includes/libs/rdbms/database/Database.php

   1 <?php
   2 /**
   3  * @defgroup Database Database
   4  *
   5  * This file deals with database interface functions
   6  * and query specifics/optimisations.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Database
  25  */
  26 namespace Wikimedia\Rdbms;
  27
  28 use Psr\Log\LoggerAwareInterface;
  29 use Psr\Log\LoggerInterface;
  30 use Psr\Log\NullLogger;
  31 use Wikimedia\ScopedCallback;
  32 use Wikimedia\Timestamp\ConvertibleTimestamp;
  33 use Wikimedia;
  34 use BagOStuff;
  35 use HashBagOStuff;
  36 use LogicException;
  37 use InvalidArgumentException;
  38 use UnexpectedValueException;
  39 use Exception;
  40 use RuntimeException;
  41
  42 /**
  43  * Relational database abstraction object
  44  *
  45  * @ingroup Database
  46  * @since 1.28
  47  */
  48 abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
  49         /** Number of times to re-try an operation in case of deadlock */
  50         const DEADLOCK_TRIES = 4;
  51         /** Minimum time to wait before retry, in microseconds */
  52         const DEADLOCK_DELAY_MIN = 500000;
  53         /** Maximum time to wait before retry */
  54         const DEADLOCK_DELAY_MAX = 1500000;
  55
  56         /** How long before it is worth doing a dummy query to test the connection */
  57         const PING_TTL = 1.0;
  58         const PING_QUERY = 'SELECT 1 AS ping';
  59
  60         const TINY_WRITE_SEC = 0.010;
  61         const SLOW_WRITE_SEC = 0.500;
  62         const SMALL_WRITE_ROWS = 100;
  63
  64         /** @var string Whether lock granularity is on the level of the entire database */
  65         const ATTR_DB_LEVEL_LOCKING = 'db-level-locking';
  66
  67         /** @var int New Database instance will not be connected yet when returned */
  68         const NEW_UNCONNECTED = 0;
  69         /** @var int New Database instance will already be connected when returned */
  70         const NEW_CONNECTED = 1;
  71
  72         /** @var string SQL query */
  73         protected $lastQuery = '';
  74         /** @var float|bool UNIX timestamp of last write query */
  75         protected $lastWriteTime = false;
  76         /** @var string|bool */
  77         protected $phpError = false;
  78         /** @var string Server that this instance is currently connected to */
  79         protected $server;
  80         /** @var string User that this instance is currently connected under the name of */
  81         protected $user;
  82         /** @var string Password used to establish the current connection */
  83         protected $password;
  84         /** @var string Database that this instance is currently connected to */
  85         protected $dbName;
  86         /** @var array[] Map of (table => (dbname, schema, prefix) map) */
  87         protected $tableAliases = [];
  88         /** @var string[] Map of (index alias => index) */
  89         protected $indexAliases = [];
  90         /** @var bool Whether this PHP instance is for a CLI script */
  91         protected $cliMode;
  92         /** @var string Agent name for query profiling */
  93         protected $agent;
  94         /** @var array Parameters used by initConnection() to establish a connection */
  95         protected $connectionParams = [];
  96         /** @var BagOStuff APC cache */
  97         protected $srvCache;
  98         /** @var LoggerInterface */
  99         protected $connLogger;
 100         /** @var LoggerInterface */
 101         protected $queryLogger;
 102         /** @var callback Error logging callback */
 103         protected $errorLogger;
 104
 105         /** @var resource|null Database connection */
 106         protected $conn = null;
 107         /** @var bool */
 108         protected $opened = false;
 109
 110         /** @var array[] List of (callable, method name) */
 111         protected $trxIdleCallbacks = [];
 112         /** @var array[] List of (callable, method name) */
 113         protected $trxPreCommitCallbacks = [];
 114         /** @var array[] List of (callable, method name) */
 115         protected $trxEndCallbacks = [];
 116         /** @var callable[] Map of (name => callable) */
 117         protected $trxRecurringCallbacks = [];
 118         /** @var bool Whether to suppress triggering of transaction end callbacks */
 119         protected $trxEndCallbacksSuppressed = false;
 120
 121         /** @var string */
 122         protected $tablePrefix = '';
 123         /** @var string */
 124         protected $schema = '';
 125         /** @var int */
 126         protected $flags;
 127         /** @var array */
 128         protected $lbInfo = [];
 129         /** @var array|bool */
 130         protected $schemaVars = false;
 131         /** @var array */
 132         protected $sessionVars = [];
 133         /** @var array|null */
 134         protected $preparedArgs;
 135         /** @var string|bool|null Stashed value of html_errors INI setting */
 136         protected $htmlErrors;
 137         /** @var string */
 138         protected $delimiter = ';';
 139         /** @var DatabaseDomain */
 140         protected $currentDomain;
 141         /** @var integer|null Rows affected by the last query to query() or its CRUD wrappers */
 142         protected $affectedRowCount;
 143
 144         /**
 145          * @var int Transaction status
 146          */
 147         protected $trxStatus = self::STATUS_TRX_NONE;
 148         /**
 149          * @var Exception|null The last error that caused the status to become STATUS_TRX_ERROR
 150          */
 151         protected $trxStatusCause;
 152         /**
 153          * Either 1 if a transaction is active or 0 otherwise.
 154          * The other Trx fields may not be meaningfull if this is 0.
 155          *
 156          * @var int
 157          */
 158         protected $trxLevel = 0;
 159         /**
 160          * Either a short hexidecimal string if a transaction is active or ""
 161          *
 162          * @var string
 163          * @see Database::trxLevel
 164          */
 165         protected $trxShortId = '';
 166         /**
 167          * The UNIX time that the transaction started. Callers can assume that if
 168          * snapshot isolation is used, then the data is *at least* up to date to that
 169          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 170          *
 171          * @var float|null
 172          * @see Database::trxLevel
 173          */
 174         private $trxTimestamp = null;
 175         /** @var float Lag estimate at the time of BEGIN */
 176         private $trxReplicaLag = null;
 177         /**
 178          * Remembers the function name given for starting the most recent transaction via begin().
 179          * Used to provide additional context for error reporting.
 180          *
 181          * @var string
 182          * @see Database::trxLevel
 183          */
 184         private $trxFname = null;
 185         /**
 186          * Record if possible write queries were done in the last transaction started
 187          *
 188          * @var bool
 189          * @see Database::trxLevel
 190          */
 191         private $trxDoneWrites = false;
 192         /**
 193          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 194          *
 195          * @var bool
 196          * @see Database::trxLevel
 197          */
 198         private $trxAutomatic = false;
 199         /**
 200          * Counter for atomic savepoint identifiers. Reset when a new transaction begins.
 201          *
 202          * @var int
 203          */
 204         private $trxAtomicCounter = 0;
 205         /**
 206          * Array of levels of atomicity within transactions
 207          *
 208          * @var array
 209          */
 210         private $trxAtomicLevels = [];
 211         /**
 212          * Record if the current transaction was started implicitly by Database::startAtomic
 213          *
 214          * @var bool
 215          */
 216         private $trxAutomaticAtomic = false;
 217         /**
 218          * Track the write query callers of the current transaction
 219          *
 220          * @var string[]
 221          */
 222         private $trxWriteCallers = [];
 223         /**
 224          * @var float Seconds spent in write queries for the current transaction
 225          */
 226         private $trxWriteDuration = 0.0;
 227         /**
 228          * @var int Number of write queries for the current transaction
 229          */
 230         private $trxWriteQueryCount = 0;
 231         /**
 232          * @var int Number of rows affected by write queries for the current transaction
 233          */
 234         private $trxWriteAffectedRows = 0;
 235         /**
 236          * @var float Like trxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 237          */
 238         private $trxWriteAdjDuration = 0.0;
 239         /**
 240          * @var int Number of write queries counted in trxWriteAdjDuration
 241          */
 242         private $trxWriteAdjQueryCount = 0;
 243         /**
 244          * @var float RTT time estimate
 245          */
 246         private $rttEstimate = 0.0;
 247
 248         /** @var array Map of (name => 1) for locks obtained via lock() */
 249         private $namedLocksHeld = [];
 250         /** @var array Map of (table name => 1) for TEMPORARY tables */
 251         protected $sessionTempTables = [];
 252
 253         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 254         private $lazyMasterHandle;
 255
 256         /** @var float UNIX timestamp */
 257         protected $lastPing = 0.0;
 258
 259         /** @var int[] Prior flags member variable values */
 260         private $priorFlags = [];
 261
 262         /** @var object|string Class name or object With profileIn/profileOut methods */
 263         protected $profiler;
 264         /** @var TransactionProfiler */
 265         protected $trxProfiler;
 266
 267         /** @var int */
 268         protected $nonNativeInsertSelectBatchSize = 10000;
 269
 270         /** @var int Transaction is in a error state requiring a full or savepoint rollback */
 271         const STATUS_TRX_ERROR = 1;
 272         /** @var int Transaction is active and in a normal state */
 273         const STATUS_TRX_OK = 2;
 274         /** @var int No transaction is active */
 275         const STATUS_TRX_NONE = 3;
 276
 277         /**
 278          * @note: exceptions for missing libraries/drivers should be thrown in initConnection()
 279          * @param array $params Parameters passed from Database::factory()
 280          */
 281         protected function __construct( array $params ) {
 282                 foreach ( [ 'host', 'user', 'password', 'dbname' ] as $name ) {
 283                         $this->connectionParams[$name] = $params[$name];
 284                 }
 285
 286                 $this->schema = $params['schema'];
 287                 $this->tablePrefix = $params['tablePrefix'];
 288
 289                 $this->cliMode = $params['cliMode'];
 290                 // Agent name is added to SQL queries in a comment, so make sure it can't break out
 291                 $this->agent = str_replace( '/', '-', $params['agent'] );
 292
 293                 $this->flags = $params['flags'];
 294                 if ( $this->flags & self::DBO_DEFAULT ) {
 295                         if ( $this->cliMode ) {
 296                                 $this->flags &= ~self::DBO_TRX;
 297                         } else {
 298                                 $this->flags |= self::DBO_TRX;
 299                         }
 300                 }
 301                 // Disregard deprecated DBO_IGNORE flag (T189999)
 302                 $this->flags &= ~self::DBO_IGNORE;
 303
 304                 $this->sessionVars = $params['variables'];
 305
 306                 $this->srvCache = isset( $params['srvCache'] )
 307                         ? $params['srvCache']
 308                         : new HashBagOStuff();
 309
 310                 $this->profiler = $params['profiler'];
 311                 $this->trxProfiler = $params['trxProfiler'];
 312                 $this->connLogger = $params['connLogger'];
 313                 $this->queryLogger = $params['queryLogger'];
 314                 $this->errorLogger = $params['errorLogger'];
 315
 316                 if ( isset( $params['nonNativeInsertSelectBatchSize'] ) ) {
 317                         $this->nonNativeInsertSelectBatchSize = $params['nonNativeInsertSelectBatchSize'];
 318                 }
 319
 320                 // Set initial dummy domain until open() sets the final DB/prefix
 321                 $this->currentDomain = DatabaseDomain::newUnspecified();
 322         }
 323
 324         /**
 325          * Initialize the connection to the database over the wire (or to local files)
 326          *
 327          * @throws LogicException
 328          * @throws InvalidArgumentException
 329          * @throws DBConnectionError
 330          * @since 1.31
 331          */
 332         final public function initConnection() {
 333                 if ( $this->isOpen() ) {
 334                         throw new LogicException( __METHOD__ . ': already connected.' );
 335                 }
 336                 // Establish the connection
 337                 $this->doInitConnection();
 338                 // Set the domain object after open() sets the relevant fields
 339                 if ( $this->dbName != '' ) {
 340                         // Domains with server scope but a table prefix are not used by IDatabase classes
 341                         $this->currentDomain = new DatabaseDomain( $this->dbName, null, $this->tablePrefix );
 342                 }
 343         }
 344
 345         /**
 346          * Actually connect to the database over the wire (or to local files)
 347          *
 348          * @throws InvalidArgumentException
 349          * @throws DBConnectionError
 350          * @since 1.31
 351          */
 352         protected function doInitConnection() {
 353                 if ( strlen( $this->connectionParams['user'] ) ) {
 354                         $this->open(
 355                                 $this->connectionParams['host'],
 356                                 $this->connectionParams['user'],
 357                                 $this->connectionParams['password'],
 358                                 $this->connectionParams['dbname']
 359                         );
 360                 } else {
 361                         throw new InvalidArgumentException( "No database user provided." );
 362                 }
 363         }
 364
 365         /**
 366          * Construct a Database subclass instance given a database type and parameters
 367          *
 368          * This also connects to the database immediately upon object construction
 369          *
 370          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 371          * @param array $p Parameter map with keys:
 372          *   - host : The hostname of the DB server
 373          *   - user : The name of the database user the client operates under
 374          *   - password : The password for the database user
 375          *   - dbname : The name of the database to use where queries do not specify one.
 376          *      The database must exist or an error might be thrown. Setting this to the empty string
 377          *      will avoid any such errors and make the handle have no implicit database scope. This is
 378          *      useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
 379          *      "database" in Postgres is rougly equivalent to an entire MySQL server. This the domain
 380          *      in which user names and such are defined, e.g. users are database-specific in Postgres.
 381          *   - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
 382          *      equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
 383          *   - tablePrefix : Optional table prefix that is implicitly added on to all table names
 384          *      recognized in queries. This can be used in place of schemas for handle site farms.
 385          *   - flags : Optional bitfield of DBO_* constants that define connection, protocol,
 386          *      buffering, and transaction behavior. It is STRONGLY adviced to leave the DBO_DEFAULT
 387          *      flag in place UNLESS this this database simply acts as a key/value store.
 388          *   - driver: Optional name of a specific DB client driver. For MySQL, there is only the
 389          *      'mysqli' driver; the old one 'mysql' has been removed.
 390          *   - variables: Optional map of session variables to set after connecting. This can be
 391          *      used to adjust lock timeouts or encoding modes and the like.
 392          *   - connLogger: Optional PSR-3 logger interface instance.
 393          *   - queryLogger: Optional PSR-3 logger interface instance.
 394          *   - profiler: Optional class name or object with profileIn()/profileOut() methods.
 395          *      These will be called in query(), using a simplified version of the SQL that also
 396          *      includes the agent as a SQL comment.
 397          *   - trxProfiler: Optional TransactionProfiler instance.
 398          *   - errorLogger: Optional callback that takes an Exception and logs it.
 399          *   - cliMode: Whether to consider the execution context that of a CLI script.
 400          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 401          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 402          *   - nonNativeInsertSelectBatchSize: Optional batch size for non-native INSERT SELECT emulation.
 403          * @param int $connect One of the class constants (NEW_CONNECTED, NEW_UNCONNECTED) [optional]
 404          * @return Database|null If the database driver or extension cannot be found
 405          * @throws InvalidArgumentException If the database driver or extension cannot be found
 406          * @since 1.18
 407          */
 408         final public static function factory( $dbType, $p = [], $connect = self::NEW_CONNECTED ) {
 409                 $class = self::getClass( $dbType, isset( $p['driver'] ) ? $p['driver'] : null );
 410
 411                 if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 412                         // Resolve some defaults for b/c
 413                         $p['host'] = isset( $p['host'] ) ? $p['host'] : false;
 414                         $p['user'] = isset( $p['user'] ) ? $p['user'] : false;
 415                         $p['password'] = isset( $p['password'] ) ? $p['password'] : false;
 416                         $p['dbname'] = isset( $p['dbname'] ) ? $p['dbname'] : false;
 417                         $p['flags'] = isset( $p['flags'] ) ? $p['flags'] : 0;
 418                         $p['variables'] = isset( $p['variables'] ) ? $p['variables'] : [];
 419                         $p['tablePrefix'] = isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : '';
 420                         $p['schema'] = isset( $p['schema'] ) ? $p['schema'] : '';
 421                         $p['cliMode'] = isset( $p['cliMode'] )
 422                                 ? $p['cliMode']
 423                                 : ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 424                         $p['agent'] = isset( $p['agent'] ) ? $p['agent'] : '';
 425                         if ( !isset( $p['connLogger'] ) ) {
 426                                 $p['connLogger'] = new NullLogger();
 427                         }
 428                         if ( !isset( $p['queryLogger'] ) ) {
 429                                 $p['queryLogger'] = new NullLogger();
 430                         }
 431                         $p['profiler'] = isset( $p['profiler'] ) ? $p['profiler'] : null;
 432                         if ( !isset( $p['trxProfiler'] ) ) {
 433                                 $p['trxProfiler'] = new TransactionProfiler();
 434                         }
 435                         if ( !isset( $p['errorLogger'] ) ) {
 436                                 $p['errorLogger'] = function ( Exception $e ) {
 437                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 438                                 };
 439                         }
 440
 441                         /** @var Database $conn */
 442                         $conn = new $class( $p );
 443                         if ( $connect == self::NEW_CONNECTED ) {
 444                                 $conn->initConnection();
 445                         }
 446                 } else {
 447                         $conn = null;
 448                 }
 449
 450                 return $conn;
 451         }
 452
 453         /**
 454          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 455          * @param string|null $driver Optional name of a specific DB client driver
 456          * @return array Map of (Database::ATTRIBUTE_* constant => value) for all such constants
 457          * @throws InvalidArgumentException
 458          * @since 1.31
 459          */
 460         final public static function attributesFromType( $dbType, $driver = null ) {
 461                 static $defaults = [ self::ATTR_DB_LEVEL_LOCKING => false ];
 462
 463                 $class = self::getClass( $dbType, $driver );
 464
 465                 return call_user_func( [ $class, 'getAttributes' ] ) + $defaults;
 466         }
 467
 468         /**
 469          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 470          * @param string|null $driver Optional name of a specific DB client driver
 471          * @return string Database subclass name to use
 472          * @throws InvalidArgumentException
 473          */
 474         private static function getClass( $dbType, $driver = null ) {
 475                 // For database types with built-in support, the below maps type to IDatabase
 476                 // implementations. For types with multipe driver implementations (PHP extensions),
 477                 // an array can be used, keyed by extension name. In case of an array, the
 478                 // optional 'driver' parameter can be used to force a specific driver. Otherwise,
 479                 // we auto-detect the first available driver. For types without built-in support,
 480                 // an class named "Database<Type>" us used, eg. DatabaseFoo for type 'foo'.
