Database.php
80546c718a04REL1_39

Database.php
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	<?php
	/**
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License along
	* with this program; if not, write to the Free Software Foundation, Inc.,
	* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
	* http://www.gnu.org/copyleft/gpl.html
	*
	* @file
	*/
	namespace Wikimedia\Rdbms;

	use BagOStuff;
	use InvalidArgumentException;
	use LogicException;
	use Psr\Log\LoggerAwareInterface;
	use Psr\Log\LoggerInterface;
	use Psr\Log\NullLogger;
	use RuntimeException;
	use Throwable;
	use Wikimedia\AtEase\AtEase;
	use Wikimedia\Rdbms\Platform\SQLPlatform;
	use Wikimedia\RequestTimeout\CriticalSectionProvider;
	use Wikimedia\RequestTimeout\CriticalSectionScope;
	use Wikimedia\ScopedCallback;

	/**
	* Relational database abstraction object
	*
	* @stable to extend
	* @ingroup Database
	* @since 1.28
	*/
	abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
	/** @var BagOStuff APC cache */
	protected $srvCache;
	/** @var CriticalSectionProvider\|null */
	protected $csProvider;
	/** @var LoggerInterface */
	protected $connLogger;
	/** @var LoggerInterface */
	protected $queryLogger;
	/** @var LoggerInterface */
	protected $replLogger;
	/** @var callable Error logging callback */
	protected $errorLogger;
	/** @var callable Deprecation logging callback */
	protected $deprecationLogger;
	/** @var callable\|null */
	protected $profiler;
	/** @var TransactionManager */
	private $transactionManager;

	/** @var DatabaseDomain */
	protected $currentDomain;

	// phpcs:ignore MediaWiki.Commenting.PropertyDocumentation.ObjectTypeHintVar
	/** @var object\|resource\|null Database connection */
	protected $conn;

	/** @var ?IDatabase Lazy handle to the most authoritative primary server for the dataset */
	protected $topologicalPrimaryConnRef;

	/** @var string\|null Server that this instance is currently connected to */
	protected $server;
	/** @var string\|null User that this instance is currently connected under the name of */
	protected $user;
	/** @var string\|null Password used to establish the current connection */
	protected $password;
	/** @var string\|null Readable name or host/IP of the database server */
	protected $serverName;
	/** @var bool Whether this PHP instance is for a CLI script */
	protected $cliMode;
	/** @var string Agent name for query profiling */
	protected $agent;
	/** @var string Replication topology role of the server; one of the class ROLE_* constants */
	protected $topologyRole;
	/** @var array<string,mixed> Connection parameters used by initConnection() and open() */
	protected $connectionParams;
	/** @var string[]\|int[]\|float[] SQL variables values to use for all new connections */
	protected $connectionVariables;
	/** @var int Row batch size to use for emulated INSERT SELECT queries */
	protected $nonNativeInsertSelectBatchSize;

	/** @var int Current bit field of class DBO_* constants */
	protected $flags;
	/** @var bool Whether to use SSL connections */
	protected $ssl;
	/** @var array Current LoadBalancer tracking information */
	protected $lbInfo = [];
	/** @var string\|false Current SQL query delimiter */
	protected $delimiter = ';';

	/** @var string\|bool\|null Stashed value of html_errors INI setting */
	private $htmlErrors;
	/** @var int[] Prior flags member variable values */
	private $priorFlags = [];

	/** @var array<string,array> Map of (name => (UNIX time,trx ID)) for current lock() mutexes */
	protected $sessionNamedLocks = [];
	/** @var array<string,array> Map of (name => (type,pristine,trx ID)) for current temp tables */
	protected $sessionTempTables = [];

	/** @var array\|null Replication lag estimate at the time of BEGIN for the last transaction */
	private $trxReplicaLagStatus = null;

	/** @var int\|null Rows affected by the last query to query() or its CRUD wrappers */
	protected $affectedRowCount;

	/** @var float UNIX timestamp */
	private $lastPing = 0.0;
	/** @var string The last SQL query attempted */
	private $lastQuery = '';
	/** @var float\|false UNIX timestamp of last write query */
	private $lastWriteTime = false;
	/** @var string\|false */
	private $lastPhpError = false;
	/** @var float Query round trip time estimate */
	private $lastRoundTripEstimate = 0.0;

	/** @var int\|null Current critical section numeric ID */
	private $csmId;
	/** @var string\|null Last critical section caller name */
	private $csmFname;
	/** @var DBUnexpectedError\|null Last unresolved critical section error */
	private $csmError;

	/** @var string Whether the database is a file on disk */
	public const ATTR_DB_IS_FILE = 'db-is-file';
	/** @var string Lock granularity is on the level of the entire database */
	public const ATTR_DB_LEVEL_LOCKING = 'db-level-locking';
	/** @var string The SCHEMA keyword refers to a grouping of tables in a database */
	public const ATTR_SCHEMAS_AS_TABLE_GROUPS = 'supports-schemas';

	/** @var int New Database instance will not be connected yet when returned */
	public const NEW_UNCONNECTED = 0;
	/** @var int New Database instance will already be connected when returned */
	public const NEW_CONNECTED = 1;

	/** No errors occurred during the query */
	protected const ERR_NONE = 0;
	/** Retry query due to a connection loss detected while sending the query (session intact) */
	protected const ERR_RETRY_QUERY = 1;
	/** Abort query (no retries) due to a statement rollback (session/transaction intact) */
	protected const ERR_ABORT_QUERY = 2;
	/** Abort any current transaction, by rolling it back, due to an error during the query */
	protected const ERR_ABORT_TRX = 4;
	/** Abort and reset session due to server-side session-level state loss (locks, temp tables) */
	protected const ERR_ABORT_SESSION = 8;

	/** Assume that queries taking this long to yield connection loss errors are at fault */
	protected const DROPPED_CONN_BLAME_THRESHOLD_SEC = 3.0;

	/** @var string Idiom used when a cancelable atomic section started the transaction */
	private const NOT_APPLICABLE = 'n/a';

	/** @var int Writes to this temporary table do not affect lastDoneWrites() */
	private const TEMP_NORMAL = 1;
	/** @var int Writes to this temporary table effect lastDoneWrites() */
	private const TEMP_PSEUDO_PERMANENT = 2;

	/** @var int Number of times to re-try an operation in case of deadlock */
	private const DEADLOCK_TRIES = 4;
	/** @var int Minimum time to wait before retry, in microseconds */
	private const DEADLOCK_DELAY_MIN = 500000;
	/** @var int Maximum time to wait before retry */
	private const DEADLOCK_DELAY_MAX = 1500000;

	/** @var float How long before it is worth doing a dummy query to test the connection */
	private const PING_TTL = 1.0;
	/** @var string Dummy SQL query */
	private const PING_QUERY = 'SELECT 1 AS ping';

	/** @var string[] List of DBO_* flags that can be changed after connection */
	protected const MUTABLE_FLAGS = [
	'DBO_DEBUG',
	'DBO_NOBUFFER',
	'DBO_TRX',
	'DBO_DDLMODE',
	];
	/** @var int Bit field of all DBO_* flags that can be changed after connection */
	protected const DBO_MUTABLE = (
	self::DBO_DEBUG \| self::DBO_NOBUFFER \| self::DBO_TRX \| self::DBO_DDLMODE
	);

	/** Hostname or IP address to use on all connections */
	protected const CONN_HOST = 'host';
	/** Database server username to use on all connections */
	protected const CONN_USER = 'user';
	/** Database server password to use on all connections */
	protected const CONN_PASSWORD = 'password';
	/** Database name to use on initial connection */
	protected const CONN_INITIAL_DB = 'dbname';
	/** Schema name to use on initial connection */
	protected const CONN_INITIAL_SCHEMA = 'schema';
	/** Table prefix to use on initial connection */
	protected const CONN_INITIAL_TABLE_PREFIX = 'tablePrefix';

	/** @var SQLPlatform */
	protected $platform;

	/**
	* @note exceptions for missing libraries/drivers should be thrown in initConnection()
	* @stable to call
	* @param array $params Parameters passed from Database::factory()
	*/
	public function __construct( array $params ) {
	$this->transactionManager = new TransactionManager(
	$params['queryLogger'],
	$params['trxProfiler']
	);
	$this->connectionParams = [
	self::CONN_HOST => ( isset( $params['host'] ) && $params['host'] !== '' )
	? $params['host']
	: null,
	self::CONN_USER => ( isset( $params['user'] ) && $params['user'] !== '' )
	? $params['user']
	: null,
	self::CONN_INITIAL_DB => ( isset( $params['dbname'] ) && $params['dbname'] !== '' )
	? $params['dbname']
	: null,
	self::CONN_INITIAL_SCHEMA => ( isset( $params['schema'] ) && $params['schema'] !== '' )
	? $params['schema']
	: null,
	self::CONN_PASSWORD => is_string( $params['password'] ) ? $params['password'] : null,
	self::CONN_INITIAL_TABLE_PREFIX => (string)$params['tablePrefix']
	];

	$this->lbInfo = $params['lbInfo'] ?? [];
	$this->topologicalPrimaryConnRef = $params['topologicalPrimaryConnRef'] ?? null;
	$this->connectionVariables = $params['variables'] ?? [];
	// Set SQL mode, default is turning them all off, can be overridden or skipped with null
	if ( is_string( $params['sqlMode'] ?? null ) ) {
	$this->connectionVariables['sql_mode'] = $params['sqlMode'];
	}

	$this->flags = (int)$params['flags'];
	$this->ssl = $params['ssl'] ?? (bool)( $this->flags & self::DBO_SSL );
	$this->cliMode = (bool)$params['cliMode'];
	$this->agent = (string)$params['agent'];
	$this->serverName = $params['serverName'];
	$this->topologyRole = $params['topologyRole'];
	$this->nonNativeInsertSelectBatchSize = $params['nonNativeInsertSelectBatchSize'] ?? 10000;

	$this->srvCache = $params['srvCache'];
	$this->profiler = is_callable( $params['profiler'] ) ? $params['profiler'] : null;
	$this->connLogger = $params['connLogger'];
	$this->queryLogger = $params['queryLogger'];
	$this->replLogger = $params['replLogger'];
	$this->errorLogger = $params['errorLogger'];
	$this->deprecationLogger = $params['deprecationLogger'];

	$this->csProvider = $params['criticalSectionProvider'] ?? null;

	// Set initial dummy domain until open() sets the final DB/prefix
	$this->currentDomain = new DatabaseDomain(
	$params['dbname'] != '' ? $params['dbname'] : null,
	$params['schema'] != '' ? $params['schema'] : null,
	$params['tablePrefix']
	);
	$this->platform = new SQLPlatform(
	$this,
	$params['queryLogger'],
	$this->currentDomain,
	$this->errorLogger
	);
	}

	/**
	* Initialize the connection to the database over the wire (or to local files)
	*
	* @throws LogicException
	* @throws InvalidArgumentException
	* @throws DBConnectionError
	* @since 1.31
	*/
	final public function initConnection() {
	if ( $this->isOpen() ) {
	throw new LogicException( __METHOD__ . ': already connected' );
	}
	// Establish the connection
	$this->doInitConnection();
	}

	/**
	* Actually connect to the database over the wire (or to local files)
	*
	* @throws DBConnectionError
	* @since 1.31
	*/
	protected function doInitConnection() {
	$this->open(
	$this->connectionParams[self::CONN_HOST],
	$this->connectionParams[self::CONN_USER],
	$this->connectionParams[self::CONN_PASSWORD],
	$this->connectionParams[self::CONN_INITIAL_DB],
	$this->connectionParams[self::CONN_INITIAL_SCHEMA],
	$this->connectionParams[self::CONN_INITIAL_TABLE_PREFIX]
	);
	}

	/**
	* Open a new connection to the database (closing any existing one)
	*
	* @param string\|null $server Server host/address and optional port {@see connectionParams}
	* @param string\|null $user User name {@see connectionParams}
	* @param string\|null $password User password {@see connectionParams}
	* @param string\|null $db Database name
	* @param string\|null $schema Database schema name
	* @param string $tablePrefix
	* @throws DBConnectionError
	*/
	abstract protected function open( $server, $user, $password, $db, $schema, $tablePrefix );

	/**
	* Construct a Database subclass instance given a database type and parameters
	*
	* This also connects to the database immediately upon object construction
	*
	* @param string $type A possible DB type (sqlite, mysql, postgres,...)
	* @param array $params Parameter map with keys:
	* - host : The hostname or IP address of the database server
	* - user : The name of the database user the client operates under
	* - password : The password for the database user
	* - dbname : The name of the database to use where queries do not specify one.
	* The database must exist or an error might be thrown. Setting this to an empty string
	* will avoid any such errors and make the handle have no implicit database scope. This is
	* useful for queries like SHOW STATUS, CREATE DATABASE, or DROP DATABASE. Note that a
	* "database" in Postgres is roughly equivalent to an entire MySQL server. This the domain
	* in which user names and such are defined, e.g. users are database-specific in Postgres.
	* - schema : The database schema to use (if supported). A "schema" in Postgres is roughly
	* equivalent to a "database" in MySQL. Note that MySQL and SQLite do not use schemas.
	* - tablePrefix : Optional table prefix that is implicitly added on to all table names
	* recognized in queries. This can be used in place of schemas for handle site farms.
	* - flags : Optional bit field of DBO_* constants that define connection, protocol,
	* buffering, and transaction behavior. It is STRONGLY advised to leave the DBO_DEFAULT
	* flag in place UNLESS this database simply acts as a key/value store.
	* - driver: Optional name of a specific DB client driver. For MySQL, there is only the
	* 'mysqli' driver; the old one 'mysql' has been removed.
	* - variables: Optional map of session variables to set after connecting. This can be
	* used to adjust lock timeouts or encoding modes and the like.
	* - serverName : Optional readable name for the database server.
	* - topologyRole: Optional IDatabase::ROLE_* constant for the database server.
	* - lbInfo: Optional map of field/values for the managing load balancer instance.
	* The "master" and "replica" fields are used to flag the replication role of this
	* database server and whether methods like getLag() should actually issue queries.
	* - topologicalPrimaryConnRef: lazy-connecting IDatabase handle to the most authoritative
	* primary database server for the cluster that this database belongs to. This handle is
	* used for replication status purposes. This is generally managed by LoadBalancer.
	* - connLogger: Optional PSR-3 logger interface instance.
	* - queryLogger: Optional PSR-3 logger interface instance.
	* - profiler : Optional callback that takes a section name argument and returns
	* a ScopedCallback instance that ends the profile section in its destructor.
	* These will be called in query(), using a simplified version of the SQL that
	* also includes the agent as a SQL comment.
	* - trxProfiler: Optional TransactionProfiler instance.
	* - errorLogger: Optional callback that takes an Exception and logs it.
	* - deprecationLogger: Optional callback that takes a string and logs it.
	* - cliMode: Whether to consider the execution context that of a CLI script.
	* - agent: Optional name used to identify the end-user in query profiling/logging.
	* - srvCache: Optional BagOStuff instance to an APC-style cache.
	* - nonNativeInsertSelectBatchSize: Optional batch size for non-native INSERT SELECT.
	* - criticalSectionProvider: Optional CriticalSectionProvider instance.
	* @param int $connect One of the class constants (NEW_CONNECTED, NEW_UNCONNECTED) [optional]
	* @return Database\|null If the database driver or extension cannot be found
	* @throws InvalidArgumentException If the database driver or extension cannot be found
	* @deprecated since 1.39, use DatabaseFactory::create instead
	* @since 1.18
	*/
	final public static function factory( $type, $params = [], $connect = self::NEW_CONNECTED ) {
	return ( new DatabaseFactory() )->create( $type, $params, $connect );
	}

