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 use Wikimedia\Rdbms\ResultWrapper;
  31 use Wikimedia\Rdbms\MssqlResultWrapper;
  32
  33 /**
  34  * @ingroup Database
  35  */
  36 class DatabaseMssql extends Database {
  37         protected $mPort;
  38         protected $mUseWindowsAuth = false;
  39
  40         protected $mInsertId = null;
  41         protected $mLastResult = null;
  42         protected $mAffectedRows = null;
  43         protected $mSubqueryId = 0;
  44         protected $mScrollableCursor = true;
  45         protected $mPrepareStatements = true;
  46         protected $mBinaryColumnCache = null;
  47         protected $mBitColumnCache = null;
  48         protected $mIgnoreDupKeyErrors = false;
  49         protected $mIgnoreErrors = [];
  50
  51         public function implicitGroupby() {
  52                 return false;
  53         }
  54
  55         public function implicitOrderby() {
  56                 return false;
  57         }
  58
  59         public function unionSupportsOrderAndLimit() {
  60                 return false;
  61         }
  62
  63         public function __construct( array $params ) {
  64                 $this->mPort = $params['port'];
  65                 $this->mUseWindowsAuth = $params['UseWindowsAuth'];
  66
  67                 parent::__construct( $params );
  68         }
  69
  70         /**
  71          * Usually aborts on failure
  72          * @param string $server
  73          * @param string $user
  74          * @param string $password
  75          * @param string $dbName
  76          * @throws DBConnectionError
  77          * @return bool|resource|null
  78          */
  79         public function open( $server, $user, $password, $dbName ) {
  80                 # Test for driver support, to avoid suppressed fatal error
  81                 if ( !function_exists( 'sqlsrv_connect' ) ) {
  82                         throw new DBConnectionError(
  83                                 $this,
  84                                 "Microsoft SQL Server Native (sqlsrv) functions missing.
  85                                 You can download the driver from: http://go.microsoft.com/fwlink/?LinkId=123470\n"
  86                         );
  87                 }
  88
  89                 # e.g. the class is being loaded
  90                 if ( !strlen( $user ) ) {
  91                         return null;
  92                 }
  93
  94                 $this->close();
  95                 $this->mServer = $server;
  96                 $this->mUser = $user;
  97                 $this->mPassword = $password;
  98                 $this->mDBname = $dbName;
  99
 100                 $connectionInfo = [];
 101
 102                 if ( $dbName ) {
 103                         $connectionInfo['Database'] = $dbName;
 104                 }
 105
 106                 // Decide which auth scenerio to use
 107                 // if we are using Windows auth, then don't add credentials to $connectionInfo
 108                 if ( !$this->mUseWindowsAuth ) {
 109                         $connectionInfo['UID'] = $user;
 110                         $connectionInfo['PWD'] = $password;
 111                 }
 112
 113                 MediaWiki\suppressWarnings();
 114                 $this->mConn = sqlsrv_connect( $server, $connectionInfo );
 115                 MediaWiki\restoreWarnings();
 116
 117                 if ( $this->mConn === false ) {
 118                         throw new DBConnectionError( $this, $this->lastError() );
 119                 }
 120
 121                 $this->mOpened = true;
 122
 123                 return $this->mConn;
 124         }
 125
 126         /**
 127          * Closes a database connection, if it is open
 128          * Returns success, true if already closed
 129          * @return bool
 130          */
 131         protected function closeConnection() {
 132                 return sqlsrv_close( $this->mConn );
 133         }
 134
 135         /**
 136          * @param bool|MssqlResultWrapper|resource $result
 137          * @return bool|MssqlResultWrapper
 138          */
 139         protected function resultObject( $result ) {
 140                 if ( !$result ) {
 141                         return false;
 142                 } elseif ( $result instanceof MssqlResultWrapper ) {
 143                         return $result;
 144                 } elseif ( $result === true ) {
 145                         // Successful write query
 146                         return $result;
 147                 } else {
 148                         return new MssqlResultWrapper( $this, $result );
 149                 }
 150         }
 151
 152         /**
 153          * @param string $sql
 154          * @return bool|MssqlResultWrapper|resource
 155          * @throws DBUnexpectedError
 156          */
 157         protected function doQuery( $sql ) {
 158                 // several extensions seem to think that all databases support limits
 159                 // via LIMIT N after the WHERE clause, but  MSSQL uses SELECT TOP N,
 160                 // so to catch any of those extensions we'll do a quick check for a
 161                 // LIMIT clause and pass $sql through $this->LimitToTopN() which parses
 162                 // the LIMIT clause and passes the result to $this->limitResult();
 163                 if ( preg_match( '/\bLIMIT\s*/i', $sql ) ) {
 164                         // massage LIMIT -> TopN
 165                         $sql = $this->LimitToTopN( $sql );
 166                 }
 167
 168                 // MSSQL doesn't have EXTRACT(epoch FROM XXX)
 169                 if ( preg_match( '#\bEXTRACT\s*?\(\s*?EPOCH\s+FROM\b#i', $sql, $matches ) ) {
 170                         // This is same as UNIX_TIMESTAMP, we need to calc # of seconds from 1970
 171                         $sql = str_replace( $matches[0], "DATEDIFF(s,CONVERT(datetime,'1/1/1970'),", $sql );
 172                 }
 173
 174                 // perform query
 175
 176                 // SQLSRV_CURSOR_STATIC is slower than SQLSRV_CURSOR_CLIENT_BUFFERED (one of the two is
 177                 // needed if we want to be able to seek around the result set), however CLIENT_BUFFERED
 178                 // has a bug in the sqlsrv driver where wchar_t types (such as nvarchar) that are empty
 179                 // strings make php throw a fatal error "Severe error translating Unicode"
 180                 if ( $this->mScrollableCursor ) {
 181                         $scrollArr = [ 'Scrollable' => SQLSRV_CURSOR_STATIC ];
 182                 } else {
 183                         $scrollArr = [];
 184                 }
 185
 186                 if ( $this->mPrepareStatements ) {
