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         /** @var callback Deprecation logging callback */
 105         protected $deprecationLogger;
 106
 107         /** @var resource|null Database connection */
 108         protected $conn = null;
 109         /** @var bool */
 110         protected $opened = false;
 111
 112         /** @var array[] List of (callable, method name) */
 113         protected $trxIdleCallbacks = [];
 114         /** @var array[] List of (callable, method name) */
 115         protected $trxPreCommitCallbacks = [];
 116         /** @var array[] List of (callable, method name) */
 117         protected $trxEndCallbacks = [];
 118         /** @var callable[] Map of (name => callable) */
 119         protected $trxRecurringCallbacks = [];
 120         /** @var bool Whether to suppress triggering of transaction end callbacks */
 121         protected $trxEndCallbacksSuppressed = false;
 122
 123         /** @var string */
 124         protected $tablePrefix = '';
 125         /** @var string */
 126         protected $schema = '';
 127         /** @var int */
 128         protected $flags;
 129         /** @var array */
 130         protected $lbInfo = [];
 131         /** @var array|bool */
 132         protected $schemaVars = false;
 133         /** @var array */
 134         protected $sessionVars = [];
 135         /** @var array|null */
 136         protected $preparedArgs;
 137         /** @var string|bool|null Stashed value of html_errors INI setting */
 138         protected $htmlErrors;
 139         /** @var string */
 140         protected $delimiter = ';';
 141         /** @var DatabaseDomain */
 142         protected $currentDomain;
 143         /** @var integer|null Rows affected by the last query to query() or its CRUD wrappers */
 144         protected $affectedRowCount;
 145
 146         /**
 147          * @var int Transaction status
 148          */
 149         protected $trxStatus = self::STATUS_TRX_NONE;
 150         /**
 151          * @var Exception|null The last error that caused the status to become STATUS_TRX_ERROR
 152          */
 153         protected $trxStatusCause;
 154         /**
 155          * @var array|null If wasKnownStatementRollbackError() prevented trxStatus from being set,
 156          *  the relevant details are stored here.
 157          */
 158         protected $trxStatusIgnoredCause;
 159         /**
 160          * Either 1 if a transaction is active or 0 otherwise.
 161          * The other Trx fields may not be meaningfull if this is 0.
 162          *
 163          * @var int
 164          */
 165         protected $trxLevel = 0;
 166         /**
 167          * Either a short hexidecimal string if a transaction is active or ""
 168          *
 169          * @var string
 170          * @see Database::trxLevel
 171          */
 172         protected $trxShortId = '';
 173         /**
 174          * The UNIX time that the transaction started. Callers can assume that if
 175          * snapshot isolation is used, then the data is *at least* up to date to that
 176          * point (possibly more up-to-date since the first SELECT defines the snapshot).
 177          *
 178          * @var float|null
 179          * @see Database::trxLevel
 180          */
 181         private $trxTimestamp = null;
 182         /** @var float Lag estimate at the time of BEGIN */
 183         private $trxReplicaLag = null;
 184         /**
 185          * Remembers the function name given for starting the most recent transaction via begin().
 186          * Used to provide additional context for error reporting.
 187          *
 188          * @var string
 189          * @see Database::trxLevel
 190          */
 191         private $trxFname = null;
 192         /**
 193          * Record if possible write queries were done in the last transaction started
 194          *
 195          * @var bool
 196          * @see Database::trxLevel
 197          */
 198         private $trxDoneWrites = false;
 199         /**
 200          * Record if the current transaction was started implicitly due to DBO_TRX being set.
 201          *
 202          * @var bool
 203          * @see Database::trxLevel
 204          */
 205         private $trxAutomatic = false;
 206         /**
 207          * Counter for atomic savepoint identifiers. Reset when a new transaction begins.
 208          *
 209          * @var int
 210          */
 211         private $trxAtomicCounter = 0;
 212         /**
 213          * Array of levels of atomicity within transactions
 214          *
 215          * @var array List of (name, unique ID, savepoint ID)
 216          */
 217         private $trxAtomicLevels = [];
 218         /**
 219          * Record if the current transaction was started implicitly by Database::startAtomic
 220          *
 221          * @var bool
 222          */
 223         private $trxAutomaticAtomic = false;
 224         /**
 225          * Track the write query callers of the current transaction
 226          *
 227          * @var string[]
 228          */
 229         private $trxWriteCallers = [];
 230         /**
 231          * @var float Seconds spent in write queries for the current transaction
 232          */
 233         private $trxWriteDuration = 0.0;
 234         /**
 235          * @var int Number of write queries for the current transaction
 236          */
 237         private $trxWriteQueryCount = 0;
 238         /**
 239          * @var int Number of rows affected by write queries for the current transaction
 240          */
 241         private $trxWriteAffectedRows = 0;
 242         /**
 243          * @var float Like trxWriteQueryCount but excludes lock-bound, easy to replicate, queries
 244          */
 245         private $trxWriteAdjDuration = 0.0;
 246         /**
 247          * @var int Number of write queries counted in trxWriteAdjDuration
 248          */
 249         private $trxWriteAdjQueryCount = 0;
 250         /**
 251          * @var float RTT time estimate
 252          */
 253         private $rttEstimate = 0.0;
 254
 255         /** @var array Map of (name => 1) for locks obtained via lock() */
 256         private $namedLocksHeld = [];
 257         /** @var array Map of (table name => 1) for TEMPORARY tables */
 258         protected $sessionTempTables = [];
 259
 260         /** @var IDatabase|null Lazy handle to the master DB this server replicates from */
 261         private $lazyMasterHandle;
 262
 263         /** @var float UNIX timestamp */
 264         protected $lastPing = 0.0;
 265
 266         /** @var int[] Prior flags member variable values */
 267         private $priorFlags = [];
 268
 269         /** @var object|string Class name or object With profileIn/profileOut methods */
 270         protected $profiler;
 271         /** @var TransactionProfiler */
 272         protected $trxProfiler;
 273
 274         /** @var int */
 275         protected $nonNativeInsertSelectBatchSize = 10000;
 276
 277         /** @var int Transaction is in a error state requiring a full or savepoint rollback */
 278         const STATUS_TRX_ERROR = 1;
 279         /** @var int Transaction is active and in a normal state */
 280         const STATUS_TRX_OK = 2;
 281         /** @var int No transaction is active */
 282         const STATUS_TRX_NONE = 3;
 283
 284         /**
 285          * @note: exceptions for missing libraries/drivers should be thrown in initConnection()
 286          * @param array $params Parameters passed from Database::factory()
 287          */
 288         protected function __construct( array $params ) {
 289                 foreach ( [ 'host', 'user', 'password', 'dbname' ] as $name ) {
 290                         $this->connectionParams[$name] = $params[$name];
 291                 }
 292
 293                 $this->schema = $params['schema'];
 294                 $this->tablePrefix = $params['tablePrefix'];
 295
 296                 $this->cliMode = $params['cliMode'];
 297                 // Agent name is added to SQL queries in a comment, so make sure it can't break out
 298                 $this->agent = str_replace( '/', '-', $params['agent'] );
 299
 300                 $this->flags = $params['flags'];
 301                 if ( $this->flags & self::DBO_DEFAULT ) {
 302                         if ( $this->cliMode ) {
 303                                 $this->flags &= ~self::DBO_TRX;
 304                         } else {
 305                                 $this->flags |= self::DBO_TRX;
 306                         }
 307                 }
 308                 // Disregard deprecated DBO_IGNORE flag (T189999)
 309                 $this->flags &= ~self::DBO_IGNORE;
 310
 311                 $this->sessionVars = $params['variables'];
 312
 313                 $this->srvCache = isset( $params['srvCache'] )
 314                         ? $params['srvCache']
 315                         : new HashBagOStuff();
 316
 317                 $this->profiler = $params['profiler'];
 318                 $this->trxProfiler = $params['trxProfiler'];
 319                 $this->connLogger = $params['connLogger'];
 320                 $this->queryLogger = $params['queryLogger'];
 321                 $this->errorLogger = $params['errorLogger'];
 322                 $this->deprecationLogger = $params['deprecationLogger'];
 323
 324                 if ( isset( $params['nonNativeInsertSelectBatchSize'] ) ) {
 325                         $this->nonNativeInsertSelectBatchSize = $params['nonNativeInsertSelectBatchSize'];
 326                 }
 327
 328                 // Set initial dummy domain until open() sets the final DB/prefix
 329                 $this->currentDomain = DatabaseDomain::newUnspecified();
 330         }
 331
 332         /**
 333          * Initialize the connection to the database over the wire (or to local files)
 334          *
 335          * @throws LogicException
 336          * @throws InvalidArgumentException
 337          * @throws DBConnectionError
 338          * @since 1.31
 339          */
 340         final public function initConnection() {
 341                 if ( $this->isOpen() ) {
 342                         throw new LogicException( __METHOD__ . ': already connected.' );
 343                 }
 344                 // Establish the connection
 345                 $this->doInitConnection();
 346                 // Set the domain object after open() sets the relevant fields
 347                 if ( $this->dbName != '' ) {
 348                         // Domains with server scope but a table prefix are not used by IDatabase classes
 349                         $this->currentDomain = new DatabaseDomain( $this->dbName, null, $this->tablePrefix );
 350                 }
 351         }
 352
 353         /**
 354          * Actually connect to the database over the wire (or to local files)
 355          *
 356          * @throws InvalidArgumentException
 357          * @throws DBConnectionError
 358          * @since 1.31
 359          */
 360         protected function doInitConnection() {
 361                 if ( strlen( $this->connectionParams['user'] ) ) {
 362                         $this->open(
 363                                 $this->connectionParams['host'],
 364                                 $this->connectionParams['user'],
 365                                 $this->connectionParams['password'],
 366                                 $this->connectionParams['dbname']
 367                         );
 368                 } else {
 369                         throw new InvalidArgumentException( "No database user provided." );
 370                 }
 371         }
 372
 373         /**
 374          * Construct a Database subclass instance given a database type and parameters
 375          *
 376          * This also connects to the database immediately upon object construction
 377          *
 378          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 379          * @param array $p Parameter map with keys:
 380          *   - host : The hostname of the DB server
 381          *   - user : The name of the database user the client operates under
 382          *   - password : The password for the database user
 383          *   - dbname : The name of the database to use where queries do not specify one.
 384          *      The database must exist or an error might be thrown. Setting this to the empty string
 385          *      will avoid any such errors and make the handle have no implicit database scope. This is
 386          *      useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
 387          *      "database" in Postgres is rougly equivalent to an entire MySQL server. This the domain
 388          *      in which user names and such are defined, e.g. users are database-specific in Postgres.
 389          *   - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
 390          *      equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
 391          *   - tablePrefix : Optional table prefix that is implicitly added on to all table names
 392          *      recognized in queries. This can be used in place of schemas for handle site farms.
 393          *   - flags : Optional bitfield of DBO_* constants that define connection, protocol,
 394          *      buffering, and transaction behavior. It is STRONGLY adviced to leave the DBO_DEFAULT
 395          *      flag in place UNLESS this this database simply acts as a key/value store.
 396          *   - driver: Optional name of a specific DB client driver. For MySQL, there is only the
 397          *      'mysqli' driver; the old one 'mysql' has been removed.
 398          *   - variables: Optional map of session variables to set after connecting. This can be
 399          *      used to adjust lock timeouts or encoding modes and the like.
 400          *   - connLogger: Optional PSR-3 logger interface instance.
 401          *   - queryLogger: Optional PSR-3 logger interface instance.
 402          *   - profiler: Optional class name or object with profileIn()/profileOut() methods.
 403          *      These will be called in query(), using a simplified version of the SQL that also
 404          *      includes the agent as a SQL comment.
 405          *   - trxProfiler: Optional TransactionProfiler instance.
 406          *   - errorLogger: Optional callback that takes an Exception and logs it.
 407          *   - deprecationLogger: Optional callback that takes a string and logs it.
 408          *   - cliMode: Whether to consider the execution context that of a CLI script.
 409          *   - agent: Optional name used to identify the end-user in query profiling/logging.
 410          *   - srvCache: Optional BagOStuff instance to an APC-style cache.
 411          *   - nonNativeInsertSelectBatchSize: Optional batch size for non-native INSERT SELECT emulation.
 412          * @param int $connect One of the class constants (NEW_CONNECTED, NEW_UNCONNECTED) [optional]
 413          * @return Database|null If the database driver or extension cannot be found
 414          * @throws InvalidArgumentException If the database driver or extension cannot be found
 415          * @since 1.18
 416          */
 417         final public static function factory( $dbType, $p = [], $connect = self::NEW_CONNECTED ) {
 418                 $class = self::getClass( $dbType, isset( $p['driver'] ) ? $p['driver'] : null );
 419
 420                 if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
 421                         // Resolve some defaults for b/c
 422                         $p['host'] = isset( $p['host'] ) ? $p['host'] : false;
 423                         $p['user'] = isset( $p['user'] ) ? $p['user'] : false;
 424                         $p['password'] = isset( $p['password'] ) ? $p['password'] : false;
 425                         $p['dbname'] = isset( $p['dbname'] ) ? $p['dbname'] : false;
 426                         $p['flags'] = isset( $p['flags'] ) ? $p['flags'] : 0;
 427                         $p['variables'] = isset( $p['variables'] ) ? $p['variables'] : [];
 428                         $p['tablePrefix'] = isset( $p['tablePrefix'] ) ? $p['tablePrefix'] : '';
 429                         $p['schema'] = isset( $p['schema'] ) ? $p['schema'] : '';
 430                         $p['cliMode'] = isset( $p['cliMode'] )
 431                                 ? $p['cliMode']
 432                                 : ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' );
 433                         $p['agent'] = isset( $p['agent'] ) ? $p['agent'] : '';
 434                         if ( !isset( $p['connLogger'] ) ) {
 435                                 $p['connLogger'] = new NullLogger();
 436                         }
 437                         if ( !isset( $p['queryLogger'] ) ) {
 438                                 $p['queryLogger'] = new NullLogger();
 439                         }
 440                         $p['profiler'] = isset( $p['profiler'] ) ? $p['profiler'] : null;
 441                         if ( !isset( $p['trxProfiler'] ) ) {
 442                                 $p['trxProfiler'] = new TransactionProfiler();
 443                         }
 444                         if ( !isset( $p['errorLogger'] ) ) {
 445                                 $p['errorLogger'] = function ( Exception $e ) {
 446                                         trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
 447                                 };
 448                         }
 449                         if ( !isset( $p['deprecationLogger'] ) ) {
 450                                 $p['deprecationLogger'] = function ( $msg ) {
 451                                         trigger_error( $msg, E_USER_DEPRECATED );
 452                                 };
 453                         }
 454
 455                         /** @var Database $conn */
 456                         $conn = new $class( $p );
 457                         if ( $connect == self::NEW_CONNECTED ) {
 458                                 $conn->initConnection();
 459                         }
 460                 } else {
 461                         $conn = null;
 462                 }
 463
 464                 return $conn;
 465         }
 466
 467         /**
 468          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 469          * @param string|null $driver Optional name of a specific DB client driver
 470          * @return array Map of (Database::ATTRIBUTE_* constant => value) for all such constants
 471          * @throws InvalidArgumentException
 472          * @since 1.31
 473          */
 474         final public static function attributesFromType( $dbType, $driver = null ) {
 475                 static $defaults = [ self::ATTR_DB_LEVEL_LOCKING => false ];
 476
 477                 $class = self::getClass( $dbType, $driver );
 478
 479                 return call_user_func( [ $class, 'getAttributes' ] ) + $defaults;
 480         }
 481
 482         /**
 483          * @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
 484          * @param string|null $driver Optional name of a specific DB client driver
 485          * @return string Database subclass name to use
 486          * @throws InvalidArgumentException
 487          */
 488         private static function getClass( $dbType, $driver = null ) {
 489                 // For database types with built-in support, the below maps type to IDatabase
 490                 // implementations. For types with multipe driver implementations (PHP extensions),
 491                 // an array can be used, keyed by extension name. In case of an array, the
 492                 // optional 'driver' parameter can be used to force a specific driver. Otherwise,
 493                 // we auto-detect the first available driver. For types without built-in support,
 494                 // an class named "Database<Type>" us used, eg. DatabaseFoo for type 'foo'.
 495                 static $builtinTypes = [
 496                         'mssql' => DatabaseMssql::class,
 497                         'mysql' => [ 'mysqli' => DatabaseMysqli::class ],
 498                         'sqlite' => DatabaseSqlite::class,
 499                         'postgres' => DatabasePostgres::class,
 500                 ];
 501
 502                 $dbType = strtolower( $dbType );
 503                 $class = false;
 504
 505                 if ( isset( $builtinTypes[$dbType] ) ) {
 506                         $possibleDrivers = $builtinTypes[$dbType];
 507                         if ( is_string( $possibleDrivers ) ) {
 508                                 $class = $possibleDrivers;
 509                         } else {
 510                                 if ( (string)$driver !== '' ) {
 511                                         if ( !isset( $possibleDrivers[$driver] ) ) {
 512                                                 throw new InvalidArgumentException( __METHOD__ .
 513                                                         " type '$dbType' does not support driver '{$driver}'" );
 514                                         } else {
 515                                                 $class = $possibleDrivers[$driver];
 516                                         }
 517                                 } else {
 518                                         foreach ( $possibleDrivers as $posDriver => $possibleClass ) {
 519                                                 if ( extension_loaded( $posDriver ) ) {
 520                                                         $class = $possibleClass;
 521                                                         break;
 522                                                 }
 523                                         }
 524                                 }
 525                         }
 526                 } else {
 527                         $class = 'Database' . ucfirst( $dbType );
 528                 }
 529
 530                 if ( $class === false ) {
 531                         throw new InvalidArgumentException( __METHOD__ .
 532                                 " no viable database extension found for type '$dbType'" );
 533                 }
 534
 535                 return $class;
 536         }
 537
 538         /**
 539          * @return array Map of (Database::ATTRIBUTE_* constant => value
 540          * @since 1.31
 541          */
 542         protected static function getAttributes() {
 543                 return [];
 544         }
 545
 546         /**
 547          * Set the PSR-3 logger interface to use for query logging. (The logger
 548          * interfaces for connection logging and error logging can be set with the
 549          * constructor.)
