {
 466                         $this->mScrollableCursor = true;
 467                         throw $e;
 468                 }
 469                 $this->mScrollableCursor = true;
 470         }
 471
 472         public function delete( $table, $conds, $fname = __METHOD__ ) {
 473                 $this->mScrollableCursor = false;
 474                 try {
 475                         parent::delete( $table, $conds, $fname );
 476                 } catch ( Exception $e ) {
 477                         $this->mScrollableCursor = true;
 478                         throw $e;
 479                 }
 480                 $this->mScrollableCursor = true;
 481         }
 482
 483         /**
 484          * Estimate rows in dataset
 485          * Returns estimated count, based on SHOWPLAN_ALL output
 486          * This is not necessarily an accurate estimate, so use sparingly
 487          * Returns -1 if count cannot be found
 488          * Takes same arguments as Database::select()
 489          * @param string $table
 490          * @param string $vars
 491          * @param string $conds
 492          * @param string $fname
 493          * @param array $options
 494          * @return int
 495          */
 496         public function estimateRowCount( $table, $vars = '*', $conds = '',
 497                 $fname = __METHOD__, $options = []
 498         ) {
 499                 // http://msdn2.microsoft.com/en-us/library/aa259203.aspx
 500                 $options['EXPLAIN'] = true;
 501                 $options['FOR COUNT'] = true;
 502                 $res = $this->select( $table, $vars, $conds, $fname, $options );
 503
 504                 $rows = -1;
 505                 if ( $res ) {
 506                         $row = $this->fetchRow( $res );
 507
 508                         if ( isset( $row['EstimateRows'] ) ) {
 509                                 $rows = (int)$row['EstimateRows'];
 510                         }
 511                 }
 512
 513                 return $rows;
 514         }
 515
 516         /**
 517          * Returns information about an index
 518          * If errors are explicitly ignored, returns NULL on failure
 519          * @param string $table
 520          * @param string $index
 521          * @param string $fname
 522          * @return array|bool|null
 523          */
 524         public function indexInfo( $table, $index, $fname = __METHOD__ ) {
 525                 # This does not return the same info as MYSQL would, but that's OK
 526                 # because MediaWiki never uses the returned value except to check for
 527                 # the existence of indexes.
 528                 $sql = "sp_helpindex '" . $this->tableName( $table ) . "'";
 529                 $res = $this->query( $sql, $fname );
 530
 531                 if ( !$res ) {
 532                         return null;
 533                 }
 534
 535                 $result = [];
 536                 foreach ( $res as $row ) {
 537                         if ( $row->index_name == $index ) {
 538                                 $row->Non_unique = !stristr( $row->index_description, "unique" );
 539                                 $cols = explode( ", ", $row->index_keys );
 540                                 foreach ( $cols as $col ) {
 541                                         $row->Column_name = trim( $col );
 542                                         $result[] = clone $row;
 543                                 }
 544                         } elseif ( $index == 'PRIMARY' && stristr( $row->index_description, 'PRIMARY' ) ) {
 545                                 $row->Non_unique = 0;
 546                                 $cols = explode( ", ", $row->index_keys );
 547                                 foreach ( $cols as $col ) {
 548                                         $row->Column_name = trim( $col );
 549                                         $result[] = clone $row;
 550                                 }
 551                         }
 552                 }
 553
 554                 return empty( $result ) ? false : $result;
 555         }
 556
 557         /**
 558          * INSERT wrapper, inserts an array into a table
 559          *
 560          * $arrToInsert may be a single associative array, or an array of these with numeric keys, for
 561          * multi-row insert.