 187                         // we do prepare + execute so we can get its field metadata for later usage if desired
 188                         $stmt = sqlsrv_prepare( $this->mConn, $sql, [], $scrollArr );
 189                         $success = sqlsrv_execute( $stmt );
 190                 } else {
 191                         $stmt = sqlsrv_query( $this->mConn, $sql, [], $scrollArr );
 192                         $success = (bool)$stmt;
 193                 }
 194
 195                 // Make a copy to ensure what we add below does not get reflected in future queries
 196                 $ignoreErrors = $this->mIgnoreErrors;
 197
 198                 if ( $this->mIgnoreDupKeyErrors ) {
 199                         // ignore duplicate key errors
 200                         // this emulates INSERT IGNORE in MySQL
 201                         $ignoreErrors[] = '2601'; // duplicate key error caused by unique index
 202                         $ignoreErrors[] = '2627'; // duplicate key error caused by primary key
 203                         $ignoreErrors[] = '3621'; // generic "the statement has been terminated" error
 204                 }
 205
 206                 if ( $success === false ) {
 207                         $errors = sqlsrv_errors();
 208                         $success = true;
 209
 210                         foreach ( $errors as $err ) {
 211                                 if ( !in_array( $err['code'], $ignoreErrors ) ) {
 212                                         $success = false;
 213                                         break;
 214                                 }
 215                         }
 216
 217                         if ( $success === false ) {
 218                                 return false;
 219                         }
 220                 }
 221                 // remember number of rows affected
 222                 $this->mAffectedRows = sqlsrv_rows_affected( $stmt );
 223
 224                 return $stmt;
 225         }
 226
 227         public function freeResult( $res ) {
 228                 if ( $res instanceof ResultWrapper ) {
 229                         $res = $res->result;
 230                 }
 231
 232                 sqlsrv_free_stmt( $res );
 233         }
 234
 235         /**
 236          * @param MssqlResultWrapper $res
 237          * @return stdClass
 238          */
 239         public function fetchObject( $res ) {
 240                 // $res is expected to be an instance of MssqlResultWrapper here
 241                 return $res->fetchObject();
 242         }
 243
 244         /**
 245          * @param MssqlResultWrapper $res
 246          * @return array
 247          */
 248         public function fetchRow( $res ) {
 249                 return $res->fetchRow();
 250         }
 251
 252         /**
 253          * @param mixed $res
 254          * @return int
 255          */
 256         public function numRows( $res ) {
 257                 if ( $res instanceof ResultWrapper ) {
 258                         $res = $res->result;
 259                 }
 260
 261                 $ret = sqlsrv_num_rows( $res );
 262
 263                 if ( $ret === false ) {
 264                         // we cannot get an amount of rows from this cursor type
 265                         // has_rows returns bool true/false if the result has rows
 266                         $ret = (int)sqlsrv_has_rows( $res );
 267                 }
 268
 269                 return $ret;
 270         }
 271
 272         /**
 273          * @param mixed $res
 274          * @return int
 275          */
 276         public function numFields( $res ) {
 277                 if ( $res instanceof ResultWrapper ) {
 278                         $res = $res->result;
 279                 }
 280
 281                 return sqlsrv_num_fields( $res );
 282         }
 283
 284         /**
 285          * @param mixed $res
 286          * @param int $n
 287          * @return int
 288          */
 289         public function fieldName( $res, $n ) {
 290                 if ( $res instanceof ResultWrapper ) {
 291                         $res = $res->result;
 292                 }
 293
 294                 return sqlsrv_field_metadata( $res )[$n]['Name'];
 295         }
 296
 297         /**
 298          * This must be called after nextSequenceVal
 299          * @return int|null
 300          */
 301         public function insertId() {
 302                 return $this->mInsertId;
 303         }
 304
 305         /**
 306          * @param MssqlResultWrapper $res
 307          * @param int $row
 308          * @return bool
 309          */
 310         public function dataSeek( $res, $row ) {
 311                 return $res->seek( $row );
 312         }
 313
 314         /**
 315          * @return string
 316          */
 317         public function lastError() {
 318                 $strRet = '';
 319                 $retErrors = sqlsrv_errors( SQLSRV_ERR_ALL );
 320                 if ( $retErrors != null ) {
 321                         foreach ( $retErrors as $arrError ) {
 322                                 $strRet .= $this->formatError( $arrError ) . "\n";
 323                         }
 324                 } else {
 325                         $strRet = "No errors found";
 326                 }
 327
 328                 return $strRet;
 329         }
 330
 331         /**
 332          * @param array $err
 333          * @return string
 334          */
 335         private function formatError( $err ) {
 336                 return '[SQLSTATE ' .
 337                         $err['SQLSTATE'] . '][Error Code ' . $err['code'] . ']' . $err['message'];
 338         }
 339
 340         /**
 341          * @return string|int
 342          */
 343         public function lastErrno() {
 344                 $err = sqlsrv_errors( SQLSRV_ERR_ALL );
 345                 if ( $err !== null && isset( $err[0] ) ) {
 346                         return $err[0]['code'];
 347                 } else {
 348                         return 0;
 349                 }
 350         }
 351
 352         /**
 353          * @return int
 354          */
 355         public function affectedRows() {
 356                 return $this->mAffectedRows;
 357         }
 358
 359         /**
 360          * SELECT wrapper
 361          *
 362          * @param mixed $table Array or string, table name(s) (prefix auto-added)
 363          * @param mixed $vars Array or string, field name(s) to be retrieved
 364          * @param mixed $conds Array or string, condition(s) for WHERE
 365          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
 366          * @param array $options Associative array of options (e.g.