	/**
	* @param string $dbType A possible DB type (sqlite, mysql, postgres,...)
	* @param string\|null $driver Optional name of a specific DB client driver
	* @return array Map of (Database::ATTR_* constant => value) for all such constants
	* @throws DBUnexpectedError
	* @deprecated since 1.39, use DatabaseFactory::attributesFromType instead
	* @since 1.31
	*/
	final public static function attributesFromType( $dbType, $driver = null ) {
	return ( new DatabaseFactory() )->attributesFromType( $dbType, $driver );
	}

	/**
	* @stable to override
	* @return array Map of (Database::ATTR_* constant => value)
	* @since 1.31
	*/
	public static function getAttributes() {
	return [];
	}

	/**
	* Set the PSR-3 logger interface to use for query logging. (The logger
	* interfaces for connection logging and error logging can be set with the
	* constructor.)
	*
	* @param LoggerInterface $logger
	*/
	public function setLogger( LoggerInterface $logger ) {
	$this->queryLogger = $logger;
	}

	public function getServerInfo() {
	return $this->getServerVersion();
	}

	public function getTopologyBasedServerId() {
	return null;
	}

	public function getTopologyRole() {
	return $this->topologyRole;
	}

	/**
	* Get important session state that cannot be recovered upon connection loss
	*
	* @return CriticalSessionInfo
	*/
	private function getCriticalSessionInfo(): CriticalSessionInfo {
	return new CriticalSessionInfo(
	$this->transactionManager->getTrxId(),
	$this->transactionManager->explicitTrxActive(),
	$this->transactionManager->pendingWriteCallers(),
	$this->transactionManager->pendingPreCommitCallbackCallers(),
	$this->sessionNamedLocks,
	$this->sessionTempTables
	);
	}

	public function tablePrefix( $prefix = null ) {
	$old = $this->currentDomain->getTablePrefix();

	if ( $prefix !== null ) {
	$this->currentDomain = new DatabaseDomain(
	$this->currentDomain->getDatabase(),
	$this->currentDomain->getSchema(),
	$prefix
	);
	$this->platform->setCurrentDomain( $this->currentDomain );
	}

	return $old;
	}

	public function dbSchema( $schema = null ) {
	$old = $this->currentDomain->getSchema();

	if ( $schema !== null ) {
	if ( $schema !== '' && $this->getDBname() === null ) {
	throw new DBUnexpectedError(
	$this,
	"Cannot set schema to '$schema'; no database set"
	);
	}

	$this->currentDomain = new DatabaseDomain(
	$this->currentDomain->getDatabase(),
	// DatabaseDomain uses null for unspecified schemas
	( $schema !== '' ) ? $schema : null,
	$this->currentDomain->getTablePrefix()
	);
	$this->platform->setCurrentDomain( $this->currentDomain );
	}

	return (string)$old;
	}

	public function getLBInfo( $name = null ) {
	if ( $name === null ) {
	return $this->lbInfo;
	}

	if ( array_key_exists( $name, $this->lbInfo ) ) {
	return $this->lbInfo[$name];
	}

	return null;
	}

	public function setLBInfo( $nameOrArray, $value = null ) {
	if ( is_array( $nameOrArray ) ) {
	$this->lbInfo = $nameOrArray;
	} elseif ( is_string( $nameOrArray ) ) {
	if ( $value !== null ) {
	$this->lbInfo[$nameOrArray] = $value;
	} else {
	unset( $this->lbInfo[$nameOrArray] );
	}
	} else {
	throw new InvalidArgumentException( "Got non-string key" );
	}
	}

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

	public function lastDoneWrites() {
	return $this->lastWriteTime ?: false;
	}

	/**
	* @return bool
	* @since 1.39
	* @internal For use by Database/LoadBalancer only
	*/
	public function sessionLocksPending() {
	return (bool)$this->sessionNamedLocks;
	}

	/**
	* @return string\|null ID of the active explicit transaction round being participating in
	*/
	final protected function getTransactionRoundId() {
	if ( $this->getFlag( self::DBO_TRX ) ) {
	// LoadBalancer transaction round participation is enabled for this DB handle;
	// get the ID of the active explicit transaction round (if any)
	$id = $this->getLBInfo( self::LB_TRX_ROUND_ID );

	return is_string( $id ) ? $id : null;
	}

	return null;
	}

	public function isOpen() {
	return (bool)$this->conn;
	}

	public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
	if ( $flag & ~static::DBO_MUTABLE ) {
	throw new DBUnexpectedError(
	$this,
	"Got $flag (allowed: " . implode( ', ', static::MUTABLE_FLAGS ) . ')'
	);
	}

	if ( $remember === self::REMEMBER_PRIOR ) {
	$this->priorFlags[] = $this->flags;
	}

	$this->flags \|= $flag;
	}

	public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
	if ( $flag & ~static::DBO_MUTABLE ) {
	throw new DBUnexpectedError(
	$this,
	"Got $flag (allowed: " . implode( ', ', static::MUTABLE_FLAGS ) . ')'
	);
	}

	if ( $remember === self::REMEMBER_PRIOR ) {
	$this->priorFlags[] = $this->flags;
	}

	$this->flags &= ~$flag;
	}

	public function restoreFlags( $state = self::RESTORE_PRIOR ) {
	if ( !$this->priorFlags ) {
	return;
	}

	if ( $state === self::RESTORE_INITIAL ) {
	$this->flags = reset( $this->priorFlags );
	$this->priorFlags = [];
	} else {
	$this->flags = array_pop( $this->priorFlags );
	}
	}

	public function getFlag( $flag ) {
	return ( ( $this->flags & $flag ) === $flag );
	}

	public function getDomainID() {
	return $this->currentDomain->getId();
	}

	/**
	* Get information about an index into an object
	*
	* @stable to override
	* @param string $table Table name
	* @param string $index Index name
	* @param string $fname Calling function name
	* @return mixed Database-specific index description class or false if the index does not exist
	*/
	abstract public function indexInfo( $table, $index, $fname = __METHOD__ );

	/**
	* Wrapper for addslashes()
	*
	* @stable to override
	* @param string $s String to be slashed.
	* @return string Slashed string.
	*/
	abstract public function strencode( $s );

	/**
	* Set a custom error handler for logging errors during database connection
	*/
	protected function installErrorHandler() {
	$this->lastPhpError = false;
	$this->htmlErrors = ini_set( 'html_errors', '0' );
	set_error_handler( [ $this, 'connectionErrorLogger' ] );
	}

	/**
	* Restore the previous error handler and return the last PHP error for this DB
	*
	* @return string\|false
	*/
	protected function restoreErrorHandler() {
	restore_error_handler();
	if ( $this->htmlErrors !== false ) {
	ini_set( 'html_errors', $this->htmlErrors );
	}

	return $this->getLastPHPError();
	}

	/**
	* @return string\|false Last PHP error for this DB (typically connection errors)
	*/
	protected function getLastPHPError() {
	if ( $this->lastPhpError ) {
	$error = preg_replace( '!\[<a.*</a>\]!', '', $this->lastPhpError );
	$error = preg_replace( '!^.?:\s?(.)$!', '$1', $error );

	return $error;
	}

	return false;
	}

	/**
	* Error handler for logging errors during database connection
	*
	* @internal This method should not be used outside of Database classes
	*
	* @param int\|string $errno
	* @param string $errstr
	*/
	public function connectionErrorLogger( $errno, $errstr ) {
	$this->lastPhpError = $errstr;
	}

	/**
	* Create a log context to pass to PSR-3 logger functions.
	*
	* @param array $extras Additional data to add to context
	* @return array
	*/
	protected function getLogContext( array $extras = [] ) {
	return array_merge(
	[
	'db_server' => $this->getServerName(),
	'db_name' => $this->getDBname(),
	'db_user' => $this->connectionParams[self::CONN_USER] ?? null,
	],
	$extras
	);
	}

	final public function close( $fname = __METHOD__ ) {
	$error = null; // error to throw after disconnecting

	$wasOpen = (bool)$this->conn;
	// This should mostly do nothing if the connection is already closed
	if ( $this->conn ) {
	// Roll back any dangling transaction first
	if ( $this->trxLevel() ) {
	$error = $this->transactionManager->trxCheckBeforeClose( $this, $fname );
	// Rollback the changes and run any callbacks as needed
	$this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
	$this->runTransactionPostRollbackCallbacks();
	}

	// Close the actual connection in the binding handle
	$closed = $this->closeConnection();
	} else {
	$closed = true; // already closed; nothing to do
	}

	$this->conn = null;

	// Log any unexpected errors after having disconnected
	if ( $error !== null ) {
	// T217819, T231443: this is probably just LoadBalancer trying to recover from
	// errors and shutdown. Log any problems and move on since the request has to
	// end one way or another. Throwing errors is not very useful at some point.
	$this->queryLogger->error( $error, [ 'db_log_category' => 'query' ] );
	}

	// Note that various subclasses call close() at the start of open(), which itself is
	// called by replaceLostConnection(). In that case, just because onTransactionResolution()
	// callbacks are pending does not mean that an exception should be thrown. Rather, they
	// will be executed after the reconnection step.
	if ( $wasOpen ) {
	// Double check that no callbacks are dangling
	$fnames = $this->pendingWriteAndCallbackCallers();
	if ( $fnames ) {
	throw new RuntimeException(
	"Transaction callbacks are still pending: " . implode( ', ', $fnames )
	);
	}
	}

	return $closed;
	}

	/**
	* Make sure there is an open connection handle (alive or not)
	*
	* This guards against fatal errors to the binding handle not being defined in cases
	* where open() was never called or close() was already called.
	*
	* @throws DBUnexpectedError
	*/
	final protected function assertHasConnectionHandle() {
	if ( !$this->isOpen() ) {
	throw new DBUnexpectedError( $this, "DB connection was already closed" );
	}
	}

	/**
	* Make sure that this server is not marked as a replica nor read-only
	*
	* @throws DBReadOnlyError
	* @since 1.37
	*/
	protected function assertIsWritablePrimary() {
	$info = $this->getReadOnlyReason();
	if ( $info ) {
	list( $reason, $source ) = $info;
	if ( $source === 'role' ) {
	throw new DBReadOnlyRoleError( $this, "Database is read-only: $reason" );
	} else {
	throw new DBReadOnlyError( $this, "Database is read-only: $reason" );
	}
	}
	}

	/**
	* Closes underlying database connection
	* @return bool Whether connection was closed successfully
	* @since 1.20
	*/
	abstract protected function closeConnection();

	/**
	* Run a query and return a QueryStatus instance with the query result information
	*
	* This is meant to handle the basic command of actually sending a query to the
	* server via the driver. No implicit transaction, reconnection, nor retry logic
	* should happen here. The higher level query() method is designed to handle those
	* sorts of concerns. This method should not trigger such higher level methods.
	*
	* The lastError() and lastErrno() methods should meaningfully reflect what error,
	* if any, occurred during the last call to this method. Methods like executeQuery(),
	* query(), select(), insert(), update(), delete(), and upsert() implement their calls
	* to doQuery() such that an immediately subsequent call to lastError()/lastErrno()
	* meaningfully reflects any error that occurred during that public query method call.
	*
	* For SELECT queries, the result field contains either:
	* - a) A driver-specific IResultWrapper describing the query results
	* - b) False, on any query failure
	*
	* For non-SELECT queries, the result field contains either:
	* - a) A driver-specific IResultWrapper, only on success
	* - b) True, only on success (e.g. no meaningful result other than "OK")
	* - c) False, on any query failure
	*
	* @param string $sql Single-statement SQL query
	* @return QueryStatus
	* @since 1.39
	*/
	abstract protected function doSingleStatementQuery( string $sql ): QueryStatus;

	/**
	* Execute a batch of query statements, aborting remaining statements if one fails
	*
	* @see Database::doQuery()
	*
	* @stable to override
	* @param string[] $sqls Non-empty map of (statement ID => SQL statement)
	* @return array<string,QueryStatus> Map of (statement ID => QueryStatus)
	* @since 1.39
	*/
	protected function doMultiStatementQuery( array $sqls ): array {
	$qsByStatementId = [];