 562          *
 563          * Usually aborts on failure
 564          * If errors are explicitly ignored, returns success
 565          * @param string $table
 566          * @param array $arrToInsert
 567          * @param string $fname
 568          * @param array $options
 569          * @return bool
 570          * @throws Exception
 571          */
 572         public function insert( $table, $arrToInsert, $fname = __METHOD__, $options = [] ) {
 573                 # No rows to insert, easy just return now
 574                 if ( !count( $arrToInsert ) ) {
 575                         return true;
 576                 }
 577
 578                 if ( !is_array( $options ) ) {
 579                         $options = [ $options ];
 580                 }
 581
 582                 $table = $this->tableName( $table );
 583
 584                 if ( !( isset( $arrToInsert[0] ) && is_array( $arrToInsert[0] ) ) ) { // Not multi row
 585                         $arrToInsert = [ 0 => $arrToInsert ]; // make everything multi row compatible
 586                 }
 587
 588                 // We know the table we're inserting into, get its identity column
 589                 $identity = null;
 590                 // strip matching square brackets and the db/schema from table name
 591                 $tableRawArr = explode( '.', preg_replace( '#\[([^\]]*)\]#', '$1', $table ) );
 592                 $tableRaw = array_pop( $tableRawArr );
 593                 $res = $this->doQuery(
 594                         "SELECT NAME AS idColumn FROM SYS.IDENTITY_COLUMNS " .
 595                                 "WHERE OBJECT_NAME(OBJECT_ID)='{$tableRaw}'"
 596                 );
 597                 if ( $res && sqlsrv_has_rows( $res ) ) {
 598                         // There is an identity for this table.
 599                         $identityArr = sqlsrv_fetch_array( $res, SQLSRV_FETCH_ASSOC );
 600                         $identity = array_pop( $identityArr );
 601                 }
 602                 sqlsrv_free_stmt( $res );
 603
 604                 // Determine binary/varbinary fields so we can encode data as a hex string like 0xABCDEF
 605                 $binaryColumns = $this->getBinaryColumns( $table );
 606
 607                 // INSERT IGNORE is not supported by SQL Server
 608                 // remove IGNORE from options list and set ignore flag to true
 609                 if ( in_array( 'IGNORE', $options ) ) {
 610                         $options = array_diff( $options, [ 'IGNORE' ] );
 611                         $this->mIgnoreDupKeyErrors = true;
 612                 }
 613
 614                 $ret = null;
 615                 foreach ( $arrToInsert as $a ) {
 616                         // start out with empty identity column, this is so we can return
 617                         // it as a result of the INSERT logic
 618                         $sqlPre = '';
 619                         $sqlPost = '';
 620                         $identityClause = '';
 621
 622                         // if we have an identity column
 623                         if ( $identity ) {
 624                                 // iterate through
 625                                 foreach ( $a as $k => $v ) {
 626                                         if ( $k == $identity ) {
 627                                                 if ( !is_null( $v ) ) {
 628                                                         // there is a value being passed to us,
 629                                                         // we need to turn on and off inserted identity
 630                                                         $sqlPre = "SET IDENTITY_INSERT $table ON;";
 631                                                         $sqlPost = ";SET IDENTITY_INSERT $table OFF;";
 632                                                 } else {
 633                                                         // we can't insert NULL into an identity column,
 634                                                         // so remove the column from the insert.
 635                                                         unset( $a[$k] );
 636                                                 }
 637                                         }
 638                                 }
 639
 640                                 // we want to output an identity column as result
 641                                 $identityClause = "OUTPUT INSERTED.$identity ";
 642                         }
 643
 644                         $keys = array_keys( $a );
 645
 646                         // Build the actual query
 647                         $sql = $sqlPre . 'INSERT ' . implode( ' ', $options ) .