 367          *   [ 'GROUP BY' => 'page_title' ]), see Database::makeSelectOptions
 368          *   code for list of supported stuff
 369          * @param array $join_conds Associative array of table join conditions
 370          *   (optional) (e.g. [ 'page' => [ 'LEFT JOIN','page_latest=rev_id' ] ]
 371          * @return mixed Database result resource (feed to Database::fetchObject
 372          *   or whatever), or false on failure
 373          * @throws DBQueryError
 374          * @throws DBUnexpectedError
 375          * @throws Exception
 376          */
 377         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
 378                 $options = [], $join_conds = []
 379         ) {
 380                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
 381                 if ( isset( $options['EXPLAIN'] ) ) {
 382                         try {
 383                                 $this->mScrollableCursor = false;
 384                                 $this->mPrepareStatements = false;
 385                                 $this->query( "SET SHOWPLAN_ALL ON" );
 386                                 $ret = $this->query( $sql, $fname );
 387                                 $this->query( "SET SHOWPLAN_ALL OFF" );
 388                         } catch ( DBQueryError $dqe ) {
 389                                 if ( isset( $options['FOR COUNT'] ) ) {
 390                                         // likely don't have privs for SHOWPLAN, so run a select count instead
 391                                         $this->query( "SET SHOWPLAN_ALL OFF" );
 392                                         unset( $options['EXPLAIN'] );
 393                                         $ret = $this->select(
 394                                                 $table,
 395                                                 'COUNT(*) AS EstimateRows',
 396                                                 $conds,
 397                                                 $fname,
 398                                                 $options,
 399                                                 $join_conds
 400                                         );
 401                                 } else {
 402                                         // someone actually wanted the query plan instead of an est row count
 403                                         // let them know of the error
 404                                         $this->mScrollableCursor = true;
 405                                         $this->mPrepareStatements = true;
 406                                         throw $dqe;
 407                                 }
 408                         }
 409                         $this->mScrollableCursor = true;
 410                         $this->mPrepareStatements = true;
 411                         return $ret;
 412                 }
 413                 return $this->query( $sql, $fname );
 414         }
 415
 416         /**
 417          * SELECT wrapper
 418          *
 419          * @param mixed $table Array or string, table name(s) (prefix auto-added)
 420          * @param mixed $vars Array or string, field name(s) to be retrieved
 421          * @param mixed $conds Array or string, condition(s) for WHERE
 422          * @param string $fname Calling function name (use __METHOD__) for logs/profiling
 423          * @param array $options Associative array of options (e.g. [ 'GROUP BY' => 'page_title' ]),
 424          *   see Database::makeSelectOptions code for list of supported stuff
 425          * @param array $join_conds Associative array of table join conditions (optional)
 426          *    (e.g. [ 'page' => [ 'LEFT JOIN','page_latest=rev_id' ] ]
 427          * @return string The SQL text
 428          */
 429         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
 430                 $options = [], $join_conds = []
 431         ) {
 432                 if ( isset( $options['EXPLAIN'] ) ) {
 433                         unset( $options['EXPLAIN'] );
 434                 }
 435
 436                 $sql = parent::selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
 437
 438                 // try to rewrite aggregations of bit columns (currently MAX and MIN)
 439                 if ( strpos( $sql, 'MAX(' ) !== false || strpos( $sql, 'MIN(' ) !== false ) {
 440                         $bitColumns = [];
 441                         if ( is_array( $table ) ) {
 442                                 foreach ( $table as $t ) {
 443                                         $bitColumns += $this->getBitColumns( $this->tableName( $t ) );
 444                                 }
 445                         } else {
 446                                 $bitColumns = $this->getBitColumns( $this->tableName( $table ) );
 447                         }
 448
 449                         foreach ( $bitColumns as $col => $info ) {
 450                                 $replace = [
 451                                         "MAX({$col})" => "MAX(CAST({$col} AS tinyint))",
 452                                         "MIN({$col})" => "MIN(CAST({$col} AS tinyint))",
 453                                 ];
 454                                 $sql = str_replace( array_keys( $replace ), array_values( $replace ), $sql );
 455                         }
 456                 }
 457
 458                 return $sql;
 459         }
 460
 461         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
 462                 $fname = __METHOD__
 463         ) {
 464                 $this->mScrollableCursor = false;
 465                 try {
 466                         parent::deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds, $fname );
 467                 } catch ( Exception $e ) {
 468                         $this->mScrollableCursor = true;
 469                         throw $e;
 470                 }
 471                 $this->mScrollableCursor = true;
 472         }
 473
 474         public function delete( $table, $conds, $fname = __METHOD__ ) {
 475                 $this->mScrollableCursor = false;
 476                 try {
 477                         parent::delete( $table, $conds, $fname );
 478                 } catch ( Exception $e ) {
 479                         $this->mScrollableCursor = true;
 480                         throw $e;
 481                 }
 482                 $this->mScrollableCursor = true;
 483         }
 484
 485         /**
 486          * Estimate rows in dataset
 487          * Returns estimated count, based on SHOWPLAN_ALL output
 488          * This is not necessarily an accurate estimate, so use sparingly
 489          * Returns -1 if count cannot be found
 490          * Takes same arguments as Database::select()
 491          * @param string $table
 492          * @param string $vars
 493          * @param string $conds
 494          * @param string $fname
 495          * @param array $options
 496          * @return int
 497          */
 498         public function estimateRowCount( $table, $vars = '*', $conds = '',
 499                 $fname = __METHOD__, $options = []
 500         ) {
 501                 // http://msdn2.microsoft.com/en-us/library/aa259203.aspx
 502                 $options['EXPLAIN'] = true;
 503                 $options['FOR COUNT'] = true;
 504                 $res = $this->select( $table, $vars, $conds, $fname, $options );
 505
 506                 $rows = -1;
 507                 if ( $res ) {
 508                         $row = $this->fetchRow( $res );
 509
 510                         if ( isset( $row['EstimateRows'] ) ) {
 511                                 $rows = (int)$row['EstimateRows'];
 512                         }
 513                 }
 514
 515                 return $rows;
 516         }
 517
 518         /**
 519          * Returns information about an index
 520          * If errors are explicitly ignored, returns NULL on failure
 521          * @param string $table
 522          * @param string $index
 523          * @param string $fname
 524          * @return array|bool|null
 525          */
 526         public function indexInfo( $table, $index, $fname = __METHOD__ ) {
 527                 # This does not return the same info as MYSQL would, but that's OK
 528                 # because MediaWiki never uses the returned value except to check for
 529                 # the existence of indexes.