 550          *
 551          * @param LoggerInterface $logger
 552          */
 553         public function setLogger( LoggerInterface $logger ) {
 554                 $this->queryLogger = $logger;
 555         }
 556
 557         public function getServerInfo() {
 558                 return $this->getServerVersion();
 559         }
 560
 561         public function bufferResults( $buffer = null ) {
 562                 $res = !$this->getFlag( self::DBO_NOBUFFER );
 563                 if ( $buffer !== null ) {
 564                         $buffer
 565                                 ? $this->clearFlag( self::DBO_NOBUFFER )
 566                                 : $this->setFlag( self::DBO_NOBUFFER );
 567                 }
 568
 569                 return $res;
 570         }
 571
 572         public function trxLevel() {
 573                 return $this->trxLevel;
 574         }
 575
 576         public function trxTimestamp() {
 577                 return $this->trxLevel ? $this->trxTimestamp : null;
 578         }
 579
 580         /**
 581          * @return int One of the STATUS_TRX_* class constants
 582          * @since 1.31
 583          */
 584         public function trxStatus() {
 585                 return $this->trxStatus;
 586         }
 587
 588         public function tablePrefix( $prefix = null ) {
 589                 $old = $this->tablePrefix;
 590                 if ( $prefix !== null ) {
 591                         $this->tablePrefix = $prefix;
 592                         $this->currentDomain = ( $this->dbName != '' )
 593                                 ? new DatabaseDomain( $this->dbName, null, $this->tablePrefix )
 594                                 : DatabaseDomain::newUnspecified();
 595                 }
 596
 597                 return $old;
 598         }
 599
 600         public function dbSchema( $schema = null ) {
 601                 $old = $this->schema;
 602                 if ( $schema !== null ) {
 603                         $this->schema = $schema;
 604                 }
 605
 606                 return $old;
 607         }
 608
 609         public function getLBInfo( $name = null ) {
 610                 if ( is_null( $name ) ) {
 611                         return $this->lbInfo;
 612                 } else {
 613                         if ( array_key_exists( $name, $this->lbInfo ) ) {
 614                                 return $this->lbInfo[$name];
 615                         } else {
 616                                 return null;
 617                         }
 618                 }
 619         }
 620
 621         public function setLBInfo( $name, $value = null ) {
 622                 if ( is_null( $value ) ) {
 623                         $this->lbInfo = $name;
 624                 } else {
 625                         $this->lbInfo[$name] = $value;
 626                 }
 627         }
 628
 629         public function setLazyMasterHandle( IDatabase $conn ) {
 630                 $this->lazyMasterHandle = $conn;
 631         }
 632
 633         /**
 634          * @return IDatabase|null
 635          * @see setLazyMasterHandle()
 636          * @since 1.27
 637          */
 638         protected function getLazyMasterHandle() {
 639                 return $this->lazyMasterHandle;
 640         }
 641
 642         public function implicitGroupby() {
 643                 return true;
 644         }
 645
 646         public function implicitOrderby() {
 647                 return true;
 648         }
 649
 650         public function lastQuery() {
 651                 return $this->lastQuery;
 652         }
 653
 654         public function doneWrites() {
 655                 return (bool)$this->lastWriteTime;
 656         }
 657
 658         public function lastDoneWrites() {
 659                 return $this->lastWriteTime ?: false;
 660         }
 661
 662         public function writesPending() {
 663                 return $this->trxLevel && $this->trxDoneWrites;
 664         }
 665
 666         public function writesOrCallbacksPending() {
 667                 return $this->trxLevel && (
 668                         $this->trxDoneWrites ||
 669                         $this->trxIdleCallbacks ||
 670                         $this->trxPreCommitCallbacks ||
 671                         $this->trxEndCallbacks
 672                 );
 673         }
 674
 675         /**
 676          * @return string|null
 677          */
 678         final protected function getTransactionRoundId() {
 679                 // If transaction round participation is enabled, see if one is active
 680                 if ( $this->getFlag( self::DBO_TRX ) ) {
 681                         $id = $this->getLBInfo( 'trxRoundId' );
 682
 683                         return is_string( $id ) ? $id : null;
 684                 }
 685
 686                 return null;
 687         }
 688
 689         public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
 690                 if ( !$this->trxLevel ) {
 691                         return false;
 692                 } elseif ( !$this->trxDoneWrites ) {
 693                         return 0.0;
 694                 }
 695
 696                 switch ( $type ) {
 697                         case self::ESTIMATE_DB_APPLY:
 698                                 $this->ping( $rtt );
 699                                 $rttAdjTotal = $this->trxWriteAdjQueryCount * $rtt;
 700                                 $applyTime = max( $this->trxWriteAdjDuration - $rttAdjTotal, 0 );
 701                                 // For omitted queries, make them count as something at least
 702                                 $omitted = $this->trxWriteQueryCount - $this->trxWriteAdjQueryCount;
 703                                 $applyTime += self::TINY_WRITE_SEC * $omitted;
 704
 705                                 return $applyTime;
 706                         default: // everything
 707                                 return $this->trxWriteDuration;
 708                 }
 709         }
 710
 711         public function pendingWriteCallers() {
 712                 return $this->trxLevel ? $this->trxWriteCallers : [];
 713         }
 714
 715         public function pendingWriteRowsAffected() {
 716                 return $this->trxWriteAffectedRows;
 717         }
 718
 719         /**
 720          * Get the list of method names that have pending write queries or callbacks
 721          * for this transaction
 722          *
 723          * @return array
 724          */
 725         protected function pendingWriteAndCallbackCallers() {
 726                 if ( !$this->trxLevel ) {
 727                         return [];
 728                 }
 729
 730                 $fnames = $this->trxWriteCallers;
 731                 foreach ( [
 732                         $this->trxIdleCallbacks,
 733                         $this->trxPreCommitCallbacks,
 734                         $this->trxEndCallbacks
 735                 ] as $callbacks ) {
 736                         foreach ( $callbacks as $callback ) {
 737                                 $fnames[] = $callback[1];
 738                         }
 739                 }
 740
 741                 return $fnames;
 742         }
 743
 744         /**
 745          * @return string
 746          */
 747         private function flatAtomicSectionList() {
 748                 return array_reduce( $this->trxAtomicLevels, function ( $accum, $v ) {
 749                         return $accum === null ? $v[0] : "$accum, " . $v[0];
 750                 } );
 751         }
 752
 753         public function isOpen() {
 754                 return $this->opened;
 755         }
 756
 757         public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 758                 if ( ( $flag & self::DBO_IGNORE ) ) {
 759                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 760                 }
 761
 762                 if ( $remember === self::REMEMBER_PRIOR ) {
 763                         array_push( $this->priorFlags, $this->flags );
 764                 }
 765                 $this->flags |= $flag;
 766         }
 767
 768         public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
 769                 if ( ( $flag & self::DBO_IGNORE ) ) {
 770                         throw new UnexpectedValueException( "Modifying DBO_IGNORE is not allowed." );
 771                 }
 772
 773                 if ( $remember === self::REMEMBER_PRIOR ) {
 774                         array_push( $this->priorFlags, $this->flags );
 775                 }
 776                 $this->flags &= ~$flag;
 777         }
 778
 779         public function restoreFlags( $state = self::RESTORE_PRIOR ) {
 780                 if ( !$this->priorFlags ) {
 781                         return;
 782                 }
 783
 784                 if ( $state === self::RESTORE_INITIAL ) {
 785                         $this->flags = reset( $this->priorFlags );
 786                         $this->priorFlags = [];
 787                 } else {
 788                         $this->flags = array_pop( $this->priorFlags );
 789                 }
 790         }
 791
 792         public function getFlag( $flag ) {
 793                 return !!( $this->flags & $flag );
 794         }
 795
 796         /**
 797          * @param string $name Class field name
 798          * @return mixed
 799          * @deprecated Since 1.28
 800          */
 801         public function getProperty( $name ) {
 802                 return $this->$name;
 803         }
 804
 805         public function getDomainID() {
 806                 return $this->currentDomain->getId();
 807         }
 808
 809         final public function getWikiID() {
 810                 return $this->getDomainID();
 811         }
 812
 813         /**
 814          * Get information about an index into an object
 815          * @param string $table Table name
 816          * @param string $index Index name
 817          * @param string $fname Calling function name
 818          * @return mixed Database-specific index description class or false if the index does not exist
 819          */
 820         abstract function indexInfo( $table, $index, $fname = __METHOD__ );
 821
 822         /**
 823          * Wrapper for addslashes()
 824          *
 825          * @param string $s String to be slashed.
 826          * @return string Slashed string.
 827          */
 828         abstract function strencode( $s );
 829
 830         /**
 831          * Set a custom error handler for logging errors during database connection
 832          */
 833         protected function installErrorHandler() {
 834                 $this->phpError = false;
 835                 $this->htmlErrors = ini_set( 'html_errors', '0' );
 836                 set_error_handler( [ $this, 'connectionErrorLogger' ] );
 837         }
 838
 839         /**
 840          * Restore the previous error handler and return the last PHP error for this DB
 841          *
 842          * @return bool|string
 843          */
 844         protected function restoreErrorHandler() {
 845                 restore_error_handler();
 846                 if ( $this->htmlErrors !== false ) {
 847                         ini_set( 'html_errors', $this->htmlErrors );
 848                 }
 849
 850                 return $this->getLastPHPError();
 851         }
 852
 853         /**
 854          * @return string|bool Last PHP error for this DB (typically connection errors)
 855          */
 856         protected function getLastPHPError() {
 857                 if ( $this->phpError ) {
 858                         $error = preg_replace( '!\[<a.*</a>\]!', '', $this->phpError );
 859                         $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 860
 861                         return $error;
 862                 }
 863
 864                 return false;
 865         }
 866
 867         /**
 868          * Error handler for logging errors during database connection
 869          * This method should not be used outside of Database classes
 870          *
 871          * @param int $errno
 872          * @param string $errstr
 873          */
 874         public function connectionErrorLogger( $errno, $errstr ) {
 875                 $this->phpError = $errstr;
 876         }
 877
 878         /**
 879          * Create a log context to pass to PSR-3 logger functions.
 880          *
 881          * @param array $extras Additional data to add to context
 882          * @return array
 883          */
 884         protected function getLogContext( array $extras = [] ) {
 885                 return array_merge(
 886                         [
 887                                 'db_server' => $this->server,
 888                                 'db_name' => $this->dbName,
 889                                 'db_user' => $this->user,
 890                         ],
 891                         $extras
 892                 );
 893         }
 894
 895         final public function close() {
 896                 $exception = null; // error to throw after disconnecting
 897
 898                 if ( $this->conn ) {
 899                         // Resolve any dangling transaction first
 900                         if ( $this->trxLevel ) {
 901                                 if ( $this->trxAtomicLevels ) {
 902                                         // Cannot let incomplete atomic sections be committed
 903                                         $levels = $this->flatAtomicSectionList();
 904                                         $exception = new DBUnexpectedError(
 905                                                 $this,
 906                                                 __METHOD__ . ": atomic sections $levels are still open."
 907                                         );
 908                                 } elseif ( $this->trxAutomatic ) {
 909                                         // Only the connection manager can commit non-empty DBO_TRX transactions
 910                                         if ( $this->writesOrCallbacksPending() ) {
 911                                                 $exception = new DBUnexpectedError(
 912                                                         $this,
 913                                                         __METHOD__ .
 914                                                         ": mass commit/rollback of peer transaction required (DBO_TRX set)."
 915                                                 );
 916                                         }
 917                                 } elseif ( $this->trxLevel ) {
 918                                         // Commit explicit transactions as if this was commit()
 919                                         $this->queryLogger->warning(
 920                                                 __METHOD__ . ": writes or callbacks still pending.",
 921                                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
 922                                         );
 923                                 }
 924
 925                                 if ( $this->trxEndCallbacksSuppressed ) {
 926                                         $exception = $exception ?: new DBUnexpectedError(
 927                                                 $this,
 928                                                 __METHOD__ . ': callbacks are suppressed; cannot properly commit.'
 929                                         );
 930                                 }
 931
 932                                 // Commit or rollback the changes and run any callbacks as needed
 933                                 if ( $this->trxStatus === self::STATUS_TRX_OK && !$exception ) {
 934                                         $this->commit(
 935                                                 __METHOD__,
 936                                                 $this->trxAutomatic ? self::FLUSHING_INTERNAL : self::FLUSHING_ONE
 937                                         );
 938                                 } else {
 939                                         $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
 940                                 }
 941                         }
 942
 943                         // Close the actual connection in the binding handle
 944                         $closed = $this->closeConnection();
 945                         $this->conn = false;
 946                 } else {
 947                         $closed = true; // already closed; nothing to do
 948                 }
 949
 950                 $this->opened = false;
 951
 952                 // Throw any unexpected errors after having disconnected
 953                 if ( $exception instanceof Exception ) {
 954                         throw $exception;
 955                 }
 956
 957                 // Sanity check that no callbacks are dangling
 958                 if (
 959                         $this->trxIdleCallbacks || $this->trxPreCommitCallbacks || $this->trxEndCallbacks
 960                 ) {
 961                         throw new RuntimeException(
 962                                 "Transaction callbacks are still pending:\n" .
 963                                 implode( ', ', $this->pendingWriteAndCallbackCallers() )
 964                         );
 965                 }
 966
 967                 return $closed;
 968         }
 969
 970         /**
 971          * Make sure isOpen() returns true as a sanity check
 972          *
 973          * @throws DBUnexpectedError
 974          */
 975         protected function assertOpen() {
 976                 if ( !$this->isOpen() ) {
 977                         throw new DBUnexpectedError( $this, "DB connection was already closed." );
 978                 }
 979         }
 980
 981         /**
 982          * Closes underlying database connection
 983          * @since 1.20
 984          * @return bool Whether connection was closed successfully
 985          */
 986         abstract protected function closeConnection();
 987
 988         /**
 989          * @param string $error Fallback error message, used if none is given by DB
 990          * @throws DBConnectionError
 991          */
 992         public function reportConnectionError( $error = 'Unknown error' ) {
 993                 $myError = $this->lastError();
 994                 if ( $myError ) {
 995                         $error = $myError;
 996                 }
 997
 998                 # New method
 999                 throw new DBConnectionError( $this, $error );
1000         }
1001
1002         /**
1003          * Run a query and return a DBMS-dependent wrapper (that has all IResultWrapper methods)
1004          *
1005          * This might return things, such as mysqli_result, that do not formally implement
1006          * IResultWrapper, but nonetheless implement all of its methods correctly
1007          *
1008          * @param string $sql SQL query.
1009          * @return IResultWrapper|bool Iterator to feed to fetchObject/fetchRow; false on failure
1010          */
1011         abstract protected function doQuery( $sql );
1012
1013         /**
1014          * Determine whether a query writes to the DB.
1015          * Should return true if unsure.
1016          *
1017          * @param string $sql
1018          * @return bool
1019          */
1020         protected function isWriteQuery( $sql ) {
1021                 return !preg_match(
1022                         '/^(?:SELECT|BEGIN|ROLLBACK|COMMIT|SET|SHOW|EXPLAIN|\(SELECT)\b/i', $sql );
1023         }
1024
1025         /**
1026          * @param string $sql
1027          * @return string|null
1028          */
1029         protected function getQueryVerb( $sql ) {
1030                 return preg_match( '/^\s*([a-z]+)/i', $sql, $m ) ? strtoupper( $m[1] ) : null;
1031         }
1032
1033         /**
1034          * Determine whether a SQL statement is sensitive to isolation level.
1035          * A SQL statement is considered transactable if its result could vary
1036          * depending on the transaction isolation level. Operational commands
1037          * such as 'SET' and 'SHOW' are not considered to be transactable.
1038          *
1039          * @param string $sql
1040          * @return bool
1041          */
1042         protected function isTransactableQuery( $sql ) {
1043                 return !in_array(
1044                         $this->getQueryVerb( $sql ),
1045                         [ 'BEGIN', 'COMMIT', 'ROLLBACK', 'SHOW', 'SET', 'CREATE', 'ALTER' ],
1046                         true
1047                 );
1048         }
1049
1050         /**
1051          * @param string $sql A SQL query
1052          * @return bool Whether $sql is SQL for TEMPORARY table operation
1053          */
1054         protected function registerTempTableOperation( $sql ) {
1055                 if ( preg_match(
1056                         '/^CREATE\s+TEMPORARY\s+TABLE\s+(?:IF\s+NOT\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1057                         $sql,
1058                         $matches
1059                 ) ) {
1060                         $this->sessionTempTables[$matches[1]] = 1;
1061
1062                         return true;
1063                 } elseif ( preg_match(
1064                         '/^DROP\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1065                         $sql,
1066                         $matches
1067                 ) ) {
1068                         $isTemp = isset( $this->sessionTempTables[$matches[1]] );
1069                         unset( $this->sessionTempTables[$matches[1]] );
1070
1071                         return $isTemp;
1072                 } elseif ( preg_match(
1073                         '/^TRUNCATE\s+(?:TEMPORARY\s+)?TABLE\s+(?:IF\s+EXISTS\s+)?[`"\']?(\w+)[`"\']?/i',
1074                         $sql,
1075                         $matches
1076                 ) ) {
1077                         return isset( $this->sessionTempTables[$matches[1]] );
1078                 } elseif ( preg_match(
1079                         '/^(?:INSERT\s+(?:\w+\s+)?INTO|UPDATE|DELETE\s+FROM)\s+[`"\']?(\w+)[`"\']?/i',
1080                         $sql,
1081                         $matches
1082                 ) ) {
1083                         return isset( $this->sessionTempTables[$matches[1]] );
1084                 }
1085
1086                 return false;
1087         }
1088
1089         public function query( $sql, $fname = __METHOD__, $tempIgnore = false ) {
1090                 $this->assertTransactionStatus( $sql, $fname );
1091
1092                 # Avoid fatals if close() was called
1093                 $this->assertOpen();
1094
1095                 $priorWritesPending = $this->writesOrCallbacksPending();
1096                 $this->lastQuery = $sql;
1097
1098                 $isWrite = $this->isWriteQuery( $sql );
1099                 if ( $isWrite ) {
1100                         $isNonTempWrite = !$this->registerTempTableOperation( $sql );
1101                 } else {
1102                         $isNonTempWrite = false;
1103                 }
1104
1105                 if ( $isWrite ) {
1106                         if ( $this->getLBInfo( 'replica' ) === true ) {
1107                                 throw new DBError(
1108                                         $this,
1109                                         'Write operations are not allowed on replica database connections.'
1110                                 );
1111                         }
1112                         # In theory, non-persistent writes are allowed in read-only mode, but due to things
1113                         # like https://bugs.mysql.com/bug.php?id=33669 that might not work anyway...
1114                         $reason = $this->getReadOnlyReason();
1115                         if ( $reason !== false ) {
1116                                 throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
1117                         }
1118                         # Set a flag indicating that writes have been done
1119                         $this->lastWriteTime = microtime( true );
1120                 }
1121
1122                 # Add trace comment to the begin of the sql string, right after the operator.
1123                 # Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598)
1124                 $commentedSql = preg_replace( '/\s|$/', " /* $fname {$this->agent} */ ", $sql, 1 );
1125
1126                 # Start implicit transactions that wrap the request if DBO_TRX is enabled
1127                 if ( !$this->trxLevel && $this->getFlag( self::DBO_TRX )
1128                         && $this->isTransactableQuery( $sql )
1129                 ) {
1130                         $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
1131                         $this->trxAutomatic = true;
1132                 }
1133
1134                 # Keep track of whether the transaction has write queries pending
1135                 if ( $this->trxLevel && !$this->trxDoneWrites && $isWrite ) {
1136                         $this->trxDoneWrites = true;
1137                         $this->trxProfiler->transactionWritingIn(
1138                                 $this->server, $this->dbName, $this->trxShortId );
1139                 }
1140
1141                 if ( $this->getFlag( self::DBO_DEBUG ) ) {
1142                         $this->queryLogger->debug( "{$this->dbName} {$commentedSql}" );
1143                 }
1144
1145                 # Send the query to the server and fetch any corresponding errors
1146                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1147                 $lastError = $this->lastError();
1148                 $lastErrno = $this->lastErrno();
1149
1150                 # Try reconnecting if the connection was lost
1151                 if ( $ret === false && $this->wasConnectionLoss() ) {
1152                         # Check if any meaningful session state was lost
1153                         $recoverable = $this->canRecoverFromDisconnect( $sql, $priorWritesPending );
1154                         # Update session state tracking and try to restore the connection
1155                         $reconnected = $this->replaceLostConnection( __METHOD__ );
1156                         # Silently resend the query to the server if it is safe and possible
1157                         if ( $reconnected && $recoverable ) {
1158                                 $ret = $this->doProfiledQuery( $sql, $commentedSql, $isNonTempWrite, $fname );
1159                                 $lastError = $this->lastError();
1160                                 $lastErrno = $this->lastErrno();
1161
1162                                 if ( $ret === false && $this->wasConnectionLoss() ) {
1163                                         # Query probably causes disconnects; reconnect and do not re-run it
1164                                         $this->replaceLostConnection( __METHOD__ );
1165                                 }
1166                         }
1167                 }
1168
1169                 if ( $ret === false ) {
1170                         if ( $this->trxLevel ) {
1171                                 if ( !$this->wasKnownStatementRollbackError() ) {
1172                                         # Either the query was aborted or all queries after BEGIN where aborted.
1173                                         if ( $this->explicitTrxActive() || $priorWritesPending ) {
1174                                                 # In the first case, the only options going forward are (a) ROLLBACK, or
1175                                                 # (b) ROLLBACK TO SAVEPOINT (if one was set). If the later case, the only
1176                                                 # option is ROLLBACK, since the snapshots would have been released.