	$aborted = false;
	foreach ( $sqls as $statementId => $sql ) {
	$qs = $aborted
	? new QueryStatus( false, 0, 'Query aborted', 0 )
	: $this->doSingleStatementQuery( $sql );
	$qsByStatementId[$statementId] = $qs;
	$aborted = ( $qs->res === false );
	}

	return $qsByStatementId;
	}

	/**
	* @param string $sql SQL query
	* @param bool $pseudoPermanent Treat any table from CREATE TEMPORARY as pseudo-permanent
	* @return array[] List of change n-tuples with:
	* - int: self::TEMP_* constant for temp table operations
	* - string: SQL query verb from $sql
	* - string: Name of the temp table changed in $sql
	*/
	protected function getTempTableWrites( $sql, $pseudoPermanent ) {
	// Regexes for basic queries that can create/change/drop temporary tables.
	// For simplicity, this only looks for tables with sensible, alphanumeric, names;
	// temporary tables only need simple programming names anyway.
	static $regexes = null;
	if ( $regexes === null ) {
	// Regex with a group for quoted table 0 and a group for quoted tables 1..N
	$qts = '((?:\w+\|`\w+`\|\'\w+\'\|"\w+")(?:\s,\s(?:\w+\|`\w+`\|\'\w+\'\|"\w+"))*)';
	// Regex to get query verb, table 0, and tables 1..N
	$regexes = [
	// DML write queries
	"/^(INSERT\|REPLACE)\s+(?:\w+\s+)*?INTO\s+$qts/i",
	"/^(UPDATE)(?:\s+OR\s+\w+\|\s+IGNORE\|\s+ONLY)?\s+$qts/i",
	"/^(DELETE)\s+(?:\w+\s+)*?FROM(?:\s+ONLY)?\s+$qts/i",
	// DDL write queries
	"/^(CREATE)\s+TEMPORARY\s+TABLE(?:\s+IF\s+NOT\s+EXISTS)?\s+$qts/i",
	"/^(DROP)\s+(?:TEMPORARY\s+)?TABLE(?:\s+IF\s+EXISTS)?\s+$qts/i",
	"/^(TRUNCATE)\s+(?:TEMPORARY\s+)?TABLE\s+$qts/i",
	"/^(ALTER)\s+TABLE\s+$qts/i"
	];
	}

	$queryVerb = null;
	$queryTables = [];
	foreach ( $regexes as $regex ) {
	if ( preg_match( $regex, $sql, $m, PREG_UNMATCHED_AS_NULL ) ) {
	$queryVerb = $m[1];
	$allTables = preg_split( '/\s,\s/', $m[2] );
	foreach ( $allTables as $quotedTable ) {
	$queryTables[] = trim( $quotedTable, "\"'`" );
	}
	break;
	}
	}

	$tempTableChanges = [];
	foreach ( $queryTables as $table ) {
	if ( $queryVerb === 'CREATE' ) {
	// Record the type of temporary table being created
	$tableType = $pseudoPermanent ? self::TEMP_PSEUDO_PERMANENT : self::TEMP_NORMAL;
	} elseif ( isset( $this->sessionTempTables[$table] ) ) {
	$tableType = $this->sessionTempTables[$table]['type'];
	} else {
	$tableType = null;
	}

	if ( $tableType !== null ) {
	$tempTableChanges[] = [ $tableType, $queryVerb, $table ];
	}
	}

	return $tempTableChanges;
	}

	/**
	* @param IResultWrapper\|bool $ret
	* @param array[] $changes List of change n-tuples with from getTempWrites()
	*/
	protected function registerTempWrites( $ret, array $changes ) {
	if ( $ret === false ) {
	return;
	}

	foreach ( $changes as list( $tmpTableType, $verb, $table ) ) {
	switch ( $verb ) {
	case 'CREATE':
	$this->sessionTempTables[$table] = [
	'type' => $tmpTableType,
	'pristine' => true,
	'trxId' => $this->transactionManager->getTrxId()
	];
	break;
	case 'DROP':
	unset( $this->sessionTempTables[$table] );
	break;
	case 'TRUNCATE':
	if ( isset( $this->sessionTempTables[$table] ) ) {
	$this->sessionTempTables[$table]['pristine'] = true;
	}
	break;
	default:
	if ( isset( $this->sessionTempTables[$table] ) ) {
	$this->sessionTempTables[$table]['pristine'] = false;
	}
	break;
	}
	}
	}

	/**
	* Check if the table is both a TEMPORARY table and has not yet received CRUD operations
	*
	* @param string $table
	* @return bool
	* @since 1.35
	*/
	protected function isPristineTemporaryTable( $table ) {
	$rawTable = $this->tableName( $table, 'raw' );

	return isset( $this->sessionTempTables[$rawTable] )
	? $this->sessionTempTables[$rawTable]['pristine']
	: false;
	}

	public function query( $sql, $fname = __METHOD__, $flags = 0 ) {
	$flags = (int)$flags; // b/c; this field used to be a bool

	// Make sure that this caller is allowed to issue this query statement
	$this->assertQueryIsCurrentlyAllowed( $sql, $fname );

	// Send the query to the server and fetch any corresponding errors
	/** @var QueryStatus $qs */
	$qs = $this->executeQuery( $sql, $fname, $flags, $sql );

	// Handle any errors that occurred
	if ( $qs->res === false ) {
	// An error occurred; log and report it as needed. Errors that corrupt the state of
	// the transaction/session cannot be silenced from the client.
	$ignore = (
	$this->fieldHasBit( $flags, self::QUERY_SILENCE_ERRORS ) &&
	!$this->fieldHasBit( $qs->flags, self::ERR_ABORT_SESSION ) &&
	!$this->fieldHasBit( $qs->flags, self::ERR_ABORT_TRX )
	);
	// Throw an error unless both the ignore flag was set and a rollback is not needed
	$this->reportQueryError( $qs->message, $qs->code, $sql, $fname, $ignore );
	}

	return $qs->res;
	}

	/**
	* Run a batch of SQL query statements and return the results.
	*
	* @see Database::query()
	*
	* @param string[] $sqls Map of (statement ID => SQL statement)
	* @param string $fname Name of the calling function
	* @param int $flags Bit field of IDatabase::QUERY_* constants
	* @param string\|null $summarySql Virtual SQL for profiling (e.g. "UPSERT INTO TABLE 'x'")
	* @return array<string,QueryStatus> Ordered map of (statement ID => QueryStatus)
	* @since 1.39
	*/
	public function queryMulti(
	array $sqls, string $fname = __METHOD__, int $flags = 0, ?string $summarySql = null
	) {
	if ( !$sqls ) {
	return [];
	}
	if ( $summarySql === null ) {
	$summarySql = reset( $sqls );
	}
	// Make sure that this caller is allowed to issue these query statements
	foreach ( $sqls as $sql ) {
	$this->assertQueryIsCurrentlyAllowed( $sql, $fname );
	}

	// Send the query statements to the server and fetch the results
	$statusByStatementId = $this->executeQuery( $sqls, $fname, $flags, $summarySql );
	// @phan-suppress-next-line PhanTypeSuspiciousNonTraversableForeach
	foreach ( $statusByStatementId as $statementId => $qs ) {
	if ( $qs->res === false ) {
	// An error occurred; log and report it as needed. Errors that corrupt the state of
	// the transaction/session cannot be silenced from the client.
	$ignore = (
	$this->fieldHasBit( $flags, self::QUERY_SILENCE_ERRORS ) &&
	!$this->fieldHasBit( $qs->flags, self::ERR_ABORT_SESSION ) &&
	!$this->fieldHasBit( $qs->flags, self::ERR_ABORT_TRX )
	);
	$this->reportQueryError(
	$qs->message,
	$qs->code,
	$sqls[$statementId],
	$fname,
	$ignore
	);
	}
	}

	return $statusByStatementId;
	}

	/**
	* Execute a set of queries without enforcing public (non-Database) caller restrictions.
	*
	* Retry it if there is a recoverable connection loss (e.g. no important state lost).
	*
	* This does not precheck for transaction/session state errors or critical section errors.
	*
	* @see Database::query()
	* @see Database::querMulti()
	*
	* @param string\|string[] $sqls SQL statment or (statement ID => SQL statement) map
	* @param string $fname Name of the calling function
	* @param int $flags Bit field of class QUERY_* constants
	* @param string $summarySql Actual/simplified SQL for profiling
	* @return QueryStatus\|array<string,QueryStatus> QueryStatus (when given a string statement)
	* or ordered map of (statement ID => QueryStatus) (when given an array of statements)
	* @throws DBUnexpectedError
	* @since 1.34
	*/
	final protected function executeQuery( $sqls, $fname, $flags, $summarySql ) {
	if ( is_array( $sqls ) ) {
	// Query consists of an atomic batch of statements
	$multiMode = true;
	$statementsById = $sqls;
	} else {
	// Query consists of a single statement
	$multiMode = false;
	$statementsById = [ '*' => $sqls ];
	}

	$this->assertHasConnectionHandle();

	$hasPermWrite = false;
	$cStatementsById = [];
	$tempTableChangesByStatementId = [];
	foreach ( $statementsById as $statementId => $sql ) {
	if ( $this->platform->isWriteQuery( $sql, $flags ) ) {
	$verb = $this->platform->getQueryVerb( $sql );
	// Temporary table writes are not "meaningful" writes, since they are only
	// visible to one (ephemeral) session, so treat them as reads instead. This
	// can be overridden during integration testing via $flags. For simplicity,
	// disallow CREATE/DROP statements during multi queries, avoiding the need
	// to speculatively track whether a table will be temporary at query time.
	if ( $multiMode && in_array( $verb, [ 'CREATE', 'DROP' ] ) ) {
	throw new DBUnexpectedError(
	$this,
	"Cannot issue CREATE/DROP as part of multi-queries"
	);
	}
	$pseudoPermanent = $this->fieldHasBit( $flags, self::QUERY_PSEUDO_PERMANENT );
	$tempTableChanges = $this->getTempTableWrites( $sql, $pseudoPermanent );
	$isPermWrite = !$tempTableChanges;
	foreach ( $tempTableChanges as list( $tmpType ) ) {
	$isPermWrite = $isPermWrite \|\| ( $tmpType !== self::TEMP_NORMAL );
	}
	// Permit temporary table writes on replica connections, but require a writable
	// master connection for writes to persistent tables.
	if ( $isPermWrite ) {
	$this->assertIsWritablePrimary();
	// DBConnRef uses QUERY_REPLICA_ROLE to enforce replica roles during query()
	if ( $this->fieldHasBit( $flags, self::QUERY_REPLICA_ROLE ) ) {
	throw new DBReadOnlyRoleError(
	$this,
	"Cannot write; target role is DB_REPLICA"
	);
	}
	}
	$hasPermWrite = $hasPermWrite \|\| $isPermWrite;
	} else {
	// No temporary tables written to either
	$tempTableChanges = [];
	}
	$tempTableChangesByStatementId[$statementId] = $tempTableChanges;
	// Add agent and calling method comments to the SQL
	$cStatementsById[$statementId] = $this->makeCommentedSql( $sql, $fname );
	}

	// Whether a silent retry attempt is left for recoverable connection loss errors
	$retryLeft = !$this->fieldHasBit( $flags, self::QUERY_NO_RETRY );
	$firstStatement = reset( $statementsById );

	$cs = $this->commenceCriticalSection( __METHOD__ );

	do {
	// Start a DBO_TRX wrapper transaction as needed (throw an error on failure)
	if ( $this->beginIfImplied( $firstStatement, $fname, $flags ) ) {
	// Since begin() was called, any connection loss was already handled
	$retryLeft = false;
	}
	// Send the query statements to the server and fetch any results. Retry all the
	// statements if the error was a recoverable connection loss on the first statement.
	// To reduce the risk of running queries twice, do not retry the statements if there
	// is a connection error during any of the subsequent statements.
	$statusByStatementId = $this->attemptQuery(
	$statementsById,
	$cStatementsById,
	$fname,
	$summarySql,
	$hasPermWrite,
	$multiMode
	);
	} while (
	// Query had at least one statement
	( $firstQs = reset( $statusByStatementId ) ) &&
	// An error occurred that can be recovered from via query retry
	$this->fieldHasBit( $firstQs->flags, self::ERR_RETRY_QUERY ) &&
	// The retry has not been exhausted (consume it now)
	$retryLeft && !( $retryLeft = false )
	);

	foreach ( $statusByStatementId as $statementId => $qs ) {
	// Register creation and dropping of temporary tables
	$this->registerTempWrites( $qs->res, $tempTableChangesByStatementId[$statementId] );
	}

	$this->completeCriticalSection( __METHOD__, $cs );

	return $multiMode ? $statusByStatementId : $statusByStatementId['*'];
	}

	/**
	* Query method wrapper handling profiling, logging, affected row count tracking, and
	* automatic reconnections (without retry) on query failure due to connection loss
	*
	* Note that this does not handle DBO_TRX logic.
	*
	* This method handles profiling, debug logging, reconnection and the tracking of:
	* - write callers
	* - last write time
	* - affected row count of the last write
	* - whether writes occurred in a transaction
	* - last successful query time (confirming that the connection was not dropped)
	*
	* @see doSingleStatementQuery()
	* @see doMultiStatementQuery()
	*
	* @param string[] $statementsById Map of (statement ID => SQL statement)
	* @param string[] $cStatementsById Map of (statement ID => commented SQL statement)
	* @param string $fname Name of the calling function
	* @param string $summarySql Actual/simplified SQL for profiling
	* @param bool $hasPermWrite Whether any of the queries write to permanent tables
	* @param bool $multiMode Whether this is for an anomic statement batch
	* @return array<string,QueryStatus> Map of (statement ID => statement result)
	* @throws DBUnexpectedError
	*/
	private function attemptQuery(
	array $statementsById,
	array $cStatementsById,
	string $fname,
	string $summarySql,
	bool $hasPermWrite,
	bool $multiMode
	) {
	// Treat empty multi-statement query lists as no query at all
	if ( !$statementsById ) {
	return [];
	}

	// Transaction attributes before issuing this query
	$priorSessInfo = $this->getCriticalSessionInfo();

	// Get the transaction-aware SQL string used for profiling
	$prefix = ( $this->topologyRole === self::ROLE_STREAMING_MASTER ) ? 'role-primary: ' : '';
	$generalizedSql = new GeneralizedSql( $summarySql, $prefix );

	$startTime = microtime( true );
	$ps = $this->profiler ? ( $this->profiler )( $generalizedSql->stringify() ) : null;
	$this->lastQuery = $summarySql;
	$this->affectedRowCount = null;
	if ( $hasPermWrite ) {
	$this->lastWriteTime = microtime( true );
	$this->transactionManager->transactionWritingIn(
	$this->getServerName(),
	$this->getDomainID()
	);
	}

	if ( $multiMode ) {
	$qsByStatementId = $this->doMultiStatementQuery( $cStatementsById );
	} else {
	$qsByStatementId = [ '' => $this->doSingleStatementQuery( $cStatementsById[''] ) ];
	}

	unset( $ps ); // profile out (if set)
	$queryRuntime = max( microtime( true ) - $startTime, 0.0 );