 530                 $sql = "sp_helpindex '" . $this->tableName( $table ) . "'";
 531                 $res = $this->query( $sql, $fname );
 532
 533                 if ( !$res ) {
 534                         return null;
 535                 }
 536
 537                 $result = [];
 538                 foreach ( $res as $row ) {
 539                         if ( $row->index_name == $index ) {
 540                                 $row->Non_unique = !stristr( $row->index_description, "unique" );
 541                                 $cols = explode( ", ", $row->index_keys );
 542                                 foreach ( $cols as $col ) {
 543                                         $row->Column_name = trim( $col );
 544                                         $result[] = clone $row;
 545                                 }
 546                         } elseif ( $index == 'PRIMARY' && stristr( $row->index_description, 'PRIMARY' ) ) {
 547                                 $row->Non_unique = 0;
 548                                 $cols = explode( ", ", $row->index_keys );
 549                                 foreach ( $cols as $col ) {
 550                                         $row->Column_name = trim( $col );
 551                                         $result[] = clone $row;
 552                                 }
 553                         }
 554                 }
 555
 556                 return empty( $result ) ? false : $result;
 557         }
 558
 559         /**
 560          * INSERT wrapper, inserts an array into a table
 561          *
 562          * $arrToInsert may be a single associative array, or an array of these with numeric keys, for
 563          * multi-row insert.
 564          *
 565          * Usually aborts on failure
 566          * If errors are explicitly ignored, returns success
 567          * @param string $table
 568          * @param array $arrToInsert
 569          * @param string $fname
 570          * @param array $options
 571          * @return bool
 572          * @throws Exception
 573          */
 574         public function insert( $table, $arrToInsert, $fname = __METHOD__, $options = [] ) {
 575                 # No rows to insert, easy just return now
 576                 if ( !count( $arrToInsert ) ) {
 577                         return true;
 578                 }
 579
 580                 if ( !is_array( $options ) ) {
 581                         $options = [ $options ];
 582                 }
 583
 584                 $table = $this->tableName( $table );
 585
 586                 if ( !( isset( $arrToInsert[0] ) && is_array( $arrToInsert[0] ) ) ) { // Not multi row
 587                         $arrToInsert = [ 0 => $arrToInsert ]; // make everything multi row compatible
 588                 }
 589
 590                 // We know the table we're inserting into, get its identity column
 591                 $identity = null;
 592                 // strip matching square brackets and the db/schema from table name
 593                 $tableRawArr = explode( '.', preg_replace( '#\[([^\]]*)\]#', '$1', $table ) );
 594                 $tableRaw = array_pop( $tableRawArr );
 595                 $res = $this->doQuery(
 596                         "SELECT NAME AS idColumn FROM SYS.IDENTITY_COLUMNS " .
 597                                 "WHERE OBJECT_NAME(OBJECT_ID)='{$tableRaw}'"
 598                 );
 599                 if ( $res && sqlsrv_has_rows( $res ) ) {
 600                         // There is an identity for this table.
 601                         $identityArr = sqlsrv_fetch_array( $res, SQLSRV_FETCH_ASSOC );
 602                         $identity = array_pop( $identityArr );
 603                 }
 604                 sqlsrv_free_stmt( $res );
 605
 606                 // Determine binary/varbinary fields so we can encode data as a hex string like 0xABCDEF
 607                 $binaryColumns = $this->getBinaryColumns( $table );
 608
 609                 // INSERT IGNORE is not supported by SQL Server
 610                 // remove IGNORE from options list and set ignore flag to true
 611                 if ( in_array( 'IGNORE', $options ) ) {
 612                         $options = array_diff( $options, [ 'IGNORE' ] );
 613                         $this->mIgnoreDupKeyErrors = true;
 614                 }
 615
 616                 $ret = null;
 617                 foreach ( $arrToInsert as $a ) {
 618                         // start out with empty identity column, this is so we can return
 619                         // it as a result of the INSERT logic
 620                         $sqlPre = '';
 621                         $sqlPost = '';
 622                         $identityClause = '';
 623
 624                         // if we have an identity column
 625                         if ( $identity ) {
 626                                 // iterate through
 627                                 foreach ( $a as $k => $v ) {
 628                                         if ( $k == $identity ) {
 629                                                 if ( !is_null( $v ) ) {
 630                                                         // there is a value being passed to us,
 631                                                         // we need to turn on and off inserted identity
 632                                                         $sqlPre = "SET IDENTITY_INSERT $table ON;";
 633                                                         $sqlPost = ";SET IDENTITY_INSERT $table OFF;";
 634                                                 } else {
 635                                                         // we can't insert NULL into an identity column,
 636                                                         // so remove the column from the insert.
 637                                                         unset( $a[$k] );
 638                                                 }
 639                                         }
 640                                 }
 641
 642                                 // we want to output an identity column as result
 643                                 $identityClause = "OUTPUT INSERTED.$identity ";
 644                         }
 645
 646                         $keys = array_keys( $a );
 647
 648                         // Build the actual query
 649                         $sql = $sqlPre . 'INSERT ' . implode( ' ', $options ) .
 650                                 " INTO $table (" . implode( ',', $keys ) . ") $identityClause VALUES (";
 651
 652                         $first = true;
 653                         foreach ( $a as $key => $value ) {
 654                                 if ( isset( $binaryColumns[$key] ) ) {
 655                                         $value = new MssqlBlob( $value );
 656                                 }
 657                                 if ( $first ) {
 658                                         $first = false;
 659                                 } else {
 660                                         $sql .= ',';
 661                                 }
 662                                 if ( is_null( $value ) ) {
 663                                         $sql .= 'null';
 664                                 } elseif ( is_array( $value ) || is_object( $value ) ) {
 665                                         if ( is_object( $value ) && $value instanceof Blob ) {
 666                                                 $sql .= $this->addQuotes( $value );
 667                                         } else {
 668                                                 $sql .= $this->addQuotes( serialize( $value ) );
 669                                         }
 670                                 } else {
 671                                         $sql .= $this->addQuotes( $value );
 672                                 }
 673                         }
 674                         $sql .= ')' . $sqlPost;
 675
 676                         // Run the query
 677                         $this->mScrollableCursor = false;
 678                         try {
 679                                 $ret = $this->query( $sql );
 680                         } catch ( Exception $e ) {
 681                                 $this->mScrollableCursor = true;
 682                                 $this->mIgnoreDupKeyErrors = false;
 683                                 throw $e;
 684                         }
 685                         $this->mScrollableCursor = true;
 686
 687                         if ( $ret instanceof ResultWrapper && !is_null( $identity ) ) {
 688                                 // Then we want to get the identity column value we were assigned and save it off
 689                                 $row = $ret->fetchObject();
 690                                 if ( is_object( $row ) ) {
 691                                         $this->mInsertId = $row->$identity;
 692                                         // It seems that mAffectedRows is -1 sometimes when OUTPUT INSERTED.identity is
 693                                         // used if we got an identity back, we know for sure a row was affected, so
 694                                         // adjust that here
 695                                         if ( $this->mAffectedRows == -1 ) {
 696                                                 $this->mAffectedRows = 1;
 697                                         }
 698                                 }
 699                         }
 700                 }
 701
 702                 $this->mIgnoreDupKeyErrors = false;
 703
 704                 return $ret;
 705         }
 706
 707         /**
 708          * INSERT SELECT wrapper
 709          * $varMap must be an associative array of the form [ 'dest1' => 'source1', ... ]
 710          * Source items may be literals rather than field names, but strings should
 711          * be quoted with Database::addQuotes().