 481                 static $builtinTypes = [
 482                         'mssql' => DatabaseMssql::class,
 483                         'mysql' => [ 'mysqli' => DatabaseMysqli::class ],
 484                         'sqlite' => DatabaseSqlite::class,
 485                         'postgres' => DatabasePostgres::class,
 486                 ];
 487
 488                 $dbType = strtolower( $dbType );
 489                 $class = false;
 490
 491                 if ( isset( $builtinTypes[$dbType] ) ) {
 492                         $possibleDrivers = $builtinTypes[$dbType];
 493                         if ( is_string( $possibleDrivers ) ) {
 494                                 $class = $possibleDrivers;
 495                         } else {
 496                                 if ( (string)$driver !== '' ) {
 497                                         if ( !isset( $possibleDrivers[$driver] ) ) {
 498                                                 throw new InvalidArgumentException( __METHOD__ .
 499                                                         " type '$dbType' does not support driver '{$driver}'" );
 500                                         } else {
 501                                                 $class = $possibleDrivers[$driver];
 502                                         }
 503                                 } else {
 504                                         foreach ( $possibleDrivers as $posDriver => $possibleClass ) {
 505                                                 if ( extension_loaded( $posDriver ) ) {
 506                                                         $class = $possibleClass;
 507                                                         break;
 508                                                 }
 509                                         }
 510                                 }
 511                         }
 512                 } else {
 513                         $class = 'Database' . ucfirst( $dbType );
 514                 }
 515
 516                 if ( $class === false ) {
 517                         throw new InvalidArgumentException( __METHOD__ .
 518                                 " no viable database extension found for type '$dbType'" );
 519                 }
 520
 521                 return $class;
 522         }
 523
 524         /**
 525          * @return array Map of (Database::ATTRIBUTE_* constant => value
 526          * @since 1.31
 527          */
 528         protected static function getAttributes() {
 529                 return [];
 530         }
 531
 532         /**
 533          * Set the PSR-3 logger interface to use for query logging. (The logger
 534          * interfaces for connection logging and error logging can be set with the
 535          * constructor.)
 536          *
 537          * @param LoggerInterface $logger
 538          */
 539         public function setLogger( LoggerInterface $logger ) {
 540                 $this->queryLogger = $logger;
 541         }
 542
 543         public function getServerInfo() {
 544                 return $this->getServerVersion();
 545         }
 546
 547         public function bufferResults( $buffer = null ) {
 548                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 549                 if ( $buffer !== null ) {
 550                         $buffer
 551                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 552                                 : $this->setFlag( self::DBO_NOBUFFER );
 553                 }
 554
 555                 return $res;
 556         }
 557
 558         public function trxLevel() {
 559                 return $this->trxLevel;
 560         }
 561
 562         public function trxTimestamp() {
 563                 return $this->trxLevel ? $this->trxTimestamp : null;
 564         }
 565
 566         /**
 567          * @return int One of the STATUS_TRX_* class constants
 568          * @since 1.31
 569          */
 570         public function trxStatus() {
 571                 return $this->trxStatus;
 572         }
 573
 574         public function tablePrefix( $prefix = null ) {
 575                 $old = $this->tablePrefix;
 576                 if ( $prefix !== null ) {
 577                         $this->tablePrefix = $prefix;
 578                         $this->currentDomain = ( $this->dbName != '' )
 579                                 ? new DatabaseDomain( $this->dbName, null, $this->tablePrefix )
 580                                 : DatabaseDomain::newUnspecified();
 581                 }
 582
 583                 return $old;
 584         }
 585
 586         public function dbSchema( $schema = null ) {
 587                 $old = $this->schema;
 588                 if ( $schema !== null ) {
 589                         $this->schema = $schema;
 590                 }
 591
 592                 return $old;
 593         }
 594
 595         public function getLBInfo( $name = null ) {
 596                 if ( is_null( $name ) ) {
 597                         return $this->lbInfo;
 598                 } else {
 599                         if ( array_key_exists( $name, $this->lbInfo ) ) {
 600                                 return $this->lbInfo[$name];
 601                         } else {
 602                                 return null;
 603                         }
 604                 }
 605         }
 606
 607         public function setLBInfo( $name, $value = null ) {
 608                 if ( is_null( $value ) ) {
 609                         $this->lbInfo = $name;
 610                 } else {
 611                         $this->lbInfo[$name] = $value;
 612                 }
 613         }
 614
 615         public function setLazyMasterHandle( IDatabase $conn ) {
 616                 $this->lazyMasterHandle = $conn;
 617         }
 618
 619         /**
 620          * @return IDatabase|null
 621          * @see setLazyMasterHandle()
 622          * @since 1.27
 623          */
 624         protected function getLazyMasterHandle() {
 625                 return $this->lazyMasterHandle;
 626         }
 627
 628         public function implicitGroupby() {
 629                 return true;
 630         }
 631
 632         public function implicitOrderby() {
 633                 return true;
 634         }
 635
 636         public function lastQuery() {
 637                 return $this->lastQuery;
 638         }
 639
 640         public function doneWrites() {
 641                 return (bool)$this->lastWriteTime;
 642         }
 643
 644         public function lastDoneWrites() {
 645                 return $this->lastWriteTime ?: false;
 646         }
 647
 648         public function writesPending() {
 649                 return $this->trxLevel && $this->trxDoneWrites;
 650         }
 651
 652         public function writesOrCallbacksPending() {
 653                 return $this->trxLevel && (
 654                         $this->trxDoneWrites ||
 655                         $this->trxIdleCallbacks ||
 656                         $this->trxPreCommitCallbacks ||
 657                         $this->trxEndCallbacks
 658                 );
 659         }
 660
 661         /**
 662          * @return string|null
 663          */
 664         final protected function getTransactionRoundId() {
 665                 // If transaction round participation is enabled, see if one is active
 666                 if ( $this->getFlag( self::DBO_TRX ) ) {
 667                         $id = $this->getLBInfo( 'trxRoundId' );
 668
 669                         return is_string( $id ) ? $id : null;
 670                 }
 671
 672                 return null;
 673         }
 674
 675         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 676                 if ( !$this->trxLevel ) {
 677                         return false;
 678                 } elseif ( !$this->trxDoneWrites ) {
 679                         return 0.0;
 680                 }
 681
 682                 switch ( $type ) {
 683                         case self::ESTIMATE_DB_APPLY:
 684                                 $this->ping( $rtt );
 685                                 $rttAdjTotal = $this->trxWriteAdjQueryCount * $rtt;
 686                                 $applyTime = max( $this->trxWriteAdjDuration - $rttAdjTotal, 0 );
 687                                 // For omitted queries, make them count as something at least
 688                                 $omitted = $this->trxWriteQueryCount - $this->trxWriteAdjQueryCount;
 689                                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 690
 691                                 return $applyTime;
 692                         default: // everything
 693                                 return $this->trxWriteDuration;
 694                 }
 695         }
 696
 697         public function pendingWriteCallers() {
 698                 return $this->trxLevel ? $this->trxWriteCallers : [];
 699         }
 700
 701         public function pendingWriteRowsAffected() {
 702                 return $this->trxWriteAffectedRows;
 703         }
 704
 705         /**
 706          * Get the list of method names that have pending write queries or callbacks
 707          * for this transaction
 708          *
 709          * @return array
 710          */
 711         protected function pendingWriteAndCallbackCallers() {
 712                 if ( !$this->trxLevel ) {
 713                         return [];
 714                 }
 715
 716                 $fnames = $this->trxWriteCallers;
 717                 foreach ( [
 718                         $this->trxIdleCallbacks,
 719                         $this->trxPreCommitCallbacks,
 720                         $this->trxEndCallbacks
 721                 ] as $callbacks ) {
 722                         foreach ( $callbacks as $callback ) {
 723                                 $fnames[] = $callback[1];
 724                         }
 725                 }
 726
 727                 return $fnames;
 728         }
 729
 730         /**
 731          * @return string
 732          */
 733         private function flatAtomicSectionList() {
 734                 return array_reduce( $this->trxAtomicLevels, function ( $accum, $v ) {
 735                         return $accum === null ? $v[0] : "$accum, " . $v[0];
 736                 } );
 737         }
 738
 739         public function isOpen() {
 740                 return $this->opened;
 741         }
 742
 743         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 744                 if ( ( $flag & self::DBO_IGNORE ) ) {
 745                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 746                 }
 747
 748                 if ( $remember === self::REMEMBER_PRIOR ) {
 749                         array_push( $this->priorFlags, $this->flags );
 750                 }
 751                 $this->flags |= $flag;
 752         }
 753
 754         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 755                 if ( ( $flag & self::DBO_IGNORE ) ) {
 756                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 757                 }
 758
 759                 if ( $remember === self::REMEMBER_PRIOR ) {
 760                         array_push( $this->priorFlags, $this->flags );
 761                 }
 762                 $this->flags &= ~$flag;
 763         }
 764
 765         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 766                 if ( !$this->priorFlags ) {
 767                         return;
 768                 }
 769
 770                 if ( $state === self::RESTORE_INITIAL ) {
 771                         $this->flags = reset( $this->priorFlags );
 772                         $this->priorFlags = [];
 773                 } else {
 774                         $this->flags = array_pop( $this->priorFlags );
 775                 }
 776         }
 777
 778         public function getFlag( $flag ) {
 779                 return !!( $this->flags & $flag );
 780         }
 781
 782         /**
 783          * @param string $name Class field name
 784          * @return mixed
 785          * @deprecated Since 1.28
 786          */
 787         public function getProperty( $name ) {
 788                 return $this->$name;
 789         }
 790
 791         public function getDomainID() {
 792                 return $this->currentDomain->getId();
 793         }
 794
 795         final public function getWikiID() {
 796                 return $this->getDomainID();
 797         }
 798
 799         /**
 800          * Get information about an index into an object
 801          * @param string $table Table name
 802          * @param string $index Index name
 803          * @param string $fname Calling function name
 804          * @return mixed Database-specific index description class or false if the index does not exist
 805          */
 806         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 807
 808         /**
 809          * Wrapper for addslashes()
 810          *
 811          * @param string $s String to be slashed.
 812          * @return string Slashed string.
 813          */
 814         abstract function strencode( $s );
 815
 816         /**
 817          * Set a custom error handler for logging errors during database connection
 818          */
 819         protected function installErrorHandler() {
 820                 $this->phpError = false;
 821                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 822                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 823         }
 824
 825         /**
 826          * Restore the previous error handler and return the last PHP error for this DB
 827          *
 828          * @return bool|string
 829          */
 830         protected function restoreErrorHandler() {
 831                 restore_error_handler();
 832                 if ( $this->htmlErrors !== false ) {
 833                         ini_set( 'html_errors', $this->htmlErrors );
 834                 }
 835
 836                 return $this->getLastPHPError();
 837         }
 838
 839         /**
 840          * @return string|bool Last PHP error for this DB (typically connection errors)
 841          */
 842         protected function getLastPHPError() {
 843                 if ( $this->phpError ) {
 844                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->phpError );
 845                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 846
 847                         return $error;
 848                 }
 849
 850                 return false;
 851         }
 852
 853         /**
 854          * Error handler for logging errors during database connection
 855          * This method should not be used outside of Database classes
 856          *
 857          * @param int $errno
 858          * @param string $errstr
 859          */
 860         public function connectionErrorLogger( $errno, $errstr ) {
 861                 $this->phpError = $errstr;
 862         }
 863
 864         /**
 865          * Create a log context to pass to PSR-3 logger functions.
 866          *
 867          * @param array $extras Additional data to add to context
 868          * @return array
 869          */
 870         protected function getLogContext( array $extras = [] ) {
 871                 return array_merge(
 872                         [
 873                                 'db_server' => $this->server,
 874                                 'db_name' => $this->dbName,
 875                                 'db_user' => $this->user,
 876                         ],
 877                         $extras
 878                 );
 879         }
 880
 881         final public function close() {
 882                 $exception = null; // error to throw after disconnecting
 883
 884                 if ( $this->conn ) {
 885                         // Resolve any dangling transaction first
 886                         if ( $this->trxLevel ) {
 887                                 // Meaningful transactions should ideally have been resolved by now
 888                                 if ( $this->writesOrCallbacksPending() ) {
 889                                         $this->queryLogger->warning(
 890                                                 __METHOD__ . ": writes or callbacks still pending.",
 891                                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
 892                                         );
 893                                         // Cannot let incomplete atomic sections be committed
 894                                         if ( $this->trxAtomicLevels ) {
 895                                                 $levels = $this->flatAtomicSectionList();
 896                                                 $exception = new DBUnexpectedError(
 897                                                         $this,
 898                                                         __METHOD__ . ": atomic sections $levels are still open."
 899                                                 );
 900                                         // Check if it is possible to properly commit and trigger callbacks
 901                                         } elseif ( $this->trxEndCallbacksSuppressed ) {
 902                                                 $exception = new DBUnexpectedError(
 903                                                         $this,
 904                                                         __METHOD__ . ': callbacks are suppressed; cannot properly commit.'
 905                                                 );
 906                                         }
 907                                 }
 908                                 // Commit or rollback the changes and run any callbacks as needed
 909                                 if ( $this->trxStatus === self::STATUS_TRX_OK && !$exception ) {
 910                                         $this->commit( __METHOD__, self::TRANSACTION_INTERNAL );
 911                                 } else {
 912                                         $this->rollback( __METHOD__, self::TRANSACTION_INTERNAL );
 913                                 }
 914                         }
 915                         // Close the actual connection in the binding handle
 916                         $closed = $this->closeConnection();
 917                         $this->conn = false;
 918                 } else {
 919                         $closed = true; // already closed; nothing to do
 920                 }
 921
 922                 $this->opened = false;
 923
 924                 // Throw any unexpected errors after having disconnected
 925                 if ( $exception instanceof Exception ) {
 926                         throw $exception;
 927                 }
 928
 929                 // Sanity check that no callbacks are dangling
 930                 if (
 931                         $this->trxIdleCallbacks || $this->trxPreCommitCallbacks || $this->trxEndCallbacks
 932                 ) {
 933                         throw new RuntimeException(
 934                                 "Transaction callbacks are still pending:\n" .
 935                                 implode( ', ', $this->pendingWriteAndCallbackCallers() )
 936                         );
 937                 }
 938
 939                 return $closed;
 940         }
 941
 942         /**
 943          * Make sure isOpen() returns true as a sanity check
 944          *
 945          * @throws DBUnexpectedError
 946          */
 947         protected function assertOpen() {
 948                 if ( !$this->isOpen() ) {
 949                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 950                 }
 951         }
 952
 953         /**
 954          * Closes underlying database connection
 955          * @since 1.20
 956          * @return bool Whether connection was closed successfully
 957          */
 958         abstract protected function closeConnection();
 959
 960         /**
 961          * @param string $error Fallback error message, used if none is given by DB
 962          * @throws DBConnectionError
 963          */
 964         public function reportConnectionError( $error = 'Unknown error' ) {
 965                 $myError = $this->lastError();
 966                 if ( $myError ) {
 967                         $error = $myError;
 968                 }
 969
 970                 # New method
 971                 throw new DBConnectionError( $this, $error );
 972         }
 973
 974         /**
 975          * Run a query and return a DBMS-dependent wrapper (that has all IResultWrapper methods)
 976          *
 977          * This might return things, such as mysqli_result, that do not formally implement
 978          * IResultWrapper, but nonetheless implement all of its methods correctly
 979          *
 980          * @param string $sql SQL query.
 981          * @return IResultWrapper|bool Iterator to feed to fetchObject/fetchRow; false on failure
 982          */
 983         abstract protected function doQuery( $sql );
 984
 985         /**
 986          * Determine whether a query writes to the DB.
 987          * Should return true if unsure.
 988          *
 989          * @param string $sql
 990          * @return bool
 991          */
 992         protected function isWriteQuery( $sql ) {
 993                 return !preg_match(
 994                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
 995         }
 996
 997         /**
 998          * @param string $sql
 999          * @return string|null
1000          */
1001         protected function getQueryVerb( $sql ) {
1002                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
1003         }
1004
1005         /**
1006          * Determine whether a SQL statement is sensitive to isolation level.
1007          * A SQL statement is considered transactable if its result could vary
1008          * depending on the transaction isolation level. Operational commands
1009          * such as 'SET' and 'SHOW' are not considered to be transactable.