1177                                                 $this->trxStatus = self::STATUS_TRX_ERROR;
1178                                                 $this->trxStatusCause =
1179                                                         $this->makeQueryException( $lastError, $lastErrno, $sql, $fname );
1180                                                 $tempIgnore = false; // cannot recover
1181                                         } else {
1182                                                 # Nothing prior was there to lose from the transaction,
1183                                                 # so just roll it back.
1184                                                 $this->rollback( __METHOD__ . " ($fname)", self::FLUSHING_INTERNAL );
1185                                         }
1186                                         $this->trxStatusIgnoredCause = null;
1187                                 } else {
1188                                         # We're ignoring an error that caused just the current query to be aborted.
1189                                         # But log the cause so we can log a deprecation notice if a
1190                                         # caller actually does ignore it.
1191                                         $this->trxStatusIgnoredCause = [ $lastError, $lastErrno, $fname ];
1192                                 }
1193                         }
1194
1195                         $this->reportQueryError( $lastError, $lastErrno, $sql, $fname, $tempIgnore );
1196                 }
1197
1198                 return $this->resultObject( $ret );
1199         }
1200
1201         /**
1202          * Wrapper for query() that also handles profiling, logging, and affected row count updates
1203          *
1204          * @param string $sql Original SQL query
1205          * @param string $commentedSql SQL query with debugging/trace comment
1206          * @param bool $isWrite Whether the query is a (non-temporary) write operation
1207          * @param string $fname Name of the calling function
1208          * @return bool|ResultWrapper True for a successful write query, ResultWrapper
1209          *     object for a successful read query, or false on failure
1210          */
1211         private function doProfiledQuery( $sql, $commentedSql, $isWrite, $fname ) {
1212                 $isMaster = !is_null( $this->getLBInfo( 'master' ) );
1213                 # generalizeSQL() will probably cut down the query to reasonable
1214                 # logging size most of the time. The substr is really just a sanity check.
1215                 if ( $isMaster ) {
1216                         $queryProf = 'query-m: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1217                 } else {
1218                         $queryProf = 'query: ' . substr( self::generalizeSQL( $sql ), 0, 255 );
1219                 }
1220
1221                 # Include query transaction state
1222                 $queryProf .= $this->trxShortId ? " [TRX#{$this->trxShortId}]" : "";
1223
1224                 $startTime = microtime( true );
1225                 if ( $this->profiler ) {
1226                         call_user_func( [ $this->profiler, 'profileIn' ], $queryProf );
1227                 }
1228                 $this->affectedRowCount = null;
1229                 $ret = $this->doQuery( $commentedSql );
1230                 $this->affectedRowCount = $this->affectedRows();
1231                 if ( $this->profiler ) {
1232                         call_user_func( [ $this->profiler, 'profileOut' ], $queryProf );
1233                 }
1234                 $queryRuntime = max( microtime( true ) - $startTime, 0.0 );
1235
1236                 unset( $queryProfSection ); // profile out (if set)
1237
1238                 if ( $ret !== false ) {
1239                         $this->lastPing = $startTime;
1240                         if ( $isWrite && $this->trxLevel ) {
1241                                 $this->updateTrxWriteQueryTime( $sql, $queryRuntime, $this->affectedRows() );
1242                                 $this->trxWriteCallers[] = $fname;
1243                         }
1244                 }
1245
1246                 if ( $sql === self::PING_QUERY ) {
1247                         $this->rttEstimate = $queryRuntime;
1248                 }
1249
1250                 $this->trxProfiler->recordQueryCompletion(
1251                         $queryProf, $startTime, $isWrite, $this->affectedRows()
1252                 );
1253                 $this->queryLogger->debug( $sql, [
1254                         'method' => $fname,
1255                         'master' => $isMaster,
1256                         'runtime' => $queryRuntime,
1257                 ] );
1258
1259                 return $ret;
1260         }
1261
1262         /**
1263          * Update the estimated run-time of a query, not counting large row lock times
1264          *
1265          * LoadBalancer can be set to rollback transactions that will create huge replication
1266          * lag. It bases this estimate off of pendingWriteQueryDuration(). Certain simple
1267          * queries, like inserting a row can take a long time due to row locking. This method
1268          * uses some simple heuristics to discount those cases.
1269          *
1270          * @param string $sql A SQL write query
1271          * @param float $runtime Total runtime, including RTT
1272          * @param int $affected Affected row count
1273          */
1274         private function updateTrxWriteQueryTime( $sql, $runtime, $affected ) {
1275                 // Whether this is indicative of replica DB runtime (except for RBR or ws_repl)
1276                 $indicativeOfReplicaRuntime = true;
1277                 if ( $runtime > self::SLOW_WRITE_SEC ) {
1278                         $verb = $this->getQueryVerb( $sql );
1279                         // insert(), upsert(), replace() are fast unless bulky in size or blocked on locks
1280                         if ( $verb === 'INSERT' ) {
1281                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS;
1282                         } elseif ( $verb === 'REPLACE' ) {
1283                                 $indicativeOfReplicaRuntime = $this->affectedRows() > self::SMALL_WRITE_ROWS / 2;
1284                         }
1285                 }
1286
1287                 $this->trxWriteDuration += $runtime;
1288                 $this->trxWriteQueryCount += 1;
1289                 $this->trxWriteAffectedRows += $affected;
1290                 if ( $indicativeOfReplicaRuntime ) {
1291                         $this->trxWriteAdjDuration += $runtime;
1292                         $this->trxWriteAdjQueryCount += 1;
1293                 }
1294         }
1295
1296         /**
1297          * @param string $sql
1298          * @param string $fname
1299          * @throws DBTransactionStateError
1300          */
1301         private function assertTransactionStatus( $sql, $fname ) {
1302                 if ( $this->getQueryVerb( $sql ) === 'ROLLBACK' ) { // transaction/savepoint
1303                         return;
1304                 }
1305
1306                 if ( $this->trxStatus < self::STATUS_TRX_OK ) {
1307                         throw new DBTransactionStateError(
1308                                 $this,
1309                                 "Cannot execute query from $fname while transaction status is ERROR.",
1310                                 [],
1311                                 $this->trxStatusCause
1312                         );
1313                 } elseif ( $this->trxStatus === self::STATUS_TRX_OK && $this->trxStatusIgnoredCause ) {
1314                         list( $iLastError, $iLastErrno, $iFname ) = $this->trxStatusIgnoredCause;
1315                         call_user_func( $this->deprecationLogger,
1316                                 "Caller from $fname ignored an error originally raised from $iFname: " .
1317                                 "[$iLastErrno] $iLastError"
1318                         );
1319                         $this->trxStatusIgnoredCause = null;
1320                 }
1321         }
1322
1323         /**
1324          * Determine whether or not it is safe to retry queries after a database
1325          * connection is lost
1326          *
1327          * @param string $sql SQL query
1328          * @param bool $priorWritesPending Whether there is a transaction open with
1329          *     possible write queries or transaction pre-commit/idle callbacks
1330          *     waiting on it to finish.
1331          * @return bool True if it is safe to retry the query, false otherwise
1332          */
1333         private function canRecoverFromDisconnect( $sql, $priorWritesPending ) {
1334                 # Transaction dropped; this can mean lost writes, or REPEATABLE-READ snapshots.
1335                 # Dropped connections also mean that named locks are automatically released.
1336                 # Only allow error suppression in autocommit mode or when the lost transaction
1337                 # didn't matter anyway (aside from DBO_TRX snapshot loss).
1338                 if ( $this->namedLocksHeld ) {
1339                         return false; // possible critical section violation
1340                 } elseif ( $this->sessionTempTables ) {
1341                         return false; // tables might be queried latter
1342                 } elseif ( $sql === 'COMMIT' ) {
1343                         return !$priorWritesPending; // nothing written anyway? (T127428)
1344                 } elseif ( $sql === 'ROLLBACK' ) {
1345                         return true; // transaction lost...which is also what was requested :)
1346                 } elseif ( $this->explicitTrxActive() ) {
1347                         return false; // don't drop atomocity and explicit snapshots
1348                 } elseif ( $priorWritesPending ) {
1349                         return false; // prior writes lost from implicit transaction
1350                 }
1351
1352                 return true;
1353         }
1354
1355         /**
1356          * Clean things up after session (and thus transaction) loss
1357          */
1358         private function handleSessionLoss() {
1359                 // Clean up tracking of session-level things...
1360                 // https://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html
1361                 // https://www.postgresql.org/docs/9.2/static/sql-createtable.html (ignoring ON COMMIT)
1362                 $this->sessionTempTables = [];
1363                 // https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
1364                 // https://www.postgresql.org/docs/9.4/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
1365                 $this->namedLocksHeld = [];
1366                 // Session loss implies transaction loss
1367                 $this->handleTransactionLoss();
1368         }
1369
1370         /**
1371          * Clean things up after transaction loss
1372          */
1373         private function handleTransactionLoss() {
1374                 $this->trxLevel = 0;
1375                 $this->trxAtomicCounter = 0;
1376                 $this->trxIdleCallbacks = []; // T67263; transaction already lost
1377                 $this->trxPreCommitCallbacks = []; // T67263; transaction already lost
1378                 try {
1379                         // Handle callbacks in trxEndCallbacks, e.g. onTransactionResolution().
1380                         // If callback suppression is set then the array will remain unhandled.
1381                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
1382                 } catch ( Exception $ex ) {
1383                         // Already logged; move on...
1384                 }
1385                 try {
1386                         // Handle callbacks in trxRecurringCallbacks, e.g. setTransactionListener()
1387                         $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
1388                 } catch ( Exception $ex ) {
1389                         // Already logged; move on...
1390                 }
1391         }
1392
1393         /**
1394          * Checks whether the cause of the error is detected to be a timeout.
1395          *
1396          * It returns false by default, and not all engines support detecting this yet.
1397          * If this returns false, it will be treated as a generic query error.
1398          *
1399          * @param string $error Error text
1400          * @param int $errno Error number
1401          * @return bool
1402          */
1403         protected function wasQueryTimeout( $error, $errno ) {
1404                 return false;
1405         }
1406
1407         /**
1408          * Report a query error. Log the error, and if neither the object ignore
1409          * flag nor the $tempIgnore flag is set, throw a DBQueryError.
1410          *
1411          * @param string $error
1412          * @param int $errno
1413          * @param string $sql
1414          * @param string $fname
1415          * @param bool $tempIgnore
1416          * @throws DBQueryError
1417          */
1418         public function reportQueryError( $error, $errno, $sql, $fname, $tempIgnore = false ) {
1419                 if ( $tempIgnore ) {
1420                         $this->queryLogger->debug( "SQL ERROR (ignored): $error\n" );
1421                 } else {
1422                         $exception = $this->makeQueryException( $error, $errno, $sql, $fname );
1423
1424                         throw $exception;
1425                 }
1426         }
1427
1428         /**
1429          * @param string $error
1430          * @param string|int $errno
1431          * @param string $sql
1432          * @param string $fname
1433          * @return DBError
1434          */
1435         private function makeQueryException( $error, $errno, $sql, $fname ) {
1436                 $sql1line = mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 );
1437                 $this->queryLogger->error(
1438                         "{fname}\t{db_server}\t{errno}\t{error}\t{sql1line}",
1439                         $this->getLogContext( [
1440                                 'method' => __METHOD__,
1441                                 'errno' => $errno,
1442                                 'error' => $error,
1443                                 'sql1line' => $sql1line,
1444                                 'fname' => $fname,
1445                         ] )
1446                 );
1447                 $this->queryLogger->debug( "SQL ERROR: " . $error . "\n" );
1448                 $wasQueryTimeout = $this->wasQueryTimeout( $error, $errno );
1449                 if ( $wasQueryTimeout ) {
1450                         $e = new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
1451                 } else {
1452                         $e = new DBQueryError( $this, $error, $errno, $sql, $fname );
1453                 }
1454
1455                 return $e;
1456         }
1457
1458         public function freeResult( $res ) {
1459         }
1460
1461         public function selectField(
1462                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1463         ) {
1464                 if ( $var === '*' ) { // sanity
1465                         throw new DBUnexpectedError( $this, "Cannot use a * field: got '$var'" );
1466                 }
1467
1468                 if ( !is_array( $options ) ) {
1469                         $options = [ $options ];
1470                 }
1471
1472                 $options['LIMIT'] = 1;
1473
1474                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1475                 if ( $res === false || !$this->numRows( $res ) ) {
1476                         return false;
1477                 }
1478
1479                 $row = $this->fetchRow( $res );
1480
1481                 if ( $row !== false ) {
1482                         return reset( $row );
1483                 } else {
1484                         return false;
1485                 }
1486         }
1487
1488         public function selectFieldValues(
1489                 $table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
1490         ) {
1491                 if ( $var === '*' ) { // sanity
1492                         throw new DBUnexpectedError( $this, "Cannot use a * field" );
1493                 } elseif ( !is_string( $var ) ) { // sanity
1494                         throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
1495                 }
1496
1497                 if ( !is_array( $options ) ) {
1498                         $options = [ $options ];
1499                 }
1500
1501                 $res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
1502                 if ( $res === false ) {
1503                         return false;
1504                 }
1505
1506                 $values = [];
1507                 foreach ( $res as $row ) {
1508                         $values[] = $row->$var;
1509                 }
1510
1511                 return $values;
1512         }
1513
1514         /**
1515          * Returns an optional USE INDEX clause to go after the table, and a
1516          * string to go at the end of the query.
1517          *
1518          * @param array $options Associative array of options to be turned into
1519          *   an SQL query, valid keys are listed in the function.
1520          * @return array
1521          * @see Database::select()
1522          */
1523         protected function makeSelectOptions( $options ) {
1524                 $preLimitTail = $postLimitTail = '';
1525                 $startOpts = '';
1526
1527                 $noKeyOptions = [];
1528
1529                 foreach ( $options as $key => $option ) {
1530                         if ( is_numeric( $key ) ) {
1531                                 $noKeyOptions[$option] = true;
1532                         }
1533                 }
1534
1535                 $preLimitTail .= $this->makeGroupByWithHaving( $options );
1536
1537                 $preLimitTail .= $this->makeOrderBy( $options );
1538
1539                 if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
1540                         $postLimitTail .= ' FOR UPDATE';
1541                 }
1542
1543                 if ( isset( $noKeyOptions['LOCK IN SHARE MODE'] ) ) {
1544                         $postLimitTail .= ' LOCK IN SHARE MODE';
1545                 }
1546
1547                 if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
1548                         $startOpts .= 'DISTINCT';
1549                 }
1550
1551                 # Various MySQL extensions
1552                 if ( isset( $noKeyOptions['STRAIGHT_JOIN'] ) ) {
1553                         $startOpts .= ' /*! STRAIGHT_JOIN */';
1554                 }
1555
1556                 if ( isset( $noKeyOptions['HIGH_PRIORITY'] ) ) {
1557                         $startOpts .= ' HIGH_PRIORITY';
1558                 }
1559
1560                 if ( isset( $noKeyOptions['SQL_BIG_RESULT'] ) ) {
1561                         $startOpts .= ' SQL_BIG_RESULT';
1562                 }
1563
1564                 if ( isset( $noKeyOptions['SQL_BUFFER_RESULT'] ) ) {
1565                         $startOpts .= ' SQL_BUFFER_RESULT';
1566                 }
1567
1568                 if ( isset( $noKeyOptions['SQL_SMALL_RESULT'] ) ) {
1569                         $startOpts .= ' SQL_SMALL_RESULT';
1570                 }
1571
1572                 if ( isset( $noKeyOptions['SQL_CALC_FOUND_ROWS'] ) ) {
1573                         $startOpts .= ' SQL_CALC_FOUND_ROWS';
1574                 }
1575
1576                 if ( isset( $noKeyOptions['SQL_CACHE'] ) ) {
1577                         $startOpts .= ' SQL_CACHE';
1578                 }
1579
1580                 if ( isset( $noKeyOptions['SQL_NO_CACHE'] ) ) {
1581                         $startOpts .= ' SQL_NO_CACHE';
1582                 }
1583
1584                 if ( isset( $options['USE INDEX'] ) && is_string( $options['USE INDEX'] ) ) {
1585                         $useIndex = $this->useIndexClause( $options['USE INDEX'] );
1586                 } else {
1587                         $useIndex = '';
1588                 }
1589                 if ( isset( $options['IGNORE INDEX'] ) && is_string( $options['IGNORE INDEX'] ) ) {
1590                         $ignoreIndex = $this->ignoreIndexClause( $options['IGNORE INDEX'] );
1591                 } else {
1592                         $ignoreIndex = '';
1593                 }
1594
1595                 return [ $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ];
1596         }
1597
1598         /**
1599          * Returns an optional GROUP BY with an optional HAVING
1600          *
1601          * @param array $options Associative array of options
1602          * @return string
1603          * @see Database::select()
1604          * @since 1.21
1605          */
1606         protected function makeGroupByWithHaving( $options ) {
1607                 $sql = '';
1608                 if ( isset( $options['GROUP BY'] ) ) {
1609                         $gb = is_array( $options['GROUP BY'] )
1610                                 ? implode( ',', $options['GROUP BY'] )
1611                                 : $options['GROUP BY'];
1612                         $sql .= ' GROUP BY ' . $gb;
1613                 }
1614                 if ( isset( $options['HAVING'] ) ) {
1615                         $having = is_array( $options['HAVING'] )
1616                                 ? $this->makeList( $options['HAVING'], self::LIST_AND )
1617                                 : $options['HAVING'];
1618                         $sql .= ' HAVING ' . $having;
1619                 }
1620
1621                 return $sql;
1622         }
1623
1624         /**
1625          * Returns an optional ORDER BY
1626          *
1627          * @param array $options Associative array of options
1628          * @return string
1629          * @see Database::select()
1630          * @since 1.21
1631          */
1632         protected function makeOrderBy( $options ) {
1633                 if ( isset( $options['ORDER BY'] ) ) {
1634                         $ob = is_array( $options['ORDER BY'] )
1635                                 ? implode( ',', $options['ORDER BY'] )
1636                                 : $options['ORDER BY'];
1637
1638                         return ' ORDER BY ' . $ob;
1639                 }
1640
1641                 return '';
1642         }
1643
1644         public function select( $table, $vars, $conds = '', $fname = __METHOD__,
1645                 $options = [], $join_conds = [] ) {
1646                 $sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
1647
1648                 return $this->query( $sql, $fname );
1649         }
1650
1651         public function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__,
1652                 $options = [], $join_conds = []
1653         ) {
1654                 if ( is_array( $vars ) ) {
1655                         $vars = implode( ',', $this->fieldNamesWithAlias( $vars ) );
1656                 }
1657
1658                 $options = (array)$options;
1659                 $useIndexes = ( isset( $options['USE INDEX'] ) && is_array( $options['USE INDEX'] ) )
1660                         ? $options['USE INDEX']
1661                         : [];
1662                 $ignoreIndexes = (
1663                         isset( $options['IGNORE INDEX'] ) &&
1664                         is_array( $options['IGNORE INDEX'] )
1665                 )
1666                         ? $options['IGNORE INDEX']
1667                         : [];
1668
1669                 if ( is_array( $table ) ) {
1670                         $from = ' FROM ' .
1671                                 $this->tableNamesWithIndexClauseOrJOIN(
1672                                         $table, $useIndexes, $ignoreIndexes, $join_conds );
1673                 } elseif ( $table != '' ) {
1674                         $from = ' FROM ' .
1675                                 $this->tableNamesWithIndexClauseOrJOIN(
1676                                         [ $table ], $useIndexes, $ignoreIndexes, [] );
1677                 } else {
1678                         $from = '';
1679                 }
1680
1681                 list( $startOpts, $useIndex, $preLimitTail, $postLimitTail, $ignoreIndex ) =
1682                         $this->makeSelectOptions( $options );
1683
1684                 if ( is_array( $conds ) ) {
1685                         $conds = $this->makeList( $conds, self::LIST_AND );
1686                 }
1687
1688                 if ( $conds === null || $conds === false ) {
1689                         $this->queryLogger->warning(
1690                                 __METHOD__
1691                                 . ' called from '
1692                                 . $fname
1693                                 . ' with incorrect parameters: $conds must be a string or an array'
1694                         );
1695                         $conds = '';
1696                 }
1697
1698                 if ( $conds === '' ) {
1699                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex $preLimitTail";
1700                 } elseif ( is_string( $conds ) ) {
1701                         $sql = "SELECT $startOpts $vars $from $useIndex $ignoreIndex " .