 712          * @param string $destTable
 713          * @param array|string $srcTable May be an array of tables.
 714          * @param array $varMap
 715          * @param array $conds May be "*" to copy the whole table.
 716          * @param string $fname
 717          * @param array $insertOptions
 718          * @param array $selectOptions
 719          * @return null|ResultWrapper
 720          * @throws Exception
 721          */
 722         public function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds, $fname = __METHOD__,
 723                 $insertOptions = [], $selectOptions = []
 724         ) {
 725                 $this->mScrollableCursor = false;
 726                 try {
 727                         $ret = parent::nativeInsertSelect(
 728                                 $destTable,
 729                                 $srcTable,
 730                                 $varMap,
 731                                 $conds,
 732                                 $fname,
 733                                 $insertOptions,
 734                                 $selectOptions
 735                         );
 736                 } catch ( Exception $e ) {
 737                         $this->mScrollableCursor = true;
 738                         throw $e;
 739                 }
 740                 $this->mScrollableCursor = true;
 741
 742                 return $ret;
 743         }
 744
 745         /**
 746          * UPDATE wrapper. Takes a condition array and a SET array.
 747          *
 748          * @param string $table Name of the table to UPDATE. This will be passed through
 749          *                Database::tableName().
 750          *
 751          * @param array $values An array of values to SET. For each array element,
 752          *                the key gives the field name, and the value gives the data
 753          *                to set that field to. The data will be quoted by
 754          *                Database::addQuotes().
 755          *
 756          * @param array $conds An array of conditions (WHERE). See
 757          *                Database::select() for the details of the format of
 758          *                condition arrays. Use '*' to update all rows.
 759          *
 760          * @param string $fname The function name of the caller (from __METHOD__),
 761          *                for logging and profiling.
 762          *
 763          * @param array $options An array of UPDATE options, can be:
 764          *                   - IGNORE: Ignore unique key conflicts
 765          *                   - LOW_PRIORITY: MySQL-specific, see MySQL manual.
 766          * @return bool
 767          * @throws DBUnexpectedError
 768          * @throws Exception
 769          */
 770         function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
 771                 $table = $this->tableName( $table );
 772                 $binaryColumns = $this->getBinaryColumns( $table );
 773
 774                 $opts = $this->makeUpdateOptions( $options );
 775                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, LIST_SET, $binaryColumns );
 776
 777                 if ( $conds !== [] && $conds !== '*' ) {
 778                         $sql .= " WHERE " . $this->makeList( $conds, LIST_AND, $binaryColumns );
 779                 }
 780
 781                 $this->mScrollableCursor = false;
 782                 try {
 783                         $this->query( $sql );
 784                 } catch ( Exception $e ) {
 785                         $this->mScrollableCursor = true;
 786                         throw $e;
 787                 }
 788                 $this->mScrollableCursor = true;
 789                 return true;
 790         }
 791
 792         /**
 793          * Makes an encoded list of strings from an array
 794          * @param array $a Containing the data
 795          * @param int $mode Constant
 796          *      - LIST_COMMA:          comma separated, no field names
 797          *      - LIST_AND:            ANDed WHERE clause (without the WHERE). See
 798          *        the documentation for $conds in Database::select().
 799          *      - LIST_OR:             ORed WHERE clause (without the WHERE)
 800          *      - LIST_SET:            comma separated with field names, like a SET clause
 801          *      - LIST_NAMES:          comma separated field names
 802          * @param array $binaryColumns Contains a list of column names that are binary types
 803          *      This is a custom parameter only present for MS SQL.
 804          *
 805          * @throws DBUnexpectedError
 806          * @return string
 807          */
 808         public function makeList( $a, $mode = LIST_COMMA, $binaryColumns = [] ) {
 809                 if ( !is_array( $a ) ) {
 810                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
 811                 }
 812
 813                 if ( $mode != LIST_NAMES ) {
 814                         // In MS SQL, values need to be specially encoded when they are
 815                         // inserted into binary fields. Perform this necessary encoding
 816                         // for the specified set of columns.