1010          *
1011          * @param string $sql
1012          * @return bool
1013          */
1014         protected function isTransactableQuery( $sql ) {
1015                 return !in_array(
1016                         $this->getQueryVerb( $sql ),
1017                         [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET', 'CREATE', 'ALTER' ],
1018                         true
1019                 );
1020         }
1021
1022         /**
1023          * @param string $sql A SQL query
1024          * @return bool Whether $sql is SQL for TEMPORARY table operation
1025          */
1026         protected function registerTempTableOperation( $sql ) {
1027                 if ( preg_match(
1028                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1029                         $sql,
1030                         $matches
1031                 ) ) {
1032                         $this->sessionTempTables[$matches[1]] = 1;
1033
1034                         return true;
1035                 } elseif ( preg_match(
1036                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1037                         $sql,
1038                         $matches
1039                 ) ) {
1040                         $isTemp = isset( $this->sessionTempTables[$matches[1]] );
1041                         unset( $this->sessionTempTables[$matches[1]] );
1042
1043                         return $isTemp;
1044                 } elseif ( preg_match(
1045                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1046                         $sql,
1047                         $matches
1048                 ) ) {
1049                         return isset( $this->sessionTempTables[$matches[1]] );
1050                 } elseif ( preg_match(
1051                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
1052                         $sql,
1053                         $matches
1054                 ) ) {
1055                         return isset( $this->sessionTempTables[$matches[1]] );
1056                 }
1057
1058                 return false;
1059         }
1060
1061         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
1062                 $this->assertTransactionStatus( $sql, $fname );
1063
1064                 $priorWritesPending = $this->writesOrCallbacksPending();
1065                 $this->lastQuery = $sql;
1066
1067                 $isWrite = $this->isWriteQuery( $sql );
1068                 if ( $isWrite ) {
1069                         $isNonTempWrite = !$this->registerTempTableOperation( $sql );
1070                 } else {
1071                         $isNonTempWrite = false;
1072                 }
1073
1074                 if ( $isWrite ) {
1075                         if ( $this->getLBInfo( 'replica' ) === true ) {
1076                                 throw new DBError(
1077                                         $this,
1078                                         'Write operations are not allowed on replica database connections.'
1079                                 );
1080                         }
1081                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
1082                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
1083                         $reason = $this->getReadOnlyReason();
1084                         if ( $reason !== false ) {
1085                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
1086                         }
1087                         # Set a flag indicating that writes have been done
1088                         $this->lastWriteTime = microtime( true );
1089                 }
1090
1091                 # Add trace comment to the begin of the sql string, right after the operator.
1092                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
1093                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
1094
1095                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
1096                 if ( !$this->trxLevel && $this->getFlag( self::DBO_TRX )
1097                         && $this->isTransactableQuery( $sql )
1098                 ) {
1099                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
1100                         $this->trxAutomatic = true;
1101                 }
1102
1103                 # Keep track of whether the transaction has write queries pending
1104                 if ( $this->trxLevel && !$this->trxDoneWrites && $isWrite ) {
1105                         $this->trxDoneWrites = true;
1106                         $this->trxProfiler->transactionWritingIn(
1107                                 $this->server, $this->dbName, $this->trxShortId );
1108                 }
1109
1110                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
1111                         $this->queryLogger->debug( "{$this->dbName} {$commentedSql}" );
1112                 }
1113
1114                 # Avoid fatals if close() was called
1115                 $this->assertOpen();
1116
1117                 # Send the query to the server and fetch any corresponding errors
1118                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1119                 $lastError = $this->lastError();
1120                 $lastErrno = $this->lastErrno();
1121
1122                 # Try reconnecting if the connection was lost
1123                 if ( $ret === false && $this->wasConnectionLoss() ) {
1124                         # Check if any meaningful session state was lost
1125                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
1126                         # Update session state tracking and try to restore the connection
1127                         $reconnected = $this->replaceLostConnection( __METHOD__ );
1128                         # Silently resend the query to the server if it is safe and possible
1129                         if ( $reconnected && $recoverable ) {
1130                                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1131                                 $lastError = $this->lastError();
1132                                 $lastErrno = $this->lastErrno();
1133
1134                                 if ( $ret === false && $this->wasConnectionLoss() ) {
1135                                         # Query probably causes disconnects; reconnect and do not re-run it
1136                                         $this->replaceLostConnection( __METHOD__ );
1137                                 }
1138                         }
1139                 }
1140
1141                 if ( $ret === false ) {
1142                         if ( $this->trxLevel && !$this->wasKnownStatementRollbackError() ) {
1143                                 # Either the query was aborted or all queries after BEGIN where aborted.
1144                                 if ( $this->explicitTrxActive() || $priorWritesPending ) {
1145                                         # In the first case, the only options going forward are (a) ROLLBACK, or
1146                                         # (b) ROLLBACK TO SAVEPOINT (if one was set). If the later case, the only
1147                                         # option is ROLLBACK, since the snapshots would have been released.
1148                                         $this->trxStatus = self::STATUS_TRX_ERROR;
1149                                         $this->trxStatusCause =
1150                                                 $this->makeQueryException( $lastError, $lastErrno, $sql, $fname );
1151                                         $tempIgnore = false; // cannot recover
1152                                 } else {
1153                                         # Nothing prior was there to lose from the transaction
1154                                         $this->trxStatus = self::STATUS_TRX_OK;
1155                                 }
1156                         }
1157
1158                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname, $tempIgnore );
1159                 }
1160
1161                 return $this->resultObject( $ret );
1162         }
1163
1164         /**
1165          * Wrapper for query() that also handles profiling, logging, and affected row count updates
1166          *
1167          * @param string $sql Original SQL query
1168          * @param string $commentedSql SQL query with debugging/trace comment
1169          * @param bool $isWrite Whether the query is a (non-temporary) write operation
1170          * @param string $fname Name of the calling function
1171          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1172          *     object for a successful read query, or false on failure
1173          */
1174         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
1175                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1176                 # generalizeSQL() will probably cut down the query to reasonable
1177                 # logging size most of the time. The substr is really just a sanity check.
1178                 if ( $isMaster ) {
1179                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1180                 } else {
1181                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1182                 }
1183
1184                 # Include query transaction state
1185                 $queryProf .= $this->trxShortId ? " [TRX#{$this->trxShortId}]" : "";
1186
1187                 $startTime = microtime( true );
1188                 if ( $this->profiler ) {
1189                         call_user_func( [ $this->profiler, 'profileIn' ], $queryProf );
1190                 }
1191                 $this->affectedRowCount = null;
1192                 $ret = $this->doQuery( $commentedSql );
1193                 $this->affectedRowCount = $this->affectedRows();
1194                 if ( $this->profiler ) {
1195                         call_user_func( [ $this->profiler, 'profileOut' ], $queryProf );
1196                 }
1197                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1198
1199                 unset( $queryProfSection ); // profile out (if set)
1200
1201                 if ( $ret !== false ) {
1202                         $this->lastPing = $startTime;
1203                         if ( $isWrite && $this->trxLevel ) {
1204                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1205                                 $this->trxWriteCallers[] = $fname;
1206                         }
1207                 }
1208
1209                 if ( $sql === self::PING_QUERY ) {
1210                         $this->rttEstimate = $queryRuntime;
1211                 }
1212
1213                 $this->trxProfiler->recordQueryCompletion(
1214                         $queryProf, $startTime, $isWrite, $this->affectedRows()
1215                 );
1216                 $this->queryLogger->debug( $sql, [
1217                         'method' => $fname,
1218                         'master' => $isMaster,
1219                         'runtime' => $queryRuntime,
1220                 ] );
1221
1222                 return $ret;
1223         }
1224
1225         /**
1226          * Update the estimated run-time of a query, not counting large row lock times
1227          *
1228          * LoadBalancer can be set to rollback transactions that will create huge replication
1229          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1230          * queries, like inserting a row can take a long time due to row locking. This method
1231          * uses some simple heuristics to discount those cases.
1232          *
1233          * @param string $sql A SQL write query
1234          * @param float $runtime Total runtime, including RTT
1235          * @param int $affected Affected row count
1236          */
1237         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1238                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1239                 $indicativeOfReplicaRuntime = true;
1240                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1241                         $verb = $this->getQueryVerb( $sql );
1242                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1243                         if ( $verb === 'INSERT' ) {
1244                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1245                         } elseif ( $verb === 'REPLACE' ) {
1246                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1247                         }
1248                 }
1249
1250                 $this->trxWriteDuration += $runtime;
1251                 $this->trxWriteQueryCount += 1;
1252                 $this->trxWriteAffectedRows += $affected;
1253                 if ( $indicativeOfReplicaRuntime ) {
1254                         $this->trxWriteAdjDuration += $runtime;
1255                         $this->trxWriteAdjQueryCount += 1;
1256                 }
1257         }
1258
1259         /**
1260          * @param string $sql
1261          * @param string $fname
1262          * @throws DBTransactionStateError
1263          */
1264         private function assertTransactionStatus( $sql, $fname ) {
1265                 if (
1266                         $this->trxStatus < self::STATUS_TRX_OK &&
1267                         $this->getQueryVerb( $sql ) !== 'ROLLBACK' // transaction/savepoint
1268                 ) {
1269                         throw new DBTransactionStateError(
1270                                 $this,
1271                                 "Cannot execute query from $fname while transaction status is ERROR. ",
1272                                 [],
1273                                 $this->trxStatusCause
1274                         );
1275                 }
1276         }
1277
1278         /**
1279          * Determine whether or not it is safe to retry queries after a database
1280          * connection is lost
1281          *
1282          * @param string $sql SQL query
1283          * @param bool $priorWritesPending Whether there is a transaction open with
1284          *     possible write queries or transaction pre-commit/idle callbacks
1285          *     waiting on it to finish.
1286          * @return bool True if it is safe to retry the query, false otherwise
1287          */
1288         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1289                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1290                 # Dropped connections also mean that named locks are automatically released.
1291                 # Only allow error suppression in autocommit mode or when the lost transaction
1292                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1293                 if ( $this->namedLocksHeld ) {
1294                         return false; // possible critical section violation
1295                 } elseif ( $this->sessionTempTables ) {
1296                         return false; // tables might be queried latter
1297                 } elseif ( $sql === 'COMMIT' ) {
1298                         return !$priorWritesPending; // nothing written anyway? (T127428)
1299                 } elseif ( $sql === 'ROLLBACK' ) {
1300                         return true; // transaction lost...which is also what was requested :)
1301                 } elseif ( $this->explicitTrxActive() ) {
1302                         return false; // don't drop atomocity and explicit snapshots
1303                 } elseif ( $priorWritesPending ) {
1304                         return false; // prior writes lost from implicit transaction
1305                 }
1306
1307                 return true;
1308         }
1309
1310         /**
1311          * Clean things up after session (and thus transaction) loss
1312          */
1313         private function handleSessionLoss() {
1314                 // Clean up tracking of session-level things...
1315                 // https://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html
1316                 // https://www.postgresql.org/docs/9.2/static/sql-createtable.html (ignoring ON COMMIT)
1317                 $this->sessionTempTables = [];
1318                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1319                 // https://www.postgresql.org/docs/9.4/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
1320                 $this->namedLocksHeld = [];
1321                 // Session loss implies transaction loss
1322                 $this->handleTransactionLoss();
1323         }
1324
1325         /**
1326          * Clean things up after transaction loss
1327          */
1328         private function handleTransactionLoss() {
1329                 $this->trxLevel = 0;
1330                 $this->trxAtomicCounter = 0;
1331                 $this->trxIdleCallbacks = []; // T67263; transaction already lost
1332                 $this->trxPreCommitCallbacks = []; // T67263; transaction already lost
1333                 try {
1334                         // Handle callbacks in trxEndCallbacks, e.g. onTransactionResolution().
1335                         // If callback suppression is set then the array will remain unhandled.
1336                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1337                 } catch ( Exception $ex ) {
1338                         // Already logged; move on...
1339                 }
1340                 try {
1341                         // Handle callbacks in trxRecurringCallbacks, e.g. setTransactionListener()
1342                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1343                 } catch ( Exception $ex ) {
1344                         // Already logged; move on...
1345                 }
1346         }
1347
1348         /**
1349          * Checks whether the cause of the error is detected to be a timeout.
1350          *
1351          * It returns false by default, and not all engines support detecting this yet.
1352          * If this returns false, it will be treated as a generic query error.
1353          *
1354          * @param string $error Error text
1355          * @param int $errno Error number
1356          * @return bool
1357          */
1358         protected function wasQueryTimeout( $error, $errno ) {
1359                 return false;
1360         }
1361
1362         /**
1363          * Report a query error. Log the error, and if neither the object ignore
1364          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1365          *
1366          * @param string $error
1367          * @param int $errno
1368          * @param string $sql
1369          * @param string $fname
1370          * @param bool $tempIgnore
1371          * @throws DBQueryError
1372          */
1373         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1374                 if ( $tempIgnore ) {
1375                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1376                 } else {
1377                         $exception = $this->makeQueryException( $error, $errno, $sql, $fname );
1378
1379                         throw $exception;
1380                 }
1381         }
1382
1383         /**
1384          * @param string $error
1385          * @param string|int $errno
1386          * @param string $sql
1387          * @param string $fname
1388          * @return DBError
1389          */
1390         private function makeQueryException( $error, $errno, $sql, $fname ) {
1391                 $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1392                 $this->queryLogger->error(
1393                         "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1394                         $this->getLogContext( [
1395                                 'method' => __METHOD__,
1396                                 'errno' => $errno,
1397                                 'error' => $error,
1398                                 'sql1line' => $sql1line,
1399                                 'fname' => $fname,
1400                         ] )
1401                 );
1402                 $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1403                 $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1404                 if ( $wasQueryTimeout ) {
1405                         $e = new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1406                 } else {
1407                         $e = new DBQueryError( $this, $error, $errno, $sql, $fname );
1408                 }
1409
1410                 return $e;
1411         }
1412
1413         public function freeResult( $res ) {
1414         }
1415
1416         public function selectField(
1417                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1418         ) {
1419                 if ( $var === '*' ) { // sanity
1420                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1421                 }
1422
1423                 if ( !is_array( $options ) ) {
1424                         $options = [ $options ];
1425                 }
1426
1427                 $options['LIMIT'] = 1;
1428
1429                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1430                 if ( $res === false || !$this->numRows( $res ) ) {
1431                         return false;
1432                 }
1433
1434                 $row = $this->fetchRow( $res );
1435
1436                 if ( $row !== false ) {
1437                         return reset( $row );
1438                 } else {
1439                         return false;
1440                 }
1441         }
1442
1443         public function selectFieldValues(
1444                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1445         ) {
1446                 if ( $var === '*' ) { // sanity
1447                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1448                 } elseif ( !is_string( $var ) ) { // sanity
1449                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1450                 }
1451
1452                 if ( !is_array( $options ) ) {
1453                         $options = [ $options ];
1454                 }
1455
1456                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1457                 if ( $res === false ) {
1458                         return false;
1459                 }
1460
1461                 $values = [];
1462                 foreach ( $res as $row ) {
1463                         $values[] = $row->$var;
1464                 }
1465
1466                 return $values;
1467         }
1468
1469         /**
1470          * Returns an optional USE INDEX clause to go after the table, and a
1471          * string to go at the end of the query.
1472          *
1473          * @param array $options Associative array of options to be turned into
1474          *   an SQL query, valid keys are listed in the function.
1475          * @return array
1476          * @see Database::select()
1477          */
1478         protected function makeSelectOptions( $options ) {
1479                 $preLimitTail = $postLimitTail = '';
1480                 $startOpts = '';
1481
1482                 $noKeyOptions = [];
1483
1484                 foreach ( $options as $key => $option ) {
1485                         if ( is_numeric( $key ) ) {
1486                                 $noKeyOptions[$option] = true;
1487                         }
1488                 }
1489
1490                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1491
1492                 $preLimitTail .= $this->makeOrderBy( $options );
1493
1494                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1495                         $postLimitTail .= ' FOR UPDATE';
1496                 }
1497
1498                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1499                         $postLimitTail .= ' LOCK IN SHARE MODE';
1500                 }
1501
1502                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1503                         $startOpts .= 'DISTINCT';
1504                 }
1505
1506                 # Various MySQL extensions
1507                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1508                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1509                 }
1510
1511                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1512                         $startOpts .= ' HIGH_PRIORITY';
1513                 }
1514
1515                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1516                         $startOpts .= ' SQL_BIG_RESULT';
1517                 }
1518
1519                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1520                         $startOpts .= ' SQL_BUFFER_RESULT';
1521                 }
1522
1523                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1524                         $startOpts .= ' SQL_SMALL_RESULT';
1525                 }
1526
1527                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1528                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1529                 }
1530
1531                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1532                         $startOpts .= ' SQL_CACHE';
1533                 }
1534
1535                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1536                         $startOpts .= ' SQL_NO_CACHE';
1537                 }
1538
1539                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1540                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1541                 } else {
1542                         $useIndex = '';
1543                 }
1544                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1545                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1546                 } else {
1547                         $ignoreIndex = '';
1548                 }
1549
1550                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1551         }
1552
1553         /**
1554          * Returns an optional GROUP BY with an optional HAVING
1555          *
1556          * @param array $options Associative array of options
1557          * @return string
1558          * @see Database::select()
1559          * @since 1.21
1560          */
1561         protected function makeGroupByWithHaving( $options ) {
1562                 $sql = '';
1563                 if ( isset( $options['GROUP BY'] ) ) {
1564                         $gb = is_array( $options['GROUP BY'] )
1565                                 ? implode( ',', $options['GROUP BY'] )
1566                                 : $options['GROUP BY'];
1567                         $sql .= ' GROUP BY ' . $gb;
1568                 }
1569                 if ( isset( $options['HAVING'] ) ) {
1570                         $having = is_array( $options['HAVING'] )
1571                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1572                                 : $options['HAVING'];
1573                         $sql .= ' HAVING ' . $having;
1574                 }
1575
1576                 return $sql;
1577         }
1578
1579         /**
1580          * Returns an optional ORDER BY
1581          *
1582          * @param array $options Associative array of options
1583          * @return string
1584          * @see Database::select()
1585          * @since 1.21
1586          */
1587         protected function makeOrderBy( $options ) {
1588                 if ( isset( $options['ORDER BY'] ) ) {
1589                         $ob = is_array( $options['ORDER BY'] )
1590                                 ? implode( ',', $options['ORDER BY'] )
1591                                 : $options['ORDER BY'];
1592
1593                         return ' ORDER BY ' . $ob;
1594                 }
1595
1596                 return '';
1597         }
1598
1599         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1600                 $options = [], $join_conds = [] ) {
1601                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1602
1603                 return $this->query( $sql, $fname );
1604         }
1605
1606         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1607                 $options = [], $join_conds = []
1608         ) {
1609                 if ( is_array( $vars ) ) {
1610                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1611                 }
1612
1613                 $options = (array)$options;
1614                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1615                         ? $options['USE INDEX']
1616                         : [];
1617                 $ignoreIndexes = (
1618                         isset( $options['IGNORE INDEX'] ) &&
1619                         is_array( $options['IGNORE INDEX'] )
1620                 )
1621                         ? $options['IGNORE INDEX']
1622                         : [];
1623
1624                 if ( is_array( $table ) ) {
1625                         $from = ' FROM ' .