1702                                 "WHERE $conds $preLimitTail";
1703                 } else {
1704                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
1705                 }
1706
1707                 if ( isset( $options['LIMIT'] ) ) {
1708                         $sql = $this->limitResult( $sql, $options['LIMIT'],
1709                                 isset( $options['OFFSET'] ) ? $options['OFFSET'] : false );
1710                 }
1711                 $sql = "$sql $postLimitTail";
1712
1713                 if ( isset( $options['EXPLAIN'] ) ) {
1714                         $sql = 'EXPLAIN ' . $sql;
1715                 }
1716
1717                 return $sql;
1718         }
1719
1720         public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
1721                 $options = [], $join_conds = []
1722         ) {
1723                 $options = (array)$options;
1724                 $options['LIMIT'] = 1;
1725                 $res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
1726
1727                 if ( $res === false ) {
1728                         return false;
1729                 }
1730
1731                 if ( !$this->numRows( $res ) ) {
1732                         return false;
1733                 }
1734
1735                 $obj = $this->fetchObject( $res );
1736
1737                 return $obj;
1738         }
1739
1740         public function estimateRowCount(
1741                 $table, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1742         ) {
1743                 $conds = $this->normalizeConditions( $conds, $fname );
1744                 $column = $this->extractSingleFieldFromList( $var );
1745                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1746                         $conds[] = "$column IS NOT NULL";
1747                 }
1748
1749                 $res = $this->select(
1750                         $table, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options, $join_conds
1751                 );
1752                 $row = $res ? $this->fetchRow( $res ) : [];
1753
1754                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1755         }
1756
1757         public function selectRowCount(
1758                 $tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
1759         ) {
1760                 $conds = $this->normalizeConditions( $conds, $fname );
1761                 $column = $this->extractSingleFieldFromList( $var );
1762                 if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
1763                         $conds[] = "$column IS NOT NULL";
1764                 }
1765
1766                 $res = $this->select(
1767                         [
1768                                 'tmp_count' => $this->buildSelectSubquery(
1769                                         $tables,
1770                                         '1',
1771                                         $conds,
1772                                         $fname,
1773                                         $options,
1774                                         $join_conds
1775                                 )
1776                         ],
1777                         [ 'rowcount' => 'COUNT(*)' ],
1778                         [],
1779                         $fname
1780                 );
1781                 $row = $res ? $this->fetchRow( $res ) : [];
1782
1783                 return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
1784         }
1785
1786         /**
1787          * @param array|string $conds
1788          * @param string $fname
1789          * @return array
1790          */
1791         final protected function normalizeConditions( $conds, $fname ) {
1792                 if ( $conds === null || $conds === false ) {
1793                         $this->queryLogger->warning(
1794                                 __METHOD__
1795                                 . ' called from '
1796                                 . $fname
1797                                 . ' with incorrect parameters: $conds must be a string or an array'
1798                         );
1799                         $conds = '';
1800                 }
1801
1802                 if ( !is_array( $conds ) ) {
1803                         $conds = ( $conds === '' ) ? [] : [ $conds ];
1804                 }
1805
1806                 return $conds;
1807         }
1808
1809         /**
1810          * @param array|string $var Field parameter in the style of select()
1811          * @return string|null Column name or null; ignores aliases
1812          * @throws DBUnexpectedError Errors out if multiple columns are given
1813          */
1814         final protected function extractSingleFieldFromList( $var ) {
1815                 if ( is_array( $var ) ) {
1816                         if ( !$var ) {
1817                                 $column = null;
1818                         } elseif ( count( $var ) == 1 ) {
1819                                 $column = isset( $var[0] ) ? $var[0] : reset( $var );
1820                         } else {
1821                                 throw new DBUnexpectedError( $this, __METHOD__ . ': got multiple columns.' );
1822                         }
1823                 } else {
1824                         $column = $var;
1825                 }
1826
1827                 return $column;
1828         }
1829
1830         /**
1831          * Removes most variables from an SQL query and replaces them with X or N for numbers.
1832          * It's only slightly flawed. Don't use for anything important.
1833          *
1834          * @param string $sql A SQL Query
1835          *
1836          * @return string
1837          */
1838         protected static function generalizeSQL( $sql ) {
1839                 # This does the same as the regexp below would do, but in such a way
1840                 # as to avoid crashing php on some large strings.
1841                 # $sql = preg_replace( "/'([^\\\\']|\\\\.)*'|\"([^\\\\\"]|\\\\.)*\"/", "'X'", $sql );
1842
1843                 $sql = str_replace( "\\\\", '', $sql );
1844                 $sql = str_replace( "\\'", '', $sql );
1845                 $sql = str_replace( "\\\"", '', $sql );
1846                 $sql = preg_replace( "/'.*'/s", "'X'", $sql );
1847                 $sql = preg_replace( '/".*"/s', "'X'", $sql );
1848
1849                 # All newlines, tabs, etc replaced by single space
1850                 $sql = preg_replace( '/\s+/', ' ', $sql );
1851
1852                 # All numbers => N,
1853                 # except the ones surrounded by characters, e.g. l10n
1854                 $sql = preg_replace( '/-?\d+(,-?\d+)+/s', 'N,...,N', $sql );
1855                 $sql = preg_replace( '/(?<![a-zA-Z])-?\d+(?![a-zA-Z])/s', 'N', $sql );
1856
1857                 return $sql;
1858         }
1859
1860         public function fieldExists( $table, $field, $fname = __METHOD__ ) {
1861                 $info = $this->fieldInfo( $table, $field );
1862
1863                 return (bool)$info;
1864         }
1865
1866         public function indexExists( $table, $index, $fname = __METHOD__ ) {
1867                 if ( !$this->tableExists( $table ) ) {
1868                         return null;
1869                 }
1870
1871                 $info = $this->indexInfo( $table, $index, $fname );
1872                 if ( is_null( $info ) ) {
1873                         return null;
1874                 } else {
1875                         return $info !== false;
1876                 }
1877         }
1878
1879         public function tableExists( $table, $fname = __METHOD__ ) {
1880                 $tableRaw = $this->tableName( $table, 'raw' );
1881                 if ( isset( $this->sessionTempTables[$tableRaw] ) ) {
1882                         return true; // already known to exist
1883                 }
1884
1885                 $table = $this->tableName( $table );
1886                 $ignoreErrors = true;
1887                 $res = $this->query( "SELECT 1 FROM $table LIMIT 1", $fname, $ignoreErrors );
1888
1889                 return (bool)$res;
1890         }
1891
1892         public function indexUnique( $table, $index ) {
1893                 $indexInfo = $this->indexInfo( $table, $index );
1894
1895                 if ( !$indexInfo ) {
1896                         return null;
1897                 }
1898
1899                 return !$indexInfo[0]->Non_unique;
1900         }
1901
1902         /**
1903          * Helper for Database::insert().
1904          *
1905          * @param array $options
1906          * @return string
1907          */
1908         protected function makeInsertOptions( $options ) {
1909                 return implode( ' ', $options );
1910         }
1911
1912         public function insert( $table, $a, $fname = __METHOD__, $options = [] ) {
1913                 # No rows to insert, easy just return now
1914                 if ( !count( $a ) ) {
1915                         return true;
1916                 }
1917
1918                 $table = $this->tableName( $table );
1919
1920                 if ( !is_array( $options ) ) {
1921                         $options = [ $options ];
1922                 }
1923
1924                 $fh = null;
1925                 if ( isset( $options['fileHandle'] ) ) {
1926                         $fh = $options['fileHandle'];
1927                 }
1928                 $options = $this->makeInsertOptions( $options );
1929
1930                 if ( isset( $a[0] ) && is_array( $a[0] ) ) {
1931                         $multi = true;
1932                         $keys = array_keys( $a[0] );
1933                 } else {
1934                         $multi = false;
1935                         $keys = array_keys( $a );
1936                 }
1937
1938                 $sql = 'INSERT ' . $options .
1939                         " INTO $table (" . implode( ',', $keys ) . ') VALUES ';
1940
1941                 if ( $multi ) {
1942                         $first = true;
1943                         foreach ( $a as $row ) {
1944                                 if ( $first ) {
1945                                         $first = false;
1946                                 } else {
1947                                         $sql .= ',';
1948                                 }
1949                                 $sql .= '(' . $this->makeList( $row ) . ')';
1950                         }
1951                 } else {
1952                         $sql .= '(' . $this->makeList( $a ) . ')';
1953                 }
1954
1955                 if ( $fh !== null && false === fwrite( $fh, $sql ) ) {
1956                         return false;
1957                 } elseif ( $fh !== null ) {
1958                         return true;
1959                 }
1960
1961                 return (bool)$this->query( $sql, $fname );
1962         }
1963
1964         /**
1965          * Make UPDATE options array for Database::makeUpdateOptions
1966          *
1967          * @param array $options
1968          * @return array
1969          */
1970         protected function makeUpdateOptionsArray( $options ) {
1971                 if ( !is_array( $options ) ) {
1972                         $options = [ $options ];
1973                 }
1974
1975                 $opts = [];
1976
1977                 if ( in_array( 'IGNORE', $options ) ) {
1978                         $opts[] = 'IGNORE';
1979                 }
1980
1981                 return $opts;
1982         }
1983
1984         /**
1985          * Make UPDATE options for the Database::update function
1986          *
1987          * @param array $options The options passed to Database::update
1988          * @return string
1989          */
1990         protected function makeUpdateOptions( $options ) {
1991                 $opts = $this->makeUpdateOptionsArray( $options );
1992
1993                 return implode( ' ', $opts );
1994         }
1995
1996         public function update( $table, $values, $conds, $fname = __METHOD__, $options = [] ) {
1997                 $table = $this->tableName( $table );
1998                 $opts = $this->makeUpdateOptions( $options );
1999                 $sql = "UPDATE $opts $table SET " . $this->makeList( $values, self::LIST_SET );
2000
2001                 if ( $conds !== [] && $conds !== '*' ) {
2002                         $sql .= " WHERE " . $this->makeList( $conds, self::LIST_AND );
2003                 }
2004
2005                 return (bool)$this->query( $sql, $fname );
2006         }
2007
2008         public function makeList( $a, $mode = self::LIST_COMMA ) {
2009                 if ( !is_array( $a ) ) {
2010                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with incorrect parameters' );
2011                 }
2012
2013                 $first = true;
2014                 $list = '';
2015
2016                 foreach ( $a as $field => $value ) {
2017                         if ( !$first ) {
2018                                 if ( $mode == self::LIST_AND ) {
2019                                         $list .= ' AND ';
2020                                 } elseif ( $mode == self::LIST_OR ) {
2021                                         $list .= ' OR ';
2022                                 } else {
2023                                         $list .= ',';
2024                                 }
2025                         } else {
2026                                 $first = false;
2027                         }
2028
2029                         if ( ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_numeric( $field ) ) {
2030                                 $list .= "($value)";
2031                         } elseif ( $mode == self::LIST_SET && is_numeric( $field ) ) {
2032                                 $list .= "$value";
2033                         } elseif (
2034                                 ( $mode == self::LIST_AND || $mode == self::LIST_OR ) && is_array( $value )
2035                         ) {
2036                                 // Remove null from array to be handled separately if found
2037                                 $includeNull = false;
2038                                 foreach ( array_keys( $value, null, true ) as $nullKey ) {
2039                                         $includeNull = true;
2040                                         unset( $value[$nullKey] );
2041                                 }
2042                                 if ( count( $value ) == 0 && !$includeNull ) {
2043                                         throw new InvalidArgumentException(
2044                                                 __METHOD__ . ": empty input for field $field" );
2045                                 } elseif ( count( $value ) == 0 ) {
2046                                         // only check if $field is null
2047                                         $list .= "$field IS NULL";
2048                                 } else {
2049                                         // IN clause contains at least one valid element
2050                                         if ( $includeNull ) {
2051                                                 // Group subconditions to ensure correct precedence
2052                                                 $list .= '(';
2053                                         }
2054                                         if ( count( $value ) == 1 ) {
2055                                                 // Special-case single values, as IN isn't terribly efficient
2056                                                 // Don't necessarily assume the single key is 0; we don't
2057                                                 // enforce linear numeric ordering on other arrays here.
2058                                                 $value = array_values( $value )[0];
2059                                                 $list .= $field . " = " . $this->addQuotes( $value );
2060                                         } else {
2061                                                 $list .= $field . " IN (" . $this->makeList( $value ) . ") ";
2062                                         }
2063                                         // if null present in array, append IS NULL
2064                                         if ( $includeNull ) {
2065                                                 $list .= " OR $field IS NULL)";
2066                                         }
2067                                 }
2068                         } elseif ( $value === null ) {
2069                                 if ( $mode == self::LIST_AND || $mode == self::LIST_OR ) {
2070                                         $list .= "$field IS ";
2071                                 } elseif ( $mode == self::LIST_SET ) {
2072                                         $list .= "$field = ";
2073                                 }
2074                                 $list .= 'NULL';
2075                         } else {
2076                                 if (
2077                                         $mode == self::LIST_AND || $mode == self::LIST_OR || $mode == self::LIST_SET
2078                                 ) {
2079                                         $list .= "$field = ";
2080                                 }
2081                                 $list .= $mode == self::LIST_NAMES ? $value : $this->addQuotes( $value );
2082                         }
2083                 }
2084
2085                 return $list;
2086         }
2087
2088         public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
2089                 $conds = [];
2090
2091                 foreach ( $data as $base => $sub ) {
2092                         if ( count( $sub ) ) {
2093                                 $conds[] = $this->makeList(
2094                                         [ $baseKey => $base, $subKey => array_keys( $sub ) ],
2095                                         self::LIST_AND );
2096                         }
2097                 }
2098
2099                 if ( $conds ) {
2100                         return $this->makeList( $conds, self::LIST_OR );
2101                 } else {
2102                         // Nothing to search for...
2103                         return false;
2104                 }
2105         }
2106
2107         public function aggregateValue( $valuedata, $valuename = 'value' ) {
2108                 return $valuename;
2109         }
2110
2111         public function bitNot( $field ) {
2112                 return "(~$field)";
2113         }
2114
2115         public function bitAnd( $fieldLeft, $fieldRight ) {
2116                 return "($fieldLeft & $fieldRight)";
2117         }
2118
2119         public function bitOr( $fieldLeft, $fieldRight ) {
2120                 return "($fieldLeft | $fieldRight)";
2121         }
2122
2123         public function buildConcat( $stringList ) {
2124                 return 'CONCAT(' . implode( ',', $stringList ) . ')';
2125         }
2126
2127         public function buildGroupConcatField(
2128                 $delim, $table, $field, $conds = '', $join_conds = []
2129         ) {
2130                 $fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
2131
2132                 return '(' . $this->selectSQLText( $table, $fld, $conds, null, [], $join_conds ) . ')';
2133         }
2134
2135         public function buildSubstring( $input, $startPosition, $length = null ) {
2136                 $this->assertBuildSubstringParams( $startPosition, $length );
2137                 $functionBody = "$input FROM $startPosition";
2138                 if ( $length !== null ) {
2139                         $functionBody .= " FOR $length";
2140                 }
2141                 return 'SUBSTRING(' . $functionBody . ')';
2142         }
2143
2144         /**
2145          * Check type and bounds for parameters to self::buildSubstring()
2146          *
2147          * All supported databases have substring functions that behave the same for
2148          * positive $startPosition and non-negative $length, but behaviors differ when
2149          * given 0 or negative $startPosition or negative $length. The simplest
2150          * solution to that is to just forbid those values.
2151          *
2152          * @param int $startPosition
2153          * @param int|null $length
2154          * @since 1.31
2155          */
2156         protected function assertBuildSubstringParams( $startPosition, $length ) {
2157                 if ( !is_int( $startPosition ) || $startPosition <= 0 ) {
2158                         throw new InvalidArgumentException(
2159                                 '$startPosition must be a positive integer'
2160                         );
2161                 }
2162                 if ( !( is_int( $length ) && $length >= 0 || $length === null ) ) {
2163                         throw new InvalidArgumentException(
2164                                 '$length must be null or an integer greater than or equal to 0'
2165                         );
2166                 }
2167         }
2168
2169         public function buildStringCast( $field ) {
2170                 return $field;
2171         }
2172
2173         public function buildIntegerCast( $field ) {
2174                 return 'CAST( ' . $field . ' AS INTEGER )';
2175         }
2176
2177         public function buildSelectSubquery(
2178                 $table, $vars, $conds = '', $fname = __METHOD__,
2179                 $options = [], $join_conds = []
2180         ) {
2181                 return new Subquery(
2182                         $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds )
2183                 );
2184         }
2185
2186         public function databasesAreIndependent() {
2187                 return false;
2188         }
2189
2190         public function selectDB( $db ) {
2191                 # Stub. Shouldn't cause serious problems if it's not overridden, but
2192                 # if your database engine supports a concept similar to MySQL's
2193                 # databases you may as well.
2194                 $this->dbName = $db;
2195
2196                 return true;
2197         }
2198
2199         public function getDBname() {
2200                 return $this->dbName;
2201         }
2202
2203         public function getServer() {
2204                 return $this->server;
2205         }
2206
2207         public function tableName( $name, $format = 'quoted' ) {
2208                 if ( $name instanceof Subquery ) {
2209                         throw new DBUnexpectedError(
2210                                 $this,
2211                                 __METHOD__ . ': got Subquery instance when expecting a string.'
2212                         );
2213                 }
2214
2215                 # Skip the entire process when we have a string quoted on both ends.
2216                 # Note that we check the end so that we will still quote any use of
2217                 # use of `database`.table. But won't break things if someone wants
2218                 # to query a database table with a dot in the name.
2219                 if ( $this->isQuotedIdentifier( $name ) ) {
2220                         return $name;
2221                 }
2222
2223                 # Lets test for any bits of text that should never show up in a table
2224                 # name. Basically anything like JOIN or ON which are actually part of
2225                 # SQL queries, but may end up inside of the table value to combine
2226                 # sql. Such as how the API is doing.
2227                 # Note that we use a whitespace test rather than a \b test to avoid
2228                 # any remote case where a word like on may be inside of a table name
2229                 # surrounded by symbols which may be considered word breaks.
2230                 if ( preg_match( '/(^|\s)(DISTINCT|JOIN|ON|AS)(\s|$)/i', $name ) !== 0 ) {
2231                         $this->queryLogger->warning(
2232                                 __METHOD__ . ": use of subqueries is not supported this way.",
2233                                 [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
2234                         );
2235
2236                         return $name;
2237                 }
2238
2239                 # Split database and table into proper variables.
2240                 list( $database, $schema, $prefix, $table ) = $this->qualifiedTableComponents( $name );
2241
2242                 # Quote $table and apply the prefix if not quoted.
2243                 # $tableName might be empty if this is called from Database::replaceVars()
2244                 $tableName = "{$prefix}{$table}";
2245                 if ( $format === 'quoted'
2246                         && !$this->isQuotedIdentifier( $tableName )
2247                         && $tableName !== ''
2248                 ) {
2249                         $tableName = $this->addIdentifierQuotes( $tableName );
2250                 }
2251
2252                 # Quote $schema and $database and merge them with the table name if needed
2253                 $tableName = $this->prependDatabaseOrSchema( $schema, $tableName, $format );
2254                 $tableName = $this->prependDatabaseOrSchema( $database, $tableName, $format );
2255
2256                 return $tableName;
2257         }
2258
2259         /**
2260          * Get the table components needed for a query given the currently selected database
2261          *
2262          * @param string $name Table name in the form of db.schema.table, db.table, or table
2263          * @return array (DB name or "" for default, schema name, table prefix, table name)
2264          */
2265         protected function qualifiedTableComponents( $name ) {
2266                 # We reverse the explode so that database.table and table both output the correct table.