 648                                 " INTO $table (" . implode( ',', $keys ) . ") $identityClause VALUES (";
 649
 650                         $first = true;
 651                         foreach ( $a as $key => $value ) {
 652                                 if ( isset( $binaryColumns[$key] ) ) {
 653                                         $value = new MssqlBlob( $value );
 654                                 }
 655                                 if ( $first ) {
 656                                         $first = false;
 657                                 } else {
 658                                         $sql .= ',';
 659                                 }
 660                                 if ( is_null( $value ) ) {
 661                                         $sql .= 'null';
 662                                 } elseif ( is_array( $value ) || is_object( $value ) ) {
 663                                         if ( is_object( $value ) && $value instanceof Blob ) {
 664                                                 $sql .= $this->addQuotes( $value );
 665                                         } else {
 666                                                 $sql .= $this->addQuotes( serialize( $value ) );
 667                                         }
 668                                 } else {
 669                                         $sql .= $this->addQuotes( $value );
 670                                 }
 671                         }
 672                         $sql .= ')' . $sqlPost;
 673
 674                         // Run the query
 675                         $this->mScrollableCursor = false;
 676                         try {
 677                                 $ret = $this->query( $sql );
 678                         } catch ( Exception $e ) {
 679                                 $this->mScrollableCursor = true;
 680                                 $this->mIgnoreDupKeyErrors = false;
 681                                 throw $e;
 682                         }
 683                         $this->mScrollableCursor = true;
 684
 685                         if ( $ret instanceof ResultWrapper && !is_null( $identity ) ) {
 686                                 // Then we want to get the identity column value we were assigned and save it off
 687                                 $row = $ret->fetchObject();
 688                                 if ( is_object( $row ) ) {
 689                                         $this->mInsertId = $row->$identity;
 690                                         // It seems that mAffectedRows is -1 sometimes when OUTPUT INSERTED.identity is
 691                                         // used if we got an identity back, we know for sure a row was affected, so
 692                                         // adjust that here
 693                                         if ( $this->mAffectedRows == -1 ) {
 694                                                 $this->mAffectedRows = 1;
 695                                         }
 696                                 }
 697                         }
 698                 }
 699
 700                 $this->mIgnoreDupKeyErrors = false;
 701
 702                 return $ret;
 703         }
 704
 705         /**
 706          * INSERT SELECT wrapper
 707          * $varMap must be an associative array of the form [ 'dest1' => 'source1', ... ]
 708          * Source items may be literals rather than field names, but strings should
 709          * be quoted with Database::addQuotes().
 710          * @param string $destTable
 711          * @param array|string $srcTable May be an array of tables.
 712          * @param array $varMap
 713          * @param array $conds May be "*" to copy the whole table.
 714          * @param string $fname
 715          * @param array $insertOptions
 716          * @param array $selectOptions
 717          * @return null|ResultWrapper
 718          * @throws Exception
 719          */
 720         public function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds, $fname = __METHOD__,
 721                 $insertOptions = [], $selectOptions = []
 722         ) {
 723                 $this->mScrollableCursor = false;
 724                 try {
 725                         $ret = parent::nativeInsertSelect(
 726                                 $destTable,
 727                                 $srcTable,
 728                                 $varMap,
 729                                 $conds,
 730                                 $fname,
 731                                 $insertOptions,
 732                                 $selectOptions
 733                         );
 734                 } catch ( Exception $e ) {
 735                         $this->mScrollableCursor = true;
 736                         throw $e;
 737                 }
 738                 $this->mScrollableCursor = true;
 739
 740                 return $ret;
 741         }
 742
 743         /**
 744          * UPDATE wrapper. Takes a condition array and a SET array.
 745          *
 746          * @param string $table Name of the table to UPDATE. This will be passed through
 747          *                Database::tableName().
 748          *
 749          * @param array $values An array of values to SET. For each array element,
 750          *                the key gives the field name, and the value gives the data
 751          *                to set that field to. The data will be quoted by
 752          *                Database::addQuotes().
 753          *
 754          * @param array $conds An array of conditions (WHERE). See
 755          *                Database::select() for the details of the format of
 756          *                condition arrays. Use '*' to update all rows.
 757          *
 758          * @param string $fname The function name of the caller (from __METHOD__),
 759          *                for logging and profiling.
 760          *
 761          * @param array $options An array of UPDATE options, can be:
 762          *                   - IGNORE: Ignore unique key conflicts
 763          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
 764          * @return bool
 765          * @throws DBUnexpectedError
 766          * @throws Exception
 767          */
 768         function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
 769                 $table = $this->tableName( $table );
 770                 $binaryColumns = $this->getBinaryColumns( $table );
 771
 772                 $opts = $this->makeUpdateOptions( $options );
 773                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET, $binaryColumns );
 774
 775                 if ( $conds !== [] && $conds !== '*' ) {
 776                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND, $binaryColumns );
 777                 }
 778
 779                 $this->mScrollableCursor = false;
 780                 try {
 781                         $this->query( $sql );
 782                 } catch ( Exception $e ) {
 783                         $this->mScrollableCursor = true;
 784                         throw $e;
 785                 }
 786                 $this->mScrollableCursor = true;
 787                 return true;
 788         }
 789
 790         /**
 791          * Makes an encoded list of strings from an array
 792          * @param array $a Containing the data
 793          * @param int $mode Constant
 794          *      - LIST_COMMA:          comma separated, no field names
 795          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
 796          *        the documentation for $conds in Database::select().