 817                         foreach ( array_keys( $a ) as $field ) {
 818                                 if ( !isset( $binaryColumns[$field] ) ) {
 819                                         continue;
 820                                 }
 821
 822                                 if ( is_array( $a[$field] ) ) {
 823                                         foreach ( $a[$field] as &$v ) {
 824                                                 $v = new MssqlBlob( $v );
 825                                         }
 826                                         unset( $v );
 827                                 } else {
 828                                         $a[$field] = new MssqlBlob( $a[$field] );
 829                                 }
 830                         }
 831                 }
 832
 833                 return parent::makeList( $a, $mode );
 834         }
 835
 836         /**
 837          * @param string $table
 838          * @param string $field
 839          * @return int Returns the size of a text field, or -1 for "unlimited"
 840          */
 841         public function textFieldSize( $table, $field ) {
 842                 $table = $this->tableName( $table );
 843                 $sql = "SELECT CHARACTER_MAXIMUM_LENGTH,DATA_TYPE FROM INFORMATION_SCHEMA.Columns
 844                         WHERE TABLE_NAME = '$table' AND COLUMN_NAME = '$field'";
 845                 $res = $this->query( $sql );
 846                 $row = $this->fetchRow( $res );
 847                 $size = -1;
 848                 if ( strtolower( $row['DATA_TYPE'] ) != 'text' ) {
 849                         $size = $row['CHARACTER_MAXIMUM_LENGTH'];
 850                 }
 851
 852                 return $size;
 853         }
 854
 855         /**
 856          * Construct a LIMIT query with optional offset
 857          * This is used for query pages
 858          *
 859          * @param string $sql SQL query we will append the limit too
 860          * @param int $limit The SQL limit
 861          * @param bool|int $offset The SQL offset (default false)
 862          * @return array|string
 863          * @throws DBUnexpectedError
 864          */
 865         public function limitResult( $sql, $limit, $offset = false ) {
 866                 if ( $offset === false || $offset == 0 ) {
 867                         if ( strpos( $sql, "SELECT" ) === false ) {
 868                                 return "TOP {$limit} " . $sql;
 869                         } else {
 870                                 return preg_replace( '/\bSELECT(\s+DISTINCT)?\b/Dsi',
 871                                         'SELECT$1 TOP ' . $limit, $sql, 1 );
 872                         }
 873                 } else {
 874                         // This one is fun, we need to pull out the select list as well as any ORDER BY clause
 875                         $select = $orderby = [];
 876                         $s1 = preg_match( '#SELECT\s+(.+?)\s+FROM#Dis', $sql, $select );
 877                         $s2 = preg_match( '#(ORDER BY\s+.+?)(\s*FOR XML .*)?$#Dis', $sql, $orderby );
 878                         $postOrder = '';
 879                         $first = $offset + 1;
 880                         $last = $offset + $limit;
 881                         $sub1 = 'sub_' . $this->mSubqueryId;
 882                         $sub2 = 'sub_' . ( $this->mSubqueryId + 1 );
 883                         $this->mSubqueryId += 2;
 884                         if ( !$s1 ) {
 885                                 // wat
 886                                 throw new DBUnexpectedError( $this, "Attempting to LIMIT a non-SELECT query\n" );
 887                         }
 888                         if ( !$s2 ) {
 889                                 // no ORDER BY
 890                                 $overOrder = 'ORDER BY (SELECT 1)';
 891                         } else {
 892                                 if ( !isset( $orderby[2] ) || !$orderby[2] ) {
 893                                         // don't need to strip it out if we're using a FOR XML clause
 894                                         $sql = str_replace( $orderby[1], '', $sql );
 895                                 }
 896                                 $overOrder = $orderby[1];
 897                                 $postOrder = ' ' . $overOrder;
 898                         }
 899                         $sql = "SELECT {$select[1]}
 900                                         FROM (
 901                                                 SELECT ROW_NUMBER() OVER({$overOrder}) AS rowNumber, *
 902                                                 FROM ({$sql}) {$sub1}
 903                                         ) {$sub2}
 904                                         WHERE rowNumber BETWEEN {$first} AND {$last}{$postOrder}";
 905
 906                         return $sql;
 907                 }
 908         }
 909
 910         /**
 911          * If there is a limit clause, parse it, strip it, and pass the remaining
 912          * SQL through limitResult() with the appropriate parameters. Not the
 913          * prettiest solution, but better than building a whole new parser. This
 914          * exists becase there are still too many extensions that don't use dynamic
 915          * sql generation.
 916          *
 917          * @param string $sql
 918          * @return array|mixed|string
 919          */
 920         public function LimitToTopN( $sql ) {
 921                 // Matches: LIMIT {[offset,] row_count | row_count OFFSET offset}
 922                 $pattern = '/\bLIMIT\s+((([0-9]+)\s*,\s*)?([0-9]+)(\s+OFFSET\s+([0-9]+))?)/i';
 923                 if ( preg_match( $pattern, $sql, $matches ) ) {
 924                         $row_count = $matches[4];
 925                         $offset = $matches[3] ?: $matches[6] ?: false;
 926
 927                         // strip the matching LIMIT clause out
 928                         $sql = str_replace( $matches[0], '', $sql );
 929
 930                         return $this->limitResult( $sql, $row_count, $offset );
 931                 }
 932
 933                 return $sql;
 934         }
 935
 936         /**
 937          * @return string Wikitext of a link to the server software's web site
 938          */
 939         public function getSoftwareLink() {
 940                 return "[{{int:version-db-mssql-url}} MS SQL Server]";
 941         }
 942
 943         /**
 944          * @return string Version information from the database
 945          */
 946         public function getServerVersion() {
 947                 $server_info = sqlsrv_server_info( $this->mConn );
 948                 $version = 'Error';
 949                 if ( isset( $server_info['SQLServerVersion'] ) ) {
 950                         $version = $server_info['SQLServerVersion'];
 951                 }
 952
 953                 return $version;
 954         }
 955
 956         /**
 957          * @param string $table
 958          * @param string $fname
 959          * @return bool
 960          */
 961         public function tableExists( $table, $fname = __METHOD__ ) {
 962                 list( $db, $schema, $table ) = $this->tableName( $table, 'split' );
 963
 964                 if ( $db !== false ) {
 965                         // remote database
 966                         $this->queryLogger->error( "Attempting to call tableExists on a remote table" );
 967                         return false;
 968                 }
 969
 970                 if ( $schema === false ) {
 971                         $schema = $this->mSchema;
 972                 }
 973
 974                 $res = $this->query( "SELECT 1 FROM INFORMATION_SCHEMA.TABLES
 975                         WHERE TABLE_TYPE = 'BASE TABLE'
 976                         AND TABLE_SCHEMA = '$schema' AND TABLE_NAME = '$table'" );
 977
 978                 if ( $res->numRows() ) {
 979                         return true;
 980                 } else {
 981                         return false;
 982                 }
 983         }
 984
 985         /**
 986          * Query whether a given column exists in the mediawiki schema
 987          * @param string $table
 988          * @param string $field
 989          * @param string $fname
 990          * @return bool
 991          */
 992         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
 993                 list( $db, $schema, $table ) = $this->tableName( $table, 'split' );
 994
 995                 if ( $db !== false ) {
 996                         // remote database
 997                         $this->queryLogger->error( "Attempting to call fieldExists on a remote table" );
 998                         return false;
 999                 }
1000
1001                 $res = $this->query( "SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS
1002                         WHERE TABLE_SCHEMA = '$schema' AND TABLE_NAME = '$table' AND COLUMN_NAME = '$field'" );
1003
1004                 if ( $res->numRows() ) {
1005                         return true;
1006                 } else {
1007                         return false;
1008                 }
1009         }
1010
1011         public function fieldInfo( $table, $field ) {
1012                 list( $db, $schema, $table ) = $this->tableName( $table, 'split' );
1013
1014                 if ( $db !== false ) {
1015                         // remote database
1016                         $this->queryLogger->error( "Attempting to call fieldInfo on a remote table" );
1017                         return false;
1018                 }
1019
1020                 $res = $this->query( "SELECT * FROM INFORMATION_SCHEMA.COLUMNS
1021                         WHERE TABLE_SCHEMA = '$schema' AND TABLE_NAME = '$table' AND COLUMN_NAME = '$field'" );
1022
1023                 $meta = $res->fetchRow();
1024                 if ( $meta ) {
1025                         return new MssqlField( $meta );
1026                 }
1027
1028                 return false;
1029         }
1030
1031         /**
1032          * Begin a transaction, committing any previously open transaction
1033          * @param string $fname
1034          */
1035         protected function doBegin( $fname = __METHOD__ ) {
1036                 sqlsrv_begin_transaction( $this->mConn );
1037                 $this->mTrxLevel = 1;
1038         }
1039
1040         /**
1041          * End a transaction
1042          * @param string $fname
1043          */
1044         protected function doCommit( $fname = __METHOD__ ) {
1045                 sqlsrv_commit( $this->mConn );
1046                 $this->mTrxLevel = 0;
1047         }
1048
1049         /**
1050          * Rollback a transaction.