	$lastStatus = end( $qsByStatementId );
	// Use the last affected row count for consistency with lastErrno()/lastError()
	$this->affectedRowCount = $lastStatus->rowsAffected;
	// Compute the total number of rows affected by all statements in the query
	$totalAffectedRowCount = 0;
	foreach ( $qsByStatementId as $qs ) {
	$totalAffectedRowCount += $qs->rowsAffected;
	}

	if ( $lastStatus->res !== false ) {
	$this->lastPing = $startTime;
	if ( $hasPermWrite && $this->trxLevel() ) {
	$this->transactionManager->updateTrxWriteQueryReport(
	$summarySql,
	$queryRuntime,
	$totalAffectedRowCount,
	$fname
	);
	}
	}

	$errflags = 0;
	$numRowsReturned = 0;
	$numRowsAffected = 0;
	if ( !$multiMode && $lastStatus->res === false ) {
	$lastSql = end( $statementsById );
	$lastError = $lastStatus->message;
	$lastErrno = $lastStatus->code;
	if ( $this->isConnectionError( $lastErrno ) ) {
	// Connection lost before or during the query...
	// Determine how to proceed given the lost session state
	$connLossFlag = $this->assessConnectionLoss(
	$lastSql,
	$queryRuntime,
	$priorSessInfo
	);
	// Update session state tracking and try to reestablish a connection
	$reconnected = $this->replaceLostConnection( $lastErrno, __METHOD__ );
	// Check if important server-side session-level state was lost
	if ( $connLossFlag >= self::ERR_ABORT_SESSION ) {
	$ex = $this->getQueryException( $lastError, $lastErrno, $lastSql, $fname );
	$this->transactionManager->setSessionError( $ex );
	}
	// Check if important server-side transaction-level state was lost
	if ( $connLossFlag >= self::ERR_ABORT_TRX ) {
	$ex = $this->getQueryException( $lastError, $lastErrno, $lastSql, $fname );
	$this->transactionManager->setTransactionError( $ex );
	}
	// Check if the query should be retried (having made the reconnection attempt)
	if ( $connLossFlag === self::ERR_RETRY_QUERY ) {
	$errflags \|= ( $reconnected ? self::ERR_RETRY_QUERY : self::ERR_ABORT_QUERY );
	} else {
	$errflags \|= $connLossFlag;
	}
	} elseif ( $this->isKnownStatementRollbackError( $lastErrno ) ) {
	// Query error triggered a server-side statement-only rollback...
	$errflags \|= self::ERR_ABORT_QUERY;
	if ( $this->trxLevel() ) {
	// Allow legacy callers to ignore such errors via QUERY_IGNORE_DBO_TRX and
	// try/catch. However, a deprecation notice will be logged on the next query.
	$cause = [ $lastError, $lastErrno, $fname ];
	$this->transactionManager->setTrxStatusIgnoredCause( $cause );
	}
	} elseif ( $this->trxLevel() ) {
	// Some other error occurred during the query, within a transaction...
	// Server-side handling of errors during transactions varies widely depending on
	// the RDBMS type and configuration. There are several possible results: (a) the
	// whole transaction is rolled back, (b) only the queries after BEGIN are rolled
	// back, (c) the transaction is marked as "aborted" and a ROLLBACK is required
	// before other queries are permitted. For compatibility reasons, pessimistically
	// require a ROLLBACK query (not using SAVEPOINT) before allowing other queries.
	$ex = $this->getQueryException( $lastError, $lastErrno, $lastSql, $fname );
	$this->transactionManager->setTransactionError( $ex );
	$errflags \|= self::ERR_ABORT_TRX;
	} else {
	// Some other error occurred during the query, without a transaction...
	$errflags \|= self::ERR_ABORT_QUERY;
	}
	}
	foreach ( $qsByStatementId as $qs ) {
	$qs->flags = $errflags;
	$numRowsReturned += $qs->rowsReturned;
	$numRowsAffected += $qs->rowsAffected;
	}

	if ( !$multiMode && $statementsById['*'] === self::PING_QUERY ) {
	$this->lastRoundTripEstimate = $queryRuntime;
	}

	$this->transactionManager->recordQueryCompletion(
	$generalizedSql,
	$startTime,
	$hasPermWrite,
	$hasPermWrite ? $numRowsAffected : $numRowsReturned,
	$this->getServerName()
	);

	// Avoid the overhead of logging calls unless debug mode is enabled
	if ( $this->getFlag( self::DBO_DEBUG ) ) {
	$this->queryLogger->debug(
	"{method} [{runtime}s] {db_server}: {sql}",
	$this->getLogContext( [
	'method' => $fname,
	'sql' => implode( "; ", $statementsById ),
	'domain' => $this->getDomainID(),
	'runtime' => round( $queryRuntime, 3 ),
	'db_log_category' => 'query'
	] )
	);
	}

	return $qsByStatementId;
	}

	/**
	* @param string $sql
	* @param string $fname
	* @return string
	*/
	private function makeCommentedSql( $sql, $fname ): string {
	// Add trace comment to the begin of the sql string, right after the operator.
	// Or, for one-word queries (like "BEGIN" or COMMIT") add it to the end (T44598).
	// NOTE: Don't add varying ids such as request id or session id to the comment.
	// It would break aggregation of similar queries in analysis tools (see T193050#7512149)
	$encName = preg_replace( '/[\x00-\x1F\/]/', '-', "$fname {$this->agent}" );

	return preg_replace( '/\s\|$/', " /* $encName */ ", $sql, 1 );
	}

	/**
	* Start an implicit transaction if DBO_TRX is enabled and no transaction is active
	*
	* @param string $sql
	* @param string $fname
	* @param int $flags
	* @return bool Whether an implicit transaction was started
	* @throws DBError
	*/
	private function beginIfImplied( $sql, $fname, $flags ) {
	if (
	!$this->fieldHasBit( $flags, self::QUERY_IGNORE_DBO_TRX ) &&
	!$this->trxLevel() &&
	$this->getFlag( self::DBO_TRX ) &&
	$this->platform->isTransactableQuery( $sql )
	) {
	$this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
	$this->transactionManager->turnOnAutomatic();

	return true;
	}

	return false;
	}

	/**
	* Check if the given query is appropriate to run in a public context
	*
	* The caller is assumed to come from outside Database.
	* In order to keep the DB handle's session state tracking in sync, certain queries
	* like "USE", "BEGIN", "COMMIT", and "ROLLBACK" must not be issued directly from
	* outside callers. Such commands should only be issued through dedicated methods
	* like selectDomain(), begin(), commit(), and rollback(), respectively.
	*
	* This also checks if the session state tracking was corrupted by a prior exception.
	*
	* @param string $sql
	* @param string $fname
	* @throws DBUnexpectedError
	* @throws DBTransactionStateError
	*/
	private function assertQueryIsCurrentlyAllowed( string $sql, string $fname ) {
	$verb = $this->platform->getQueryVerb( $sql );

	if ( $verb === 'USE' ) {
	throw new DBUnexpectedError( $this, "Got USE query; use selectDomain() instead" );
	}

	if ( $verb === 'ROLLBACK' ) {
	// Whole transaction rollback is used for recovery
	// @TODO: T269161; prevent "BEGIN"/"COMMIT"/"ROLLBACK" from outside callers
	return;
	}

	if ( $this->csmError ) {
	throw new DBTransactionStateError(
	$this,
	"Cannot execute query from $fname while session state is out of sync",
	[],
	$this->csmError
	);
	}

	$this->transactionManager->assertSessionStatus( $this, $fname );

	if ( $verb !== 'ROLLBACK TO SAVEPOINT' ) {
	$this->transactionManager->assertTransactionStatus(
	$this,
	$this->deprecationLogger,
	$fname
	);
	}
	}

	/**
	* Determine how to handle a connection lost discovered during a query attempt
	*
	* This checks if explicit transactions, pending transaction writes, and important
	* session-level state (locks, temp tables) was lost. Point-in-time read snapshot loss
	* is considered acceptable for DBO_TRX logic.
	*
	* If state was lost, but that loss was discovered during a ROLLBACK that would have
	* destroyed that state anyway, treat the error as recoverable.
	*
	* @param string $sql SQL query statement that encountered or caused the connection loss
	* @param float $walltime How many seconds passes while attempting the query
	* @param CriticalSessionInfo $priorSessInfo Session state just before the query
	* @return int Recovery approach. One of the following ERR_* class constants:
	* - Database::ERR_RETRY_QUERY: reconnect silently, retry query
	* - Database::ERR_ABORT_QUERY: reconnect silently, do not retry query
	* - Database::ERR_ABORT_TRX: reconnect, throw error, enforce transaction rollback
	* - Database::ERR_ABORT_SESSION: reconnect, throw error, enforce session rollback
	*/
	private function assessConnectionLoss(
	string $sql,
	float $walltime,
	CriticalSessionInfo $priorSessInfo
	) {
	$verb = $this->platform->getQueryVerb( $sql );

	if ( $walltime < self::DROPPED_CONN_BLAME_THRESHOLD_SEC ) {
	// Query failed quickly; the connection was probably lost before the query was sent
	$res = self::ERR_RETRY_QUERY;
	} else {
	// Query took a long time; the connection was probably lost during query execution
	$res = self::ERR_ABORT_QUERY;
	}

	// List of problems causing session/transaction state corruption
	$blockers = [];
	// Loss of named locks breaks future callers relying on those locks for critical sections
	foreach ( $priorSessInfo->namedLocks as $lockName => $lockInfo ) {
	if ( $lockInfo['trxId'] && $lockInfo['trxId'] === $priorSessInfo->trxId ) {
	// Treat lost locks acquired during the lost transaction as a transaction state
	// problem. Connection loss on ROLLBACK (non-SAVEPOINT) is tolerable since
	// rollback automatically triggered server-side.
	if ( $verb !== 'ROLLBACK' ) {
	$res = max( $res, self::ERR_ABORT_TRX );
	$blockers[] = "named lock '$lockName'";
	}
	} else {
	// Treat lost locks acquired either during prior transactions or during no
	// transaction as a session state problem.
	$res = max( $res, self::ERR_ABORT_SESSION );
	$blockers[] = "named lock '$lockName'";
	}
	}
	// Loss of temp tables breaks future callers relying on those tables for queries
	foreach ( $priorSessInfo->tempTables as $tableName => $tableInfo ) {
	if ( $tableInfo['trxId'] && $tableInfo['trxId'] === $priorSessInfo->trxId ) {
	// Treat lost temp tables created during the lost transaction as a transaction
	// state problem. Connection loss on ROLLBACK (non-SAVEPOINT) is tolerable since
	// rollback automatically triggered server-side.
	if ( $verb !== 'ROLLBACK' ) {
	$res = max( $res, self::ERR_ABORT_TRX );
	$blockers[] = "temp table '$tableName'";
	}
	} else {
	// Treat lost temp tables created either during prior transactions or during
	// no transaction as a session state problem.
	$res = max( $res, self::ERR_ABORT_SESSION );
	$blockers[] = "temp table '$tableName'";
	}
	}
	// Loss of transaction writes breaks future callers and DBO_TRX logic relying on those
	// writes to be atomic and still pending. Connection loss on ROLLBACK (non-SAVEPOINT) is
	// tolerable since rollback automatically triggered server-side.
	if ( $priorSessInfo->trxWriteCallers && $verb !== 'ROLLBACK' ) {
	$res = max( $res, self::ERR_ABORT_TRX );
	$blockers[] = 'uncommitted writes';
	}
	if ( $priorSessInfo->trxPreCommitCbCallers && $verb !== 'ROLLBACK' ) {
	$res = max( $res, self::ERR_ABORT_TRX );
	$blockers[] = 'pre-commit callbacks';
	}
	if ( $priorSessInfo->trxExplicit && $verb !== 'ROLLBACK' && $sql !== 'COMMIT' ) {
	// Transaction automatically rolled back, breaking the expectations of callers
	// relying on that transaction to provide atomic writes, serializability, or use
	// one point-in-time snapshot for all reads. Assume that connection loss is OK
	// with ROLLBACK (non-SAVEPOINT). Likewise for COMMIT (T127428).
	$res = max( $res, self::ERR_ABORT_TRX );
	$blockers[] = 'explicit transaction';
	}

	if ( $blockers ) {
	$this->connLogger->warning(
	"Silent reconnection to {db_server} could not be attempted: {error}",
	$this->getLogContext( [
	'error' => 'session state loss (' . implode( ', ', $blockers ) . ')',
	'exception' => new RuntimeException(),
	'db_log_category' => 'connection'
	] )
	);
	}

	return $res;
	}

	/**
	* Clean things up after session (and thus transaction) loss before reconnect
	*/
	private function handleSessionLossPreconnect() {
	// Clean up tracking of session-level things...
	// https://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html
	// https://www.postgresql.org/docs/9.2/static/sql-createtable.html (ignoring ON COMMIT)
	$this->sessionTempTables = [];
	// https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
	// https://www.postgresql.org/docs/9.4/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
	$this->sessionNamedLocks = [];
	// Session loss implies transaction loss (T67263)
	$this->transactionManager->clearPreEndCallbacks();
	// Clear additional subclass fields
	$oldTrxId = $this->transactionManager->consumeTrxId();
	$this->doHandleSessionLossPreconnect();
	$this->transactionManager->transactionWritingOut( $this, (string)$oldTrxId );
	}

	/**
	* Reset any additional subclass trx* and session* fields
	* @stable to override
	*/
	protected function doHandleSessionLossPreconnect() {
	// no-op
	}

	/**
	* Clean things up after session (and thus transaction) loss after reconnect
	*/
	private function handleSessionLossPostconnect() {
	// Handle callbacks in trxEndCallbacks, e.g. onTransactionResolution().
	// If callback suppression is set then the array will remain unhandled.
	$this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
	// Handle callbacks in trxRecurringCallbacks, e.g. setTransactionListener().
	// If callback suppression is set then the array will remain unhandled.
	$this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
	}

	/**
	* Checks whether the cause of the error is detected to be a timeout.
	*
	* It returns false by default, and not all engines support detecting this yet.
	* If this returns false, it will be treated as a generic query error.
	*
	* @stable to override
	* @param int\|string $errno Error number
	* @return bool
	* @since 1.39
	*/
	protected function isQueryTimeoutError( $errno ) {
	return false;
	}