 797          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
 798          *      - LIST_SET:            comma separated with field names, like a SET clause
 799          *      - LIST_NAMES:          comma separated field names
 800          * @param array $binaryColumns Contains a list of column names that are binary types
 801          *      This is a custom parameter only present for MS SQL.
 802          *
 803          * @throws DBUnexpectedError
 804          * @return string
 805          */
 806         public function makeList( $a, $mode = LIST_COMMA, $binaryColumns = [] ) {
 807                 if ( !is_array( $a ) ) {
 808                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
 809                 }
 810
 811                 if ( $mode != LIST_NAMES ) {
 812                         // In MS SQL, values need to be specially encoded when they are
 813                         // inserted into binary fields. Perform this necessary encoding
 814                         // for the specified set of columns.
 815                         foreach ( array_keys( $a ) as $field ) {
 816                                 if ( !isset( $binaryColumns[$field] ) ) {
 817                                         continue;
 818                                 }
 819
 820                                 if ( is_array( $a[$field] ) ) {
 821                                         foreach ( $a[$field] as &$v ) {
 822                                                 $v = new MssqlBlob( $v );
 823                                         }
 824                                         unset( $v );
 825                                 } else {
 826                                         $a[$field] = new MssqlBlob( $a[$field] );
 827                                 }
 828                         }
 829                 }
 830
 831                 return parent::makeList( $a, $mode );
 832         }
 833
 834         /**
 835          * @param string $table
 836          * @param string $field
 837          * @return int Returns the size of a text field, or -1 for "unlimited"
 838          */
 839         public function textFieldSize( $table, $field ) {
 840                 $table = $this->tableName( $table );
 841                 $sql = "SELECT CHARACTER_MAXIMUM_LENGTH,DATA_TYPE FROM INFORMATION_SCHEMA.Columns
 842                         WHERE TABLE_NAME = '$table' AND COLUMN_NAME = '$field'";
 843                 $res = $this->query( $sql );
 844                 $row = $this->fetchRow( $res );
 845                 $size = -1;
 846                 if ( strtolower( $row['DATA_TYPE'] ) != 'text' ) {
 847                         $size = $row['CHARACTER_MAXIMUM_LENGTH'];
 848                 }
 849
 850                 return $size;
 851         }
 852
 853         /**
 854          * Construct a LIMIT query with optional offset
 855          * This is used for query pages
 856          *
 857          * @param string $sql SQL query we will append the limit too
 858          * @param int $limit The SQL limit
 859          * @param bool|int $offset The SQL offset (default false)
 860          * @return array|string
 861          * @throws DBUnexpectedError
 862          */
 863         public function limitResult( $sql, $limit, $offset = false ) {
 864                 if ( $offset === false || $offset == 0 ) {
 865                         if ( strpos( $sql, "SELECT" ) === false ) {
 866                                 return "TOP {$limit} " . $sql;
 867                         } else {
 868                                 return preg_replace( '/\bSELECT(\s+DISTINCT)?\b/Dsi',
 869                                         'SELECT$1 TOP ' . $limit, $sql, 1 );
 870                         }
 871                 } else {
 872                         // This one is fun, we need to pull out the select list as well as any ORDER BY clause
 873                         $select = $orderby = [];
 874                         $s1 = preg_match( '#SELECT\s+(.+?)\s+FROM#Dis', $sql, $select );
 875                         $s2 = preg_match( '#(ORDER BY\s+.+?)(\s*FOR XML .*)?$#Dis', $sql, $orderby );
 876                         $postOrder = '';
 877                         $first = $offset + 1;
 878                         $last = $offset + $limit;
 879                         $sub1 = 'sub_' . $this->mSubqueryId;
 880                         $sub2 = 'sub_' . ( $this->mSubqueryId + 1 );
 881                         $this->mSubqueryId += 2;
 882                         if ( !$s1 ) {
 883                                 // wat
 884                                 throw new DBUnexpectedError( $this, "Attempting to LIMIT a non-SELECT query\n" );
 885                         }
 886                         if ( !$s2 ) {
 887                                 // no ORDER BY
 888                                 $overOrder = 'ORDER BY (SELECT 1)';
 889                         } else {
 890                                 if ( !isset( $orderby[2] ) || !$orderby[2] ) {
 891                                         // don't need to strip it out if we're using a FOR XML clause
 892                                         $sql = str_replace( $orderby[1], '', $sql );
 893                                 }
 894                                 $overOrder = $orderby[1];
 895                                 $postOrder = ' ' . $overOrder;
 896                         }
 897                         $sql = "SELECT {$select[1]}
 898                                         FROM (
 899                                                 SELECT ROW_NUMBER() OVER({$overOrder}) AS rowNumber, *
 900                                                 FROM ({$sql}) {$sub1}
 901                                         ) {$sub2}
 902                                         WHERE rowNumber BETWEEN {$first} AND {$last}{$postOrder}";
 903
 904                         return $sql;
 905                 }
 906         }
 907
 908         /**
 909          * If there is a limit clause, parse it, strip it, and pass the remaining
 910          * SQL through limitResult() with the appropriate parameters. Not the
 911          * prettiest solution, but better than building a whole new parser. This
 912          * exists becase there are still too many extensions that don't use dynamic
 913          * sql generation.