2267                 $dbDetails = explode( '.', $name, 3 );
2268                 if ( count( $dbDetails ) == 3 ) {
2269                         list( $database, $schema, $table ) = $dbDetails;
2270                         # We don't want any prefix added in this case
2271                         $prefix = '';
2272                 } elseif ( count( $dbDetails ) == 2 ) {
2273                         list( $database, $table ) = $dbDetails;
2274                         # We don't want any prefix added in this case
2275                         $prefix = '';
2276                         # In dbs that support it, $database may actually be the schema
2277                         # but that doesn't affect any of the functionality here
2278                         $schema = '';
2279                 } else {
2280                         list( $table ) = $dbDetails;
2281                         if ( isset( $this->tableAliases[$table] ) ) {
2282                                 $database = $this->tableAliases[$table]['dbname'];
2283                                 $schema = is_string( $this->tableAliases[$table]['schema'] )
2284                                         ? $this->tableAliases[$table]['schema']
2285                                         : $this->schema;
2286                                 $prefix = is_string( $this->tableAliases[$table]['prefix'] )
2287                                         ? $this->tableAliases[$table]['prefix']
2288                                         : $this->tablePrefix;
2289                         } else {
2290                                 $database = '';
2291                                 $schema = $this->schema; # Default schema
2292                                 $prefix = $this->tablePrefix; # Default prefix
2293                         }
2294                 }
2295
2296                 return [ $database, $schema, $prefix, $table ];
2297         }
2298
2299         /**
2300          * @param string|null $namespace Database or schema
2301          * @param string $relation Name of table, view, sequence, etc...
2302          * @param string $format One of (raw, quoted)
2303          * @return string Relation name with quoted and merged $namespace as needed
2304          */
2305         private function prependDatabaseOrSchema( $namespace, $relation, $format ) {
2306                 if ( strlen( $namespace ) ) {
2307                         if ( $format === 'quoted' && !$this->isQuotedIdentifier( $namespace ) ) {
2308                                 $namespace = $this->addIdentifierQuotes( $namespace );
2309                         }
2310                         $relation = $namespace . '.' . $relation;
2311                 }
2312
2313                 return $relation;
2314         }
2315
2316         public function tableNames() {
2317                 $inArray = func_get_args();
2318                 $retVal = [];
2319
2320                 foreach ( $inArray as $name ) {
2321                         $retVal[$name] = $this->tableName( $name );
2322                 }
2323
2324                 return $retVal;
2325         }
2326
2327         public function tableNamesN() {
2328                 $inArray = func_get_args();
2329                 $retVal = [];
2330
2331                 foreach ( $inArray as $name ) {
2332                         $retVal[] = $this->tableName( $name );
2333                 }
2334
2335                 return $retVal;
2336         }
2337
2338         /**
2339          * Get an aliased table name
2340          *
2341          * This returns strings like "tableName AS newTableName" for aliased tables
2342          * and "(SELECT * from tableA) newTablename" for subqueries (e.g. derived tables)
2343          *
2344          * @see Database::tableName()
2345          * @param string|Subquery $table Table name or object with a 'sql' field
2346          * @param string|bool $alias Table alias (optional)
2347          * @return string SQL name for aliased table. Will not alias a table to its own name
2348          */
2349         protected function tableNameWithAlias( $table, $alias = false ) {
2350                 if ( is_string( $table ) ) {
2351                         $quotedTable = $this->tableName( $table );
2352                 } elseif ( $table instanceof Subquery ) {
2353                         $quotedTable = (string)$table;
2354                 } else {
2355                         throw new InvalidArgumentException( "Table must be a string or Subquery." );
2356                 }
2357
2358                 if ( !strlen( $alias ) || $alias === $table ) {
2359                         if ( $table instanceof Subquery ) {
2360                                 throw new InvalidArgumentException( "Subquery table missing alias." );
2361                         }
2362
2363                         return $quotedTable;
2364                 } else {
2365                         return $quotedTable . ' ' . $this->addIdentifierQuotes( $alias );
2366                 }
2367         }
2368
2369         /**
2370          * Gets an array of aliased table names
2371          *
2372          * @param array $tables [ [alias] => table ]
2373          * @return string[] See tableNameWithAlias()
2374          */
2375         protected function tableNamesWithAlias( $tables ) {
2376                 $retval = [];
2377                 foreach ( $tables as $alias => $table ) {
2378                         if ( is_numeric( $alias ) ) {
2379                                 $alias = $table;
2380                         }
2381                         $retval[] = $this->tableNameWithAlias( $table, $alias );
2382                 }
2383
2384                 return $retval;
2385         }
2386
2387         /**
2388          * Get an aliased field name
2389          * e.g. fieldName AS newFieldName
2390          *
2391          * @param string $name Field name
2392          * @param string|bool $alias Alias (optional)
2393          * @return string SQL name for aliased field. Will not alias a field to its own name
2394          */
2395         protected function fieldNameWithAlias( $name, $alias = false ) {
2396                 if ( !$alias || (string)$alias === (string)$name ) {
2397                         return $name;
2398                 } else {
2399                         return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
2400                 }
2401         }
2402
2403         /**
2404          * Gets an array of aliased field names
2405          *
2406          * @param array $fields [ [alias] => field ]
2407          * @return string[] See fieldNameWithAlias()
2408          */
2409         protected function fieldNamesWithAlias( $fields ) {
2410                 $retval = [];
2411                 foreach ( $fields as $alias => $field ) {
2412                         if ( is_numeric( $alias ) ) {
2413                                 $alias = $field;
2414                         }
2415                         $retval[] = $this->fieldNameWithAlias( $field, $alias );
2416                 }
2417
2418                 return $retval;
2419         }
2420
2421         /**
2422          * Get the aliased table name clause for a FROM clause
2423          * which might have a JOIN and/or USE INDEX or IGNORE INDEX clause
2424          *
2425          * @param array $tables ( [alias] => table )
2426          * @param array $use_index Same as for select()
2427          * @param array $ignore_index Same as for select()
2428          * @param array $join_conds Same as for select()
2429          * @return string
2430          */
2431         protected function tableNamesWithIndexClauseOrJOIN(
2432                 $tables, $use_index = [], $ignore_index = [], $join_conds = []
2433         ) {
2434                 $ret = [];
2435                 $retJOIN = [];
2436                 $use_index = (array)$use_index;
2437                 $ignore_index = (array)$ignore_index;
2438                 $join_conds = (array)$join_conds;
2439
2440                 foreach ( $tables as $alias => $table ) {
2441                         if ( !is_string( $alias ) ) {
2442                                 // No alias? Set it equal to the table name
2443                                 $alias = $table;
2444                         }
2445
2446                         if ( is_array( $table ) ) {
2447                                 // A parenthesized group
2448                                 if ( count( $table ) > 1 ) {
2449                                         $joinedTable = '(' .
2450                                                 $this->tableNamesWithIndexClauseOrJOIN(
2451                                                         $table, $use_index, $ignore_index, $join_conds ) . ')';
2452                                 } else {
2453                                         // Degenerate case
2454                                         $innerTable = reset( $table );
2455                                         $innerAlias = key( $table );
2456                                         $joinedTable = $this->tableNameWithAlias(
2457                                                 $innerTable,
2458                                                 is_string( $innerAlias ) ? $innerAlias : $innerTable
2459                                         );
2460                                 }
2461                         } else {
2462                                 $joinedTable = $this->tableNameWithAlias( $table, $alias );
2463                         }
2464
2465                         // Is there a JOIN clause for this table?
2466                         if ( isset( $join_conds[$alias] ) ) {
2467                                 list( $joinType, $conds ) = $join_conds[$alias];
2468                                 $tableClause = $joinType;
2469                                 $tableClause .= ' ' . $joinedTable;
2470                                 if ( isset( $use_index[$alias] ) ) { // has USE INDEX?
2471                                         $use = $this->useIndexClause( implode( ',', (array)$use_index[$alias] ) );
2472                                         if ( $use != '' ) {
2473                                                 $tableClause .= ' ' . $use;
2474                                         }
2475                                 }
2476                                 if ( isset( $ignore_index[$alias] ) ) { // has IGNORE INDEX?
2477                                         $ignore = $this->ignoreIndexClause(
2478                                                 implode( ',', (array)$ignore_index[$alias] ) );
2479                                         if ( $ignore != '' ) {
2480                                                 $tableClause .= ' ' . $ignore;
2481                                         }
2482                                 }
2483                                 $on = $this->makeList( (array)$conds, self::LIST_AND );
2484                                 if ( $on != '' ) {
2485                                         $tableClause .= ' ON (' . $on . ')';
2486                                 }
2487
2488                                 $retJOIN[] = $tableClause;
2489                         } elseif ( isset( $use_index[$alias] ) ) {
2490                                 // Is there an INDEX clause for this table?
2491                                 $tableClause = $joinedTable;
2492                                 $tableClause .= ' ' . $this->useIndexClause(
2493                                                 implode( ',', (array)$use_index[$alias] )
2494                                         );
2495
2496                                 $ret[] = $tableClause;
2497                         } elseif ( isset( $ignore_index[$alias] ) ) {
2498                                 // Is there an INDEX clause for this table?
2499                                 $tableClause = $joinedTable;
2500                                 $tableClause .= ' ' . $this->ignoreIndexClause(
2501                                                 implode( ',', (array)$ignore_index[$alias] )
2502                                         );
2503
2504                                 $ret[] = $tableClause;
2505                         } else {
2506                                 $tableClause = $joinedTable;
2507
2508                                 $ret[] = $tableClause;
2509                         }
2510                 }
2511
2512                 // We can't separate explicit JOIN clauses with ',', use ' ' for those
2513                 $implicitJoins = $ret ? implode( ',', $ret ) : "";
2514                 $explicitJoins = $retJOIN ? implode( ' ', $retJOIN ) : "";
2515
2516                 // Compile our final table clause
2517                 return implode( ' ', [ $implicitJoins, $explicitJoins ] );
2518         }
2519
2520         /**
2521          * Allows for index remapping in queries where this is not consistent across DBMS
2522          *
2523          * @param string $index
2524          * @return string
2525          */
2526         protected function indexName( $index ) {
2527                 return isset( $this->indexAliases[$index] )
2528                         ? $this->indexAliases[$index]
2529                         : $index;
2530         }
2531
2532         public function addQuotes( $s ) {
2533                 if ( $s instanceof Blob ) {
2534                         $s = $s->fetch();
2535                 }
2536                 if ( $s === null ) {
2537                         return 'NULL';
2538                 } elseif ( is_bool( $s ) ) {
2539                         return (int)$s;
2540                 } else {
2541                         # This will also quote numeric values. This should be harmless,
2542                         # and protects against weird problems that occur when they really
2543                         # _are_ strings such as article titles and string->number->string
2544                         # conversion is not 1:1.
2545                         return "'" . $this->strencode( $s ) . "'";
2546                 }
2547         }
2548
2549         /**
2550          * Quotes an identifier using `backticks` or "double quotes" depending on the database type.
2551          * MySQL uses `backticks` while basically everything else uses double quotes.
2552          * Since MySQL is the odd one out here the double quotes are our generic
2553          * and we implement backticks in DatabaseMysqlBase.
2554          *
2555          * @param string $s
2556          * @return string
2557          */
2558         public function addIdentifierQuotes( $s ) {
2559                 return '"' . str_replace( '"', '""', $s ) . '"';
2560         }
2561
2562         /**
2563          * Returns if the given identifier looks quoted or not according to
2564          * the database convention for quoting identifiers .
2565          *
2566          * @note Do not use this to determine if untrusted input is safe.
2567          *   A malicious user can trick this function.
2568          * @param string $name
2569          * @return bool
2570          */
2571         public function isQuotedIdentifier( $name ) {
2572                 return $name[0] == '"' && substr( $name, -1, 1 ) == '"';
2573         }
2574
2575         /**
2576          * @param string $s
2577          * @param string $escapeChar
2578          * @return string
2579          */
2580         protected function escapeLikeInternal( $s, $escapeChar = '`' ) {
2581                 return str_replace( [ $escapeChar, '%', '_' ],
2582                         [ "{$escapeChar}{$escapeChar}", "{$escapeChar}%", "{$escapeChar}_" ],
2583                         $s );
2584         }
2585
2586         public function buildLike() {
2587                 $params = func_get_args();
2588
2589                 if ( count( $params ) > 0 && is_array( $params[0] ) ) {
2590                         $params = $params[0];
2591                 }
2592
2593                 $s = '';
2594
2595                 // We use ` instead of \ as the default LIKE escape character, since addQuotes()
2596                 // may escape backslashes, creating problems of double escaping. The `
2597                 // character has good cross-DBMS compatibility, avoiding special operators
2598                 // in MS SQL like ^ and %
2599                 $escapeChar = '`';
2600
2601                 foreach ( $params as $value ) {
2602                         if ( $value instanceof LikeMatch ) {
2603                                 $s .= $value->toString();
2604                         } else {
2605                                 $s .= $this->escapeLikeInternal( $value, $escapeChar );
2606                         }
2607                 }
2608
2609                 return ' LIKE ' .
2610                         $this->addQuotes( $s ) . ' ESCAPE ' . $this->addQuotes( $escapeChar ) . ' ';
2611         }
2612
2613         public function anyChar() {
2614                 return new LikeMatch( '_' );
2615         }
2616
2617         public function anyString() {
2618                 return new LikeMatch( '%' );
2619         }
2620
2621         public function nextSequenceValue( $seqName ) {
2622                 return null;
2623         }
2624
2625         /**
2626          * USE INDEX clause. Unlikely to be useful for anything but MySQL. This
2627          * is only needed because a) MySQL must be as efficient as possible due to
2628          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2629          * which index to pick. Anyway, other databases might have different
2630          * indexes on a given table. So don't bother overriding this unless you're
2631          * MySQL.
2632          * @param string $index
2633          * @return string
2634          */
2635         public function useIndexClause( $index ) {
2636                 return '';
2637         }
2638
2639         /**
2640          * IGNORE INDEX clause. Unlikely to be useful for anything but MySQL. This
2641          * is only needed because a) MySQL must be as efficient as possible due to
2642          * its use on Wikipedia, and b) MySQL 4.0 is kind of dumb sometimes about
2643          * which index to pick. Anyway, other databases might have different
2644          * indexes on a given table. So don't bother overriding this unless you're
2645          * MySQL.
2646          * @param string $index
2647          * @return string
2648          */
2649         public function ignoreIndexClause( $index ) {
2650                 return '';
2651         }
2652
2653         public function replace( $table, $uniqueIndexes, $rows, $fname = __METHOD__ ) {
2654                 if ( count( $rows ) == 0 ) {
2655                         return;
2656                 }
2657
2658                 // Single row case
2659                 if ( !is_array( reset( $rows ) ) ) {
2660                         $rows = [ $rows ];
2661                 }
2662
2663                 try {
2664                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2665                         $affectedRowCount = 0;
2666                         foreach ( $rows as $row ) {
2667                                 // Delete rows which collide with this one
2668                                 $indexWhereClauses = [];
2669                                 foreach ( $uniqueIndexes as $index ) {
2670                                         $indexColumns = (array)$index;
2671                                         $indexRowValues = array_intersect_key( $row, array_flip( $indexColumns ) );
2672                                         if ( count( $indexRowValues ) != count( $indexColumns ) ) {
2673                                                 throw new DBUnexpectedError(
2674                                                         $this,
2675                                                         'New record does not provide all values for unique key (' .
2676                                                         implode( ', ', $indexColumns ) . ')'
2677                                                 );
2678                                         } elseif ( in_array( null, $indexRowValues, true ) ) {
2679                                                 throw new DBUnexpectedError(
2680                                                         $this,
2681                                                         'New record has a null value for unique key (' .
2682                                                         implode( ', ', $indexColumns ) . ')'
2683                                                 );
2684                                         }
2685                                         $indexWhereClauses[] = $this->makeList( $indexRowValues, LIST_AND );
2686                                 }
2687
2688                                 if ( $indexWhereClauses ) {
2689                                         $this->delete( $table, $this->makeList( $indexWhereClauses, LIST_OR ), $fname );
2690                                         $affectedRowCount += $this->affectedRows();
2691                                 }
2692
2693                                 // Now insert the row
2694                                 $this->insert( $table, $row, $fname );
2695                                 $affectedRowCount += $this->affectedRows();
2696                         }
2697                         $this->endAtomic( $fname );
2698                         $this->affectedRowCount = $affectedRowCount;
2699                 } catch ( Exception $e ) {
2700                         $this->cancelAtomic( $fname );
2701                         throw $e;
2702                 }
2703         }
2704
2705         /**
2706          * REPLACE query wrapper for MySQL and SQLite, which have a native REPLACE
2707          * statement.
2708          *
2709          * @param string $table Table name
2710          * @param array|string $rows Row(s) to insert
2711          * @param string $fname Caller function name
2712          *
2713          * @return ResultWrapper
2714          */
2715         protected function nativeReplace( $table, $rows, $fname ) {
2716                 $table = $this->tableName( $table );
2717
2718                 # Single row case
2719                 if ( !is_array( reset( $rows ) ) ) {
2720                         $rows = [ $rows ];
2721                 }
2722
2723                 $sql = "REPLACE INTO $table (" . implode( ',', array_keys( $rows[0] ) ) . ') VALUES ';
2724                 $first = true;
2725
2726                 foreach ( $rows as $row ) {
2727                         if ( $first ) {
2728                                 $first = false;
2729                         } else {
2730                                 $sql .= ',';
2731                         }
2732
2733                         $sql .= '(' . $this->makeList( $row ) . ')';
2734                 }
2735
2736                 return $this->query( $sql, $fname );
2737         }
2738
2739         public function upsert( $table, array $rows, array $uniqueIndexes, array $set,
2740                 $fname = __METHOD__
2741         ) {
2742                 if ( !count( $rows ) ) {
2743                         return true; // nothing to do
2744                 }
2745
2746                 if ( !is_array( reset( $rows ) ) ) {
2747                         $rows = [ $rows ];
2748                 }
2749
2750                 if ( count( $uniqueIndexes ) ) {
2751                         $clauses = []; // list WHERE clauses that each identify a single row
2752                         foreach ( $rows as $row ) {
2753                                 foreach ( $uniqueIndexes as $index ) {
2754                                         $index = is_array( $index ) ? $index : [ $index ]; // columns
2755                                         $rowKey = []; // unique key to this row
2756                                         foreach ( $index as $column ) {
2757                                                 $rowKey[$column] = $row[$column];
2758                                         }
2759                                         $clauses[] = $this->makeList( $rowKey, self::LIST_AND );
2760                                 }
2761                         }
2762                         $where = [ $this->makeList( $clauses, self::LIST_OR ) ];
2763                 } else {
2764                         $where = false;
2765                 }
2766
2767                 $affectedRowCount = 0;
2768                 try {
2769                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2770                         # Update any existing conflicting row(s)
2771                         if ( $where !== false ) {
2772                                 $ok = $this->update( $table, $set, $where, $fname );
2773                                 $affectedRowCount += $this->affectedRows();
2774                         } else {
2775                                 $ok = true;
2776                         }
2777                         # Now insert any non-conflicting row(s)
2778                         $ok = $this->insert( $table, $rows, $fname, [ 'IGNORE' ] ) && $ok;
2779                         $affectedRowCount += $this->affectedRows();
2780                         $this->endAtomic( $fname );
2781                         $this->affectedRowCount = $affectedRowCount;
2782                 } catch ( Exception $e ) {
2783                         $this->cancelAtomic( $fname );
2784                         throw $e;
2785                 }
2786
2787                 return $ok;
2788         }
2789
2790         public function deleteJoin( $delTable, $joinTable, $delVar, $joinVar, $conds,
2791                 $fname = __METHOD__
2792         ) {
2793                 if ( !$conds ) {
2794                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
2795                 }
2796
2797                 $delTable = $this->tableName( $delTable );
2798                 $joinTable = $this->tableName( $joinTable );
2799                 $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
2800                 if ( $conds != '*' ) {
2801                         $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
2802                 }
2803                 $sql .= ')';
2804
2805                 $this->query( $sql, $fname );
2806         }
2807
2808         public function textFieldSize( $table, $field ) {
2809                 $table = $this->tableName( $table );
2810                 $sql = "SHOW COLUMNS FROM $table LIKE \"$field\";";
2811                 $res = $this->query( $sql, __METHOD__ );
2812                 $row = $this->fetchObject( $res );
2813
2814                 $m = [];
2815
2816                 if ( preg_match( '/\((.*)\)/', $row->Type, $m ) ) {
2817                         $size = $m[1];
2818                 } else {
2819                         $size = -1;
2820                 }
2821
2822                 return $size;
2823         }
2824
2825         public function delete( $table, $conds, $fname = __METHOD__ ) {
2826                 if ( !$conds ) {
2827                         throw new DBUnexpectedError( $this, __METHOD__ . ' called with no conditions' );
2828                 }
2829
2830                 $table = $this->tableName( $table );
2831                 $sql = "DELETE FROM $table";
2832
2833                 if ( $conds != '*' ) {
2834                         if ( is_array( $conds ) ) {
2835                                 $conds = $this->makeList( $conds, self::LIST_AND );
2836                         }
2837                         $sql .= ' WHERE ' . $conds;
2838                 }
2839
2840                 return $this->query( $sql, $fname );
2841         }
2842
2843         final public function insertSelect(
2844                 $destTable, $srcTable, $varMap, $conds,
2845                 $fname = __METHOD__, $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2846         ) {
2847                 static $hints = [ 'NO_AUTO_COLUMNS' ];
2848
2849                 $insertOptions = (array)$insertOptions;
2850                 $selectOptions = (array)$selectOptions;
2851
2852                 if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions ) ) {
2853                         // For massive migrations with downtime, we don't want to select everything
2854                         // into memory and OOM, so do all this native on the server side if possible.