1051          * No-op on non-transactional databases.
1052          * @param string $fname
1053          */
1054         protected function doRollback( $fname = __METHOD__ ) {
1055                 sqlsrv_rollback( $this->mConn );
1056                 $this->mTrxLevel = 0;
1057         }
1058
1059         /**
1060          * @param string $s
1061          * @return string
1062          */
1063         public function strencode( $s ) {
1064                 // Should not be called by us
1065
1066                 return str_replace( "'", "''", $s );
1067         }
1068
1069         /**
1070          * @param string|int|null|bool|Blob $s
1071          * @return string|int
1072          */
1073         public function addQuotes( $s ) {
1074                 if ( $s instanceof MssqlBlob ) {
1075                         return $s->fetch();
1076                 } elseif ( $s instanceof Blob ) {
1077                         // this shouldn't really ever be called, but it's here if needed
1078                         // (and will quite possibly make the SQL error out)
1079                         $blob = new MssqlBlob( $s->fetch() );
1080                         return $blob->fetch();
1081                 } else {
1082                         if ( is_bool( $s ) ) {
1083                                 $s = $s ? 1 : 0;
1084                         }
1085                         return parent::addQuotes( $s );
1086                 }
1087         }
1088
1089         /**
1090          * @param string $s
1091          * @return string
1092          */
1093         public function addIdentifierQuotes( $s ) {
1094                 // http://msdn.microsoft.com/en-us/library/aa223962.aspx
1095                 return '[' . $s . ']';
1096         }
1097
1098         /**
1099          * @param string $name
1100          * @return bool
1101          */
1102         public function isQuotedIdentifier( $name ) {
1103                 return strlen( $name ) && $name[0] == '[' && substr( $name, -1, 1 ) == ']';
1104         }
1105
1106         /**
1107          * MS SQL supports more pattern operators than other databases (ex: [,],^)
1108          *
1109          * @param string $s
1110          * @return string
1111          */
1112         protected function escapeLikeInternal( $s ) {
1113                 return addcslashes( $s, '\%_[]^' );
1114         }
1115
1116         /**
1117          * MS SQL requires specifying the escape character used in a LIKE query
1118          * or using Square brackets to surround characters that are to be escaped
1119          * https://msdn.microsoft.com/en-us/library/ms179859.aspx
1120          * Here we take the Specify-Escape-Character approach since it's less
1121          * invasive, renders a query that is closer to other DB's and better at
1122          * handling square bracket escaping
1123          *
1124          * @return string Fully built LIKE statement
1125          */
1126         public function buildLike() {
1127                 $params = func_get_args();
1128                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
1129                         $params = $params[0];
1130                 }
1131
1132                 return parent::buildLike( $params ) . " ESCAPE '\' ";
1133         }
1134
1135         /**
1136          * @param string $db
1137          * @return bool
1138          */
1139         public function selectDB( $db ) {
1140                 try {
1141                         $this->mDBname = $db;
1142                         $this->query( "USE $db" );
1143                         return true;
1144                 } catch ( Exception $e ) {
1145                         return false;
1146                 }
1147         }
1148
1149         /**
1150          * @param array $options An associative array of options to be turned into
1151          *   an SQL query, valid keys are listed in the function.
1152          * @return array
1153          */
1154         public function makeSelectOptions( $options ) {
1155                 $tailOpts = '';
1156                 $startOpts = '';
1157
1158                 $noKeyOptions = [];
1159                 foreach ( $options as $key => $option ) {
1160                         if ( is_numeric( $key ) ) {
1161                                 $noKeyOptions[$option] = true;
1162                         }
1163                 }
1164
1165                 $tailOpts .= $this->makeGroupByWithHaving( $options );
1166
1167                 $tailOpts .= $this->makeOrderBy( $options );
1168
1169                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1170                         $startOpts .= 'DISTINCT';
1171                 }
1172
1173                 if ( isset( $noKeyOptions['FOR XML'] ) ) {
1174                         // used in group concat field emulation
1175                         $tailOpts .= " FOR XML PATH('')";
1176                 }
1177
1178                 // we want this to be compatible with the output of parent::makeSelectOptions()
1179                 return [ $startOpts, '', $tailOpts, '', '' ];
1180         }
1181
1182         public function getType() {
1183                 return 'mssql';
1184         }
1185
1186         /**
1187          * @param array $stringList
1188          * @return string
1189          */
1190         public function buildConcat( $stringList ) {
1191                 return implode( ' + ', $stringList );
1192         }
1193
1194         /**
1195          * Build a GROUP_CONCAT or equivalent statement for a query.