 914          *
 915          * @param string $sql
 916          * @return array|mixed|string
 917          */
 918         public function LimitToTopN( $sql ) {
 919                 // Matches: LIMIT {[offset,] row_count | row_count OFFSET offset}
 920                 $pattern = '/\bLIMIT\s+((([0-9]+)\s*,\s*)?([0-9]+)(\s+OFFSET\s+([0-9]+))?)/i';
 921                 if ( preg_match( $pattern, $sql, $matches ) ) {
 922                         $row_count = $matches[4];
 923                         $offset = $matches[3] ?: $matches[6] ?: false;
 924
 925                         // strip the matching LIMIT clause out
 926                         $sql = str_replace( $matches[0], '', $sql );
 927
 928                         return $this->limitResult( $sql, $row_count, $offset );
 929                 }
 930
 931                 return $sql;
 932         }
 933
 934         /**
 935          * @return string Wikitext of a link to the server software's web site
 936          */
 937         public function getSoftwareLink() {
 938                 return "[{{int:version-db-mssql-url}} MS SQL Server]";
 939         }
 940
 941         /**
 942          * @return string Version information from the database
 943          */
 944         public function getServerVersion() {
 945                 $server_info = sqlsrv_server_info( $this->mConn );
 946                 $version = 'Error';
 947                 if ( isset( $server_info['SQLServerVersion'] ) ) {
 948                         $version = $server_info['SQLServerVersion'];
 949                 }
 950
 951                 return $version;
 952         }
 953
 954         /**
 955          * @param string $table
 956          * @param string $fname
 957          * @return bool
 958          */
 959         public function tableExists( $table, $fname = __METHOD__ ) {
 960                 list( $db, $schema, $table ) = $this->tableName( $table, 'split' );
 961
 962                 if ( $db !== false ) {
 963                         // remote database
 964                         $this->queryLogger->error( "Attempting to call tableExists on a remote table" );
 965                         return false;
 966                 }
 967
 968                 if ( $schema === false ) {
 969                         $schema = $this->mSchema;
 970                 }
 971
 972                 $res = $this->query( "SELECT 1 FROM INFORMATION_SCHEMA.TABLES
 973                         WHERE TABLE_TYPE = 'BASE TABLE'
 974                         AND TABLE_SCHEMA = '$schema' AND TABLE_NAME = '$table'" );
 975
 976                 if ( $res->numRows() ) {
 977                         return true;
 978                 } else {
 979                         return false;
 980                 }
 981         }
 982
 983         /**
 984          * Query whether a given column exists in the mediawiki schema
 985          * @param string $table
 986          * @param string $field
 987          * @param string $fname
 988          * @return bool
 989          */
 990         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
 991                 list( $db, $schema, $table ) = $this->tableName( $table, 'split' );
 992
 993                 if ( $db !== false ) {
 994                         // remote database
 995                         $this->queryLogger->error( "Attempting to call fieldExists on a remote table" );
 996                         return false;
 997                 }
 998
 999                 $res = $this->query( "SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS
1000                         WHERE TABLE_SCHEMA = '$schema' AND TABLE_NAME = '$table' AND COLUMN_NAME = '$field'" );
1001
1002                 if ( $res->numRows() ) {
1003                         return true;
1004                 } else {
1005                         return false;
1006                 }
1007         }
1008
1009         public function fieldInfo( $table, $field ) {
1010                 list( $db, $schema, $table ) = $this->tableName( $table, 'split' );
1011
1012                 if ( $db !== false ) {
1013                         // remote database
1014                         $this->queryLogger->error( "Attempting to call fieldInfo on a remote table" );
1015                         return false;
1016                 }
1017
1018                 $res = $this->query( "SELECT * FROM INFORMATION_SCHEMA.COLUMNS
1019                         WHERE TABLE_SCHEMA = '$schema' AND TABLE_NAME = '$table' AND COLUMN_NAME = '$field'" );
1020
1021                 $meta = $res->fetchRow();
1022                 if ( $meta ) {
1023                         return new MssqlField( $meta );