2855                         return $this->nativeInsertSelect(
2856                                 $destTable,
2857                                 $srcTable,
2858                                 $varMap,
2859                                 $conds,
2860                                 $fname,
2861                                 array_diff( $insertOptions, $hints ),
2862                                 $selectOptions,
2863                                 $selectJoinConds
2864                         );
2865                 }
2866
2867                 return $this->nonNativeInsertSelect(
2868                         $destTable,
2869                         $srcTable,
2870                         $varMap,
2871                         $conds,
2872                         $fname,
2873                         array_diff( $insertOptions, $hints ),
2874                         $selectOptions,
2875                         $selectJoinConds
2876                 );
2877         }
2878
2879         /**
2880          * @param array $insertOptions INSERT options
2881          * @param array $selectOptions SELECT options
2882          * @return bool Whether an INSERT SELECT with these options will be replication safe
2883          * @since 1.31
2884          */
2885         protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
2886                 return true;
2887         }
2888
2889         /**
2890          * Implementation of insertSelect() based on select() and insert()
2891          *
2892          * @see IDatabase::insertSelect()
2893          * @since 1.30
2894          * @param string $destTable
2895          * @param string|array $srcTable
2896          * @param array $varMap
2897          * @param array $conds
2898          * @param string $fname
2899          * @param array $insertOptions
2900          * @param array $selectOptions
2901          * @param array $selectJoinConds
2902          * @return bool
2903          */
2904         protected function nonNativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2905                 $fname = __METHOD__,
2906                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2907         ) {
2908                 // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
2909                 // on only the master (without needing row-based-replication). It also makes it easy to
2910                 // know how big the INSERT is going to be.
2911                 $fields = [];
2912                 foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
2913                         $fields[] = $this->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
2914                 }
2915                 $selectOptions[] = 'FOR UPDATE';
2916                 $res = $this->select(
2917                         $srcTable, implode( ',', $fields ), $conds, $fname, $selectOptions, $selectJoinConds
2918                 );
2919                 if ( !$res ) {
2920                         return false;
2921                 }
2922
2923                 try {
2924                         $affectedRowCount = 0;
2925                         $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
2926                         $rows = [];
2927                         $ok = true;
2928                         foreach ( $res as $row ) {
2929                                 $rows[] = (array)$row;
2930
2931                                 // Avoid inserts that are too huge
2932                                 if ( count( $rows ) >= $this->nonNativeInsertSelectBatchSize ) {
2933                                         $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
2934                                         if ( !$ok ) {
2935                                                 break;
2936                                         }
2937                                         $affectedRowCount += $this->affectedRows();
2938                                         $rows = [];
2939                                 }
2940                         }
2941                         if ( $rows && $ok ) {
2942                                 $ok = $this->insert( $destTable, $rows, $fname, $insertOptions );
2943                                 if ( $ok ) {
2944                                         $affectedRowCount += $this->affectedRows();
2945                                 }
2946                         }
2947                         if ( $ok ) {
2948                                 $this->endAtomic( $fname );
2949                                 $this->affectedRowCount = $affectedRowCount;
2950                         } else {
2951                                 $this->cancelAtomic( $fname );
2952                         }
2953                         return $ok;
2954                 } catch ( Exception $e ) {
2955                         $this->cancelAtomic( $fname );
2956                         throw $e;
2957                 }
2958         }
2959
2960         /**
2961          * Native server-side implementation of insertSelect() for situations where
2962          * we don't want to select everything into memory
2963          *
2964          * @see IDatabase::insertSelect()
2965          * @param string $destTable
2966          * @param string|array $srcTable
2967          * @param array $varMap
2968          * @param array $conds
2969          * @param string $fname
2970          * @param array $insertOptions
2971          * @param array $selectOptions
2972          * @param array $selectJoinConds
2973          * @return bool
2974          */
2975         protected function nativeInsertSelect( $destTable, $srcTable, $varMap, $conds,
2976                 $fname = __METHOD__,
2977                 $insertOptions = [], $selectOptions = [], $selectJoinConds = []
2978         ) {
2979                 $destTable = $this->tableName( $destTable );
2980
2981                 if ( !is_array( $insertOptions ) ) {
2982                         $insertOptions = [ $insertOptions ];
2983                 }
2984
2985                 $insertOptions = $this->makeInsertOptions( $insertOptions );
2986
2987                 $selectSql = $this->selectSQLText(
2988                         $srcTable,
2989                         array_values( $varMap ),
2990                         $conds,
2991                         $fname,
2992                         $selectOptions,
2993                         $selectJoinConds
2994                 );
2995
2996                 $sql = "INSERT $insertOptions" .
2997                         " INTO $destTable (" . implode( ',', array_keys( $varMap ) ) . ') ' .
2998                         $selectSql;
2999
3000                 return $this->query( $sql, $fname );
3001         }
3002
3003         /**
3004          * Construct a LIMIT query with optional offset. This is used for query
3005          * pages. The SQL should be adjusted so that only the first $limit rows
3006          * are returned. If $offset is provided as well, then the first $offset
3007          * rows should be discarded, and the next $limit rows should be returned.
3008          * If the result of the query is not ordered, then the rows to be returned
3009          * are theoretically arbitrary.
3010          *
3011          * $sql is expected to be a SELECT, if that makes a difference.
3012          *
3013          * The version provided by default works in MySQL and SQLite. It will very
3014          * likely need to be overridden for most other DBMSes.
3015          *
3016          * @param string $sql SQL query we will append the limit too
3017          * @param int $limit The SQL limit
3018          * @param int|bool $offset The SQL offset (default false)
3019          * @throws DBUnexpectedError
3020          * @return string
3021          */
3022         public function limitResult( $sql, $limit, $offset = false ) {
3023                 if ( !is_numeric( $limit ) ) {
3024                         throw new DBUnexpectedError( $this,
3025                                 "Invalid non-numeric limit passed to limitResult()\n" );
3026                 }
3027
3028                 return "$sql LIMIT "
3029                 . ( ( is_numeric( $offset ) && $offset != 0 ) ? "{$offset}," : "" )
3030                 . "{$limit} ";
3031         }
3032
3033         public function unionSupportsOrderAndLimit() {
3034                 return true; // True for almost every DB supported
3035         }
3036
3037         public function unionQueries( $sqls, $all ) {
3038                 $glue = $all ? ') UNION ALL (' : ') UNION (';
3039
3040                 return '(' . implode( $glue, $sqls ) . ')';
3041         }
3042
3043         public function unionConditionPermutations(
3044                 $table, $vars, array $permute_conds, $extra_conds = '', $fname = __METHOD__,
3045                 $options = [], $join_conds = []
3046         ) {
3047                 // First, build the Cartesian product of $permute_conds
3048                 $conds = [ [] ];
3049                 foreach ( $permute_conds as $field => $values ) {
3050                         if ( !$values ) {
3051                                 // Skip empty $values
3052                                 continue;
3053                         }
3054                         $values = array_unique( $values ); // For sanity
3055                         $newConds = [];
3056                         foreach ( $conds as $cond ) {
3057                                 foreach ( $values as $value ) {
3058                                         $cond[$field] = $value;
3059                                         $newConds[] = $cond; // Arrays are by-value, not by-reference, so this works
3060                                 }
3061                         }
3062                         $conds = $newConds;
3063                 }
3064
3065                 $extra_conds = $extra_conds === '' ? [] : (array)$extra_conds;
3066
3067                 // If there's just one condition and no subordering, hand off to
3068                 // selectSQLText directly.
3069                 if ( count( $conds ) === 1 &&
3070                         ( !isset( $options['INNER ORDER BY'] ) || !$this->unionSupportsOrderAndLimit() )
3071                 ) {
3072                         return $this->selectSQLText(
3073                                 $table, $vars, $conds[0] + $extra_conds, $fname, $options, $join_conds
3074                         );
3075                 }
3076
3077                 // Otherwise, we need to pull out the order and limit to apply after
3078                 // the union. Then build the SQL queries for each set of conditions in
3079                 // $conds. Then union them together (using UNION ALL, because the
3080                 // product *should* already be distinct).
3081                 $orderBy = $this->makeOrderBy( $options );
3082                 $limit = isset( $options['LIMIT'] ) ? $options['LIMIT'] : null;
3083                 $offset = isset( $options['OFFSET'] ) ? $options['OFFSET'] : false;
3084                 $all = empty( $options['NOTALL'] ) && !in_array( 'NOTALL', $options );
3085                 if ( !$this->unionSupportsOrderAndLimit() ) {
3086                         unset( $options['ORDER BY'], $options['LIMIT'], $options['OFFSET'] );
3087                 } else {
3088                         if ( array_key_exists( 'INNER ORDER BY', $options ) ) {
3089                                 $options['ORDER BY'] = $options['INNER ORDER BY'];
3090                         }
3091                         if ( $limit !== null && is_numeric( $offset ) && $offset != 0 ) {
3092                                 // We need to increase the limit by the offset rather than
3093                                 // using the offset directly, otherwise it'll skip incorrectly
3094                                 // in the subqueries.
3095                                 $options['LIMIT'] = $limit + $offset;
3096                                 unset( $options['OFFSET'] );
3097                         }
3098                 }
3099
3100                 $sqls = [];
3101                 foreach ( $conds as $cond ) {
3102                         $sqls[] = $this->selectSQLText(
3103                                 $table, $vars, $cond + $extra_conds, $fname, $options, $join_conds
3104                         );
3105                 }
3106                 $sql = $this->unionQueries( $sqls, $all ) . $orderBy;
3107                 if ( $limit !== null ) {
3108                         $sql = $this->limitResult( $sql, $limit, $offset );
3109                 }
3110
3111                 return $sql;
3112         }
3113
3114         public function conditional( $cond, $trueVal, $falseVal ) {
3115                 if ( is_array( $cond ) ) {
3116                         $cond = $this->makeList( $cond, self::LIST_AND );
3117                 }
3118
3119                 return " (CASE WHEN $cond THEN $trueVal ELSE $falseVal END) ";
3120         }
3121
3122         public function strreplace( $orig, $old, $new ) {
3123                 return "REPLACE({$orig}, {$old}, {$new})";
3124         }
3125
3126         public function getServerUptime() {
3127                 return 0;
3128         }
3129
3130         public function wasDeadlock() {
3131                 return false;
3132         }
3133
3134         public function wasLockTimeout() {
3135                 return false;
3136         }
3137
3138         public function wasConnectionLoss() {
3139                 return $this->wasConnectionError( $this->lastErrno() );
3140         }
3141
3142         public function wasReadOnlyError() {
3143                 return false;
3144         }
3145
3146         public function wasErrorReissuable() {
3147                 return (
3148                         $this->wasDeadlock() ||
3149                         $this->wasLockTimeout() ||
3150                         $this->wasConnectionLoss()
3151                 );
3152         }
3153
3154         /**
3155          * Do not use this method outside of Database/DBError classes
3156          *
3157          * @param int|string $errno
3158          * @return bool Whether the given query error was a connection drop
3159          */
3160         public function wasConnectionError( $errno ) {
3161                 return false;
3162         }
3163
3164         /**
3165          * @return bool Whether it is safe to assume the given error only caused statement rollback
3166          * @note This is for backwards compatibility for callers catching DBError exceptions in
3167          *   order to ignore problems like duplicate key errors or foriegn key violations
3168          * @since 1.31
3169          */
3170         protected function wasKnownStatementRollbackError() {
3171                 return false; // don't know; it could have caused a transaction rollback
3172         }
3173
3174         public function deadlockLoop() {
3175                 $args = func_get_args();
3176                 $function = array_shift( $args );
3177                 $tries = self::DEADLOCK_TRIES;
3178
3179                 $this->begin( __METHOD__ );
3180
3181                 $retVal = null;
3182                 /** @var Exception $e */
3183                 $e = null;
3184                 do {
3185                         try {
3186                                 $retVal = call_user_func_array( $function, $args );
3187                                 break;
3188                         } catch ( DBQueryError $e ) {
3189                                 if ( $this->wasDeadlock() ) {
3190                                         // Retry after a randomized delay
3191                                         usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
3192                                 } else {
3193                                         // Throw the error back up
3194                                         throw $e;
3195                                 }
3196                         }
3197                 } while ( --$tries > 0 );
3198
3199                 if ( $tries <= 0 ) {
3200                         // Too many deadlocks; give up
3201                         $this->rollback( __METHOD__ );
3202                         throw $e;
3203                 } else {
3204                         $this->commit( __METHOD__ );
3205
3206                         return $retVal;
3207                 }
3208         }
3209
3210         public function masterPosWait( DBMasterPos $pos, $timeout ) {
3211                 # Real waits are implemented in the subclass.
3212                 return 0;
3213         }
3214
3215         public function getReplicaPos() {
3216                 # Stub
3217                 return false;
3218         }
3219
3220         public function getMasterPos() {
3221                 # Stub
3222                 return false;
3223         }
3224
3225         public function serverIsReadOnly() {
3226                 return false;
3227         }
3228
3229         final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
3230                 if ( !$this->trxLevel ) {
3231                         throw new DBUnexpectedError( $this, "No transaction is active." );
3232                 }
3233                 $this->trxEndCallbacks[] = [ $callback, $fname ];
3234         }
3235
3236         final public function onTransactionIdle( callable $callback, $fname = __METHOD__ ) {
3237                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3238                         // Start an implicit transaction similar to how query() does
3239                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3240                         $this->trxAutomatic = true;
3241                 }
3242
3243                 $this->trxIdleCallbacks[] = [ $callback, $fname ];
3244                 if ( !$this->trxLevel ) {
3245                         $this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE );
3246                 }
3247         }
3248
3249         final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
3250                 if ( !$this->trxLevel && $this->getTransactionRoundId() ) {
3251                         // Start an implicit transaction similar to how query() does
3252                         $this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
3253                         $this->trxAutomatic = true;
3254                 }
3255
3256                 if ( $this->trxLevel ) {
3257                         $this->trxPreCommitCallbacks[] = [ $callback, $fname ];
3258                 } else {
3259                         // No transaction is active nor will start implicitly, so make one for this callback
3260                         $this->startAtomic( __METHOD__, self::ATOMIC_CANCELABLE );
3261                         try {
3262                                 call_user_func( $callback );
3263                                 $this->endAtomic( __METHOD__ );
3264                         } catch ( Exception $e ) {
3265                                 $this->cancelAtomic( __METHOD__ );
3266                                 throw $e;
3267                         }
3268                 }
3269         }
3270
3271         final public function setTransactionListener( $name, callable $callback = null ) {
3272                 if ( $callback ) {
3273                         $this->trxRecurringCallbacks[$name] = $callback;
3274                 } else {
3275                         unset( $this->trxRecurringCallbacks[$name] );
3276                 }
3277         }
3278
3279         /**
3280          * Whether to disable running of post-COMMIT/ROLLBACK callbacks
3281          *
3282          * This method should not be used outside of Database/LoadBalancer
3283          *
3284          * @param bool $suppress
3285          * @since 1.28
3286          */
3287         final public function setTrxEndCallbackSuppression( $suppress ) {
3288                 $this->trxEndCallbacksSuppressed = $suppress;
3289         }
3290
3291         /**
3292          * Actually run and consume any "on transaction idle/resolution" callbacks.
3293          *
3294          * This method should not be used outside of Database/LoadBalancer
3295          *
3296          * @param int $trigger IDatabase::TRIGGER_* constant
3297          * @since 1.20
3298          * @throws Exception
3299          */
3300         public function runOnTransactionIdleCallbacks( $trigger ) {
3301                 if ( $this->trxEndCallbacksSuppressed ) {
3302                         return;
3303                 }
3304
3305                 $autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
3306                 /** @var Exception $e */
3307                 $e = null; // first exception
3308                 do { // callbacks may add callbacks :)
3309                         $callbacks = array_merge(
3310                                 $this->trxIdleCallbacks,
3311                                 $this->trxEndCallbacks // include "transaction resolution" callbacks
3312                         );
3313                         $this->trxIdleCallbacks = []; // consumed (and recursion guard)
3314                         $this->trxEndCallbacks = []; // consumed (recursion guard)
3315                         foreach ( $callbacks as $callback ) {
3316                                 try {
3317                                         list( $phpCallback ) = $callback;
3318                                         $this->clearFlag( self::DBO_TRX ); // make each query its own transaction
3319                                         call_user_func_array( $phpCallback, [ $trigger ] );
3320                                         if ( $autoTrx ) {
3321                                                 $this->setFlag( self::DBO_TRX ); // restore automatic begin()
3322                                         } else {
3323                                                 $this->clearFlag( self::DBO_TRX ); // restore auto-commit
3324                                         }
3325                                 } catch ( Exception $ex ) {
3326                                         call_user_func( $this->errorLogger, $ex );
3327                                         $e = $e ?: $ex;
3328                                         // Some callbacks may use startAtomic/endAtomic, so make sure
3329                                         // their transactions are ended so other callbacks don't fail
3330                                         if ( $this->trxLevel() ) {
3331                                                 $this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
3332                                         }
3333                                 }
3334                         }
3335                 } while ( count( $this->trxIdleCallbacks ) );
3336
3337                 if ( $e instanceof Exception ) {
3338                         throw $e; // re-throw any first exception
3339                 }
3340         }
3341
3342         /**
3343          * Actually run and consume any "on transaction pre-commit" callbacks.
3344          *
3345          * This method should not be used outside of Database/LoadBalancer
3346          *
3347          * @since 1.22
3348          * @throws Exception
3349          */
3350         public function runOnTransactionPreCommitCallbacks() {
3351                 $e = null; // first exception
3352                 do { // callbacks may add callbacks :)
3353                         $callbacks = $this->trxPreCommitCallbacks;
3354                         $this->trxPreCommitCallbacks = []; // consumed (and recursion guard)
3355                         foreach ( $callbacks as $callback ) {
3356                                 try {
3357                                         list( $phpCallback ) = $callback;
3358                                         call_user_func( $phpCallback );
3359                                 } catch ( Exception $ex ) {
3360                                         call_user_func( $this->errorLogger, $ex );
3361                                         $e = $e ?: $ex;
3362                                 }
3363                         }
3364                 } while ( count( $this->trxPreCommitCallbacks ) );
3365
3366                 if ( $e instanceof Exception ) {
3367                         throw $e; // re-throw any first exception
3368                 }
3369         }
3370
3371         /**
3372          * Actually run any "transaction listener" callbacks.