1196          * MS SQL doesn't have GROUP_CONCAT so we emulate it with other stuff (and boy is it nasty)
1197          *
1198          * This is useful for combining a field for several rows into a single string.
1199          * NULL values will not appear in the output, duplicated values will appear,
1200          * and the resulting delimiter-separated values have no defined sort order.
1201          * Code using the results may need to use the PHP unique() or sort() methods.
1202          *
1203          * @param string $delim Glue to bind the results together
1204          * @param string|array $table Table name
1205          * @param string $field Field name
1206          * @param string|array $conds Conditions
1207          * @param string|array $join_conds Join conditions
1208          * @return string SQL text
1209          * @since 1.23
1210          */
1211         public function buildGroupConcatField( $delim, $table, $field, $conds = '',
1212                 $join_conds = []
1213         ) {
1214                 $gcsq = 'gcsq_' . $this->mSubqueryId;
1215                 $this->mSubqueryId++;
1216
1217                 $delimLen = strlen( $delim );
1218                 $fld = "{$field} + {$this->addQuotes( $delim )}";
1219                 $sql = "(SELECT LEFT({$field}, LEN({$field}) - {$delimLen}) FROM ("
1220                         . $this->selectSQLText( $table, $fld, $conds, null, [ 'FOR XML' ], $join_conds )
1221                         . ") {$gcsq} ({$field}))";
1222
1223                 return $sql;
1224         }
1225
1226         /**
1227          * Returns an associative array for fields that are of type varbinary, binary, or image
1228          * $table can be either a raw table name or passed through tableName() first
1229          * @param string $table
1230          * @return array
1231          */
1232         private function getBinaryColumns( $table ) {
1233                 $tableRawArr = explode( '.', preg_replace( '#\[([^\]]*)\]#', '$1', $table ) );
1234                 $tableRaw = array_pop( $tableRawArr );
1235
1236                 if ( $this->mBinaryColumnCache === null ) {
1237                         $this->populateColumnCaches();
1238                 }
1239
1240                 return isset( $this->mBinaryColumnCache[$tableRaw] )
1241                         ? $this->mBinaryColumnCache[$tableRaw]
1242                         : [];
1243         }
1244
1245         /**
1246          * @param string $table
1247          * @return array
1248          */
1249         private function getBitColumns( $table ) {
1250                 $tableRawArr = explode( '.', preg_replace( '#\[([^\]]*)\]#', '$1', $table ) );
1251                 $tableRaw = array_pop( $tableRawArr );
1252
1253                 if ( $this->mBitColumnCache === null ) {
1254                         $this->populateColumnCaches();
1255                 }
1256
1257                 return isset( $this->mBitColumnCache[$tableRaw] )
1258                         ? $this->mBitColumnCache[$tableRaw]
1259                         : [];
1260         }
1261
1262         private function populateColumnCaches() {
1263                 $res = $this->select( 'INFORMATION_SCHEMA.COLUMNS', '*',
1264                         [
1265                                 'TABLE_CATALOG' => $this->mDBname,
1266                                 'TABLE_SCHEMA' => $this->mSchema,
1267                                 'DATA_TYPE' => [ 'varbinary', 'binary', 'image', 'bit' ]
1268                         ] );
1269
1270                 $this->mBinaryColumnCache = [];
1271                 $this->mBitColumnCache = [];
1272                 foreach ( $res as $row ) {
1273                         if ( $row->DATA_TYPE == 'bit' ) {
1274                                 $this->mBitColumnCache[$row->TABLE_NAME][$row->COLUMN_NAME] = $row;
1275                         } else {
1276                                 $this->mBinaryColumnCache[$row->TABLE_NAME][$row->COLUMN_NAME] = $row;
1277                         }
1278                 }
1279         }
1280
1281         /**
1282          * @param string $name
1283          * @param string $format
1284          * @return string
1285          */
1286         function tableName( $name, $format = 'quoted' ) {
1287                 # Replace reserved words with better ones
1288                 switch ( $name ) {
1289                         case 'user':
1290                                 return $this->realTableName( 'mwuser', $format );
1291                         default:
1292                                 return $this->realTableName( $name, $format );
1293                 }
1294         }
1295
1296         /**
1297          * call this instead of tableName() in the updater when renaming tables
1298          * @param string $name
1299          * @param string $format One of quoted, raw, or split
1300          * @return string
1301          */
1302         function realTableName( $name, $format = 'quoted' ) {
1303                 $table = parent::tableName( $name, $format );
1304                 if ( $format == 'split' ) {
1305                         // Used internally, we want the schema split off from the table name and returned
1306                         // as a list with 3 elements (database, schema, table)
1307                         $table = explode( '.', $table );
1308                         while ( count( $table ) < 3 ) {
1309                                 array_unshift( $table, false );
1310                         }
1311                 }
1312                 return $table;
1313         }
1314
1315         /**
1316          * Delete a table
1317          * @param string $tableName
1318          * @param string $fName
1319          * @return bool|ResultWrapper
1320          * @since 1.18
1321          */
1322         public function dropTable( $tableName, $fName = __METHOD__ ) {
1323                 if ( !$this->tableExists( $tableName, $fName ) ) {
1324                         return false;
1325                 }
1326
1327                 // parent function incorrectly appends CASCADE, which we don't want
1328                 $sql = "DROP TABLE " . $this->tableName( $tableName );
1329
1330                 return $this->query( $sql, $fName );
1331         }
1332
1333         /**
1334          * Called in the installer and updater.
1335          * Probably doesn't need to be called anywhere else in the codebase.
1336          * @param bool|null $value
1337          * @return bool|null
1338          */
1339         public function prepareStatements( $value = null ) {
1340                 $old = $this->mPrepareStatements;
1341                 if ( $value !== null ) {
1342                         $this->mPrepareStatements = $value;
1343                 }
1344
1345                 return $old;
1346         }
1347
1348         /**
1349          * Called in the installer and updater.
1350          * Probably doesn't need to be called anywhere else in the codebase.
1351          * @param bool|null $value
1352          * @return bool|null
1353          */
1354         public function scrollableCursor( $value = null ) {
1355                 $old = $this->mScrollableCursor;
1356                 if ( $value !== null ) {
1357                         $this->mScrollableCursor = $value;
1358                 }
1359
1360                 return $old;
1361         }
1362 }