1024                 }
1025
1026                 return false;
1027         }
1028
1029         /**
1030          * Begin a transaction, committing any previously open transaction
1031          * @param string $fname
1032          */
1033         protected function doBegin( $fname = __METHOD__ ) {
1034                 sqlsrv_begin_transaction( $this->mConn );
1035                 $this->mTrxLevel = 1;
1036         }
1037
1038         /**
1039          * End a transaction
1040          * @param string $fname
1041          */
1042         protected function doCommit( $fname = __METHOD__ ) {
1043                 sqlsrv_commit( $this->mConn );
1044                 $this->mTrxLevel = 0;
1045         }
1046
1047         /**
1048          * Rollback a transaction.
1049          * No-op on non-transactional databases.
1050          * @param string $fname
1051          */
1052         protected function doRollback( $fname = __METHOD__ ) {
1053                 sqlsrv_rollback( $this->mConn );
1054                 $this->mTrxLevel = 0;
1055         }
1056
1057         /**
1058          * @param string $s
1059          * @return string
1060          */
1061         public function strencode( $s ) {
1062                 // Should not be called by us
1063
1064                 return str_replace( "'", "''", $s );
1065         }
1066
1067         /**
1068          * @param string|int|null|bool|Blob $s
1069          * @return string|int
1070          */
1071         public function addQuotes( $s ) {
1072                 if ( $s instanceof MssqlBlob ) {
1073                         return $s->fetch();
1074                 } elseif ( $s instanceof Blob ) {
1075                         // this shouldn't really ever be called, but it's here if needed
1076                         // (and will quite possibly make the SQL error out)
1077                         $blob = new MssqlBlob( $s->fetch() );
1078                         return $blob->fetch();
1079                 } else {
1080                         if ( is_bool( $s ) ) {
1081                                 $s = $s ? 1 : 0;
1082                         }
1083                         return parent::addQuotes( $s );
1084                 }
1085         }
1086
1087         /**
1088          * @param string $s
1089          * @return string
1090          */
1091         public function addIdentifierQuotes( $s ) {
1092                 // http://msdn.microsoft.com/en-us/library/aa223962.aspx
1093                 return '[' . $s . ']';
1094         }
1095
1096         /**
1097          * @param string $name
1098          * @return bool
1099          */
1100         public function isQuotedIdentifier( $name ) {
1101                 return strlen( $name ) && $name[0] == '[' && substr( $name, -1, 1 ) == ']';
1102         }
1103
1104         /**
1105          * MS SQL supports more pattern operators than other databases (ex: [,],^)
1106          *
1107          * @param string $s
1108          * @return string
1109          */
1110         protected function escapeLikeInternal( $s ) {
1111                 return addcslashes( $s, '\%_[]^' );
1112         }
1113
1114         /**
1115          * MS SQL requires specifying the escape character used in a LIKE query
1116          * or using Square brackets to surround characters that are to be escaped
1117          * https://msdn.microsoft.com/en-us/library/ms179859.aspx
1118          * Here we take the Specify-Escape-Character approach since it's less
1119          * invasive, renders a query that is closer to other DB's and better at
1120          * handling square bracket escaping
1121          *
1122          * @return string Fully built LIKE statement
1123          */
1124         public function buildLike() {
1125                 $params = func_get_args();
1126                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
1127                         $params = $params[0];
1128                 }
1129
1130                 return parent::buildLike( $params ) . " ESCAPE '\' ";
1131         }
1132
1133         /**
1134          * @param string $db
1135          * @return bool
1136          */
1137         public function selectDB( $db ) {
1138                 try {
1139                         $this->mDBname = $db;
1140                         $this->query( "USE $db" );
1141                         return true;
1142                 } catch ( Exception $e ) {
1143                         return false;
1144                 }
1145         }
1146
1147         /**
1148          * @param array $options An associative array of options to be turned into
1149          *   an SQL query, valid keys are listed in the function.