3373          *
3374          * This method should not be used outside of Database/LoadBalancer
3375          *
3376          * @param int $trigger IDatabase::TRIGGER_* constant
3377          * @throws Exception
3378          * @since 1.20
3379          */
3380         public function runTransactionListenerCallbacks( $trigger ) {
3381                 if ( $this->trxEndCallbacksSuppressed ) {
3382                         return;
3383                 }
3384
3385                 /** @var Exception $e */
3386                 $e = null; // first exception
3387
3388                 foreach ( $this->trxRecurringCallbacks as $phpCallback ) {
3389                         try {
3390                                 $phpCallback( $trigger, $this );
3391                         } catch ( Exception $ex ) {
3392                                 call_user_func( $this->errorLogger, $ex );
3393                                 $e = $e ?: $ex;
3394                         }
3395                 }
3396
3397                 if ( $e instanceof Exception ) {
3398                         throw $e; // re-throw any first exception
3399                 }
3400         }
3401
3402         /**
3403          * Create a savepoint
3404          *
3405          * This is used internally to implement atomic sections. It should not be
3406          * used otherwise.
3407          *
3408          * @since 1.31
3409          * @param string $identifier Identifier for the savepoint
3410          * @param string $fname Calling function name
3411          */
3412         protected function doSavepoint( $identifier, $fname ) {
3413                 $this->query( 'SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3414         }
3415
3416         /**
3417          * Release a savepoint
3418          *
3419          * This is used internally to implement atomic sections. It should not be
3420          * used otherwise.
3421          *
3422          * @since 1.31
3423          * @param string $identifier Identifier for the savepoint
3424          * @param string $fname Calling function name
3425          */
3426         protected function doReleaseSavepoint( $identifier, $fname ) {
3427                 $this->query( 'RELEASE SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3428         }
3429
3430         /**
3431          * Rollback to a savepoint
3432          *
3433          * This is used internally to implement atomic sections. It should not be
3434          * used otherwise.
3435          *
3436          * @since 1.31
3437          * @param string $identifier Identifier for the savepoint
3438          * @param string $fname Calling function name
3439          */
3440         protected function doRollbackToSavepoint( $identifier, $fname ) {
3441                 $this->query( 'ROLLBACK TO SAVEPOINT ' . $this->addIdentifierQuotes( $identifier ), $fname );
3442         }
3443
3444         final public function startAtomic(
3445                 $fname = __METHOD__, $cancelable = self::ATOMIC_NOT_CANCELABLE
3446         ) {
3447                 $savepointId = $cancelable === self::ATOMIC_CANCELABLE ? 'n/a' : null;
3448                 if ( !$this->trxLevel ) {
3449                         $this->begin( $fname, self::TRANSACTION_INTERNAL );
3450                         // If DBO_TRX is set, a series of startAtomic/endAtomic pairs will result
3451                         // in all changes being in one transaction to keep requests transactional.
3452                         if ( !$this->getFlag( self::DBO_TRX ) ) {
3453                                 $this->trxAutomaticAtomic = true;
3454                         }
3455                 } elseif ( $cancelable === self::ATOMIC_CANCELABLE ) {
3456                         $savepointId = 'wikimedia_rdbms_atomic' . ++$this->trxAtomicCounter;
3457                         if ( strlen( $savepointId ) > 30 ) { // 30 == Oracle's identifier length limit (pre 12c)
3458                                 $this->queryLogger->warning(
3459                                         'There have been an excessively large number of atomic sections in a transaction'
3460                                         . " started by $this->trxFname, reusing IDs (at $fname)",
3461                                         [ 'trace' => ( new RuntimeException() )->getTraceAsString() ]
3462                                 );
3463                                 $this->trxAtomicCounter = 0;
3464                                 $savepointId = 'wikimedia_rdbms_atomic' . ++$this->trxAtomicCounter;
3465                         }
3466                         $this->doSavepoint( $savepointId, $fname );
3467                 }
3468
3469                 $sectionId = new AtomicSectionIdentifier;
3470                 $this->trxAtomicLevels[] = [ $fname, $sectionId, $savepointId ];
3471
3472                 return $sectionId;
3473         }
3474
3475         final public function endAtomic( $fname = __METHOD__ ) {
3476                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3477                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3478                 }
3479
3480                 // Check if the current section matches $fname
3481                 $pos = count( $this->trxAtomicLevels ) - 1;
3482                 list( $savedFname, , $savepointId ) = $this->trxAtomicLevels[$pos];
3483
3484                 if ( $savedFname !== $fname ) {
3485                         throw new DBUnexpectedError(
3486                                 $this,
3487                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3488                         );
3489                 }
3490
3491                 // Remove the last section and re-index the array
3492                 $this->trxAtomicLevels = array_slice( $this->trxAtomicLevels, 0, $pos );
3493
3494                 if ( !$this->trxAtomicLevels && $this->trxAutomaticAtomic ) {
3495                         $this->commit( $fname, self::FLUSHING_INTERNAL );
3496                 } elseif ( $savepointId !== null && $savepointId !== 'n/a' ) {
3497                         $this->doReleaseSavepoint( $savepointId, $fname );
3498                 }
3499         }
3500
3501         final public function cancelAtomic(
3502                 $fname = __METHOD__, AtomicSectionIdentifier $sectionId = null
3503         ) {
3504                 if ( !$this->trxLevel || !$this->trxAtomicLevels ) {
3505                         throw new DBUnexpectedError( $this, "No atomic section is open (got $fname)." );
3506                 }
3507
3508                 if ( $sectionId !== null ) {
3509                         // Find the (last) section with the given $sectionId
3510                         $pos = -1;
3511                         foreach ( $this->trxAtomicLevels as $i => list( $asFname, $asId, $spId ) ) {
3512                                 if ( $asId === $sectionId ) {
3513                                         $pos = $i;
3514                                 }
3515                         }
3516                         if ( $pos < 0 ) {
3517                                 throw new DBUnexpectedError( "Atomic section not found (for $fname)" );
3518                         }
3519                         // Remove all descendant sections and re-index the array
3520                         $this->trxAtomicLevels = array_slice( $this->trxAtomicLevels, 0, $pos + 1 );
3521                 }
3522
3523                 // Check if the current section matches $fname
3524                 $pos = count( $this->trxAtomicLevels ) - 1;
3525                 list( $savedFname, , $savepointId ) = $this->trxAtomicLevels[$pos];
3526
3527                 if ( $savedFname !== $fname ) {
3528                         throw new DBUnexpectedError(
3529                                 $this,
3530                                 "Invalid atomic section ended (got $fname but expected $savedFname)."
3531                         );
3532                 }
3533
3534                 // Remove the last section and re-index the array
3535                 $this->trxAtomicLevels = array_slice( $this->trxAtomicLevels, 0, $pos );
3536
3537                 if ( $savepointId !== null ) {
3538                         // Rollback the transaction to the state just before this atomic section
3539                         if ( $savepointId === 'n/a' ) {
3540                                 $this->rollback( $fname, self::FLUSHING_INTERNAL );
3541                         } else {
3542                                 $this->doRollbackToSavepoint( $savepointId, $fname );
3543                                 $this->trxStatus = self::STATUS_TRX_OK; // no exception; recovered
3544                                 $this->trxStatusIgnoredCause = null;
3545                         }
3546                 } elseif ( $this->trxStatus > self::STATUS_TRX_ERROR ) {
3547                         // Put the transaction into an error state if it's not already in one
3548                         $this->trxStatus = self::STATUS_TRX_ERROR;
3549                         $this->trxStatusCause = new DBUnexpectedError(
3550                                 $this,
3551                                 "Uncancelable atomic section canceled (got $fname)."
3552                         );
3553                 }
3554
3555                 $this->affectedRowCount = 0; // for the sake of consistency
3556         }
3557
3558         final public function doAtomicSection(
3559                 $fname, callable $callback, $cancelable = self::ATOMIC_NOT_CANCELABLE
3560         ) {
3561                 $sectionId = $this->startAtomic( $fname, $cancelable );
3562                 try {
3563                         $res = call_user_func_array( $callback, [ $this, $fname ] );
3564                 } catch ( Exception $e ) {
3565                         $this->cancelAtomic( $fname, $sectionId );
3566
3567                         throw $e;
3568                 }
3569                 $this->endAtomic( $fname );
3570
3571                 return $res;
3572         }
3573
3574         final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
3575                 static $modes = [ self::TRANSACTION_EXPLICIT, self::TRANSACTION_INTERNAL ];
3576                 if ( !in_array( $mode, $modes, true ) ) {
3577                         throw new DBUnexpectedError( $this, "$fname: invalid mode parameter '$mode'." );
3578                 }
3579
3580                 // Protect against mismatched atomic section, transaction nesting, and snapshot loss
3581                 if ( $this->trxLevel ) {
3582                         if ( $this->trxAtomicLevels ) {
3583                                 $levels = $this->flatAtomicSectionList();
3584                                 $msg = "$fname: Got explicit BEGIN while atomic section(s) $levels are open.";
3585                                 throw new DBUnexpectedError( $this, $msg );
3586                         } elseif ( !$this->trxAutomatic ) {
3587                                 $msg = "$fname: Explicit transaction already active (from {$this->trxFname}).";
3588                                 throw new DBUnexpectedError( $this, $msg );
3589                         } else {
3590                                 $msg = "$fname: Implicit transaction already active (from {$this->trxFname}).";
3591                                 throw new DBUnexpectedError( $this, $msg );
3592                         }
3593                 } elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
3594                         $msg = "$fname: Implicit transaction expected (DBO_TRX set).";
3595                         throw new DBUnexpectedError( $this, $msg );
3596                 }
3597
3598                 // Avoid fatals if close() was called
3599                 $this->assertOpen();
3600
3601                 $this->doBegin( $fname );
3602                 $this->trxStatus = self::STATUS_TRX_OK;
3603                 $this->trxStatusIgnoredCause = null;
3604                 $this->trxAtomicCounter = 0;
3605                 $this->trxTimestamp = microtime( true );
3606                 $this->trxFname = $fname;
3607                 $this->trxDoneWrites = false;
3608                 $this->trxAutomaticAtomic = false;
3609                 $this->trxAtomicLevels = [];
3610                 $this->trxShortId = sprintf( '%06x', mt_rand( 0, 0xffffff ) );
3611                 $this->trxWriteDuration = 0.0;
3612                 $this->trxWriteQueryCount = 0;
3613                 $this->trxWriteAffectedRows = 0;
3614                 $this->trxWriteAdjDuration = 0.0;
3615                 $this->trxWriteAdjQueryCount = 0;
3616                 $this->trxWriteCallers = [];
3617                 // First SELECT after BEGIN will establish the snapshot in REPEATABLE-READ.
3618                 // Get an estimate of the replication lag before any such queries.
3619                 $this->trxReplicaLag = null; // clear cached value first
3620                 $this->trxReplicaLag = $this->getApproximateLagStatus()['lag'];
3621                 // T147697: make explicitTrxActive() return true until begin() finishes. This way, no
3622                 // caller will think its OK to muck around with the transaction just because startAtomic()
3623                 // has not yet completed (e.g. setting trxAtomicLevels).
3624                 $this->trxAutomatic = ( $mode === self::TRANSACTION_INTERNAL );
3625         }
3626
3627         /**
3628          * Issues the BEGIN command to the database server.
3629          *
3630          * @see Database::begin()
3631          * @param string $fname
3632          */
3633         protected function doBegin( $fname ) {
3634                 $this->query( 'BEGIN', $fname );
3635                 $this->trxLevel = 1;
3636         }
3637
3638         final public function commit( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
3639                 static $modes = [ self::FLUSHING_ONE, self::FLUSHING_ALL_PEERS, self::FLUSHING_INTERNAL ];
3640                 if ( !in_array( $flush, $modes, true ) ) {
3641                         throw new DBUnexpectedError( $this, "$fname: invalid flush parameter '$flush'." );
3642                 }
3643
3644                 if ( $this->trxLevel && $this->trxAtomicLevels ) {
3645                         // There are still atomic sections open; this cannot be ignored
3646                         $levels = $this->flatAtomicSectionList();
3647                         throw new DBUnexpectedError(
3648                                 $this,
3649                                 "$fname: Got COMMIT while atomic sections $levels are still open."
3650                         );
3651                 }
3652
3653                 if ( $flush === self::FLUSHING_INTERNAL || $flush === self::FLUSHING_ALL_PEERS ) {
3654                         if ( !$this->trxLevel ) {
3655                                 return; // nothing to do
3656                         } elseif ( !$this->trxAutomatic ) {
3657                                 throw new DBUnexpectedError(
3658                                         $this,
3659                                         "$fname: Flushing an explicit transaction, getting out of sync."
3660                                 );
3661                         }
3662                 } else {
3663                         if ( !$this->trxLevel ) {
3664                                 $this->queryLogger->error(
3665                                         "$fname: No transaction to commit, something got out of sync." );
3666                                 return; // nothing to do
3667                         } elseif ( $this->trxAutomatic ) {
3668                                 throw new DBUnexpectedError(
3669                                         $this,
3670                                         "$fname: Expected mass commit of all peer transactions (DBO_TRX set)."
3671                                 );
3672                         }
3673                 }
3674
3675                 // Avoid fatals if close() was called
3676                 $this->assertOpen();
3677
3678                 $this->runOnTransactionPreCommitCallbacks();
3679                 $writeTime = $this->pendingWriteQueryDuration( self::ESTIMATE_DB_APPLY );
3680                 $this->doCommit( $fname );
3681                 $this->trxStatus = self::STATUS_TRX_NONE;
3682                 if ( $this->trxDoneWrites ) {
3683                         $this->lastWriteTime = microtime( true );
3684                         $this->trxProfiler->transactionWritingOut(
3685                                 $this->server,
3686                                 $this->dbName,
3687                                 $this->trxShortId,
3688                                 $writeTime,
3689                                 $this->trxWriteAffectedRows
3690                         );
3691                 }
3692
3693                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT );
3694                 $this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT );
3695         }
3696
3697         /**
3698          * Issues the COMMIT command to the database server.
3699          *
3700          * @see Database::commit()
3701          * @param string $fname
3702          */
3703         protected function doCommit( $fname ) {
3704                 if ( $this->trxLevel ) {
3705                         $this->query( 'COMMIT', $fname );
3706                         $this->trxLevel = 0;
3707                 }
3708         }
3709
3710         final public function rollback( $fname = __METHOD__, $flush = '' ) {
3711                 $trxActive = $this->trxLevel;
3712
3713                 if ( $flush !== self::FLUSHING_INTERNAL && $flush !== self::FLUSHING_ALL_PEERS ) {
3714                         if ( $this->getFlag( self::DBO_TRX ) ) {
3715                                 throw new DBUnexpectedError(
3716                                         $this,
3717                                         "$fname: Expected mass rollback of all peer transactions (DBO_TRX set)."
3718                                 );
3719                         }
3720                 }
3721
3722                 if ( $trxActive ) {
3723                         // Avoid fatals if close() was called
3724                         $this->assertOpen();
3725
3726                         $this->doRollback( $fname );
3727                         $this->trxStatus = self::STATUS_TRX_NONE;
3728                         $this->trxAtomicLevels = [];
3729                         if ( $this->trxDoneWrites ) {
3730                                 $this->trxProfiler->transactionWritingOut(
3731                                         $this->server,
3732                                         $this->dbName,
3733                                         $this->trxShortId
3734                                 );
3735                         }
3736                 }
3737
3738                 // Clear any commit-dependant callbacks. They might even be present
3739                 // only due to transaction rounds, with no SQL transaction being active
3740                 $this->trxIdleCallbacks = [];
3741                 $this->trxPreCommitCallbacks = [];
3742
3743                 if ( $trxActive ) {
3744                         try {
3745                                 $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
3746                         } catch ( Exception $e ) {
3747                                 // already logged; finish and let LoadBalancer move on during mass-rollback
3748                         }
3749                         try {
3750                                 $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
3751                         } catch ( Exception $e ) {
3752                                 // already logged; let LoadBalancer move on during mass-rollback
3753                         }
3754
3755                         $this->affectedRowCount = 0; // for the sake of consistency
3756                 }
3757         }
3758
3759         /**
3760          * Issues the ROLLBACK command to the database server.
3761          *
3762          * @see Database::rollback()
3763          * @param string $fname
3764          */
3765         protected function doRollback( $fname ) {
3766                 if ( $this->trxLevel ) {
3767                         # Disconnects cause rollback anyway, so ignore those errors
3768                         $ignoreErrors = true;
3769                         $this->query( 'ROLLBACK', $fname, $ignoreErrors );
3770                         $this->trxLevel = 0;
3771                 }
3772         }
3773
3774         public function flushSnapshot( $fname = __METHOD__ ) {
3775                 if ( $this->writesOrCallbacksPending() || $this->explicitTrxActive() ) {
3776                         // This only flushes transactions to clear snapshots, not to write data
3777                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
3778                         throw new DBUnexpectedError(
3779                                 $this,
3780                                 "$fname: Cannot flush snapshot because writes are pending ($fnames)."
3781                         );
3782                 }
3783
3784                 $this->commit( $fname, self::FLUSHING_INTERNAL );
3785         }
3786
3787         public function explicitTrxActive() {
3788                 return $this->trxLevel && ( $this->trxAtomicLevels || !$this->trxAutomatic );
3789         }
3790
3791         public function duplicateTableStructure(
3792                 $oldName, $newName, $temporary = false, $fname = __METHOD__
3793         ) {
3794                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3795         }
3796
3797         public function listTables( $prefix = null, $fname = __METHOD__ ) {
3798                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3799         }
3800
3801         public function listViews( $prefix = null, $fname = __METHOD__ ) {
3802                 throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
3803         }
3804
3805         public function timestamp( $ts = 0 ) {
3806                 $t = new ConvertibleTimestamp( $ts );
3807                 // Let errors bubble up to avoid putting garbage in the DB
3808                 return $t->getTimestamp( TS_MW );
3809         }
3810
3811         public function timestampOrNull( $ts = null ) {
3812                 if ( is_null( $ts ) ) {
3813                         return null;
3814                 } else {
3815                         return $this->timestamp( $ts );
3816                 }
3817         }
3818
3819         public function affectedRows() {
3820                 return ( $this->affectedRowCount === null )
3821                         ? $this->fetchAffectedRowCount() // default to driver value
3822                         : $this->affectedRowCount;
3823         }
3824
3825         /**
3826          * @return int Number of retrieved rows according to the driver
3827          */
3828         abstract protected function fetchAffectedRowCount();
3829
3830         /**
3831          * Take the result from a query, and wrap it in a ResultWrapper if
3832          * necessary. Boolean values are passed through as is, to indicate success
3833          * of write queries or failure.
3834          *
3835          * Once upon a time, Database::query() returned a bare MySQL result
3836          * resource, and it was necessary to call this function to convert it to
3837          * a wrapper. Nowadays, raw database objects are never exposed to external
3838          * callers, so this is unnecessary in external code.