1626                                 $this->tableNamesWithIndexClauseOrJOIN(
1627                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1628                 } elseif ( $table != '' ) {
1629                         $from = ' FROM ' .
1630                                 $this->tableNamesWithIndexClauseOrJOIN(
1631                                         [ $table ], $useIndexes, $ignoreIndexes, [] );
1632                 } else {
1633                         $from = '';
1634                 }
1635
1636                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1637                         $this->makeSelectOptions( $options );
1638
1639                 if ( is_array( $conds ) ) {
1640                         $conds = $this->makeList( $conds, self::LIST_AND );
1641                 }
1642
1643                 if ( $conds === null || $conds === false ) {
1644                         $this->queryLogger->warning(
1645                                 __METHOD__
1646                                 . ' called from '
1647                                 . $fname
1648                                 . ' with incorrect parameters: $conds must be a string or an array'
1649                         );
1650                         $conds = '';
1651                 }
1652
1653                 if ( $conds === '' ) {
1654                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1655                 } elseif ( is_string( $conds ) ) {
1656                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1657                                 "WHERE $conds $preLimitTail";
1658                 } else {
1659                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1660                 }
1661
1662                 if ( isset( $options['LIMIT'] ) ) {
1663                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1664                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1665                 }
1666                 $sql = "$sql $postLimitTail";
1667
1668                 if ( isset( $options['EXPLAIN'] ) ) {
1669                         $sql = 'EXPLAIN ' . $sql;
1670                 }
1671
1672                 return $sql;
1673         }
1674
1675         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1676                 $options = [], $join_conds = []
1677         ) {
1678                 $options = (array)$options;
1679                 $options['LIMIT'] = 1;
1680                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1681
1682                 if ( $res === false ) {
1683                         return false;
1684                 }
1685
1686                 if ( !$this->numRows( $res ) ) {
1687                         return false;
1688                 }
1689
1690                 $obj = $this->fetchObject( $res );
1691
1692                 return $obj;
1693         }
1694
1695         public function estimateRowCount(
1696                 $table, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1697         ) {
1698                 $conds = $this->normalizeConditions( $conds, $fname );
1699                 $column = $this->extractSingleFieldFromList( $var );
1700                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1701                         $conds[] = "$column IS NOT NULL";
1702                 }
1703
1704                 $res = $this->select(
1705                         $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options, $join_conds
1706                 );
1707                 $row = $res ? $this->fetchRow( $res ) : [];
1708
1709                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1710         }
1711
1712         public function selectRowCount(
1713                 $tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1714         ) {
1715                 $conds = $this->normalizeConditions( $conds, $fname );
1716                 $column = $this->extractSingleFieldFromList( $var );
1717                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1718                         $conds[] = "$column IS NOT NULL";
1719                 }
1720
1721                 $res = $this->select(
1722                         [
1723                                 'tmp_count' => $this->buildSelectSubquery(
1724                                         $tables,
1725                                         '1',
1726                                         $conds,
1727                                         $fname,
1728                                         $options,
1729                                         $join_conds
1730                                 )
1731                         ],
1732                         [ 'rowcount' => 'COUNT(*)' ],
1733                         [],
1734                         $fname
1735                 );
1736                 $row = $res ? $this->fetchRow( $res ) : [];
1737
1738                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1739         }
1740
1741         /**
1742          * @param array|string $conds
1743          * @param string $fname
1744          * @return array
1745          */
1746         final protected function normalizeConditions( $conds, $fname ) {
1747                 if ( $conds === null || $conds === false ) {
1748                         $this->queryLogger->warning(
1749                                 __METHOD__
1750                                 . ' called from '
1751                                 . $fname
1752                                 . ' with incorrect parameters: $conds must be a string or an array'
1753                         );
1754                         $conds = '';
1755                 }
1756
1757                 if ( !is_array( $conds ) ) {
1758                         $conds = ( $conds === '' ) ? [] : [ $conds ];
1759                 }
1760
1761                 return $conds;
1762         }
1763
1764         /**
1765          * @param array|string $var Field parameter in the style of select()
1766          * @return string|null Column name or null; ignores aliases
1767          * @throws DBUnexpectedError Errors out if multiple columns are given
1768          */
1769         final protected function extractSingleFieldFromList( $var ) {
1770                 if ( is_array( $var ) ) {
1771                         if ( !$var ) {
1772                                 $column = null;
1773                         } elseif ( count( $var ) == 1 ) {
1774                                 $column = isset( $var[0] ) ? $var[0] : reset( $var );
1775                         } else {
1776                                 throw new DBUnexpectedError( $this, __METHOD__ . ': got multiple columns.' );
1777                         }
1778                 } else {
1779                         $column = $var;
1780                 }
1781
1782                 return $column;
1783         }
1784
1785         /**
1786          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1787          * It's only slightly flawed. Don't use for anything important.
1788          *
1789          * @param string $sql A SQL Query
1790          *
1791          * @return string
1792          */
1793         protected static function generalizeSQL( $sql ) {
1794                 # This does the same as the regexp below would do, but in such a way
1795                 # as to avoid crashing php on some large strings.
1796                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1797
1798                 $sql = str_replace( "\\\\", '', $sql );
1799                 $sql = str_replace( "\\'", '', $sql );
1800                 $sql = str_replace( "\\\"", '', $sql );
1801                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1802                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1803
1804                 # All newlines, tabs, etc replaced by single space
1805                 $sql = preg_replace( '/\s+/', ' ', $sql );
1806
1807                 # All numbers => N,
1808                 # except the ones surrounded by characters, e.g. l10n
1809                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1810                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1811
1812                 return $sql;
1813         }
1814
1815         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1816                 $info = $this->fieldInfo( $table, $field );
1817
1818                 return (bool)$info;
1819         }
1820
1821         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1822                 if ( !$this->tableExists( $table ) ) {
1823                         return null;
1824                 }
1825
1826                 $info = $this->indexInfo( $table, $index, $fname );
1827                 if ( is_null( $info ) ) {
1828                         return null;
1829                 } else {
1830                         return $info !== false;
1831                 }
1832         }
1833
1834         public function tableExists( $table, $fname = __METHOD__ ) {
1835                 $tableRaw = $this->tableName( $table, 'raw' );
1836                 if ( isset( $this->sessionTempTables[$tableRaw] ) ) {
1837                         return true; // already known to exist
1838                 }
1839
1840                 $table = $this->tableName( $table );
1841                 $ignoreErrors = true;
1842                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1843
1844                 return (bool)$res;
1845         }
1846
1847         public function indexUnique( $table, $index ) {
1848                 $indexInfo = $this->indexInfo( $table, $index );
1849
1850                 if ( !$indexInfo ) {
1851                         return null;
1852                 }
1853
1854                 return !$indexInfo[0]->Non_unique;
1855         }
1856
1857         /**
1858          * Helper for Database::insert().
1859          *
1860          * @param array $options
1861          * @return string
1862          */
1863         protected function makeInsertOptions( $options ) {
1864                 return implode( ' ', $options );
1865         }
1866
1867         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1868                 # No rows to insert, easy just return now
1869                 if ( !count( $a ) ) {
1870                         return true;
1871                 }
1872
1873                 $table = $this->tableName( $table );
1874
1875                 if ( !is_array( $options ) ) {
1876                         $options = [ $options ];
1877                 }
1878
1879                 $fh = null;
1880                 if ( isset( $options['fileHandle'] ) ) {
1881                         $fh = $options['fileHandle'];
1882                 }
1883                 $options = $this->makeInsertOptions( $options );
1884
1885                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1886                         $multi = true;
1887                         $keys = array_keys( $a[0] );
1888                 } else {
1889                         $multi = false;
1890                         $keys = array_keys( $a );
1891                 }
1892
1893                 $sql = 'INSERT ' . $options .
1894                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1895
1896                 if ( $multi ) {
1897                         $first = true;
1898                         foreach ( $a as $row ) {
1899                                 if ( $first ) {
1900                                         $first = false;
1901                                 } else {
1902                                         $sql .= ',';
1903                                 }
1904                                 $sql .= '(' . $this->makeList( $row ) . ')';
1905                         }
1906                 } else {
1907                         $sql .= '(' . $this->makeList( $a ) . ')';
1908                 }
1909
1910                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1911                         return false;
1912                 } elseif ( $fh !== null ) {
1913                         return true;
1914                 }
1915
1916                 return (bool)$this->query( $sql, $fname );
1917         }
1918
1919         /**
1920          * Make UPDATE options array for Database::makeUpdateOptions
1921          *
1922          * @param array $options
1923          * @return array
1924          */
1925         protected function makeUpdateOptionsArray( $options ) {
1926                 if ( !is_array( $options ) ) {
1927                         $options = [ $options ];
1928                 }
1929
1930                 $opts = [];
1931
1932                 if ( in_array( 'IGNORE', $options ) ) {
1933                         $opts[] = 'IGNORE';
1934                 }
1935
1936                 return $opts;
1937         }
1938
1939         /**
1940          * Make UPDATE options for the Database::update function
1941          *
1942          * @param array $options The options passed to Database::update
1943          * @return string
1944          */
1945         protected function makeUpdateOptions( $options ) {
1946                 $opts = $this->makeUpdateOptionsArray( $options );
1947
1948                 return implode( ' ', $opts );
1949         }
1950
1951         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1952                 $table = $this->tableName( $table );
1953                 $opts = $this->makeUpdateOptions( $options );
1954                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
1955
1956                 if ( $conds !== [] && $conds !== '*' ) {
1957                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
1958                 }
1959
1960                 return (bool)$this->query( $sql, $fname );
1961         }
1962
1963         public function makeList( $a, $mode = self::LIST_COMMA ) {
1964                 if ( !is_array( $a ) ) {
1965                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1966                 }
1967
1968                 $first = true;
1969                 $list = '';
1970
1971                 foreach ( $a as $field => $value ) {
1972                         if ( !$first ) {
1973                                 if ( $mode == self::LIST_AND ) {
1974                                         $list .= ' AND ';
1975                                 } elseif ( $mode == self::LIST_OR ) {
1976                                         $list .= ' OR ';
1977                                 } else {
1978                                         $list .= ',';
1979                                 }
1980                         } else {
1981                                 $first = false;
1982                         }
1983
1984                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
1985                                 $list .= "($value)";
1986                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
1987                                 $list .= "$value";
1988                         } elseif (
1989                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
1990                         ) {
1991                                 // Remove null from array to be handled separately if found
1992                                 $includeNull = false;
1993                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
1994                                         $includeNull = true;
1995                                         unset( $value[$nullKey] );
1996                                 }
1997                                 if ( count( $value ) == 0 && !$includeNull ) {
1998                                         throw new InvalidArgumentException(
1999                                                 __METHOD__ . ": empty input for field $field" );
2000                                 } elseif ( count( $value ) == 0 ) {
2001                                         // only check if $field is null
2002                                         $list .= "$field IS NULL";
2003                                 } else {
2004                                         // IN clause contains at least one valid element
2005                                         if ( $includeNull ) {
2006                                                 // Group subconditions to ensure correct precedence
2007                                                 $list .= '(';
2008                                         }
2009                                         if ( count( $value ) == 1 ) {
2010                                                 // Special-case single values, as IN isn't terribly efficient
2011                                                 // Don't necessarily assume the single key is 0; we don't
2012                                                 // enforce linear numeric ordering on other arrays here.
2013                                                 $value = array_values( $value )[0];
2014                                                 $list .= $field . " = " . $this->addQuotes( $value );
2015                                         } else {
2016                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
2017                                         }
2018                                         // if null present in array, append IS NULL
2019                                         if ( $includeNull ) {
2020                                                 $list .= " OR $field IS NULL)";
2021                                         }
2022                                 }
2023                         } elseif ( $value === null ) {
2024                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
2025                                         $list .= "$field IS ";
2026                                 } elseif ( $mode == self::LIST_SET ) {
2027                                         $list .= "$field = ";
2028                                 }
2029                                 $list .= 'NULL';
2030                         } else {
2031                                 if (
2032                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
2033                                 ) {
2034                                         $list .= "$field = ";
2035                                 }
2036                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
2037                         }
2038                 }
2039
2040                 return $list;
2041         }
2042
2043         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2044                 $conds = [];
2045
2046                 foreach ( $data as $base => $sub ) {
2047                         if ( count( $sub ) ) {
2048                                 $conds[] = $this->makeList(
2049                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
2050                                         self::LIST_AND );
2051                         }
2052                 }
2053
2054                 if ( $conds ) {
2055                         return $this->makeList( $conds, self::LIST_OR );
2056                 } else {
2057                         // Nothing to search for...
2058                         return false;
2059                 }
2060         }
2061
2062         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2063                 return $valuename;
2064         }
2065
2066         public function bitNot( $field ) {
2067                 return "(~$field)";
2068         }
2069
2070         public function bitAnd( $fieldLeft, $fieldRight ) {
2071                 return "($fieldLeft & $fieldRight)";
2072         }
2073
2074         public function bitOr( $fieldLeft, $fieldRight ) {
2075                 return "($fieldLeft | $fieldRight)";
2076         }
2077
2078         public function buildConcat( $stringList ) {
2079                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2080         }
2081
2082         public function buildGroupConcatField(
2083                 $delim, $table, $field, $conds = '', $join_conds = []
2084         ) {
2085                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2086
2087                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
2088         }
2089
2090         public function buildSubstring( $input, $startPosition, $length = null ) {
2091                 $this->assertBuildSubstringParams( $startPosition, $length );
2092                 $functionBody = "$input FROM $startPosition";
2093                 if ( $length !== null ) {
2094                         $functionBody .= " FOR $length";
2095                 }
2096                 return 'SUBSTRING(' . $functionBody . ')';
2097         }
2098
2099         /**
2100          * Check type and bounds for parameters to self::buildSubstring()
2101          *
2102          * All supported databases have substring functions that behave the same for
2103          * positive $startPosition and non-negative $length, but behaviors differ when
2104          * given 0 or negative $startPosition or negative $length. The simplest
2105          * solution to that is to just forbid those values.
2106          *
2107          * @param int $startPosition
2108          * @param int|null $length
2109          * @since 1.31
2110          */
2111         protected function assertBuildSubstringParams( $startPosition, $length ) {
2112                 if ( !is_int( $startPosition ) || $startPosition <= 0 ) {
2113                         throw new InvalidArgumentException(
2114                                 '$startPosition must be a positive integer'
2115                         );
2116                 }
2117                 if ( !( is_int( $length ) && $length >= 0 || $length === null ) ) {
2118                         throw new InvalidArgumentException(
2119                                 '$length must be null or an integer greater than or equal to 0'
2120                         );
2121                 }
2122         }
2123
2124         public function buildStringCast( $field ) {
2125                 return $field;
2126         }
2127
2128         public function buildIntegerCast( $field ) {
2129                 return 'CAST( ' . $field . ' AS INTEGER )';
2130         }
2131
2132         public function buildSelectSubquery(
2133                 $table, $vars, $conds = '', $fname = __METHOD__,
2134                 $options = [], $join_conds = []
2135         ) {
2136                 return new Subquery(
2137                         $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds )
2138                 );
2139         }
2140
2141         public function databasesAreIndependent() {
2142                 return false;
2143         }
2144
2145         public function selectDB( $db ) {
2146                 # Stub. Shouldn't cause serious problems if it's not overridden, but
2147                 # if your database engine supports a concept similar to MySQL's
2148                 # databases you may as well.
2149                 $this->dbName = $db;
2150
2151                 return true;
2152         }
2153
2154         public function getDBname() {
2155                 return $this->dbName;
2156         }
2157
2158         public function getServer() {
2159                 return $this->server;
2160         }
2161
2162         public function tableName( $name, $format = 'quoted' ) {
2163                 if ( $name instanceof Subquery ) {
2164                         throw new DBUnexpectedError(
2165                                 $this,
2166                                 __METHOD__ . ': got Subquery instance when expecting a string.'
2167                         );
2168                 }
2169
2170                 # Skip the entire process when we have a string quoted on both ends.