1150          * @return array
1151          */
1152         public function makeSelectOptions( $options ) {
1153                 $tailOpts = '';
1154                 $startOpts = '';
1155
1156                 $noKeyOptions = [];
1157                 foreach ( $options as $key => $option ) {
1158                         if ( is_numeric( $key ) ) {
1159                                 $noKeyOptions[$option] = true;
1160                         }
1161                 }
1162
1163                 $tailOpts .= $this->makeGroupByWithHaving( $options );
1164
1165                 $tailOpts .= $this->makeOrderBy( $options );
1166
1167                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1168                         $startOpts .= 'DISTINCT';
1169                 }
1170
1171                 if ( isset( $noKeyOptions['FOR XML'] ) ) {
1172                         // used in group concat field emulation
1173                         $tailOpts .= " FOR XML PATH('')";
1174                 }
1175
1176                 // we want this to be compatible with the output of parent::makeSelectOptions()
1177                 return [ $startOpts, '', $tailOpts, '', '' ];
1178         }
1179
1180         public function getType() {
1181                 return 'mssql';
1182         }
1183
1184         /**
1185          * @param array $stringList
1186          * @return string
1187          */
1188         public function buildConcat( $stringList ) {
1189                 return implode( ' + ', $stringList );
1190         }
1191
1192         /**
1193          * Build a GROUP_CONCAT or equivalent statement for a query.
1194          * MS SQL doesn't have GROUP_CONCAT so we emulate it with other stuff (and boy is it nasty)
1195          *
1196          * This is useful for combining a field for several rows into a single string.
1197          * NULL values will not appear in the output, duplicated values will appear,
1198          * and the resulting delimiter-separated values have no defined sort order.
1199          * Code using the results may need to use the PHP unique() or sort() methods.
1200          *
1201          * @param string $delim Glue to bind the results together
1202          * @param string|array $table Table name
1203          * @param string $field Field name
1204          * @param string|array $conds Conditions
1205          * @param string|array $join_conds Join conditions
1206          * @return string SQL text
1207          * @since 1.23
1208          */
1209         public function buildGroupConcatField( $delim, $table, $field, $conds = '',
1210                 $join_conds = []
1211         ) {
1212                 $gcsq = 'gcsq_' . $this->mSubqueryId;
1213                 $this->mSubqueryId++;
1214
1215                 $delimLen = strlen( $delim );
1216                 $fld = "{$field} + {$this->addQuotes( $delim )}";
1217                 $sql = "(SELECT LEFT({$field}, LEN({$field}) - {$delimLen}) FROM ("
1218                         . $this->selectSQLText( $table, $fld, $conds, null, [ 'FOR XML' ], $join_conds )
1219                         . ") {$gcsq} ({$field}))";
1220
1221                 return $sql;
1222         }
1223
1224         /**
1225          * Returns an associative array for fields that are of type varbinary, binary, or image
1226          * $table can be either a raw table name or passed through tableName() first
1227          * @param string $table
1228          * @return array
1229          */
1230         private function getBinaryColumns( $table ) {
1231                 $tableRawArr = explode( '.', preg_replace( '#\[([^\]]*)\]#', '$1', $table ) );
1232                 $tableRaw = array_pop( $tableRawArr );
1233
1234                 if ( $this->mBinaryColumnCache === null ) {
1235                         $this->populateColumnCaches();
1236                 }
1237
1238                 return isset( $this->mBinaryColumnCache[$tableRaw] )
1239                         ? $this->mBinaryColumnCache[$tableRaw]
1240                         : [];
1241         }
1242
1243         /**
1244          * @param string $table
1245          * @return array
1246          */
1247         private function getBitColumns( $table ) {
1248                 $tableRawArr = explode( '.', preg_replace( '#\[([^\]]*)\]#', '$1', $table ) );
1249                 $tableRaw = array_pop( $tableRawArr );
1250
1251                 if ( $this->mBitColumnCache === null ) {
1252                         $this->populateColumnCaches();