	/**
	* Report a query error
	*
	* If $ignore is set, emit a DEBUG level log entry and continue,
	* otherwise, emit an ERROR level log entry and throw an exception.
	*
	* @param string $error
	* @param int\|string $errno
	* @param string $sql
	* @param string $fname
	* @param bool $ignore Whether to just log an error rather than throw an exception
	* @throws DBQueryError
	*/
	public function reportQueryError( $error, $errno, $sql, $fname, $ignore = false ) {
	if ( $ignore ) {
	$this->queryLogger->debug(
	"SQL ERROR (ignored): $error",
	[ 'db_log_category' => 'query' ]
	);
	} else {
	throw $this->getQueryExceptionAndLog( $error, $errno, $sql, $fname );
	}
	}

	/**
	* @param string $error
	* @param string\|int $errno
	* @param string $sql
	* @param string $fname
	* @return DBError
	*/
	private function getQueryExceptionAndLog( $error, $errno, $sql, $fname ) {
	// Information that instances of the same problem have in common should
	// not be normalized (T255202).
	$this->queryLogger->error(
	"Error $errno from $fname, {error} {sql1line} {db_server}",
	$this->getLogContext( [
	'method' => __METHOD__,
	'errno' => $errno,
	'error' => $error,
	'sql1line' => mb_substr( str_replace( "\n", "\\n", $sql ), 0, 5 * 1024 ),
	'fname' => $fname,
	'db_log_category' => 'query',
	'exception' => new RuntimeException()
	] )
	);
	return $this->getQueryException( $error, $errno, $sql, $fname );
	}

	/**
	* @param string $error
	* @param string\|int $errno
	* @param string $sql
	* @param string $fname
	* @return DBError
	*/
	private function getQueryException( $error, $errno, $sql, $fname ) {
	if ( $this->isQueryTimeoutError( $errno ) ) {
	return new DBQueryTimeoutError( $this, $error, $errno, $sql, $fname );
	} elseif ( $this->isConnectionError( $errno ) ) {
	return new DBQueryDisconnectedError( $this, $error, $errno, $sql, $fname );
	} else {
	return new DBQueryError( $this, $error, $errno, $sql, $fname );
	}
	}

	/**
	* @param string $error
	* @return DBConnectionError
	*/
	final protected function newExceptionAfterConnectError( $error ) {
	// Connection was not fully initialized and is not safe for use
	$this->conn = null;

	$this->connLogger->error(
	"Error connecting to {db_server} as user {db_user}: {error}",
	$this->getLogContext( [
	'error' => $error,
	'exception' => new RuntimeException(),
	'db_log_category' => 'connection',
	] )
	);

	return new DBConnectionError( $this, $error );
	}

	/**
	* Get a SelectQueryBuilder bound to this connection. This is overridden by
	* DBConnRef.
	*
	* @return SelectQueryBuilder
	*/
	public function newSelectQueryBuilder(): SelectQueryBuilder {
	return new SelectQueryBuilder( $this );
	}

	public function selectField(
	$table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
	) {
	if ( $var === '*' ) {
	throw new DBUnexpectedError( $this, "Cannot use a * field" );
	} elseif ( is_array( $var ) && count( $var ) !== 1 ) {
	throw new DBUnexpectedError( $this, 'Cannot use more than one field' );
	}

	$options = $this->platform->normalizeOptions( $options );
	$options['LIMIT'] = 1;

	$res = $this->select( $table, $var, $cond, $fname, $options, $join_conds );
	if ( $res === false ) {
	throw new DBUnexpectedError( $this, "Got false from select()" );
	}

	$row = $res->fetchRow();
	if ( $row === false ) {
	return false;
	}

	return reset( $row );
	}

	public function selectFieldValues(
	$table, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
	): array {
	if ( $var === '*' ) {
	throw new DBUnexpectedError( $this, "Cannot use a * field" );
	} elseif ( !is_string( $var ) ) {
	throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
	}

	$options = $this->platform->normalizeOptions( $options );
	$res = $this->select( $table, [ 'value' => $var ], $cond, $fname, $options, $join_conds );
	if ( $res === false ) {
	throw new DBUnexpectedError( $this, "Got false from select()" );
	}

	$values = [];
	foreach ( $res as $row ) {
	$values[] = $row->value;
	}

	return $values;
	}

	public function select(
	$table, $vars, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
	) {
	$options = (array)$options;
	$sql = $this->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
	// Treat SELECT queries with FOR UPDATE as writes. This matches
	// how MySQL enforces read_only (FOR SHARE and LOCK IN SHADE MODE are allowed).
	$flags = in_array( 'FOR UPDATE', $options, true )
	? self::QUERY_CHANGE_ROWS
	: self::QUERY_CHANGE_NONE;

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

	public function selectRow( $table, $vars, $conds, $fname = __METHOD__,
	$options = [], $join_conds = []
	) {
	$options = (array)$options;
	$options['LIMIT'] = 1;

	$res = $this->select( $table, $vars, $conds, $fname, $options, $join_conds );
	if ( $res === false ) {
	throw new DBUnexpectedError( $this, "Got false from select()" );
	}

	if ( !$res->numRows() ) {
	return false;
	}

	return $res->fetchObject();
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function estimateRowCount(
	$tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
	) {
	$conds = $this->platform->normalizeConditions( $conds, $fname );
	$column = $this->platform->extractSingleFieldFromList( $var );
	if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
	$conds[] = "$column IS NOT NULL";
	}

	$res = $this->select(
	$tables, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options, $join_conds
	);
	$row = $res ? $res->fetchRow() : [];

	return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
	}

	public function selectRowCount(
	$tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
	) {
	$conds = $this->platform->normalizeConditions( $conds, $fname );
	$column = $this->platform->extractSingleFieldFromList( $var );
	if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
	$conds[] = "$column IS NOT NULL";
	}

	$res = $this->select(
	[
	'tmp_count' => $this->buildSelectSubquery(
	$tables,
	'1',
	$conds,
	$fname,
	$options,
	$join_conds
	)
	],
	[ 'rowcount' => 'COUNT(*)' ],
	[],
	$fname
	);
	$row = $res ? $res->fetchRow() : [];

	return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
	}

	public function lockForUpdate(
	$table, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
	) {
	if ( !$this->trxLevel() && !$this->getFlag( self::DBO_TRX ) ) {
	throw new DBUnexpectedError(
	$this,
	__METHOD__ . ': no transaction is active nor is DBO_TRX set'
	);
	}

	$options = (array)$options;
	$options[] = 'FOR UPDATE';

	return $this->selectRowCount( $table, '*', $conds, $fname, $options, $join_conds );
	}

	public function fieldExists( $table, $field, $fname = __METHOD__ ) {
	$info = $this->fieldInfo( $table, $field );

	return (bool)$info;
	}

	public function indexExists( $table, $index, $fname = __METHOD__ ) {
	if ( !$this->tableExists( $table, $fname ) ) {
	return null;
	}

	$info = $this->indexInfo( $table, $index, $fname );
	if ( $info === null ) {
	return null;
	} else {
	return $info !== false;
	}
	}

	abstract public function tableExists( $table, $fname = __METHOD__ );

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function indexUnique( $table, $index, $fname = __METHOD__ ) {
	$indexInfo = $this->indexInfo( $table, $index, $fname );

	if ( !$indexInfo ) {
	return false;
	}

	return !$indexInfo[0]->Non_unique;
	}

	public function insert( $table, $rows, $fname = __METHOD__, $options = [] ) {
	$sql = $this->platform->dispatchingInsertSqlText( $table, $rows, $options );
	if ( !$sql ) {
	return true;
	}
	$this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );

	return true;
	}

	public function update( $table, $set, $conds, $fname = __METHOD__, $options = [] ) {
	$sql = $this->platform->updateSqlText( $table, $set, $conds, $options );
	$this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );

	return true;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function databasesAreIndependent() {
	return false;
	}

	final public function selectDB( $db ) {
	$this->selectDomain( new DatabaseDomain(
	$db,
	$this->currentDomain->getSchema(),
	$this->currentDomain->getTablePrefix()
	) );

	return true;
	}

	final public function selectDomain( $domain ) {
	$cs = $this->commenceCriticalSection( __METHOD__ );

	try {
	$this->doSelectDomain( DatabaseDomain::newFromId( $domain ) );
	} catch ( DBError $e ) {
	$this->completeCriticalSection( __METHOD__, $cs );
	throw $e;
	}

	$this->completeCriticalSection( __METHOD__, $cs );
	}

	/**
	* @stable to override
	* @param DatabaseDomain $domain
	* @throws DBConnectionError
	* @throws DBError
	* @since 1.32
	*/
	protected function doSelectDomain( DatabaseDomain $domain ) {
	$this->currentDomain = $domain;
	$this->platform->setCurrentDomain( $this->currentDomain );
	}

	public function getDBname() {
	return $this->currentDomain->getDatabase();
	}

	public function getServer() {
	return $this->connectionParams[self::CONN_HOST] ?? null;
	}

	public function getServerName() {
	return $this->serverName ?? $this->getServer() ?? 'unknown';
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function addQuotes( $s ) {
	if ( $s instanceof Blob ) {
	$s = $s->fetch();
	}
	if ( $s === null ) {
	return 'NULL';
	} elseif ( is_bool( $s ) ) {
	return (string)(int)$s;
	} elseif ( is_int( $s ) ) {
	return (string)$s;
	} else {
	return "'" . $this->strencode( $s ) . "'";
	}
	}

	public function nextSequenceValue( $seqName ) {
	return null;
	}

	public function replace( $table, $uniqueKeys, $rows, $fname = __METHOD__ ) {
	$identityKey = $this->platform->normalizeUpsertParams( $uniqueKeys, $rows );
	if ( !$rows ) {
	return;
	}
	if ( $identityKey ) {
	$this->doReplace( $table, $identityKey, $rows, $fname );
	} else {
	$sql = $this->platform->insertSqlText( $table, $rows );
	$this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
	}
	}

	/**
	* @param string $table
	* @param string[] $identityKey List of columns defining a unique key
	* @param array $rows Non-empty list of rows
	* @param string $fname
	* @see Database::replace()
	* @stable to override
	* @since 1.35
	*/
	protected function doReplace( $table, array $identityKey, array $rows, $fname ) {
	$affectedRowCount = 0;
	$this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
	try {
	foreach ( $rows as $row ) {
	// Delete any conflicting rows (including ones inserted from $rows)
	$sqlCondition = $this->platform->makeKeyCollisionCondition( [ $row ], $identityKey );
	$this->delete( $table, [ $sqlCondition ], $fname );
	$affectedRowCount += $this->affectedRows();
	// Insert the new row
	$this->insert( $table, $row, $fname );
	$affectedRowCount += $this->affectedRows();
	}
	$this->endAtomic( $fname );
	} catch ( DBError $e ) {
	$this->cancelAtomic( $fname );
	throw $e;
	}
	$this->affectedRowCount = $affectedRowCount;
	}

	public function upsert( $table, array $rows, $uniqueKeys, array $set, $fname = __METHOD__ ) {
	$identityKey = $this->platform->normalizeUpsertParams( $uniqueKeys, $rows );
	if ( !$rows ) {
	return true;
	}
	if ( $identityKey ) {
	$this->platform->assertValidUpsertSetArray( $set, $identityKey, $rows );
	$this->doUpsert( $table, $rows, $identityKey, $set, $fname );
	} else {
	$sql = $this->platform->insertSqlText( $table, $rows );
	$this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
	}

	return true;
	}

	/**
	* Perform an UPSERT query
	*
	* @see Database::upsert()
	* @see Database::buildExcludedValue()
	*
	* @stable to override
	*
	* @param string $table Table name
	* @param array[] $rows Non-empty list of rows to insert
	* @param string[] $identityKey Columns of the (unique) identity key to UPSERT upon
	* @param string[] $set Non-empty map of (column name => SQL expression or literal)
	* @param string $fname
	* @since 1.35
	*/
	protected function doUpsert(
	string $table,
	array $rows,
	array $identityKey,
	array $set,
	string $fname
	) {
	$encTable = $this->tableName( $table );
	$sqlColumnAssignments = $this->makeList( $set, self::LIST_SET );
	// Check if there is a SQL assignment expression in $set
	$useWith = isset( $set[0] );

	$affectedRowCount = 0;
	$this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
	try {
	foreach ( $rows as $row ) {
	// Update any existing conflicting row (including ones inserted from $rows)
	[ $sqlColumns, $sqlTuples, $sqlVals ] = $this->platform->makeInsertLists( [ $row ], '__' );
	$sqlConditions = $this->platform->makeKeyCollisionCondition( [ $row ], $identityKey );
	// Since "WITH...AS (VALUES ...)" loses type information, subclasses should
	// override with method if that might cause problems with the SET clause.
	// https://www.sqlite.org/lang_update.html
	// https://mariadb.com/kb/en/with/
	// https://dev.mysql.com/doc/refman/8.0/en/update.html
	// https://www.postgresql.org/docs/9.2/sql-update.html
	$sql =
	( $useWith ? "WITH __VALS ($sqlVals) AS (VALUES $sqlTuples) " : "" ) .
	"UPDATE $encTable SET $sqlColumnAssignments " .
	"WHERE ($sqlConditions)";
	$this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
	$rowsUpdated = $this->affectedRows();
	$affectedRowCount += $rowsUpdated;
	// Insert the new row if there are no conflicts
	if ( $rowsUpdated <= 0 ) {
	// https://sqlite.org/lang_insert.html
	// https://mariadb.com/kb/en/with/
	// https://dev.mysql.com/doc/refman/8.0/en/with.html
	// https://www.postgresql.org/docs/9.2/sql-insert.html
	$sql = "INSERT INTO $encTable ($sqlColumns) VALUES $sqlTuples";
	$this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
	$affectedRowCount += $this->affectedRows();
	}
	}
	} catch ( DBError $e ) {
	$this->cancelAtomic( $fname );
	throw $e;
	}
	$this->endAtomic( $fname );
	// Set the affected row count for the whole operation
	$this->affectedRowCount = $affectedRowCount;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function deleteJoin(
	$delTable,
	$joinTable,
	$delVar,
	$joinVar,
	$conds,
	$fname = __METHOD__
	) {
	$sql = $this->platform->deleteJoinSqlText( $delTable, $joinTable, $delVar, $joinVar, $conds );
	$this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function textFieldSize( $table, $field ) {
	$table = $this->tableName( $table );
	$res = $this->query(
	"SHOW COLUMNS FROM $table LIKE \"$field\"",
	__METHOD__,
	self::QUERY_IGNORE_DBO_TRX \| self::QUERY_CHANGE_NONE
	);
	$row = $res->fetchObject();