2171                 # Note that we check the end so that we will still quote any use of
2172                 # use of `database`.table. But won't break things if someone wants
2173                 # to query a database table with a dot in the name.
2174                 if ( $this->isQuotedIdentifier( $name ) ) {
2175                         return $name;
2176                 }
2177
2178                 # Lets test for any bits of text that should never show up in a table
2179                 # name. Basically anything like JOIN or ON which are actually part of
2180                 # SQL queries, but may end up inside of the table value to combine
2181                 # sql. Such as how the API is doing.
2182                 # Note that we use a whitespace test rather than a \b test to avoid
2183                 # any remote case where a word like on may be inside of a table name
2184                 # surrounded by symbols which may be considered word breaks.
2185                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2186                         $this->queryLogger->warning(
2187                                 __METHOD__ . ": use of subqueries is not supported this way.",
2188                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
2189                         );
2190
2191                         return $name;
2192                 }
2193
2194                 # Split database and table into proper variables.
2195                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
2196
2197                 # Quote $table and apply the prefix if not quoted.
2198                 # $tableName might be empty if this is called from Database::replaceVars()
2199                 $tableName = "{$prefix}{$table}";
2200                 if ( $format === 'quoted'
2201                         && !$this->isQuotedIdentifier( $tableName )
2202                         && $tableName !== ''
2203                 ) {
2204                         $tableName = $this->addIdentifierQuotes( $tableName );
2205                 }
2206
2207                 # Quote $schema and $database and merge them with the table name if needed
2208                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
2209                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
2210
2211                 return $tableName;
2212         }
2213
2214         /**
2215          * Get the table components needed for a query given the currently selected database
2216          *
2217          * @param string $name Table name in the form of db.schema.table, db.table, or table
2218          * @return array (DB name or "" for default, schema name, table prefix, table name)
2219          */
2220         protected function qualifiedTableComponents( $name ) {
2221                 # We reverse the explode so that database.table and table both output the correct table.
2222                 $dbDetails = explode( '.', $name, 3 );
2223                 if ( count( $dbDetails ) == 3 ) {
2224                         list( $database, $schema, $table ) = $dbDetails;
2225                         # We don't want any prefix added in this case
2226                         $prefix = '';
2227                 } elseif ( count( $dbDetails ) == 2 ) {
2228                         list( $database, $table ) = $dbDetails;
2229                         # We don't want any prefix added in this case
2230                         $prefix = '';
2231                         # In dbs that support it, $database may actually be the schema
2232                         # but that doesn't affect any of the functionality here
2233                         $schema = '';
2234                 } else {
2235                         list( $table ) = $dbDetails;
2236                         if ( isset( $this->tableAliases[$table] ) ) {
2237                                 $database = $this->tableAliases[$table]['dbname'];
2238                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
2239                                         ? $this->tableAliases[$table]['schema']
2240                                         : $this->schema;
2241                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
2242                                         ? $this->tableAliases[$table]['prefix']
2243                                         : $this->tablePrefix;
2244                         } else {
2245                                 $database = '';
2246                                 $schema = $this->schema; # Default schema
2247                                 $prefix = $this->tablePrefix; # Default prefix
2248                         }
2249                 }
2250
2251                 return [ $database, $schema, $prefix, $table ];
2252         }
2253
2254         /**
2255          * @param string|null $namespace Database or schema
2256          * @param string $relation Name of table, view, sequence, etc...
2257          * @param string $format One of (raw, quoted)
2258          * @return string Relation name with quoted and merged $namespace as needed
2259          */
2260         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
2261                 if ( strlen( $namespace ) ) {
2262                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
2263                                 $namespace = $this->addIdentifierQuotes( $namespace );
2264                         }
2265                         $relation = $namespace . '.' . $relation;
2266                 }
2267
2268                 return $relation;
2269         }
2270
2271         public function tableNames() {
2272                 $inArray = func_get_args();
2273                 $retVal = [];
2274
2275                 foreach ( $inArray as $name ) {
2276                         $retVal[$name] = $this->tableName( $name );
2277                 }
2278
2279                 return $retVal;
2280         }
2281
2282         public function tableNamesN() {
2283                 $inArray = func_get_args();
2284                 $retVal = [];
2285
2286                 foreach ( $inArray as $name ) {
2287                         $retVal[] = $this->tableName( $name );
2288                 }
2289
2290                 return $retVal;
2291         }
2292
2293         /**
2294          * Get an aliased table name
2295          *
2296          * This returns strings like "tableName AS newTableName" for aliased tables
2297          * and "(SELECT * from tableA) newTablename" for subqueries (e.g. derived tables)
2298          *
2299          * @see Database::tableName()
2300          * @param string|Subquery $table Table name or object with a 'sql' field
2301          * @param string|bool $alias Table alias (optional)
2302          * @return string SQL name for aliased table. Will not alias a table to its own name
2303          */
2304         protected function tableNameWithAlias( $table, $alias = false ) {
2305                 if ( is_string( $table ) ) {
2306                         $quotedTable = $this->tableName( $table );
2307                 } elseif ( $table instanceof Subquery ) {
2308                         $quotedTable = (string)$table;
2309                 } else {
2310                         throw new InvalidArgumentException( "Table must be a string or Subquery." );
2311                 }
2312
2313                 if ( !strlen( $alias ) || $alias === $table ) {
2314                         if ( $table instanceof Subquery ) {
2315                                 throw new InvalidArgumentException( "Subquery table missing alias." );
2316                         }
2317
2318                         return $quotedTable;
2319                 } else {
2320                         return $quotedTable . ' ' . $this->addIdentifierQuotes( $alias );
2321                 }
2322         }
2323
2324         /**
2325          * Gets an array of aliased table names
2326          *
2327          * @param array $tables [ [alias] => table ]
2328          * @return string[] See tableNameWithAlias()
2329          */
2330         protected function tableNamesWithAlias( $tables ) {
2331                 $retval = [];
2332                 foreach ( $tables as $alias => $table ) {
2333                         if ( is_numeric( $alias ) ) {
2334                                 $alias = $table;
2335                         }
2336                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2337                 }
2338
2339                 return $retval;
2340         }
2341
2342         /**
2343          * Get an aliased field name
2344          * e.g. fieldName AS newFieldName
2345          *
2346          * @param string $name Field name
2347          * @param string|bool $alias Alias (optional)
2348          * @return string SQL name for aliased field. Will not alias a field to its own name
2349          */
2350         protected function fieldNameWithAlias( $name, $alias = false ) {
2351                 if ( !$alias || (string)$alias === (string)$name ) {
2352                         return $name;
2353                 } else {
2354                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
2355                 }
2356         }
2357
2358         /**
2359          * Gets an array of aliased field names
2360          *
2361          * @param array $fields [ [alias] => field ]
2362          * @return string[] See fieldNameWithAlias()
2363          */
2364         protected function fieldNamesWithAlias( $fields ) {
2365                 $retval = [];
2366                 foreach ( $fields as $alias => $field ) {
2367                         if ( is_numeric( $alias ) ) {
2368                                 $alias = $field;
2369                         }
2370                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2371                 }
2372
2373                 return $retval;
2374         }
2375
2376         /**
2377          * Get the aliased table name clause for a FROM clause
2378          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2379          *
2380          * @param array $tables ( [alias] => table )
2381          * @param array $use_index Same as for select()
2382          * @param array $ignore_index Same as for select()
2383          * @param array $join_conds Same as for select()
2384          * @return string
2385          */
2386         protected function tableNamesWithIndexClauseOrJOIN(
2387                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2388         ) {
2389                 $ret = [];
2390                 $retJOIN = [];
2391                 $use_index = (array)$use_index;
2392                 $ignore_index = (array)$ignore_index;
2393                 $join_conds = (array)$join_conds;
2394
2395                 foreach ( $tables as $alias => $table ) {
2396                         if ( !is_string( $alias ) ) {
2397                                 // No alias? Set it equal to the table name
2398                                 $alias = $table;
2399                         }
2400
2401                         if ( is_array( $table ) ) {
2402                                 // A parenthesized group
2403                                 if ( count( $table ) > 1 ) {
2404                                         $joinedTable = '(' .
2405                                                 $this->tableNamesWithIndexClauseOrJOIN(
2406                                                         $table, $use_index, $ignore_index, $join_conds ) . ')';
2407                                 } else {
2408                                         // Degenerate case
2409                                         $innerTable = reset( $table );
2410                                         $innerAlias = key( $table );
2411                                         $joinedTable = $this->tableNameWithAlias(
2412                                                 $innerTable,
2413                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2414                                         );
2415                                 }
2416                         } else {
2417                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2418                         }
2419
2420                         // Is there a JOIN clause for this table?
2421                         if ( isset( $join_conds[$alias] ) ) {
2422                                 list( $joinType, $conds ) = $join_conds[$alias];
2423                                 $tableClause = $joinType;
2424                                 $tableClause .= ' ' . $joinedTable;
2425                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2426                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2427                                         if ( $use != '' ) {
2428                                                 $tableClause .= ' ' . $use;
2429                                         }
2430                                 }
2431                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2432                                         $ignore = $this->ignoreIndexClause(
2433                                                 implode( ',', (array)$ignore_index[$alias] ) );
2434                                         if ( $ignore != '' ) {
2435                                                 $tableClause .= ' ' . $ignore;
2436                                         }
2437                                 }
2438                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2439                                 if ( $on != '' ) {
2440                                         $tableClause .= ' ON (' . $on . ')';
2441                                 }
2442
2443                                 $retJOIN[] = $tableClause;
2444                         } elseif ( isset( $use_index[$alias] ) ) {
2445                                 // Is there an INDEX clause for this table?
2446                                 $tableClause = $joinedTable;
2447                                 $tableClause .= ' ' . $this->useIndexClause(
2448                                                 implode( ',', (array)$use_index[$alias] )
2449                                         );
2450
2451                                 $ret[] = $tableClause;
2452                         } elseif ( isset( $ignore_index[$alias] ) ) {
2453                                 // Is there an INDEX clause for this table?
2454                                 $tableClause = $joinedTable;
2455                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2456                                                 implode( ',', (array)$ignore_index[$alias] )
2457                                         );
2458
2459                                 $ret[] = $tableClause;
2460                         } else {
2461                                 $tableClause = $joinedTable;
2462
2463                                 $ret[] = $tableClause;
2464                         }
2465                 }
2466
2467                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2468                 $implicitJoins = $ret ? implode( ',', $ret ) : "";
2469                 $explicitJoins = $retJOIN ? implode( ' ', $retJOIN ) : "";
2470
2471                 // Compile our final table clause
2472                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2473         }
2474
2475         /**
2476          * Allows for index remapping in queries where this is not consistent across DBMS
2477          *
2478          * @param string $index
2479          * @return string
2480          */
2481         protected function indexName( $index ) {
2482                 return isset( $this->indexAliases[$index] )
2483                         ? $this->indexAliases[$index]
2484                         : $index;
2485         }
2486
2487         public function addQuotes( $s ) {
2488                 if ( $s instanceof Blob ) {
2489                         $s = $s->fetch();
2490                 }
2491                 if ( $s === null ) {
2492                         return 'NULL';
2493                 } elseif ( is_bool( $s ) ) {
2494                         return (int)$s;
2495                 } else {
2496                         # This will also quote numeric values. This should be harmless,
2497                         # and protects against weird problems that occur when they really
2498                         # _are_ strings such as article titles and string->number->string
2499                         # conversion is not 1:1.
2500                         return "'" . $this->strencode( $s ) . "'";
2501                 }
2502         }
2503
2504         /**
2505          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2506          * MySQL uses `backticks` while basically everything else uses double quotes.
2507          * Since MySQL is the odd one out here the double quotes are our generic
2508          * and we implement backticks in DatabaseMysqlBase.
2509          *
2510          * @param string $s
2511          * @return string
2512          */
2513         public function addIdentifierQuotes( $s ) {
2514                 return '"' . str_replace( '"', '""', $s ) . '"';
2515         }
2516
2517         /**
2518          * Returns if the given identifier looks quoted or not according to
2519          * the database convention for quoting identifiers .
2520          *
2521          * @note Do not use this to determine if untrusted input is safe.
2522          *   A malicious user can trick this function.
2523          * @param string $name
2524          * @return bool
2525          */
2526         public function isQuotedIdentifier( $name ) {
2527                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2528         }
2529
2530         /**
2531          * @param string $s
2532          * @param string $escapeChar
2533          * @return string
2534          */
2535         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2536                 return str_replace( [ $escapeChar, '%', '_' ],
2537                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2538                         $s );
2539         }
2540
2541         public function buildLike() {
2542                 $params = func_get_args();
2543
2544                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2545                         $params = $params[0];
2546                 }
2547
2548                 $s = '';
2549
2550                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2551                 // may escape backslashes, creating problems of double escaping. The `
2552                 // character has good cross-DBMS compatibility, avoiding special operators
2553                 // in MS SQL like ^ and %
2554                 $escapeChar = '`';
2555
2556                 foreach ( $params as $value ) {
2557                         if ( $value instanceof LikeMatch ) {
2558                                 $s .= $value->toString();
2559                         } else {
2560                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2561                         }
2562                 }
2563
2564                 return ' LIKE ' .
2565                         $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2566         }
2567
2568         public function anyChar() {
2569                 return new LikeMatch( '_' );
2570         }
2571
2572         public function anyString() {
2573                 return new LikeMatch( '%' );
2574         }
2575
2576         public function nextSequenceValue( $seqName ) {
2577                 return null;
2578         }
2579
2580         /**
2581          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2582          * is only needed because a) MySQL must be as efficient as possible due to
2583          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2584          * which index to pick. Anyway, other databases might have different
2585          * indexes on a given table. So don't bother overriding this unless you're
2586          * MySQL.
2587          * @param string $index
2588          * @return string
2589          */
2590         public function useIndexClause( $index ) {
2591                 return '';
2592         }
2593
2594         /**
2595          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2596          * is only needed because a) MySQL must be as efficient as possible due to
2597          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2598          * which index to pick. Anyway, other databases might have different
2599          * indexes on a given table. So don't bother overriding this unless you're
2600          * MySQL.
2601          * @param string $index
2602          * @return string
2603          */
2604         public function ignoreIndexClause( $index ) {
2605                 return '';
2606         }
2607
2608         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2609                 if ( count( $rows ) == 0 ) {
2610                         return;
2611                 }
2612
2613                 // Single row case
2614                 if ( !is_array( reset( $rows ) ) ) {
2615                         $rows = [ $rows ];
2616                 }
2617
2618                 try {
2619                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2620                         $affectedRowCount = 0;
2621                         foreach ( $rows as $row ) {
2622                                 // Delete rows which collide with this one
2623                                 $indexWhereClauses = [];
2624                                 foreach ( $uniqueIndexes as $index ) {
2625                                         $indexColumns = (array)$index;
2626                                         $indexRowValues = array_intersect_key( $row, array_flip( $indexColumns ) );
2627                                         if ( count( $indexRowValues ) != count( $indexColumns ) ) {
2628                                                 throw new DBUnexpectedError(
2629                                                         $this,
2630                                                         'New record does not provide all values for unique key (' .
2631                                                         implode( ', ', $indexColumns ) . ')'
2632                                                 );
2633                                         } elseif ( in_array( null, $indexRowValues, true ) ) {
2634                                                 throw new DBUnexpectedError(
2635                                                         $this,
2636                                                         'New record has a null value for unique key (' .
2637                                                         implode( ', ', $indexColumns ) . ')'
2638                                                 );
2639                                         }
2640                                         $indexWhereClauses[] = $this->makeList( $indexRowValues, LIST_AND );
2641                                 }
2642
2643                                 if ( $indexWhereClauses ) {
2644                                         $this->delete( $table, $this->makeList( $indexWhereClauses, LIST_OR ), $fname );
2645                                         $affectedRowCount += $this->affectedRows();
2646                                 }
2647
2648                                 // Now insert the row
2649                                 $this->insert( $table, $row, $fname );
2650                                 $affectedRowCount += $this->affectedRows();
2651                         }
2652                         $this->endAtomic( $fname );
2653                         $this->affectedRowCount = $affectedRowCount;
2654                 } catch ( Exception $e ) {
2655                         $this->cancelAtomic( $fname );
2656                         throw $e;
2657                 }
2658         }
2659
2660         /**
2661          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2662          * statement.