1253                 }
1254
1255                 return isset( $this->mBitColumnCache[$tableRaw] )
1256                         ? $this->mBitColumnCache[$tableRaw]
1257                         : [];
1258         }
1259
1260         private function populateColumnCaches() {
1261                 $res = $this->select( 'INFORMATION_SCHEMA.COLUMNS', '*',
1262                         [
1263                                 'TABLE_CATALOG' => $this->mDBname,
1264                                 'TABLE_SCHEMA' => $this->mSchema,
1265                                 'DATA_TYPE' => [ 'varbinary', 'binary', 'image', 'bit' ]
1266                         ] );
1267
1268                 $this->mBinaryColumnCache = [];
1269                 $this->mBitColumnCache = [];
1270                 foreach ( $res as $row ) {
1271                         if ( $row->DATA_TYPE == 'bit' ) {
1272                                 $this->mBitColumnCache[$row->TABLE_NAME][$row->COLUMN_NAME] = $row;
1273                         } else {
1274                                 $this->mBinaryColumnCache[$row->TABLE_NAME][$row->COLUMN_NAME] = $row;
1275                         }
1276                 }
1277         }
1278
1279         /**
1280          * @param string $name
1281          * @param string $format
1282          * @return string
1283          */
1284         function tableName( $name, $format = 'quoted' ) {
1285                 # Replace reserved words with better ones
1286                 switch ( $name ) {
1287                         case 'user':
1288                                 return $this->realTableName( 'mwuser', $format );
1289                         default:
1290                                 return $this->realTableName( $name, $format );
1291                 }
1292         }
1293
1294         /**
1295          * call this instead of tableName() in the updater when renaming tables
1296          * @param string $name
1297          * @param string $format One of quoted, raw, or split
1298          * @return string
1299          */
1300         function realTableName( $name, $format = 'quoted' ) {
1301                 $table = parent::tableName( $name, $format );
1302                 if ( $format == 'split' ) {
1303                         // Used internally, we want the schema split off from the table name and returned
1304                         // as a list with 3 elements (database, schema, table)
1305                         $table = explode( '.', $table );
1306                         while ( count( $table ) < 3 ) {
1307                                 array_unshift( $table, false );
1308                         }
1309                 }
1310                 return $table;
1311         }
1312
1313         /**
1314          * Delete a table
1315          * @param string $tableName
1316          * @param string $fName
1317          * @return bool|ResultWrapper
1318          * @since 1.18
1319          */
1320         public function dropTable( $tableName, $fName = __METHOD__ ) {
1321                 if ( !$this->tableExists( $tableName, $fName ) ) {
1322                         return false;
1323                 }
1324
1325                 // parent function incorrectly appends CASCADE, which we don't want
1326                 $sql = "DROP TABLE " . $this->tableName( $tableName );
1327
1328                 return $this->query( $sql, $fName );
1329         }
1330
1331         /**
1332          * Called in the installer and updater.
1333          * Probably doesn't need to be called anywhere else in the codebase.
1334          * @param bool|null $value
1335          * @return bool|null
1336          */
1337         public function prepareStatements( $value = null ) {
1338                 $old = $this->mPrepareStatements;
1339                 if ( $value !== null ) {
1340                         $this->mPrepareStatements = $value;
1341                 }
1342
1343                 return $old;
1344         }
1345
1346         /**
1347          * Called in the installer and updater.
1348          * Probably doesn't need to be called anywhere else in the codebase.
1349          * @param bool|null $value
1350          * @return bool|null
1351          */
1352         public function scrollableCursor( $value = null ) {
1353                 $old = $this->mScrollableCursor;
1354                 if ( $value !== null ) {
1355                         $this->mScrollableCursor = $value;
1356                 }
1357
1358                 return $old;
1359         }
1360 }