	$m = [];

	if ( preg_match( '/$(.*)$/', $row->Type, $m ) ) {
	$size = $m[1];
	} else {
	$size = -1;
	}

	return $size;
	}

	public function delete( $table, $conds, $fname = __METHOD__ ) {
	$sql = $this->platform->deleteSqlText( $table, $conds );
	$this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );

	return true;
	}

	final public function insertSelect(
	$destTable,
	$srcTable,
	$varMap,
	$conds,
	$fname = __METHOD__,
	$insertOptions = [],
	$selectOptions = [],
	$selectJoinConds = []
	) {
	static $hints = [ 'NO_AUTO_COLUMNS' ];

	$insertOptions = $this->platform->normalizeOptions( $insertOptions );
	$selectOptions = $this->platform->normalizeOptions( $selectOptions );

	if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions ) ) {
	// For massive migrations with downtime, we don't want to select everything
	// into memory and OOM, so do all this native on the server side if possible.
	$this->doInsertSelectNative(
	$destTable,
	$srcTable,
	$varMap,
	$conds,
	$fname,
	array_diff( $insertOptions, $hints ),
	$selectOptions,
	$selectJoinConds
	);
	} else {
	$this->doInsertSelectGeneric(
	$destTable,
	$srcTable,
	$varMap,
	$conds,
	$fname,
	array_diff( $insertOptions, $hints ),
	$selectOptions,
	$selectJoinConds
	);
	}

	return true;
	}

	/**
	* @stable to override
	* @param array $insertOptions
	* @param array $selectOptions
	* @return bool Whether an INSERT SELECT with these options will be replication safe
	* @since 1.31
	*/
	protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
	return true;
	}

	/**
	* Implementation of insertSelect() based on select() and insert()
	*
	* @see IDatabase::insertSelect()
	* @param string $destTable
	* @param string\|array $srcTable
	* @param array $varMap
	* @param array $conds
	* @param string $fname
	* @param array $insertOptions
	* @param array $selectOptions
	* @param array $selectJoinConds
	* @since 1.35
	*/
	protected function doInsertSelectGeneric(
	$destTable,
	$srcTable,
	array $varMap,
	$conds,
	$fname,
	array $insertOptions,
	array $selectOptions,
	$selectJoinConds
	) {
	// For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
	// on only the primary DB (without needing row-based-replication). It also makes it easy to
	// know how big the INSERT is going to be.
	$fields = [];
	foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
	$fields[] = $this->platform->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
	}
	$res = $this->select(
	$srcTable,
	implode( ',', $fields ),
	$conds,
	$fname,
	array_merge( $selectOptions, [ 'FOR UPDATE' ] ),
	$selectJoinConds
	);
	if ( !$res ) {
	return;
	}

	$affectedRowCount = 0;
	$this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
	try {
	$rows = [];
	foreach ( $res as $row ) {
	$rows[] = (array)$row;
	}
	// Avoid inserts that are too huge
	$rowBatches = array_chunk( $rows, $this->nonNativeInsertSelectBatchSize );
	foreach ( $rowBatches as $rows ) {
	$this->insert( $destTable, $rows, $fname, $insertOptions );
	$affectedRowCount += $this->affectedRows();
	}
	} catch ( DBError $e ) {
	$this->cancelAtomic( $fname );
	throw $e;
	}
	$this->endAtomic( $fname );
	$this->affectedRowCount = $affectedRowCount;
	}

	/**
	* Native server-side implementation of insertSelect() for situations where
	* we don't want to select everything into memory
	*
	* @see IDatabase::insertSelect()
	* @param string $destTable
	* @param string\|array $srcTable
	* @param array $varMap
	* @param array $conds
	* @param string $fname
	* @param array $insertOptions
	* @param array $selectOptions
	* @param array $selectJoinConds
	* @since 1.35
	*/
	protected function doInsertSelectNative(
	$destTable,
	$srcTable,
	array $varMap,
	$conds,
	$fname,
	array $insertOptions,
	array $selectOptions,
	$selectJoinConds
	) {
	$sql = $this->platform->insertSelectNativeSqlText(
	$destTable,
	$srcTable,
	$varMap,
	$conds,
	$fname,
	$insertOptions,
	$selectOptions,
	$selectJoinConds
	);
	$this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function wasDeadlock() {
	return false;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function wasLockTimeout() {
	return false;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function wasConnectionLoss() {
	return $this->isConnectionError( $this->lastErrno() );
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function wasReadOnlyError() {
	return false;
	}

	public function wasErrorReissuable() {
	return (
	$this->wasDeadlock() \|\|
	$this->wasLockTimeout() \|\|
	$this->wasConnectionLoss()
	);
	}

	/**
	* Do not use this method outside of Database/DBError classes
	*
	* @stable to override
	* @param int\|string $errno
	* @return bool Whether the given query error was a connection drop
	* @since 1.38
	*/
	protected function isConnectionError( $errno ) {
	return false;
	}

	/**
	* @stable to override
	* @param int\|string $errno
	* @return bool Whether it is known that the last query error only caused statement rollback
	* @note This is for backwards compatibility for callers catching DBError exceptions in
	* order to ignore problems like duplicate key errors or foreign key violations
	* @since 1.39
	*/
	protected function isKnownStatementRollbackError( $errno ) {
	return false; // don't know; it could have caused a transaction rollback
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function deadlockLoop( ...$args ) {
	$function = array_shift( $args );
	$tries = self::DEADLOCK_TRIES;

	$this->begin( __METHOD__ );

	$retVal = null;
	/** @var Throwable $e */
	$e = null;
	do {
	try {
	$retVal = $function( ...$args );
	break;
	} catch ( DBQueryError $e ) {
	if ( $this->wasDeadlock() ) {
	// Retry after a randomized delay
	usleep( mt_rand( self::DEADLOCK_DELAY_MIN, self::DEADLOCK_DELAY_MAX ) );
	} else {
	// Throw the error back up
	throw $e;
	}
	}
	} while ( --$tries > 0 );

	if ( $tries <= 0 ) {
	// Too many deadlocks; give up
	$this->rollback( __METHOD__ );
	throw $e;
	} else {
	$this->commit( __METHOD__ );

	return $retVal;
	}
	}

	/**
	* @inheritDoc
	* @since 1.37
	* @stable to override
	*/
	public function primaryPosWait( DBPrimaryPos $pos, $timeout ) {
	# Real waits are implemented in the subclass.
	return 0;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function getReplicaPos() {
	# Stub
	return false;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function getPrimaryPos() {
	# Stub
	return false;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function serverIsReadOnly() {
	return false;
	}

	final public function onTransactionResolution( callable $callback, $fname = __METHOD__ ) {
	$this->transactionManager->onTransactionResolution( $this, $callback, $fname );
	}

	final public function onTransactionCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
	if ( !$this->trxLevel() && $this->getTransactionRoundId() ) {
	// This DB handle is set to participate in LoadBalancer transaction rounds and
	// an explicit transaction round is active. Start an implicit transaction on this
	// DB handle (setting trxAutomatic) similar to how query() does in such situations.
	$this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
	}

	$this->transactionManager->addPostCommitOrIdleCallback( $callback, $fname );
	if ( !$this->trxLevel() ) {
	$dbErrors = [];
	$this->runOnTransactionIdleCallbacks( self::TRIGGER_IDLE, $dbErrors );
	if ( $dbErrors ) {
	throw $dbErrors[0];
	}
	}
	}

	final public function onTransactionPreCommitOrIdle( callable $callback, $fname = __METHOD__ ) {
	if ( !$this->trxLevel() && $this->getTransactionRoundId() ) {
	// This DB handle is set to participate in LoadBalancer transaction rounds and
	// an explicit transaction round is active. Start an implicit transaction on this
	// DB handle (setting trxAutomatic) similar to how query() does in such situations.
	$this->begin( __METHOD__, self::TRANSACTION_INTERNAL );
	}

	if ( $this->trxLevel() ) {
	$this->transactionManager->addPreCommitOrIdleCallback(
	$callback,
	$fname
	);
	} else {
	// No transaction is active nor will start implicitly, so make one for this callback
	$this->startAtomic( __METHOD__, self::ATOMIC_CANCELABLE );
	try {
	$callback( $this );
	} catch ( Throwable $e ) {
	// Avoid confusing error reporting during critical section errors
	if ( !$this->csmError ) {
	$this->cancelAtomic( __METHOD__ );
	}
	throw $e;
	}
	$this->endAtomic( __METHOD__ );
	}
	}

	final public function onAtomicSectionCancel( callable $callback, $fname = __METHOD__ ) {
	$this->transactionManager->onAtomicSectionCancel( $this, $callback, $fname );
	}

	final public function setTransactionListener( $name, callable $callback = null ) {
	$this->transactionManager->setTransactionListener( $name, $callback );
	}

	/**
	* Whether to disable running of post-COMMIT/ROLLBACK callbacks
	*
	* @internal This method should not be used outside of Database/LoadBalancer
	*
	* @since 1.28
	* @param bool $suppress
	*/
	final public function setTrxEndCallbackSuppression( $suppress ) {
	$this->transactionManager->setTrxEndCallbackSuppression( $suppress );
	}

	/**
	* Consume and run any "on transaction idle/resolution" callbacks
	*
	* @internal This method should not be used outside of Database/LoadBalancer
	*
	* @since 1.20
	* @param int $trigger IDatabase::TRIGGER_* constant
	* @param DBError[] &$errors DB exceptions caught [returned]
	* @return int Number of callbacks attempted
	* @throws DBUnexpectedError
	* @throws Throwable Any non-DBError exception thrown by a callback
	*/
	public function runOnTransactionIdleCallbacks( $trigger, array &$errors = [] ) {
	if ( $this->trxLevel() ) {
	throw new DBUnexpectedError( $this, __METHOD__ . ': a transaction is still open' );
	}

	if ( $this->transactionManager->isEndCallbacksSuppressed() ) {
	// Execution deferred by LoadBalancer for explicit execution later
	return 0;
	}

	$cs = $this->commenceCriticalSection( __METHOD__ );

	$count = 0;
	$autoTrx = $this->getFlag( self::DBO_TRX ); // automatic begin() enabled?
	// Drain the queues of transaction "idle" and "end" callbacks until they are empty
	do {
	$callbackEntries = $this->transactionManager->consumeEndCallbacks( $trigger );
	$count += count( $callbackEntries );
	foreach ( $callbackEntries as $entry ) {
	$this->clearFlag( self::DBO_TRX ); // make each query its own transaction
	try {
	$entry[0]( $trigger, $this );
	} catch ( DBError $ex ) {
	call_user_func( $this->errorLogger, $ex );
	$errors[] = $ex;
	// Some callbacks may use startAtomic/endAtomic, so make sure
	// their transactions are ended so other callbacks don't fail
	if ( $this->trxLevel() ) {
	$this->rollback( __METHOD__, self::FLUSHING_INTERNAL );
	}
	} finally {
	if ( $autoTrx ) {
	$this->setFlag( self::DBO_TRX ); // restore automatic begin()
	} else {
	$this->clearFlag( self::DBO_TRX ); // restore auto-commit
	}
	}
	}
	} while ( $this->transactionManager->countPostCommitOrIdleCallbacks() );

	$this->completeCriticalSection( __METHOD__, $cs );

	return $count;
	}

	/**
	* Actually run any "transaction listener" callbacks
	*
	* @internal This method should not be used outside of Database/LoadBalancer
	*
	* @since 1.20
	* @param int $trigger IDatabase::TRIGGER_* constant
	* @param DBError[] &$errors DB exceptions caught [returned]
	* @throws Throwable Any non-DBError exception thrown by a callback
	*/
	public function runTransactionListenerCallbacks( $trigger, array &$errors = [] ) {
	if ( $this->transactionManager->isEndCallbacksSuppressed() ) {
	// Execution deferred by LoadBalancer for explicit execution later
	return;
	}

	// These callbacks should only be registered in setup, thus no iteration is needed
	foreach ( $this->transactionManager->getRecurringCallbacks() as $callback ) {
	try {
	$callback( $trigger, $this );
	} catch ( DBError $ex ) {
	( $this->errorLogger )( $ex );
	$errors[] = $ex;
	}
	}
	}

	/**
	* Handle "on transaction idle/resolution" and "transaction listener" callbacks post-COMMIT
	*
	* @throws DBError The first DBError exception thrown by a callback
	* @throws Throwable Any non-DBError exception thrown by a callback
	*/
	private function runTransactionPostCommitCallbacks() {
	$dbErrors = [];
	$this->runOnTransactionIdleCallbacks( self::TRIGGER_COMMIT, $dbErrors );
	$this->runTransactionListenerCallbacks( self::TRIGGER_COMMIT, $dbErrors );
	$this->affectedRowCount = 0; // for the sake of consistency
	if ( $dbErrors ) {
	throw $dbErrors[0];
	}
	}