2663          *
2664          * @param string $table Table name
2665          * @param array|string $rows Row(s) to insert
2666          * @param string $fname Caller function name
2667          *
2668          * @return ResultWrapper
2669          */
2670         protected function nativeReplace( $table, $rows, $fname ) {
2671                 $table = $this->tableName( $table );
2672
2673                 # Single row case
2674                 if ( !is_array( reset( $rows ) ) ) {
2675                         $rows = [ $rows ];
2676                 }
2677
2678                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2679                 $first = true;
2680
2681                 foreach ( $rows as $row ) {
2682                         if ( $first ) {
2683                                 $first = false;
2684                         } else {
2685                                 $sql .= ',';
2686                         }
2687
2688                         $sql .= '(' . $this->makeList( $row ) . ')';
2689                 }
2690
2691                 return $this->query( $sql, $fname );
2692         }
2693
2694         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2695                 $fname = __METHOD__
2696         ) {
2697                 if ( !count( $rows ) ) {
2698                         return true; // nothing to do
2699                 }
2700
2701                 if ( !is_array( reset( $rows ) ) ) {
2702                         $rows = [ $rows ];
2703                 }
2704
2705                 if ( count( $uniqueIndexes ) ) {
2706                         $clauses = []; // list WHERE clauses that each identify a single row
2707                         foreach ( $rows as $row ) {
2708                                 foreach ( $uniqueIndexes as $index ) {
2709                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2710                                         $rowKey = []; // unique key to this row
2711                                         foreach ( $index as $column ) {
2712                                                 $rowKey[$column] = $row[$column];
2713                                         }
2714                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2715                                 }
2716                         }
2717                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2718                 } else {
2719                         $where = false;
2720                 }
2721
2722                 $affectedRowCount = 0;
2723                 try {
2724                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2725                         # Update any existing conflicting row(s)
2726                         if ( $where !== false ) {
2727                                 $ok = $this->update( $table, $set, $where, $fname );
2728                                 $affectedRowCount += $this->affectedRows();
2729                         } else {
2730                                 $ok = true;
2731                         }
2732                         # Now insert any non-conflicting row(s)
2733                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2734                         $affectedRowCount += $this->affectedRows();
2735                         $this->endAtomic( $fname );
2736                         $this->affectedRowCount = $affectedRowCount;
2737                 } catch ( Exception $e ) {
2738                         $this->cancelAtomic( $fname );
2739                         throw $e;
2740                 }
2741
2742                 return $ok;
2743         }
2744
2745         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2746                 $fname = __METHOD__
2747         ) {
2748                 if ( !$conds ) {
2749                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2750                 }
2751
2752                 $delTable = $this->tableName( $delTable );
2753                 $joinTable = $this->tableName( $joinTable );
2754                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2755                 if ( $conds != '*' ) {
2756                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2757                 }
2758                 $sql .= ')';
2759
2760                 $this->query( $sql, $fname );
2761         }
2762
2763         public function textFieldSize( $table, $field ) {
2764                 $table = $this->tableName( $table );
2765                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2766                 $res = $this->query( $sql, __METHOD__ );
2767                 $row = $this->fetchObject( $res );
2768
2769                 $m = [];
2770
2771                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2772                         $size = $m[1];
2773                 } else {
2774                         $size = -1;
2775                 }
2776
2777                 return $size;
2778         }
2779
2780         public function delete( $table, $conds, $fname = __METHOD__ ) {
2781                 if ( !$conds ) {
2782                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2783                 }
2784
2785                 $table = $this->tableName( $table );
2786                 $sql = "DELETE FROM $table";
2787
2788                 if ( $conds != '*' ) {
2789                         if ( is_array( $conds ) ) {
2790                                 $conds = $this->makeList( $conds, self::LIST_AND );
2791                         }
2792                         $sql .= ' WHERE ' . $conds;
2793                 }
2794
2795                 return $this->query( $sql, $fname );
2796         }
2797
2798         final public function insertSelect(
2799                 $destTable, $srcTable, $varMap, $conds,
2800                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2801         ) {
2802                 static $hints = [ 'NO_AUTO_COLUMNS' ];
2803
2804                 $insertOptions = (array)$insertOptions;
2805                 $selectOptions = (array)$selectOptions;
2806
2807                 if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions ) ) {
2808                         // For massive migrations with downtime, we don't want to select everything
2809                         // into memory and OOM, so do all this native on the server side if possible.
2810                         return $this->nativeInsertSelect(
2811                                 $destTable,
2812                                 $srcTable,
2813                                 $varMap,
2814                                 $conds,
2815                                 $fname,
2816                                 array_diff( $insertOptions, $hints ),
2817                                 $selectOptions,
2818                                 $selectJoinConds
2819                         );
2820                 }
2821
2822                 return $this->nonNativeInsertSelect(
2823                         $destTable,
2824                         $srcTable,
2825                         $varMap,
2826                         $conds,
2827                         $fname,
2828                         array_diff( $insertOptions, $hints ),
2829                         $selectOptions,
2830                         $selectJoinConds
2831                 );
2832         }
2833
2834         /**
2835          * @param array $insertOptions INSERT options
2836          * @param array $selectOptions SELECT options
2837          * @return bool Whether an INSERT SELECT with these options will be replication safe
2838          * @since 1.31
2839          */
2840         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
2841                 return true;
2842         }
2843
2844         /**
2845          * Implementation of insertSelect() based on select() and insert()
2846          *
2847          * @see IDatabase::insertSelect()
2848          * @since 1.30
2849          * @param string $destTable
2850          * @param string|array $srcTable
2851          * @param array $varMap
2852          * @param array $conds
2853          * @param string $fname
2854          * @param array $insertOptions
2855          * @param array $selectOptions
2856          * @param array $selectJoinConds
2857          * @return bool
2858          */
2859         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2860                 $fname = __METHOD__,
2861                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2862         ) {
2863                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2864                 // on only the master (without needing row-based-replication). It also makes it easy to
2865                 // know how big the INSERT is going to be.
2866                 $fields = [];
2867                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2868                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2869                 }
2870                 $selectOptions[] = 'FOR UPDATE';
2871                 $res = $this->select(
2872                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
2873                 );
2874                 if ( !$res ) {
2875                         return false;
2876                 }
2877
2878                 try {
2879                         $affectedRowCount = 0;
2880                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2881                         $rows = [];
2882                         $ok = true;
2883                         foreach ( $res as $row ) {
2884                                 $rows[] = (array)$row;
2885
2886                                 // Avoid inserts that are too huge
2887                                 if ( count( $rows ) >= $this->nonNativeInsertSelectBatchSize ) {
2888                                         $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
2889                                         if ( !$ok ) {
2890                                                 break;
2891                                         }
2892                                         $affectedRowCount += $this->affectedRows();
2893                                         $rows = [];
2894                                 }
2895                         }
2896                         if ( $rows && $ok ) {
2897                                 $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
2898                                 if ( $ok ) {
2899                                         $affectedRowCount += $this->affectedRows();
2900                                 }
2901                         }
2902                         if ( $ok ) {
2903                                 $this->endAtomic( $fname );
2904                                 $this->affectedRowCount = $affectedRowCount;
2905                         } else {
2906                                 $this->cancelAtomic( $fname );
2907                         }
2908                         return $ok;
2909                 } catch ( Exception $e ) {
2910                         $this->cancelAtomic( $fname );
2911                         throw $e;
2912                 }
2913         }
2914
2915         /**
2916          * Native server-side implementation of insertSelect() for situations where
2917          * we don't want to select everything into memory
2918          *
2919          * @see IDatabase::insertSelect()
2920          * @param string $destTable
2921          * @param string|array $srcTable
2922          * @param array $varMap
2923          * @param array $conds
2924          * @param string $fname
2925          * @param array $insertOptions
2926          * @param array $selectOptions
2927          * @param array $selectJoinConds
2928          * @return bool
2929          */
2930         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2931                 $fname = __METHOD__,
2932                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2933         ) {
2934                 $destTable = $this->tableName( $destTable );
2935
2936                 if ( !is_array( $insertOptions ) ) {
2937                         $insertOptions = [ $insertOptions ];
2938                 }
2939
2940                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2941
2942                 $selectSql = $this->selectSQLText(
2943                         $srcTable,
2944                         array_values( $varMap ),
2945                         $conds,
2946                         $fname,
2947                         $selectOptions,
2948                         $selectJoinConds
2949                 );
2950
2951                 $sql = "INSERT $insertOptions" .
2952                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
2953                         $selectSql;
2954
2955                 return $this->query( $sql, $fname );
2956         }
2957
2958         /**
2959          * Construct a LIMIT query with optional offset. This is used for query
2960          * pages. The SQL should be adjusted so that only the first $limit rows
2961          * are returned. If $offset is provided as well, then the first $offset
2962          * rows should be discarded, and the next $limit rows should be returned.
2963          * If the result of the query is not ordered, then the rows to be returned
2964          * are theoretically arbitrary.
2965          *
2966          * $sql is expected to be a SELECT, if that makes a difference.
2967          *
2968          * The version provided by default works in MySQL and SQLite. It will very
2969          * likely need to be overridden for most other DBMSes.
2970          *
2971          * @param string $sql SQL query we will append the limit too
2972          * @param int $limit The SQL limit
2973          * @param int|bool $offset The SQL offset (default false)
2974          * @throws DBUnexpectedError
2975          * @return string
2976          */
2977         public function limitResult( $sql, $limit, $offset = false ) {
2978                 if ( !is_numeric( $limit ) ) {
2979                         throw new DBUnexpectedError( $this,
2980                                 "Invalid non-numeric limit passed to limitResult()\n" );
2981                 }
2982
2983                 return "$sql LIMIT "
2984                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
2985                 . "{$limit} ";
2986         }
2987
2988         public function unionSupportsOrderAndLimit() {
2989                 return true; // True for almost every DB supported
2990         }
2991
2992         public function unionQueries( $sqls, $all ) {
2993                 $glue = $all ? ') UNION ALL (' : ') UNION (';
2994
2995                 return '(' . implode( $glue, $sqls ) . ')';
2996         }
2997
2998         public function unionConditionPermutations(
2999                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
3000                 $options = [], $join_conds = []
3001         ) {
3002                 // First, build the Cartesian product of $permute_conds
3003                 $conds = [ [] ];
3004                 foreach ( $permute_conds as $field => $values ) {
3005                         if ( !$values ) {
3006                                 // Skip empty $values
3007                                 continue;
3008                         }
3009                         $values = array_unique( $values ); // For sanity
3010                         $newConds = [];
3011                         foreach ( $conds as $cond ) {
3012                                 foreach ( $values as $value ) {
3013                                         $cond[$field] = $value;
3014                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
3015                                 }
3016                         }
3017                         $conds = $newConds;
3018                 }
3019
3020                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
3021
3022                 // If there's just one condition and no subordering, hand off to
3023                 // selectSQLText directly.
3024                 if ( count( $conds ) === 1 &&
3025                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
3026                 ) {
3027                         return $this->selectSQLText(
3028                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
3029                         );
3030                 }
3031
3032                 // Otherwise, we need to pull out the order and limit to apply after
3033                 // the union. Then build the SQL queries for each set of conditions in
3034                 // $conds. Then union them together (using UNION ALL, because the
3035                 // product *should* already be distinct).
3036                 $orderBy = $this->makeOrderBy( $options );
3037                 $limit = isset( $options['LIMIT'] ) ? $options['LIMIT'] : null;
3038                 $offset = isset( $options['OFFSET'] ) ? $options['OFFSET'] : false;
3039                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
3040                 if ( !$this->unionSupportsOrderAndLimit() ) {
3041                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
3042                 } else {
3043                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
3044                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
3045                         }
3046                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
3047                                 // We need to increase the limit by the offset rather than
3048                                 // using the offset directly, otherwise it'll skip incorrectly
3049                                 // in the subqueries.
3050                                 $options['LIMIT'] = $limit + $offset;
3051                                 unset( $options['OFFSET'] );
3052                         }
3053                 }
3054
3055                 $sqls = [];
3056                 foreach ( $conds as $cond ) {
3057                         $sqls[] = $this->selectSQLText(
3058                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
3059                         );
3060                 }
3061                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
3062                 if ( $limit !== null ) {
3063                         $sql = $this->limitResult( $sql, $limit, $offset );
3064                 }
3065
3066                 return $sql;
3067         }
3068
3069         public function conditional( $cond, $trueVal, $falseVal ) {
3070                 if ( is_array( $cond ) ) {
3071                         $cond = $this->makeList( $cond, self::LIST_AND );
3072                 }
3073
3074                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
3075         }
3076
3077         public function strreplace( $orig, $old, $new ) {
3078                 return "REPLACE({$orig}, {$old}, {$new})";
3079         }
3080
3081         public function getServerUptime() {
3082                 return 0;
3083         }
3084
3085         public function wasDeadlock() {
3086                 return false;
3087         }
3088
3089         public function wasLockTimeout() {
3090                 return false;
3091         }
3092
3093         public function wasConnectionLoss() {
3094                 return $this->wasConnectionError( $this->lastErrno() );
3095         }
3096
3097         public function wasReadOnlyError() {
3098                 return false;
3099         }
3100
3101         public function wasErrorReissuable() {
3102                 return (
3103                         $this->wasDeadlock() ||
3104                         $this->wasLockTimeout() ||
3105                         $this->wasConnectionLoss()
3106                 );
3107         }
3108
3109         /**
3110          * Do not use this method outside of Database/DBError classes
3111          *
3112          * @param int|string $errno
3113          * @return bool Whether the given query error was a connection drop
3114          */
3115         public function wasConnectionError( $errno ) {
3116                 return false;
3117         }
3118
3119         /**
3120          * @return bool Whether it is safe to assume the given error only caused statement rollback
3121          * @note This is for backwards compatibility for callers catching DBError exceptions in
3122          *   order to ignore problems like duplicate key errors or foriegn key violations
3123          * @since 1.31
3124          */
3125         protected function wasKnownStatementRollbackError() {
3126                 return false; // don't know; it could have caused a transaction rollback
3127         }
3128
3129         public function deadlockLoop() {
3130                 $args = func_get_args();
3131                 $function = array_shift( $args );
3132                 $tries = self::DEADLOCK_TRIES;
3133
3134                 $this->begin( __METHOD__ );
3135
3136                 $retVal = null;
3137                 /** @var Exception $e */
3138                 $e = null;
3139                 do {
3140                         try {
3141                                 $retVal = call_user_func_array( $function, $args );
3142                                 break;
3143                         } catch ( DBQueryError $e ) {
3144                                 if ( $this->wasDeadlock() ) {
3145                                         // Retry after a randomized delay
3146                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3147                                 } else {
3148                                         // Throw the error back up
3149                                         throw $e;
3150                                 }
3151                         }
3152                 } while ( --$tries > 0 );
3153
3154                 if ( $tries <= 0 ) {
3155                         // Too many deadlocks; give up
3156                         $this->rollback( __METHOD__ );
3157                         throw $e;
3158                 } else {
3159                         $this->commit( __METHOD__ );
3160
3161                         return $retVal;
3162                 }
3163         }
3164
3165         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3166                 # Real waits are implemented in the subclass.
3167                 return 0;
3168         }
3169
3170         public function getReplicaPos() {
3171                 # Stub
3172                 return false;
3173         }
3174
3175         public function getMasterPos() {
3176                 # Stub
3177                 return false;
3178         }
3179
3180         public function serverIsReadOnly() {
3181                 return false;
3182         }
3183
3184         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
3185                 if ( !$this->trxLevel ) {
3186                         throw new DBUnexpectedError( $this, "No transaction is active." );
3187                 }
3188                 $this->trxEndCallbacks[] = [ $callback, $fname ];
3189         }
3190
3191         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
3192                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3193                         // Start an implicit transaction similar to how query() does
3194                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3195                         $this->trxAutomatic = true;
3196                 }
3197
3198                 $this->trxIdleCallbacks[] = [ $callback, $fname ];
3199                 if ( !$this->trxLevel ) {
3200                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
3201                 }
3202         }
3203
3204         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3205                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3206                         // Start an implicit transaction similar to how query() does
3207                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3208                         $this->trxAutomatic = true;
3209                 }
3210
3211                 if ( $this->trxLevel ) {
3212                         $this->trxPreCommitCallbacks[] = [ $callback, $fname ];
3213                 } else {
3214                         // No transaction is active nor will start implicitly, so make one for this callback
3215                         $this->startAtomic( __METHOD__, self::ATOMIC_CANCELABLE );
3216                         try {
3217                                 call_user_func( $callback );
3218                                 $this->endAtomic( __METHOD__ );
3219                         } catch ( Exception $e ) {
3220                                 $this->cancelAtomic( __METHOD__ );
3221                                 throw $e;
3222                         }
3223                 }
3224         }
3225
3226         final public function setTransactionListener( $name, callable $callback = null ) {
3227                 if ( $callback ) {
3228                         $this->trxRecurringCallbacks[$name] = $callback;
3229                 } else {
3230                         unset( $this->trxRecurringCallbacks[$name] );
3231                 }
3232         }
3233
3234         /**
3235          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
3236          *
3237          * This method should not be used outside of Database/LoadBalancer
3238          *
3239          * @param bool $suppress
3240          * @since 1.28
3241          */
3242         final public function setTrxEndCallbackSuppression( $suppress ) {
3243                 $this->trxEndCallbacksSuppressed = $suppress;
3244         }
3245
3246         /**
3247          * Actually run and consume any "on transaction idle/resolution" callbacks.
3248          *
3249          * This method should not be used outside of Database/LoadBalancer
3250          *
3251          * @param int $trigger IDatabase::TRIGGER_* constant
3252          * @since 1.20
3253          * @throws Exception
3254          */
3255         public function runOnTransactionIdleCallbacks( $trigger ) {
3256                 if ( $this->trxEndCallbacksSuppressed ) {
3257                         return;
3258                 }
3259
3260                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
3261                 /** @var Exception $e */
3262                 $e = null; // first exception
3263                 do { // callbacks may add callbacks :)
3264                         $callbacks = array_merge(
3265                                 $this->trxIdleCallbacks,
3266                                 $this->trxEndCallbacks // include "transaction resolution" callbacks
3267                         );
3268                         $this->trxIdleCallbacks = []; // consumed (and recursion guard)
3269                         $this->trxEndCallbacks = []; // consumed (recursion guard)
3270                         foreach ( $callbacks as $callback ) {
3271                                 try {
3272                                         list( $phpCallback ) = $callback;
3273                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
3274                                         call_user_func_array( $phpCallback, [ $trigger ] );
3275                                         if ( $autoTrx ) {
3276                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
3277                                         } else {
3278                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
3279                                         }
3280                                 } catch ( Exception $ex ) {
3281                                         call_user_func( $this->errorLogger, $ex );
3282                                         $e = $e ?: $ex;
3283                                         // Some callbacks may use startAtomic/endAtomic, so make sure
3284                                         // their transactions are ended so other callbacks don't fail
3285                                         if ( $this->trxLevel() ) {
3286                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
3287                                         }
3288                                 }
3289                         }
3290                 } while ( count( $this->trxIdleCallbacks ) );
3291
3292                 if ( $e instanceof Exception ) {
3293                         throw $e; // re-throw any first exception
3294                 }
3295         }
3296
3297         /**
3298          * Actually run and consume any "on transaction pre-commit" callbacks.