3839          *
3840          * @param bool|ResultWrapper|resource|object $result
3841          * @return bool|ResultWrapper
3842          */
3843         protected function resultObject( $result ) {
3844                 if ( !$result ) {
3845                         return false;
3846                 } elseif ( $result instanceof ResultWrapper ) {
3847                         return $result;
3848                 } elseif ( $result === true ) {
3849                         // Successful write query
3850                         return $result;
3851                 } else {
3852                         return new ResultWrapper( $this, $result );
3853                 }
3854         }
3855
3856         public function ping( &$rtt = null ) {
3857                 // Avoid hitting the server if it was hit recently
3858                 if ( $this->isOpen() && ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
3859                         if ( !func_num_args() || $this->rttEstimate > 0 ) {
3860                                 $rtt = $this->rttEstimate;
3861                                 return true; // don't care about $rtt
3862                         }
3863                 }
3864
3865                 // This will reconnect if possible or return false if not
3866                 $this->clearFlag( self::DBO_TRX, self::REMEMBER_PRIOR );
3867                 $ok = ( $this->query( self::PING_QUERY, __METHOD__, true ) !== false );
3868                 $this->restoreFlags( self::RESTORE_PRIOR );
3869
3870                 if ( $ok ) {
3871                         $rtt = $this->rttEstimate;
3872                 }
3873
3874                 return $ok;
3875         }
3876
3877         /**
3878          * Close any existing (dead) database connection and open a new connection
3879          *
3880          * @param string $fname
3881          * @return bool True if new connection is opened successfully, false if error
3882          */
3883         protected function replaceLostConnection( $fname ) {
3884                 $this->closeConnection();
3885                 $this->opened = false;
3886                 $this->conn = false;
3887                 try {
3888                         $this->open( $this->server, $this->user, $this->password, $this->dbName );
3889                         $this->lastPing = microtime( true );
3890                         $ok = true;
3891
3892                         $this->connLogger->warning(
3893                                 $fname . ': lost connection to {dbserver}; reconnected',
3894                                 [
3895                                         'dbserver' => $this->getServer(),
3896                                         'trace' => ( new RuntimeException() )->getTraceAsString()
3897                                 ]
3898                         );
3899                 } catch ( DBConnectionError $e ) {
3900                         $ok = false;
3901
3902                         $this->connLogger->error(
3903                                 $fname . ': lost connection to {dbserver} permanently',
3904                                 [ 'dbserver' => $this->getServer() ]
3905                         );
3906                 }
3907
3908                 $this->handleSessionLoss();
3909
3910                 return $ok;
3911         }
3912
3913         public function getSessionLagStatus() {
3914                 return $this->getRecordedTransactionLagStatus() ?: $this->getApproximateLagStatus();
3915         }
3916
3917         /**
3918          * Get the replica DB lag when the current transaction started
3919          *
3920          * This is useful when transactions might use snapshot isolation
3921          * (e.g. REPEATABLE-READ in innodb), so the "real" lag of that data
3922          * is this lag plus transaction duration. If they don't, it is still
3923          * safe to be pessimistic. This returns null if there is no transaction.
3924          *
3925          * This returns null if the lag status for this transaction was not yet recorded.
3926          *
3927          * @return array|null ('lag': seconds or false on error, 'since': UNIX timestamp of BEGIN)
3928          * @since 1.27
3929          */
3930         final protected function getRecordedTransactionLagStatus() {
3931                 return ( $this->trxLevel && $this->trxReplicaLag !== null )
3932                         ? [ 'lag' => $this->trxReplicaLag, 'since' => $this->trxTimestamp() ]
3933                         : null;
3934         }
3935
3936         /**
3937          * Get a replica DB lag estimate for this server
3938          *
3939          * @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
3940          * @since 1.27
3941          */
3942         protected function getApproximateLagStatus() {
3943                 return [
3944                         'lag'   => $this->getLBInfo( 'replica' ) ? $this->getLag() : 0,
3945                         'since' => microtime( true )
3946                 ];
3947         }
3948
3949         /**
3950          * Merge the result of getSessionLagStatus() for several DBs
3951          * using the most pessimistic values to estimate the lag of
3952          * any data derived from them in combination
3953          *
3954          * This is information is useful for caching modules
3955          *
3956          * @see WANObjectCache::set()
3957          * @see WANObjectCache::getWithSetCallback()
3958          *
3959          * @param IDatabase $db1
3960          * @param IDatabase $db2 [optional]
3961          * @return array Map of values:
3962          *   - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
3963          *   - since: oldest UNIX timestamp of any of the DB lag estimates
3964          *   - pending: whether any of the DBs have uncommitted changes
3965          * @throws DBError
3966          * @since 1.27
3967          */
3968         public static function getCacheSetOptions( IDatabase $db1, IDatabase $db2 = null ) {
3969                 $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
3970                 foreach ( func_get_args() as $db ) {
3971                         /** @var IDatabase $db */
3972                         $status = $db->getSessionLagStatus();
3973                         if ( $status['lag'] === false ) {
3974                                 $res['lag'] = false;
3975                         } elseif ( $res['lag'] !== false ) {
3976                                 $res['lag'] = max( $res['lag'], $status['lag'] );
3977                         }
3978                         $res['since'] = min( $res['since'], $status['since'] );
3979                         $res['pending'] = $res['pending'] ?: $db->writesPending();
3980                 }
3981
3982                 return $res;
3983         }
3984
3985         public function getLag() {
3986                 return 0;
3987         }
3988
3989         public function maxListLen() {
3990                 return 0;
3991         }
3992
3993         public function encodeBlob( $b ) {
3994                 return $b;
3995         }
3996
3997         public function decodeBlob( $b ) {
3998                 if ( $b instanceof Blob ) {
3999                         $b = $b->fetch();
4000                 }
4001                 return $b;
4002         }
4003
4004         public function setSessionOptions( array $options ) {
4005         }
4006
4007         public function sourceFile(
4008                 $filename,
4009                 callable $lineCallback = null,
4010                 callable $resultCallback = null,
4011                 $fname = false,
4012                 callable $inputCallback = null
4013         ) {
4014                 Wikimedia\suppressWarnings();
4015                 $fp = fopen( $filename, 'r' );
4016                 Wikimedia\restoreWarnings();
4017
4018                 if ( false === $fp ) {
4019                         throw new RuntimeException( "Could not open \"{$filename}\".\n" );
4020                 }
4021
4022                 if ( !$fname ) {
4023                         $fname = __METHOD__ . "( $filename )";
4024                 }
4025
4026                 try {
4027                         $error = $this->sourceStream(
4028                                 $fp, $lineCallback, $resultCallback, $fname, $inputCallback );
4029                 } catch ( Exception $e ) {
4030                         fclose( $fp );
4031                         throw $e;
4032                 }
4033
4034                 fclose( $fp );
4035
4036                 return $error;
4037         }
4038
4039         public function setSchemaVars( $vars ) {
4040                 $this->schemaVars = $vars;
4041         }
4042
4043         public function sourceStream(
4044                 $fp,
4045                 callable $lineCallback = null,
4046                 callable $resultCallback = null,
4047                 $fname = __METHOD__,
4048                 callable $inputCallback = null
4049         ) {
4050                 $delimiterReset = new ScopedCallback(
4051                         function ( $delimiter ) {
4052                                 $this->delimiter = $delimiter;
4053                         },
4054                         [ $this->delimiter ]
4055                 );
4056                 $cmd = '';
4057
4058                 while ( !feof( $fp ) ) {
4059                         if ( $lineCallback ) {
4060                                 call_user_func( $lineCallback );
4061                         }
4062
4063                         $line = trim( fgets( $fp ) );
4064
4065                         if ( $line == '' ) {
4066                                 continue;
4067                         }
4068
4069                         if ( '-' == $line[0] && '-' == $line[1] ) {
4070                                 continue;
4071                         }
4072
4073                         if ( $cmd != '' ) {
4074                                 $cmd .= ' ';
4075                         }
4076
4077                         $done = $this->streamStatementEnd( $cmd, $line );
4078
4079                         $cmd .= "$line\n";
4080
4081                         if ( $done || feof( $fp ) ) {
4082                                 $cmd = $this->replaceVars( $cmd );
4083
4084                                 if ( $inputCallback ) {
4085                                         $callbackResult = call_user_func( $inputCallback, $cmd );
4086
4087                                         if ( is_string( $callbackResult ) || !$callbackResult ) {
4088                                                 $cmd = $callbackResult;
4089                                         }
4090                                 }
4091
4092                                 if ( $cmd ) {
4093                                         $res = $this->query( $cmd, $fname );
4094
4095                                         if ( $resultCallback ) {
4096                                                 call_user_func( $resultCallback, $res, $this );
4097                                         }
4098
4099                                         if ( false === $res ) {
4100                                                 $err = $this->lastError();
4101
4102                                                 return "Query \"{$cmd}\" failed with error code \"$err\".\n";
4103                                         }
4104                                 }
4105                                 $cmd = '';
4106                         }
4107                 }
4108
4109                 ScopedCallback::consume( $delimiterReset );
4110                 return true;
4111         }
4112
4113         /**
4114          * Called by sourceStream() to check if we've reached a statement end
4115          *
4116          * @param string &$sql SQL assembled so far
4117          * @param string &$newLine New line about to be added to $sql
4118          * @return bool Whether $newLine contains end of the statement
4119          */
4120         public function streamStatementEnd( &$sql, &$newLine ) {
4121                 if ( $this->delimiter ) {
4122                         $prev = $newLine;
4123                         $newLine = preg_replace(
4124                                 '/' . preg_quote( $this->delimiter, '/' ) . '$/', '', $newLine );
4125                         if ( $newLine != $prev ) {
4126                                 return true;
4127                         }
4128                 }
4129
4130                 return false;
4131         }
4132
4133         /**
4134          * Database independent variable replacement. Replaces a set of variables
4135          * in an SQL statement with their contents as given by $this->getSchemaVars().
4136          *
4137          * Supports '{$var}' `{$var}` and / *$var* / (without the spaces) style variables.
4138          *
4139          * - '{$var}' should be used for text and is passed through the database's
4140          *   addQuotes method.
4141          * - `{$var}` should be used for identifiers (e.g. table and database names).
4142          *   It is passed through the database's addIdentifierQuotes method which
4143          *   can be overridden if the database uses something other than backticks.
4144          * - / *_* / or / *$wgDBprefix* / passes the name that follows through the
4145          *   database's tableName method.
4146          * - / *i* / passes the name that follows through the database's indexName method.
4147          * - In all other cases, / *$var* / is left unencoded. Except for table options,
4148          *   its use should be avoided. In 1.24 and older, string encoding was applied.
4149          *
4150          * @param string $ins SQL statement to replace variables in
4151          * @return string The new SQL statement with variables replaced
4152          */
4153         protected function replaceVars( $ins ) {
4154                 $vars = $this->getSchemaVars();
4155                 return preg_replace_callback(
4156                         '!
4157                                 /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
4158                                 \'\{\$ (\w+) }\'                  | # 3. addQuotes
4159                                 `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
4160                                 /\*\$ (\w+) \*/                     # 5. leave unencoded
4161                         !x',
4162                         function ( $m ) use ( $vars ) {
4163                                 // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
4164                                 // check for both nonexistent keys *and* the empty string.
4165                                 if ( isset( $m[1] ) && $m[1] !== '' ) {
4166                                         if ( $m[1] === 'i' ) {
4167                                                 return $this->indexName( $m[2] );
4168                                         } else {
4169                                                 return $this->tableName( $m[2] );
4170                                         }
4171                                 } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
4172                                         return $this->addQuotes( $vars[$m[3]] );
4173                                 } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
4174                                         return $this->addIdentifierQuotes( $vars[$m[4]] );
4175                                 } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
4176                                         return $vars[$m[5]];
4177                                 } else {
4178                                         return $m[0];
4179                                 }
4180                         },
4181                         $ins
4182                 );
4183         }
4184
4185         /**
4186          * Get schema variables. If none have been set via setSchemaVars(), then
4187          * use some defaults from the current object.
4188          *
4189          * @return array
4190          */
4191         protected function getSchemaVars() {
4192                 if ( $this->schemaVars ) {
4193                         return $this->schemaVars;
4194                 } else {
4195                         return $this->getDefaultSchemaVars();
4196                 }
4197         }
4198
4199         /**
4200          * Get schema variables to use if none have been set via setSchemaVars().
4201          *
4202          * Override this in derived classes to provide variables for tables.sql
4203          * and SQL patch files.
4204          *
4205          * @return array
4206          */
4207         protected function getDefaultSchemaVars() {
4208                 return [];
4209         }
4210
4211         public function lockIsFree( $lockName, $method ) {
4212                 // RDBMs methods for checking named locks may or may not count this thread itself.
4213                 // In MySQL, IS_FREE_LOCK() returns 0 if the thread already has the lock. This is
4214                 // the behavior choosen by the interface for this method.
4215                 return !isset( $this->namedLocksHeld[$lockName] );
4216         }
4217
4218         public function lock( $lockName, $method, $timeout = 5 ) {
4219                 $this->namedLocksHeld[$lockName] = 1;
4220
4221                 return true;
4222         }
4223
4224         public function unlock( $lockName, $method ) {
4225                 unset( $this->namedLocksHeld[$lockName] );
4226
4227                 return true;
4228         }
4229
4230         public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
4231                 if ( $this->writesOrCallbacksPending() ) {
4232                         // This only flushes transactions to clear snapshots, not to write data
4233                         $fnames = implode( ', ', $this->pendingWriteAndCallbackCallers() );
4234                         throw new DBUnexpectedError(
4235                                 $this,
4236                                 "$fname: Cannot flush pre-lock snapshot because writes are pending ($fnames)."
4237                         );
4238                 }
4239
4240                 if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
4241                         return null;
4242                 }
4243
4244                 $unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
4245                         if ( $this->trxLevel() ) {
4246                                 // There is a good chance an exception was thrown, causing any early return
4247                                 // from the caller. Let any error handler get a chance to issue rollback().
4248                                 // If there isn't one, let the error bubble up and trigger server-side rollback.
4249                                 $this->onTransactionResolution(
4250                                         function () use ( $lockKey, $fname ) {
4251                                                 $this->unlock( $lockKey, $fname );
4252                                         },
4253                                         $fname
4254                                 );
4255                         } else {
4256                                 $this->unlock( $lockKey, $fname );
4257                         }
4258                 } );
4259
4260                 $this->commit( $fname, self::FLUSHING_INTERNAL );
4261
4262                 return $unlocker;
4263         }
4264
4265         public function namedLocksEnqueue() {
4266                 return false;
4267         }
4268
4269         public function tableLocksHaveTransactionScope() {
4270                 return true;
4271         }
4272
4273         final public function lockTables( array $read, array $write, $method ) {
4274                 if ( $this->writesOrCallbacksPending() ) {
4275                         throw new DBUnexpectedError( $this, "Transaction writes or callbacks still pending." );
4276                 }
4277
4278                 if ( $this->tableLocksHaveTransactionScope() ) {
4279                         $this->startAtomic( $method );
4280                 }
4281
4282                 return $this->doLockTables( $read, $write, $method );
4283         }
4284
4285         /**
4286          * Helper function for lockTables() that handles the actual table locking
4287          *
4288          * @param array $read Array of tables to lock for read access
4289          * @param array $write Array of tables to lock for write access
4290          * @param string $method Name of caller
4291          * @return true
4292          */
4293         protected function doLockTables( array $read, array $write, $method ) {
4294                 return true;
4295         }
4296
4297         final public function unlockTables( $method ) {
4298                 if ( $this->tableLocksHaveTransactionScope() ) {
4299                         $this->endAtomic( $method );
4300
4301                         return true; // locks released on COMMIT/ROLLBACK
4302                 }
4303
4304                 return $this->doUnlockTables( $method );
4305         }
4306
4307         /**
4308          * Helper function for unlockTables() that handles the actual table unlocking
4309          *
4310          * @param string $method Name of caller
4311          * @return true
4312          */
4313         protected function doUnlockTables( $method ) {
4314                 return true;
4315         }
4316
4317         /**
4318          * Delete a table
4319          * @param string $tableName
4320          * @param string $fName
4321          * @return bool|ResultWrapper
4322          * @since 1.18
4323          */
4324         public function dropTable( $tableName, $fName = __METHOD__ ) {
4325                 if ( !$this->tableExists( $tableName, $fName ) ) {
4326                         return false;
4327                 }
4328                 $sql = "DROP TABLE " . $this->tableName( $tableName ) . " CASCADE";
4329
4330                 return $this->query( $sql, $fName );
4331         }
4332
4333         public function getInfinity() {
4334                 return 'infinity';
4335         }
4336
4337         public function encodeExpiry( $expiry ) {
4338                 return ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() )
4339                         ? $this->getInfinity()
4340                         : $this->timestamp( $expiry );
4341         }
4342
4343         public function decodeExpiry( $expiry, $format = TS_MW ) {
4344                 if ( $expiry == '' || $expiry == 'infinity' || $expiry == $this->getInfinity() ) {
4345                         return 'infinity';
4346                 }
4347
4348                 return ConvertibleTimestamp::convert( $format, $expiry );
4349         }
4350
4351         public function setBigSelects( $value = true ) {
4352                 // no-op
4353         }
4354
4355         public function isReadOnly() {
4356                 return ( $this->getReadOnlyReason() !== false );
4357         }
4358
4359         /**
4360          * @return string|bool Reason this DB is read-only or false if it is not
4361          */
4362         protected function getReadOnlyReason() {
4363                 $reason = $this->getLBInfo( 'readOnlyReason' );
4364
4365                 return is_string( $reason ) ? $reason : false;
4366         }
4367
4368         public function setTableAliases( array $aliases ) {
4369                 $this->tableAliases = $aliases;
4370         }
4371
4372         public function setIndexAliases( array $aliases ) {
4373                 $this->indexAliases = $aliases;
4374         }
4375
4376         /**
4377          * Get the underlying binding connection handle
4378          *
4379          * Makes sure the connection resource is set (disconnects and ping() failure can unset it).
4380          * This catches broken callers than catch and ignore disconnection exceptions.
4381          * Unlike checking isOpen(), this is safe to call inside of open().
4382          *
4383          * @return mixed
4384          * @throws DBUnexpectedError
4385          * @since 1.26
4386          */
4387         protected function getBindingHandle() {
4388                 if ( !$this->conn ) {
4389                         throw new DBUnexpectedError(
4390                                 $this,
4391                                 'DB connection was already closed or the connection dropped.'
4392                         );
4393                 }
4394
4395                 return $this->conn;
4396         }
4397
4398         /**
4399          * @since 1.19
4400          * @return string
4401          */
4402         public function __toString() {
4403                 return (string)$this->conn;
4404         }
4405
4406         /**
4407          * Make sure that copies do not share the same client binding handle
4408          * @throws DBConnectionError
4409          */
4410         public function __clone() {
4411                 $this->connLogger->warning(
4412                         "Cloning " . static::class . " is not recomended; forking connection:\n" .
4413                         ( new RuntimeException() )->getTraceAsString()
4414                 );
4415
4416                 if ( $this->isOpen() ) {
4417                         // Open a new connection resource without messing with the old one
4418                         $this->opened = false;
4419                         $this->conn = false;
4420                         $this->trxEndCallbacks = []; // don't copy
4421                         $this->handleSessionLoss(); // no trx or locks anymore
4422                         $this->open( $this->server, $this->user, $this->password, $this->dbName );
4423                         $this->lastPing = microtime( true );
4424                 }
4425         }
4426
4427         /**
4428          * Called by serialize. Throw an exception when DB connection is serialized.
4429          * This causes problems on some database engines because the connection is
4430          * not restored on unserialize.
4431          */
4432         public function __sleep() {
4433                 throw new RuntimeException( 'Database serialization may cause problems, since ' .
4434                         'the connection is not restored on wakeup.' );
4435         }
4436
4437         /**
4438          * Run a few simple sanity checks and close dangling connections
4439          */
4440         public function __destruct() {
4441                 if ( $this->trxLevel && $this->trxDoneWrites ) {
4442                         trigger_error( "Uncommitted DB writes (transaction from {$this->trxFname})." );
4443                 }
4444
4445                 $danglingWriters = $this->pendingWriteAndCallbackCallers();
4446                 if ( $danglingWriters ) {
4447                         $fnames = implode( ', ', $danglingWriters );
4448                         trigger_error( "DB transaction writes or callbacks still pending ($fnames)." );
4449                 }
4450
4451                 if ( $this->conn ) {
4452                         // Avoid connection leaks for sanity. Normally, resources close at script completion.
4453                         // The connection might already be closed in zend/hhvm by now, so suppress warnings.
4454                         Wikimedia\suppressWarnings();
4455                         $this->closeConnection();
4456                         Wikimedia\restoreWarnings();
4457                         $this->conn = false;
4458                         $this->opened = false;
4459                 }
4460         }
4461 }
4462
4463 class_alias( Database::class, 'DatabaseBase' ); // b/c for old name
4464 class_alias( Database::class, 'Database' ); // b/c global alias