	/**
	* Handle "on transaction idle/resolution" and "transaction listener" callbacks post-ROLLBACK
	*
	* This will suppress and log any DBError exceptions
	*
	* @throws Throwable Any non-DBError exception thrown by a callback
	*/
	private function runTransactionPostRollbackCallbacks() {
	$this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
	$this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
	$this->affectedRowCount = 0; // for the sake of consistency
	}

	final public function startAtomic(
	$fname = __METHOD__,
	$cancelable = self::ATOMIC_NOT_CANCELABLE
	) {
	$cs = $this->commenceCriticalSection( __METHOD__ );

	if ( $this->trxLevel() ) {
	// This atomic section is only one part of a larger transaction
	$sectionOwnsTrx = false;
	} else {
	// Start an implicit transaction (sets trxAutomatic)
	try {
	$this->begin( $fname, self::TRANSACTION_INTERNAL );
	} catch ( DBError $e ) {
	$this->completeCriticalSection( __METHOD__, $cs );
	throw $e;
	}
	if ( $this->getFlag( self::DBO_TRX ) ) {
	// This DB handle participates in LoadBalancer transaction rounds; all atomic
	// sections should be buffered into one transaction (e.g. to keep web requests
	// transactional). Note that an implicit transaction round is considered to be
	// active when no there is no explicit transaction round.
	$sectionOwnsTrx = false;
	} else {
	// This DB handle does not participate in LoadBalancer transaction rounds;
	// each topmost atomic section will use its own transaction.
	$sectionOwnsTrx = true;
	}
	$this->transactionManager->setAutomaticAtomic( $sectionOwnsTrx );
	}

	if ( $cancelable === self::ATOMIC_CANCELABLE ) {
	if ( $sectionOwnsTrx ) {
	// This atomic section is synonymous with the whole transaction; just
	// use full COMMIT/ROLLBACK in endAtomic()/cancelAtomic(), respectively
	$savepointId = self::NOT_APPLICABLE;
	} else {
	// This atomic section is only part of the whole transaction; use a SAVEPOINT
	// query so that its changes can be cancelled without losing the rest of the
	// transaction (e.g. changes from other sections or from outside of sections)
	try {
	$savepointId = $this->nextSavepointId( $fname );
	$sql = $this->platform->savepointSqlText( $savepointId );
	$this->query( $sql, $fname, self::QUERY_CHANGE_TRX );
	} catch ( DBError $e ) {
	$this->completeCriticalSection( __METHOD__, $cs, $e );
	throw $e;
	}
	}
	} else {
	$savepointId = null;
	}

	$sectionId = new AtomicSectionIdentifier;
	$this->transactionManager->addToAtomicLevels( $fname, $sectionId, $savepointId );

	$this->completeCriticalSection( __METHOD__, $cs );

	return $sectionId;
	}

	final public function endAtomic( $fname = __METHOD__ ) {
	list( $savepointId, $sectionId ) = $this->transactionManager->onEndAtomic( $this, $fname );

	$runPostCommitCallbacks = false;

	$cs = $this->commenceCriticalSection( __METHOD__ );

	// Remove the last section (no need to re-index the array)
	$this->transactionManager->popAtomicLevel();

	try {
	if ( $this->transactionManager->isClean() ) {
	$this->commit( $fname, self::FLUSHING_INTERNAL );
	$runPostCommitCallbacks = true;
	} elseif ( $savepointId !== null && $savepointId !== self::NOT_APPLICABLE ) {
	$sql = $this->platform->releaseSavepointSqlText( $savepointId );
	$this->query( $sql, $fname, self::QUERY_CHANGE_TRX );
	}
	} catch ( DBError $e ) {
	$this->completeCriticalSection( __METHOD__, $cs, $e );
	throw $e;
	}

	$this->transactionManager->onEndAtomicInCriticalSection( $sectionId );

	$this->completeCriticalSection( __METHOD__, $cs );

	if ( $runPostCommitCallbacks ) {
	$this->runTransactionPostCommitCallbacks();
	}
	}

	final public function cancelAtomic(
	$fname = __METHOD__,
	AtomicSectionIdentifier $sectionId = null
	) {
	$this->transactionManager->onCancelAtomicBeforeCriticalSection( $this, $fname );
	$pos = $this->transactionManager->getPositionFromSectionId( $sectionId );
	if ( $pos < 0 ) {
	throw new DBUnexpectedError( $this, "Atomic section not found (for $fname)" );
	}

	$cs = $this->commenceCriticalSection( __METHOD__ );
	$runPostRollbackCallbacks = false;
	list( $savedFname, $excisedIds, $newTopSection, $savedSectionId, $savepointId ) =
	$this->transactionManager->cancelAtomic( $pos );

	try {
	if ( $savedFname !== $fname ) {
	$e = new DBUnexpectedError(
	$this,
	"Invalid atomic section ended (got $fname but expected $savedFname)"
	);
	$this->completeCriticalSection( __METHOD__, $cs, $e );
	throw $e;
	}

	// Remove the last section (no need to re-index the array)
	$this->transactionManager->popAtomicLevel();
	$excisedIds[] = $savedSectionId;
	$newTopSection = $this->transactionManager->currentAtomicSectionId();

	if ( $savepointId !== null ) {
	// Rollback the transaction changes proposed within this atomic section
	if ( $savepointId === self::NOT_APPLICABLE ) {
	// Atomic section started the transaction; rollback the whole transaction
	// and trigger cancellation callbacks for all active atomic sections
	$this->rollback( $fname, self::FLUSHING_INTERNAL );
	$runPostRollbackCallbacks = true;
	} else {
	// Atomic section nested within the transaction; rollback the transaction
	// to the state prior to this section and trigger its cancellation callbacks
	$sql = $this->platform->rollbackToSavepointSqlText( $savepointId );
	$this->query( $sql, $fname, self::QUERY_CHANGE_TRX );
	$this->transactionManager->setTrxStatusToOk(); // no exception; recovered
	$this->transactionManager->runOnAtomicSectionCancelCallbacks(
	$this,
	self::TRIGGER_CANCEL,
	$excisedIds
	);
	}
	} else {
	// Put the transaction into an error state if it's not already in one
	$trxError = new DBUnexpectedError(
	$this,
	"Uncancelable atomic section canceled (got $fname)"
	);
	$this->transactionManager->setTransactionError( $trxError );
	}
	} finally {
	// Fix up callbacks owned by the sections that were just cancelled.
	// All callbacks should have an owner that is present in trxAtomicLevels.
	$this->transactionManager->modifyCallbacksForCancel( $this, $excisedIds, $newTopSection );
	}

	$this->affectedRowCount = 0; // for the sake of consistency

	$this->completeCriticalSection( __METHOD__, $cs );

	if ( $runPostRollbackCallbacks ) {
	$this->runTransactionPostRollbackCallbacks();
	}
	}

	final public function doAtomicSection(
	$fname,
	callable $callback,
	$cancelable = self::ATOMIC_NOT_CANCELABLE
	) {
	$sectionId = $this->startAtomic( $fname, $cancelable );
	try {
	$res = $callback( $this, $fname );
	} catch ( Throwable $e ) {
	// Avoid confusing error reporting during critical section errors
	if ( !$this->csmError ) {
	$this->cancelAtomic( $fname, $sectionId );
	}

	throw $e;
	}
	$this->endAtomic( $fname );

	return $res;
	}

	final public function begin( $fname = __METHOD__, $mode = self::TRANSACTION_EXPLICIT ) {
	static $modes = [ self::TRANSACTION_EXPLICIT, self::TRANSACTION_INTERNAL ];
	if ( !in_array( $mode, $modes, true ) ) {
	throw new DBUnexpectedError( $this, "$fname: invalid mode parameter '$mode'" );
	}

	// Protect against mismatched atomic section, transaction nesting, and snapshot loss
	if ( $this->trxLevel() ) {
	$this->transactionManager->onBeginTransaction( $this, $fname );
	} elseif ( $this->getFlag( self::DBO_TRX ) && $mode !== self::TRANSACTION_INTERNAL ) {
	$msg = "$fname: implicit transaction expected (DBO_TRX set)";
	throw new DBUnexpectedError( $this, $msg );
	}

	$this->assertHasConnectionHandle();

	$cs = $this->commenceCriticalSection( __METHOD__ );
	try {
	$this->doBegin( $fname );
	} catch ( DBError $e ) {
	$this->completeCriticalSection( __METHOD__, $cs );
	throw $e;
	}
	$this->transactionManager->newTrxId( $mode, $fname );
	// With REPEATABLE-READ isolation, the first SELECT establishes the read snapshot,
	// so get the replication lag estimate before any transaction SELECT queries come in.
	// This way, the lag estimate reflects what will actually be read. Also, if heartbeat
	// tables are used, this avoids counting snapshot lag as part of replication lag.
	$this->trxReplicaLagStatus = null; // clear cached value first
	$this->trxReplicaLagStatus = $this->getApproximateLagStatus();

	$this->completeCriticalSection( __METHOD__, $cs );
	}

	/**
	* Issues the BEGIN command to the database server.
	*
	* @see Database::begin()
	* @stable to override
	* @param string $fname
	* @throws DBError
	*/
	protected function doBegin( $fname ) {
	$this->query( 'BEGIN', $fname, self::QUERY_CHANGE_TRX );
	}

	final public function commit( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
	static $modes = [ self::FLUSHING_ONE, self::FLUSHING_ALL_PEERS, self::FLUSHING_INTERNAL ];
	if ( !in_array( $flush, $modes, true ) ) {
	throw new DBUnexpectedError( $this, "$fname: invalid flush parameter '$flush'" );
	}

	if ( !$this->transactionManager->onCommit( $this, $fname, $flush ) ) {
	return;
	}

	$this->assertHasConnectionHandle();

	$this->runOnTransactionPreCommitCallbacks();

	$cs = $this->commenceCriticalSection( __METHOD__ );
	try {
	$this->doCommit( $fname );
	} catch ( DBError $e ) {
	$this->completeCriticalSection( __METHOD__, $cs );
	throw $e;
	}
	$lastWriteTime = $this->transactionManager->onCommitInCriticalSection( $this );
	if ( $lastWriteTime ) {
	$this->lastWriteTime = $lastWriteTime;
	}
	// With FLUSHING_ALL_PEERS, callbacks will run when requested by a dedicated phase
	// within LoadBalancer. With FLUSHING_INTERNAL, callbacks will run when requested by
	// the Database caller during a safe point. This avoids isolation and recursion issues.
	if ( $flush === self::FLUSHING_ONE ) {
	$this->runTransactionPostCommitCallbacks();
	}
	$this->completeCriticalSection( __METHOD__, $cs );
	}

	/**
	* Issues the COMMIT command to the database server.
	*
	* @stable to override
	* @see Database::commit()
	* @param string $fname
	* @throws DBError
	*/
	protected function doCommit( $fname ) {
	if ( $this->trxLevel() ) {
	$this->query( 'COMMIT', $fname, self::QUERY_CHANGE_TRX );
	}
	}

	final public function rollback( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
	if (
	$flush !== self::FLUSHING_INTERNAL &&
	$flush !== self::FLUSHING_ALL_PEERS &&
	$this->getFlag( self::DBO_TRX )
	) {
	throw new DBUnexpectedError(
	$this,
	"$fname: Expected mass rollback of all peer transactions (DBO_TRX set)"
	);
	}

	if ( !$this->trxLevel() ) {
	$this->transactionManager->setTrxStatusToNone();
	$this->transactionManager->clearPreEndCallbacks();
	if ( $this->transactionManager->trxLevel() <= TransactionManager::STATUS_TRX_ERROR ) {
	$this->connLogger->info(
	"$fname: acknowledged server-side transaction loss on {db_server}",
	$this->getLogContext()
	);
	}

	return;
	}

	$this->assertHasConnectionHandle();

	$cs = $this->commenceCriticalSection( __METHOD__ );
	$sql = $this->platform->rollbackSqlText();
	if ( $this->trxLevel() ) {
	# Disconnects cause rollback anyway, so ignore those errors
	$this->query( $sql, $fname, self::QUERY_SILENCE_ERRORS \| self::QUERY_CHANGE_TRX );
	}
	$this->transactionManager->onRollback( $this );
	// With FLUSHING_ALL_PEERS, callbacks will run when requested by a dedicated phase
	// within LoadBalancer. With FLUSHING_INTERNAL, callbacks will run when requested by
	// the Database caller during a safe point. This avoids isolation and recursion issues.
	if ( $flush === self::FLUSHING_ONE ) {
	$this->runTransactionPostRollbackCallbacks();
	}
	$this->completeCriticalSection( __METHOD__, $cs );
	}

	/**
	* @internal Only for tests and highly discouraged
	* @param TransactionManager $transactionManager
	*/
	public function setTransactionManager( TransactionManager $transactionManager ) {
	$this->transactionManager = $transactionManager;
	}

	public function flushSession( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
	if ( $this->trxLevel() ) {
	// Any existing transaction should have been rolled back already
	throw new DBUnexpectedError(
	$this,
	"$fname: transaction still in progress (not yet rolled back)"
	);
	}

	if (
	$flush !== self::FLUSHING_INTERNAL &&
	$flush !== self::FLUSHING_ALL_PEERS &&
	$this->getFlag( self::DBO_TRX )
	) {
	throw new DBUnexpectedError(
	$this,
	"$fname: Expected mass flush of all peer connections (DBO_TRX set)"
	);
	}

	// If the session state was already lost due to either an unacknowledged session
	// state loss error (e.g. dropped connection) or an explicit connection close call,
	// then there is nothing to do here. Note that such cases, even temporary tables and
	// server-side config variables are lost (the invocation of this method is assumed to
	// imply that such losses are tolerable).
	if ( $this->transactionManager->sessionStatus() <= TransactionManager::STATUS_SESS_ERROR ) {
	$this->connLogger->info(
	"$fname: acknowledged server-side session loss on {db_server}",
	$this->getLogContext()
	);
	} elseif ( $this->isOpen() ) {
	// Connection handle exists; server-side session state must be flushed
	$this->doFlushSession( $fname );
	$this->sessionNamedLocks = [];
	}

	$this->transactionManager->clearSessionError();
	}

	/**
	* Reset the server-side session state for named locks and table locks
	*
	* Connection and query errors will be suppressed and logged
	*
	* @param string $fname
	* @since 1.38
	*/
	protected function doFlushSession( $fname ) {
	// no-op
	}

	public function flushSnapshot( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
	$this->transactionManager->onFlushSnapshot( $this, $fname, $flush, $this->getTransactionRoundId() );
	$this->commit( $fname, self::FLUSHING_INTERNAL );
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function duplicateTableStructure(
	$oldName,
	$newName,
	$temporary = false,
	$fname = __METHOD__
	) {
	throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function listTables( $prefix = null, $fname = __METHOD__ ) {
	throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function listViews( $prefix = null, $fname = __METHOD__ ) {
	throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
	}

	public function affectedRows() {
	return $this->affectedRowCount ?? $this->fetchAffectedRowCount();
	}