3299          *
3300          * This method should not be used outside of Database/LoadBalancer
3301          *
3302          * @since 1.22
3303          * @throws Exception
3304          */
3305         public function runOnTransactionPreCommitCallbacks() {
3306                 $e = null; // first exception
3307                 do { // callbacks may add callbacks :)
3308                         $callbacks = $this->trxPreCommitCallbacks;
3309                         $this->trxPreCommitCallbacks = []; // consumed (and recursion guard)
3310                         foreach ( $callbacks as $callback ) {
3311                                 try {
3312                                         list( $phpCallback ) = $callback;
3313                                         call_user_func( $phpCallback );
3314                                 } catch ( Exception $ex ) {
3315                                         call_user_func( $this->errorLogger, $ex );
3316                                         $e = $e ?: $ex;
3317                                 }
3318                         }
3319                 } while ( count( $this->trxPreCommitCallbacks ) );
3320
3321                 if ( $e instanceof Exception ) {
3322                         throw $e; // re-throw any first exception
3323                 }
3324         }
3325
3326         /**
3327          * Actually run any "transaction listener" callbacks.
3328          *
3329          * This method should not be used outside of Database/LoadBalancer
3330          *
3331          * @param int $trigger IDatabase::TRIGGER_* constant
3332          * @throws Exception
3333          * @since 1.20
3334          */
3335         public function runTransactionListenerCallbacks( $trigger ) {
3336                 if ( $this->trxEndCallbacksSuppressed ) {
3337                         return;
3338                 }
3339
3340                 /** @var Exception $e */
3341                 $e = null; // first exception
3342
3343                 foreach ( $this->trxRecurringCallbacks as $phpCallback ) {
3344                         try {
3345                                 $phpCallback( $trigger, $this );
3346                         } catch ( Exception $ex ) {
3347                                 call_user_func( $this->errorLogger, $ex );
3348                                 $e = $e ?: $ex;
3349                         }
3350                 }
3351
3352                 if ( $e instanceof Exception ) {
3353                         throw $e; // re-throw any first exception
3354                 }
3355         }
3356
3357         /**
3358          * Create a savepoint
3359          *
3360          * This is used internally to implement atomic sections. It should not be
3361          * used otherwise.
3362          *
3363          * @since 1.31
3364          * @param string $identifier Identifier for the savepoint
3365          * @param string $fname Calling function name
3366          */
3367         protected function doSavepoint( $identifier, $fname ) {
3368                 $this->query( 'SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3369         }
3370
3371         /**
3372          * Release a savepoint
3373          *
3374          * This is used internally to implement atomic sections. It should not be
3375          * used otherwise.
3376          *
3377          * @since 1.31
3378          * @param string $identifier Identifier for the savepoint
3379          * @param string $fname Calling function name
3380          */
3381         protected function doReleaseSavepoint( $identifier, $fname ) {
3382                 $this->query( 'RELEASE SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3383         }
3384
3385         /**
3386          * Rollback to a savepoint
3387          *
3388          * This is used internally to implement atomic sections. It should not be
3389          * used otherwise.
3390          *
3391          * @since 1.31
3392          * @param string $identifier Identifier for the savepoint
3393          * @param string $fname Calling function name
3394          */
3395         protected function doRollbackToSavepoint( $identifier, $fname ) {
3396                 $this->query( 'ROLLBACK TO SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3397         }
3398
3399         final public function startAtomic(
3400                 $fname = __METHOD__, $cancelable = self::ATOMIC_NOT_CANCELABLE
3401         ) {
3402                 $savepointId = $cancelable === self::ATOMIC_CANCELABLE ? 'n/a' : null;
3403                 if ( !$this->trxLevel ) {
3404                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
3405                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
3406                         // in all changes being in one transaction to keep requests transactional.
3407                         if ( !$this->getFlag( self::DBO_TRX ) ) {
3408                                 $this->trxAutomaticAtomic = true;
3409                         }
3410                 } elseif ( $cancelable === self::ATOMIC_CANCELABLE ) {
3411                         $savepointId = 'wikimedia_rdbms_atomic' . ++$this->trxAtomicCounter;
3412                         if ( strlen( $savepointId ) > 30 ) { // 30 == Oracle's identifier length limit (pre 12c)
3413                                 $this->queryLogger->warning(
3414                                         'There have been an excessively large number of atomic sections in a transaction'
3415                                         . " started by $this->trxFname, reusing IDs (at $fname)",
3416                                         [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
3417                                 );
3418                                 $this->trxAtomicCounter = 0;
3419                                 $savepointId = 'wikimedia_rdbms_atomic' . ++$this->trxAtomicCounter;
3420                         }
3421                         $this->doSavepoint( $savepointId, $fname );
3422                 }
3423
3424                 $this->trxAtomicLevels[] = [ $fname, $savepointId ];
3425         }
3426
3427         final public function endAtomic( $fname = __METHOD__ ) {
3428                 if ( !$this->trxLevel ) {
3429                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
3430                 }
3431
3432                 list( $savedFname, $savepointId ) = $this->trxAtomicLevels
3433                         ? array_pop( $this->trxAtomicLevels ) : [ null, null ];
3434                 if ( $savedFname !== $fname ) {
3435                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
3436                 }
3437
3438                 if ( !$this->trxAtomicLevels && $this->trxAutomaticAtomic ) {
3439                         $this->commit( $fname, self::FLUSHING_INTERNAL );
3440                 } elseif ( $savepointId && $savepointId !== 'n/a' ) {
3441                         $this->doReleaseSavepoint( $savepointId, $fname );
3442                 }
3443         }
3444
3445         final public function cancelAtomic( $fname = __METHOD__ ) {
3446                 if ( !$this->trxLevel ) {
3447                         throw new DBUnexpectedError( $this, "No atomic transaction is open (got $fname)." );
3448                 }
3449
3450                 list( $savedFname, $savepointId ) = $this->trxAtomicLevels
3451                         ? array_pop( $this->trxAtomicLevels ) : [ null, null ];
3452                 if ( $savedFname !== $fname ) {
3453                         throw new DBUnexpectedError( $this, "Invalid atomic section ended (got $fname)." );
3454                 }
3455                 if ( !$savepointId ) {
3456                         throw new DBUnexpectedError( $this, "Uncancelable atomic section canceled (got $fname)." );
3457                 }
3458
3459                 if ( !$this->trxAtomicLevels && $this->trxAutomaticAtomic ) {
3460                         $this->rollback( $fname, self::FLUSHING_INTERNAL );
3461                 } elseif ( $savepointId !== 'n/a' ) {
3462                         $this->doRollbackToSavepoint( $savepointId, $fname );
3463                         $this->trxStatus = self::STATUS_TRX_OK; // no exception; recovered
3464                 }
3465
3466                 $this->affectedRowCount = 0; // for the sake of consistency
3467         }
3468
3469         final public function doAtomicSection( $fname, callable $callback ) {
3470                 $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
3471                 try {
3472                         $res = call_user_func_array( $callback, [ $this, $fname ] );
3473                 } catch ( Exception $e ) {
3474                         $this->cancelAtomic( $fname );
3475                         throw $e;
3476                 }
3477                 $this->endAtomic( $fname );
3478
3479                 return $res;
3480         }
3481
3482         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
3483                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
3484                 if ( $this->trxLevel ) {
3485                         if ( $this->trxAtomicLevels ) {
3486                                 $levels = $this->flatAtomicSectionList();
3487                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
3488                                 throw new DBUnexpectedError( $this, $msg );
3489                         } elseif ( !$this->trxAutomatic ) {
3490                                 $msg = "$fname: Explicit transaction already active (from {$this->trxFname}).";
3491                                 throw new DBUnexpectedError( $this, $msg );
3492                         } else {
3493                                 $msg = "$fname: Implicit transaction already active (from {$this->trxFname}).";
3494                                 throw new DBUnexpectedError( $this, $msg );
3495                         }
3496                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
3497                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
3498                         throw new DBUnexpectedError( $this, $msg );
3499                 }
3500
3501                 // Avoid fatals if close() was called
3502                 $this->assertOpen();
3503
3504                 $this->doBegin( $fname );
3505                 $this->trxStatus = self::STATUS_TRX_OK;
3506                 $this->trxAtomicCounter = 0;
3507                 $this->trxTimestamp = microtime( true );
3508                 $this->trxFname = $fname;
3509                 $this->trxDoneWrites = false;
3510                 $this->trxAutomaticAtomic = false;
3511                 $this->trxAtomicLevels = [];
3512                 $this->trxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
3513                 $this->trxWriteDuration = 0.0;
3514                 $this->trxWriteQueryCount = 0;
3515                 $this->trxWriteAffectedRows = 0;
3516                 $this->trxWriteAdjDuration = 0.0;
3517                 $this->trxWriteAdjQueryCount = 0;
3518                 $this->trxWriteCallers = [];
3519                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3520                 // Get an estimate of the replication lag before any such queries.
3521                 $this->trxReplicaLag = null; // clear cached value first
3522                 $this->trxReplicaLag = $this->getApproximateLagStatus()['lag'];
3523                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3524                 // caller will think its OK to muck around with the transaction just because startAtomic()
3525                 // has not yet completed (e.g. setting trxAtomicLevels).
3526                 $this->trxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3527         }
3528
3529         /**
3530          * Issues the BEGIN command to the database server.
3531          *
3532          * @see Database::begin()
3533          * @param string $fname
3534          */
3535         protected function doBegin( $fname ) {
3536                 $this->query( 'BEGIN', $fname );
3537                 $this->trxLevel = 1;
3538         }
3539
3540         final public function commit( $fname = __METHOD__, $flush = '' ) {
3541                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3542                         // There are still atomic sections open. This cannot be ignored
3543                         $levels = $this->flatAtomicSectionList();
3544                         throw new DBUnexpectedError(
3545                                 $this,
3546                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3547                         );
3548                 }
3549
3550                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3551                         if ( !$this->trxLevel ) {
3552                                 return; // nothing to do
3553                         } elseif ( !$this->trxAutomatic ) {
3554                                 throw new DBUnexpectedError(
3555                                         $this,
3556                                         "$fname: Flushing an explicit transaction, getting out of sync."
3557                                 );
3558                         }
3559                 } else {
3560                         if ( !$this->trxLevel ) {
3561                                 $this->queryLogger->error(
3562                                         "$fname: No transaction to commit, something got out of sync." );
3563                                 return; // nothing to do
3564                         } elseif ( $this->trxAutomatic ) {
3565                                 throw new DBUnexpectedError(
3566                                         $this,
3567                                         "$fname: Expected mass commit of all peer transactions (DBO_TRX set)."
3568                                 );
3569                         }
3570                 }
3571
3572                 // Avoid fatals if close() was called
3573                 $this->assertOpen();
3574
3575                 $this->runOnTransactionPreCommitCallbacks();
3576                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3577                 $this->doCommit( $fname );
3578                 $this->trxStatus = self::STATUS_TRX_NONE;
3579                 if ( $this->trxDoneWrites ) {
3580                         $this->lastWriteTime = microtime( true );
3581                         $this->trxProfiler->transactionWritingOut(
3582                                 $this->server,
3583                                 $this->dbName,
3584                                 $this->trxShortId,
3585                                 $writeTime,
3586                                 $this->trxWriteAffectedRows
3587                         );
3588                 }
3589
3590                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3591                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3592         }
3593
3594         /**
3595          * Issues the COMMIT command to the database server.
3596          *
3597          * @see Database::commit()
3598          * @param string $fname
3599          */
3600         protected function doCommit( $fname ) {
3601                 if ( $this->trxLevel ) {
3602                         $this->query( 'COMMIT', $fname );
3603                         $this->trxLevel = 0;
3604                 }
3605         }
3606
3607         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3608                 $trxActive = $this->trxLevel;
3609
3610                 if ( $flush !== self::FLUSHING_INTERNAL && $flush !== self::FLUSHING_ALL_PEERS ) {
3611                         if ( $this->getFlag( self::DBO_TRX ) ) {
3612                                 throw new DBUnexpectedError(
3613                                         $this,
3614                                         "$fname: Expected mass rollback of all peer transactions (DBO_TRX set)."
3615                                 );
3616                         }
3617                 }
3618
3619                 if ( $trxActive ) {
3620                         // Avoid fatals if close() was called
3621                         $this->assertOpen();
3622
3623                         $this->doRollback( $fname );
3624                         $this->trxStatus = self::STATUS_TRX_NONE;
3625                         $this->trxAtomicLevels = [];
3626                         if ( $this->trxDoneWrites ) {
3627                                 $this->trxProfiler->transactionWritingOut(
3628                                         $this->server,
3629                                         $this->dbName,
3630                                         $this->trxShortId
3631                                 );
3632                         }
3633                 }
3634
3635                 // Clear any commit-dependant callbacks. They might even be present
3636                 // only due to transaction rounds, with no SQL transaction being active
3637                 $this->trxIdleCallbacks = [];
3638                 $this->trxPreCommitCallbacks = [];
3639
3640                 if ( $trxActive ) {
3641                         try {
3642                                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3643                         } catch ( Exception $e ) {
3644                                 // already logged; finish and let LoadBalancer move on during mass-rollback
3645                         }
3646                         try {
3647                                 $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3648                         } catch ( Exception $e ) {
3649                                 // already logged; let LoadBalancer move on during mass-rollback
3650                         }
3651
3652                         $this->affectedRowCount = 0; // for the sake of consistency
3653                 }
3654         }
3655
3656         /**
3657          * Issues the ROLLBACK command to the database server.
3658          *
3659          * @see Database::rollback()
3660          * @param string $fname
3661          */
3662         protected function doRollback( $fname ) {
3663                 if ( $this->trxLevel ) {
3664                         # Disconnects cause rollback anyway, so ignore those errors
3665                         $ignoreErrors = true;
3666                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3667                         $this->trxLevel = 0;
3668                 }
3669         }
3670
3671         public function flushSnapshot( $fname = __METHOD__ ) {
3672                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3673                         // This only flushes transactions to clear snapshots, not to write data
3674                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3675                         throw new DBUnexpectedError(
3676                                 $this,
3677                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
3678                         );
3679                 }
3680
3681                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3682         }
3683
3684         public function explicitTrxActive() {
3685                 return $this->trxLevel && ( $this->trxAtomicLevels || !$this->trxAutomatic );
3686         }
3687
3688         public function duplicateTableStructure(
3689                 $oldName, $newName, $temporary = false, $fname = __METHOD__
3690         ) {
3691                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3692         }
3693
3694         public function listTables( $prefix = null, $fname = __METHOD__ ) {
3695                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3696         }
3697
3698         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3699                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3700         }
3701
3702         public function timestamp( $ts = 0 ) {
3703                 $t = new ConvertibleTimestamp( $ts );
3704                 // Let errors bubble up to avoid putting garbage in the DB
3705                 return $t->getTimestamp( TS_MW );
3706         }
3707
3708         public function timestampOrNull( $ts = null ) {
3709                 if ( is_null( $ts ) ) {
3710                         return null;
3711                 } else {
3712                         return $this->timestamp( $ts );
3713                 }
3714         }
3715
3716         public function affectedRows() {
3717                 return ( $this->affectedRowCount === null )
3718                         ? $this->fetchAffectedRowCount() // default to driver value
3719                         : $this->affectedRowCount;
3720         }
3721
3722         /**
3723          * @return int Number of retrieved rows according to the driver
3724          */
3725         abstract protected function fetchAffectedRowCount();
3726
3727         /**
3728          * Take the result from a query, and wrap it in a ResultWrapper if
3729          * necessary. Boolean values are passed through as is, to indicate success
3730          * of write queries or failure.
3731          *
3732          * Once upon a time, Database::query() returned a bare MySQL result
3733          * resource, and it was necessary to call this function to convert it to
3734          * a wrapper. Nowadays, raw database objects are never exposed to external
3735          * callers, so this is unnecessary in external code.
3736          *
3737          * @param bool|ResultWrapper|resource|object $result
3738          * @return bool|ResultWrapper
3739          */
3740         protected function resultObject( $result ) {
3741                 if ( !$result ) {
3742                         return false;
3743                 } elseif ( $result instanceof ResultWrapper ) {
3744                         return $result;
3745                 } elseif ( $result === true ) {
3746                         // Successful write query
3747                         return $result;
3748                 } else {
3749                         return new ResultWrapper( $this, $result );
3750                 }
3751         }
3752
3753         public function ping( &$rtt = null ) {
3754                 // Avoid hitting the server if it was hit recently
3755                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3756                         if ( !func_num_args() || $this->rttEstimate > 0 ) {
3757                                 $rtt = $this->rttEstimate;
3758                                 return true; // don't care about $rtt
3759                         }
3760                 }
3761
3762                 // This will reconnect if possible or return false if not
3763                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
3764                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3765                 $this->restoreFlags( self::RESTORE_PRIOR );
3766
3767                 if ( $ok ) {
3768                         $rtt = $this->rttEstimate;
3769                 }
3770
3771                 return $ok;
3772         }
3773
3774         /**
3775          * Close any existing (dead) database connection and open a new connection
3776          *
3777          * @param string $fname
3778          * @return bool True if new connection is opened successfully, false if error
3779          */
3780         protected function replaceLostConnection( $fname ) {
3781                 $this->closeConnection();
3782                 $this->opened = false;
3783                 $this->conn = false;
3784                 try {
3785                         $this->open( $this->server, $this->user, $this->password, $this->dbName );
3786                         $this->lastPing = microtime( true );
3787                         $ok = true;
3788
3789                         $this->connLogger->warning(
3790                                 $fname . ': lost connection to {dbserver}; reconnected',
3791                                 [
3792                                         'dbserver' => $this->getServer(),
3793                                         'trace' => ( new RuntimeException() )->getTraceAsString()
3794                                 ]
3795                         );
3796                 } catch ( DBConnectionError $e ) {
3797                         $ok = false;
3798
3799                         $this->connLogger->error(
3800                                 $fname . ': lost connection to {dbserver} permanently',
3801                                 [ 'dbserver' => $this->getServer() ]
3802                         );
3803                 }
3804
3805                 $this->handleSessionLoss();
3806
3807                 return $ok;
3808         }
3809
3810         public function getSessionLagStatus() {
3811                 return $this->getRecordedTransactionLagStatus() ?: $this->getApproximateLagStatus();
3812         }
3813
3814         /**
3815          * Get the replica DB lag when the current transaction started
3816          *
3817          * This is useful when transactions might use snapshot isolation
3818          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3819          * is this lag plus transaction duration. If they don't, it is still
3820          * safe to be pessimistic. This returns null if there is no transaction.
3821          *
3822          * This returns null if the lag status for this transaction was not yet recorded.
3823          *
3824          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3825          * @since 1.27
3826          */
3827         final protected function getRecordedTransactionLagStatus() {
3828                 return ( $this->trxLevel && $this->trxReplicaLag !== null )
3829                         ? [ 'lag' => $this->trxReplicaLag, 'since' => $this->trxTimestamp() ]
3830                         : null;
3831         }
3832
3833         /**
3834          * Get a replica DB lag estimate for this server
3835          *
3836          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3837          * @since 1.27
3838          */
3839         protected function getApproximateLagStatus() {
3840                 return [
3841                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3842                         'since' => microtime( true )
3843                 ];
3844         }
3845
3846         /**
3847          * Merge the result of getSessionLagStatus() for several DBs
3848          * using the most pessimistic values to estimate the lag of
3849          * any data derived from them in combination
3850          *
3851          * This is information is useful for caching modules
3852          *
3853          * @see WANObjectCache::set()
3854          * @see WANObjectCache::getWithSetCallback()
3855          *
3856          * @param IDatabase $db1
3857          * @param IDatabase $db2 [optional]
3858          * @return array Map of values:
3859          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3860          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3861          *   - pending: whether any of the DBs have uncommitted changes
3862          * @throws DBError
3863          * @since 1.27
3864          */
3865         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
3866                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3867                 foreach ( func_get_args() as $db ) {
3868                         /** @var IDatabase $db */
3869                         $status = $db->getSessionLagStatus();
3870                         if ( $status['lag'] === false ) {
3871                                 $res['lag'] = false;
3872                         } elseif ( $res['lag'] !== false ) {
3873                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3874                         }
3875                         $res['since'] = min( $res['since'], $status['since'] );
3876                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3877                 }
3878
3879                 return $res;
3880         }
3881
3882         public function getLag() {
3883                 return 0;
3884         }
3885
3886         public function maxListLen() {
3887                 return 0;
3888         }
3889
3890         public function encodeBlob( $b ) {
3891                 return $b;
3892         }
3893
3894         public function decodeBlob( $b ) {
3895                 if ( $b instanceof Blob ) {
3896                         $b = $b->fetch();
3897                 }
3898                 return $b;
3899         }
3900
3901         public function setSessionOptions( array $options ) {
3902         }
3903
3904         public function sourceFile(
3905                 $filename,
3906                 callable $lineCallback = null,
3907                 callable $resultCallback = null,
3908                 $fname = false,
3909                 callable $inputCallback = null
3910         ) {
3911                 Wikimedia\suppressWarnings();
3912                 $fp = fopen( $filename, 'r' );
3913                 Wikimedia\restoreWarnings();
3914
3915                 if ( false === $fp ) {
3916                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
3917                 }
3918
3919                 if ( !$fname ) {
3920                         $fname = __METHOD__ . "( $filename )";
3921                 }
3922
3923                 try {
3924                         $error = $this->sourceStream(
3925                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
3926                 } catch ( Exception $e ) {
3927                         fclose( $fp );
3928                         throw $e;
3929                 }
3930
3931                 fclose( $fp );
3932
3933                 return $error;
3934         }
3935
3936         public function setSchemaVars( $vars ) {
3937                 $this->schemaVars = $vars;
3938         }
3939
3940         public function sourceStream(
3941                 $fp,
3942                 callable $lineCallback = null,
3943                 callable $resultCallback = null,
3944                 $fname = __METHOD__,
3945                 callable $inputCallback = null
3946         ) {
3947                 $delimiterReset = new ScopedCallback(
3948                         function ( $delimiter ) {
3949                                 $this->delimiter = $delimiter;
3950                         },
3951                         [ $this->delimiter ]
3952                 );
3953                 $cmd = '';
3954
3955                 while ( !feof( $fp ) ) {
3956                         if ( $lineCallback ) {
3957                                 call_user_func( $lineCallback );
3958                         }
3959
3960                         $line = trim( fgets( $fp ) );
3961
3962                         if ( $line == '' ) {
3963                                 continue;
3964                         }
3965
3966                         if ( '-' == $line[0] && '-' == $line[1] ) {
3967                                 continue;
3968                         }
3969
3970                         if ( $cmd != '' ) {
3971                                 $cmd .= ' ';
3972                         }
3973
3974                         $done = $this->streamStatementEnd( $cmd, $line );
3975
3976                         $cmd .= "$line\n";
3977
3978                         if ( $done || feof( $fp ) ) {
3979                                 $cmd = $this->replaceVars( $cmd );
3980
3981                                 if ( $inputCallback ) {
3982                                         $callbackResult = call_user_func( $inputCallback, $cmd );
3983
3984                                         if ( is_string( $callbackResult ) || !$callbackResult ) {
3985                                                 $cmd = $callbackResult;
3986                                         }
3987                                 }
3988
3989                                 if ( $cmd ) {
3990                                         $res = $this->query( $cmd, $fname );
3991
3992                                         if ( $resultCallback ) {
3993                                                 call_user_func( $resultCallback, $res, $this );
3994                                         }
3995
3996                                         if ( false === $res ) {
3997                                                 $err = $this->lastError();
3998
3999                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
4000                                         }
4001                                 }
4002                                 $cmd = '';
4003                         }
4004                 }
4005
4006                 ScopedCallback::consume( $delimiterReset );
4007                 return true;
4008         }
4009
4010         /**
4011          * Called by sourceStream() to check if we've reached a statement end
4012          *
4013          * @param string &$sql SQL assembled so far
4014          * @param string &$newLine New line about to be added to $sql
4015          * @return bool Whether $newLine contains end of the statement
4016          */
4017         public function streamStatementEnd( &$sql, &$newLine ) {
4018                 if ( $this->delimiter ) {
4019                         $prev = $newLine;
4020                         $newLine = preg_replace(
4021                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
4022                         if ( $newLine != $prev ) {
4023                                 return true;
4024                         }
4025                 }
4026
4027                 return false;
4028         }
4029
4030         /**
4031          * Database independent variable replacement. Replaces a set of variables
4032          * in an SQL statement with their contents as given by $this->getSchemaVars().
4033          *
4034          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
4035          *
4036          * - '{$var}' should be used for text and is passed through the database's
4037          *   addQuotes method.
4038          * - `{$var}` should be used for identifiers (e.g. table and database names).
4039          *   It is passed through the database's addIdentifierQuotes method which
4040          *   can be overridden if the database uses something other than backticks.
4041          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
4042          *   database's tableName method.
4043          * - / *i* / passes the name that follows through the database's indexName method.
4044          * - In all other cases, / *$var* / is left unencoded. Except for table options,
4045          *   its use should be avoided. In 1.24 and older, string encoding was applied.
4046          *
4047          * @param string $ins SQL statement to replace variables in
4048          * @return string The new SQL statement with variables replaced
4049          */
4050         protected function replaceVars( $ins ) {
4051                 $vars = $this->getSchemaVars();
4052                 return preg_replace_callback(
4053                         '!
4054                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
4055                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
4056                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
4057                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
4058                         !x',
4059                         function ( $m ) use ( $vars ) {
4060                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
4061                                 // check for both nonexistent keys *and* the empty string.
4062                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
4063                                         if ( $m[1] === 'i' ) {
4064                                                 return $this->indexName( $m[2] );
4065                                         } else {
4066                                                 return $this->tableName( $m[2] );
4067                                         }
4068                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
4069                                         return $this->addQuotes( $vars[$m[3]] );
4070                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
4071                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
4072                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
4073                                         return $vars[$m[5]];
4074                                 } else {
4075                                         return $m[0];
4076                                 }
4077                         },
4078                         $ins
4079                 );
4080         }
4081
4082         /**
4083          * Get schema variables. If none have been set via setSchemaVars(), then
4084          * use some defaults from the current object.
4085          *
4086          * @return array
4087          */
4088         protected function getSchemaVars() {
4089                 if ( $this->schemaVars ) {
4090                         return $this->schemaVars;
4091                 } else {
4092                         return $this->getDefaultSchemaVars();
4093                 }
4094         }
4095
4096         /**
4097          * Get schema variables to use if none have been set via setSchemaVars().
4098          *
4099          * Override this in derived classes to provide variables for tables.sql
4100          * and SQL patch files.
4101          *
4102          * @return array
4103          */
4104         protected function getDefaultSchemaVars() {
4105                 return [];
4106         }
4107
4108         public function lockIsFree( $lockName, $method ) {
4109                 // RDBMs methods for checking named locks may or may not count this thread itself.
4110                 // In MySQL, IS_FREE_LOCK() returns 0 if the thread already has the lock. This is
4111                 // the behavior choosen by the interface for this method.
4112                 return !isset( $this->namedLocksHeld[$lockName] );
4113         }
4114
4115         public function lock( $lockName, $method, $timeout = 5 ) {
4116                 $this->namedLocksHeld[$lockName] = 1;
4117
4118                 return true;
4119         }
4120
4121         public function unlock( $lockName, $method ) {
4122                 unset( $this->namedLocksHeld[$lockName] );
4123
4124                 return true;
4125         }
4126
4127         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
4128                 if ( $this->writesOrCallbacksPending() ) {
4129                         // This only flushes transactions to clear snapshots, not to write data
4130                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4131                         throw new DBUnexpectedError(
4132                                 $this,
4133                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
4134                         );
4135                 }
4136
4137                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
4138                         return null;
4139                 }
4140
4141                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
4142                         if ( $this->trxLevel() ) {
4143                                 // There is a good chance an exception was thrown, causing any early return
4144                                 // from the caller. Let any error handler get a chance to issue rollback().
4145                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
4146                                 $this->onTransactionResolution(
4147                                         function () use ( $lockKey, $fname ) {
4148                                                 $this->unlock( $lockKey, $fname );
4149                                         },
4150                                         $fname
4151                                 );
4152                         } else {
4153                                 $this->unlock( $lockKey, $fname );
4154                         }
4155                 } );
4156
4157                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4158
4159                 return $unlocker;
4160         }
4161
4162         public function namedLocksEnqueue() {
4163                 return false;
4164         }
4165
4166         public function tableLocksHaveTransactionScope() {
4167                 return true;
4168         }
4169
4170         final public function lockTables( array $read, array $write, $method ) {
4171                 if ( $this->writesOrCallbacksPending() ) {
4172                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
4173                 }
4174
4175                 if ( $this->tableLocksHaveTransactionScope() ) {
4176                         $this->startAtomic( $method );
4177                 }
4178
4179                 return $this->doLockTables( $read, $write, $method );
4180         }
4181
4182         /**
4183          * Helper function for lockTables() that handles the actual table locking
4184          *
4185          * @param array $read Array of tables to lock for read access
4186          * @param array $write Array of tables to lock for write access
4187          * @param string $method Name of caller
4188          * @return true
4189          */
4190         protected function doLockTables( array $read, array $write, $method ) {
4191                 return true;
4192         }
4193
4194         final public function unlockTables( $method ) {
4195                 if ( $this->tableLocksHaveTransactionScope() ) {
4196                         $this->endAtomic( $method );
4197
4198                         return true; // locks released on COMMIT/ROLLBACK
4199                 }
4200
4201                 return $this->doUnlockTables( $method );
4202         }
4203
4204         /**
4205          * Helper function for unlockTables() that handles the actual table unlocking
4206          *
4207          * @param string $method Name of caller
4208          * @return true
4209          */
4210         protected function doUnlockTables( $method ) {
4211                 return true;
4212         }
4213
4214         /**
4215          * Delete a table
4216          * @param string $tableName
4217          * @param string $fName
4218          * @return bool|ResultWrapper
4219          * @since 1.18
4220          */
4221         public function dropTable( $tableName, $fName = __METHOD__ ) {
4222                 if ( !$this->tableExists( $tableName, $fName ) ) {
4223                         return false;
4224                 }
4225                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
4226
4227                 return $this->query( $sql, $fName );
4228         }
4229
4230         public function getInfinity() {
4231                 return 'infinity';
4232         }
4233
4234         public function encodeExpiry( $expiry ) {
4235                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4236                         ? $this->getInfinity()
4237                         : $this->timestamp( $expiry );
4238         }
4239
4240         public function decodeExpiry( $expiry, $format = TS_MW ) {
4241                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
4242                         return 'infinity';
4243                 }
4244
4245                 return ConvertibleTimestamp::convert( $format, $expiry );
4246         }
4247
4248         public function setBigSelects( $value = true ) {
4249                 // no-op
4250         }
4251
4252         public function isReadOnly() {
4253                 return ( $this->getReadOnlyReason() !== false );
4254         }
4255
4256         /**
4257          * @return string|bool Reason this DB is read-only or false if it is not
4258          */
4259         protected function getReadOnlyReason() {
4260                 $reason = $this->getLBInfo( 'readOnlyReason' );
4261
4262                 return is_string( $reason ) ? $reason : false;
4263         }
4264
4265         public function setTableAliases( array $aliases ) {
4266                 $this->tableAliases = $aliases;
4267         }
4268
4269         public function setIndexAliases( array $aliases ) {
4270                 $this->indexAliases = $aliases;
4271         }
4272
4273         /**
4274          * Get the underlying binding connection handle
4275          *
4276          * Makes sure the connection resource is set (disconnects and ping() failure can unset it).
4277          * This catches broken callers than catch and ignore disconnection exceptions.
4278          * Unlike checking isOpen(), this is safe to call inside of open().
4279          *
4280          * @return mixed
4281          * @throws DBUnexpectedError
4282          * @since 1.26
4283          */
4284         protected function getBindingHandle() {
4285                 if ( !$this->conn ) {
4286                         throw new DBUnexpectedError(
4287                                 $this,
4288                                 'DB connection was already closed or the connection dropped.'
4289                         );
4290                 }
4291
4292                 return $this->conn;
4293         }
4294
4295         /**
4296          * @since 1.19
4297          * @return string
4298          */
4299         public function __toString() {
4300                 return (string)$this->conn;
4301         }
4302
4303         /**
4304          * Make sure that copies do not share the same client binding handle
4305          * @throws DBConnectionError
4306          */
4307         public function __clone() {
4308                 $this->connLogger->warning(
4309                         "Cloning " . static::class . " is not recomended; forking connection:\n" .
4310                         ( new RuntimeException() )->getTraceAsString()
4311                 );
4312
4313                 if ( $this->isOpen() ) {
4314                         // Open a new connection resource without messing with the old one
4315                         $this->opened = false;
4316                         $this->conn = false;
4317                         $this->trxEndCallbacks = []; // don't copy
4318                         $this->handleSessionLoss(); // no trx or locks anymore
4319                         $this->open( $this->server, $this->user, $this->password, $this->dbName );
4320                         $this->lastPing = microtime( true );
4321                 }
4322         }
4323
4324         /**
4325          * Called by serialize. Throw an exception when DB connection is serialized.
4326          * This causes problems on some database engines because the connection is
4327          * not restored on unserialize.
4328          */
4329         public function __sleep() {
4330                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
4331                         'the connection is not restored on wakeup.' );
4332         }
4333
4334         /**
4335          * Run a few simple sanity checks and close dangling connections
4336          */
4337         public function __destruct() {
4338                 if ( $this->trxLevel && $this->trxDoneWrites ) {
4339                         trigger_error( "Uncommitted DB writes (transaction from {$this->trxFname})." );
4340                 }
4341
4342                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
4343                 if ( $danglingWriters ) {
4344                         $fnames = implode( ', ', $danglingWriters );
4345                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
4346                 }
4347
4348                 if ( $this->conn ) {
4349                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
4350                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
4351                         Wikimedia\suppressWarnings();
4352                         $this->closeConnection();
4353                         Wikimedia\restoreWarnings();
4354                         $this->conn = false;
4355                         $this->opened = false;
4356                 }
4357         }
4358 }
4359
4360 class_alias( Database::class, 'DatabaseBase' ); // b/c for old name
4361 class_alias( Database::class, 'Database' ); // b/c global alias