	/**
	* @return int Number of retrieved rows according to the driver
	*/
	abstract protected function fetchAffectedRowCount();

	public function ping( &$rtt = null ) {
	// Avoid hitting the server if it was hit recently
	if ( $this->isOpen() ) {
	if ( ( microtime( true ) - $this->lastPing ) < self::PING_TTL &&
	( !func_num_args() \|\| $this->lastRoundTripEstimate > 0 )
	) {
	$rtt = $this->lastRoundTripEstimate;
	return true; // don't care about $rtt
	}
	// This will reconnect if possible or return false if not
	$flags = self::QUERY_IGNORE_DBO_TRX \| self::QUERY_SILENCE_ERRORS \| self::QUERY_CHANGE_NONE;
	$ok = ( $this->query( self::PING_QUERY, __METHOD__, $flags ) !== false );
	if ( $ok ) {
	$rtt = $this->lastRoundTripEstimate;
	}
	} else {
	$ok = $this->replaceLostConnection( null, __METHOD__ );
	}

	return $ok;
	}

	/**
	* Close any existing (dead) database connection and open a new connection
	*
	* @param int\|null $lastErrno
	* @param string $fname
	* @return bool True if new connection is opened successfully, false if error
	*/
	protected function replaceLostConnection( $lastErrno, $fname ) {
	if ( $this->conn ) {
	$this->closeConnection();
	$this->conn = null;
	$this->handleSessionLossPreconnect();
	}

	try {
	$this->open(
	$this->connectionParams[self::CONN_HOST],
	$this->connectionParams[self::CONN_USER],
	$this->connectionParams[self::CONN_PASSWORD],
	$this->currentDomain->getDatabase(),
	$this->currentDomain->getSchema(),
	$this->tablePrefix()
	);
	$this->lastPing = microtime( true );
	$ok = true;

	$this->connLogger->warning(
	$fname . ': lost connection to {db_server} with error {errno}; reconnected',
	$this->getLogContext( [
	'exception' => new RuntimeException(),
	'db_log_category' => 'connection',
	'errno' => $lastErrno
	] )
	);
	} catch ( DBConnectionError $e ) {
	$ok = false;

	$this->connLogger->error(
	$fname . ': lost connection to {db_server} with error {errno}; reconnection failed: {connect_msg}',
	$this->getLogContext( [
	'exception' => new RuntimeException(),
	'db_log_category' => 'connection',
	'errno' => $lastErrno,
	'connect_msg' => $e->getMessage()
	] )
	);
	}

	$this->handleSessionLossPostconnect();

	return $ok;
	}

	public function getSessionLagStatus() {
	return $this->getRecordedTransactionLagStatus() ?: $this->getApproximateLagStatus();
	}

	/**
	* Get the replica DB lag when the current transaction started
	*
	* This is useful given that transactions might use point-in-time read snapshots,
	* in which case the lag estimate should be recorded just before the transaction
	* establishes the read snapshot (either BEGIN or the first SELECT/write query).
	*
	* If snapshots are not used, it is still safe to be pessimistic.
	*
	* This returns null if there is no transaction or the lag status was not yet recorded.
	*
	* @return array\|null ('lag': seconds or false, 'since': UNIX timestamp of BEGIN) or null
	* @since 1.27
	*/
	final protected function getRecordedTransactionLagStatus() {
	return $this->trxLevel() ? $this->trxReplicaLagStatus : null;
	}

	/**
	* Get a replica DB lag estimate for this server at the start of a transaction
	*
	* This is a no-op unless the server is known a priori to be a replica DB
	*
	* @stable to override
	* @return array ('lag': seconds or false on error, 'since': UNIX timestamp of estimate)
	* @since 1.27
	*/
	protected function getApproximateLagStatus() {
	if ( $this->topologyRole === self::ROLE_STREAMING_REPLICA ) {
	// Avoid exceptions as this is used internally in critical sections
	try {
	$lag = $this->getLag();
	} catch ( DBError $e ) {
	$lag = false;
	}
	} else {
	$lag = 0;
	}

	return [ 'lag' => $lag, 'since' => microtime( true ) ];
	}

	/**
	* Merge the result of getSessionLagStatus() for several DBs
	* using the most pessimistic values to estimate the lag of
	* any data derived from them in combination
	*
	* This is information is useful for caching modules
	*
	* @see WANObjectCache::set()
	* @see WANObjectCache::getWithSetCallback()
	*
	* @param IDatabase\|null ...$dbs
	* Note: For backward compatibility, it is allowed for null values
	* to be passed among the parameters. This is deprecated since 1.36,
	* only IDatabase objects should be passed.
	*
	* @return array Map of values:
	* - lag: highest lag of any of the DBs or false on error (e.g. replication stopped)
	* - since: oldest UNIX timestamp of any of the DB lag estimates
	* - pending: whether any of the DBs have uncommitted changes
	* @throws DBError
	* @since 1.27
	*/
	public static function getCacheSetOptions( ?IDatabase ...$dbs ) {
	$res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];

	foreach ( func_get_args() as $db ) {
	if ( $db instanceof IDatabase ) {
	$status = $db->getSessionLagStatus();

	if ( $status['lag'] === false ) {
	$res['lag'] = false;
	} elseif ( $res['lag'] !== false ) {
	$res['lag'] = max( $res['lag'], $status['lag'] );
	}
	$res['since'] = min( $res['since'], $status['since'] );
	$res['pending'] = $res['pending'] ?: $db->writesPending();
	}
	}

	return $res;
	}

	public function getLag() {
	if ( $this->topologyRole === self::ROLE_STREAMING_MASTER ) {
	return 0; // this is the primary DB
	} elseif ( $this->topologyRole === self::ROLE_STATIC_CLONE ) {
	return 0; // static dataset
	}

	return $this->doGetLag();
	}

	/**
	* Get the amount of replication lag for this database server
	*
	* Callers should avoid using this method while a transaction is active
	*
	* @see getLag()
	*
	* @stable to override
	* @return float\|int\|false Database replication lag in seconds or false on error
	* @throws DBError
	*/
	protected function doGetLag() {
	return 0;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function encodeBlob( $b ) {
	return $b;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function decodeBlob( $b ) {
	if ( $b instanceof Blob ) {
	$b = $b->fetch();
	}
	return $b;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function setSessionOptions( array $options ) {
	}

	public function sourceFile(
	$filename,
	callable $lineCallback = null,
	callable $resultCallback = null,
	$fname = false,
	callable $inputCallback = null
	) {
	AtEase::suppressWarnings();
	$fp = fopen( $filename, 'r' );
	AtEase::restoreWarnings();

	if ( $fp === false ) {
	throw new RuntimeException( "Could not open \"{$filename}\"" );
	}

	if ( !$fname ) {
	$fname = __METHOD__ . "( $filename )";
	}

	try {
	return $this->sourceStream(
	$fp,
	$lineCallback,
	$resultCallback,
	$fname,
	$inputCallback
	);
	} finally {
	fclose( $fp );
	}
	}

	public function sourceStream(
	$fp,
	callable $lineCallback = null,
	callable $resultCallback = null,
	$fname = __METHOD__,
	callable $inputCallback = null
	) {
	$delimiterReset = new ScopedCallback(
	function ( $delimiter ) {
	$this->delimiter = $delimiter;
	},
	[ $this->delimiter ]
	);
	$cmd = '';

	while ( !feof( $fp ) ) {
	if ( $lineCallback ) {
	call_user_func( $lineCallback );
	}

	$line = trim( fgets( $fp ) );

	if ( $line == '' ) {
	continue;
	}

	if ( $line[0] == '-' && $line[1] == '-' ) {
	continue;
	}

	if ( $cmd != '' ) {
	$cmd .= ' ';
	}

	$done = $this->streamStatementEnd( $cmd, $line );

	$cmd .= "$line\n";

	if ( $done \|\| feof( $fp ) ) {
	$cmd = $this->platform->replaceVars( $cmd );

	if ( $inputCallback ) {
	$callbackResult = $inputCallback( $cmd );

	if ( is_string( $callbackResult ) \|\| !$callbackResult ) {
	$cmd = $callbackResult;
	}
	}

	if ( $cmd ) {
	$res = $this->query( $cmd, $fname );

	if ( $resultCallback ) {
	$resultCallback( $res, $this );
	}

	if ( $res === false ) {
	$err = $this->lastError();

	return "Query \"{$cmd}\" failed with error code \"$err\".\n";
	}
	}
	$cmd = '';
	}
	}

	ScopedCallback::consume( $delimiterReset );
	return true;
	}

	/**
	* Called by sourceStream() to check if we've reached a statement end
	*
	* @stable to override
	* @param string &$sql SQL assembled so far
	* @param string &$newLine New line about to be added to $sql
	* @return bool Whether $newLine contains end of the statement
	*/
	public function streamStatementEnd( &$sql, &$newLine ) {
	if ( $this->delimiter ) {
	$prev = $newLine;
	$newLine = preg_replace(
	'/' . preg_quote( $this->delimiter, '/' ) . '$/',
	'',
	$newLine
	);
	if ( $newLine != $prev ) {
	return true;
	}
	}

	return false;
	}

	/**
	* @inheritDoc
	*/
	public function lockIsFree( $lockName, $method ) {
	// RDBMs methods for checking named locks may or may not count this thread itself.
	// In MySQL, IS_FREE_LOCK() returns 0 if the thread already has the lock. This is
	// the behavior chosen by the interface for this method.
	if ( isset( $this->sessionNamedLocks[$lockName] ) ) {
	$lockIsFree = false;
	} else {
	$lockIsFree = $this->doLockIsFree( $lockName, $method );
	}

	return $lockIsFree;
	}

	/**
	* @see lockIsFree()
	*
	* @param string $lockName
	* @param string $method
	* @return bool Success
	* @throws DBError
	* @stable to override
	*/
	protected function doLockIsFree( string $lockName, string $method ) {
	return true; // not implemented
	}

	/**
	* @inheritDoc
	*/
	public function lock( $lockName, $method, $timeout = 5, $flags = 0 ) {
	$lockTsUnix = $this->doLock( $lockName, $method, $timeout );
	if ( $lockTsUnix !== null ) {
	$locked = true;
	$this->sessionNamedLocks[$lockName] = [
	'ts' => $lockTsUnix,
	'trxId' => $this->transactionManager->getTrxId()
	];
	} else {
	$locked = false;
	$this->queryLogger->info(
	__METHOD__ . " failed to acquire lock '{lockname}'",
	[
	'lockname' => $lockName,
	'db_log_category' => 'locking'
	]
	);
	}

	return $this->fieldHasBit( $flags, self::LOCK_TIMESTAMP ) ? $lockTsUnix : $locked;
	}

	/**
	* @see lock()
	*
	* @param string $lockName
	* @param string $method
	* @param int $timeout
	* @return float\|null UNIX timestamp of lock acquisition; null on failure
	* @throws DBError
	* @stable to override
	*/
	protected function doLock( string $lockName, string $method, int $timeout ) {
	return microtime( true ); // not implemented
	}

	/**
	* @inheritDoc
	*/
	public function unlock( $lockName, $method ) {
	$released = $this->doUnlock( $lockName, $method );
	if ( $released ) {
	unset( $this->sessionNamedLocks[$lockName] );
	} else {
	$this->queryLogger->warning(
	__METHOD__ . " failed to release lock '$lockName'\n",
	[ 'db_log_category' => 'locking' ]
	);
	}

	return $released;
	}

	/**
	* @see unlock()
	*
	* @param string $lockName
	* @param string $method
	* @return bool Success
	* @throws DBError
	* @stable to override
	*/
	protected function doUnlock( string $lockName, string $method ) {
	return true; // not implemented
	}

	public function getScopedLockAndFlush( $lockKey, $fname, $timeout ) {
	$this->transactionManager->onGetScopedLockAndFlush( $this, $fname );

	if ( !$this->lock( $lockKey, $fname, $timeout ) ) {
	return null;
	}

	$unlocker = new ScopedCallback( function () use ( $lockKey, $fname ) {
	if ( $this->trxLevel() ) {
	// There is a good chance an exception was thrown, causing any early return
	// from the caller. Let any error handler get a chance to issue rollback().
	// If there isn't one, let the error bubble up and trigger server-side rollback.
	$this->onTransactionResolution(
	function () use ( $lockKey, $fname ) {
	$this->unlock( $lockKey, $fname );
	},
	$fname
	);
	} else {
	$this->unlock( $lockKey, $fname );
	}
	} );

	$this->commit( $fname, self::FLUSHING_INTERNAL );

	return $unlocker;
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function namedLocksEnqueue() {
	return false;
	}

	public function dropTable( $table, $fname = __METHOD__ ) {
	if ( !$this->tableExists( $table, $fname ) ) {
	return false;
	}

	$sql = $this->platform->dropTableSqlText( $table );
	$this->query( $sql, $fname, self::QUERY_CHANGE_SCHEMA );

	return true;
	}

	public function truncate( $tables, $fname = __METHOD__ ) {
	$tables = is_array( $tables ) ? $tables : [ $tables ];

	$tablesTruncate = [];
	foreach ( $tables as $table ) {
	// Skip TEMPORARY tables with no writes nor sequence updates detected.
	// This mostly is an optimization for integration testing.
	if ( !$this->isPristineTemporaryTable( $table ) ) {
	$tablesTruncate[] = $table;
	}
	}

	if ( $tablesTruncate ) {
	$this->doTruncate( $tablesTruncate, $fname );
	}
	}

	/**
	* @see Database::truncate()
	* @stable to override
	* @param string[] $tables
	* @param string $fname
	*/
	protected function doTruncate( array $tables, $fname ) {
	foreach ( $tables as $table ) {
	$sql = "TRUNCATE TABLE " . $this->tableName( $table );
	$this->query( $sql, $fname, self::QUERY_CHANGE_SCHEMA );
	}
	}

	/**
	* @inheritDoc
	* @stable to override
	*/
	public function setBigSelects( $value = true ) {
	// no-op
	}

	public function isReadOnly() {
	return ( $this->getReadOnlyReason() !== false );
	}

	/**
	* @return array\|false Tuple of (read-only reason, "role" or "lb") or false if it is not
	*/
	protected function getReadOnlyReason() {
	if ( $this->topologyRole === self::ROLE_STREAMING_REPLICA ) {
	return [ 'Server is configured as a read-only replica database.', 'role' ];
	} elseif ( $this->topologyRole === self::ROLE_STATIC_CLONE ) {
	return [ 'Server is configured as a read-only static clone database.', 'role' ];
	}

	$reason = $this->getLBInfo( self::LB_READ_ONLY_REASON );
	if ( is_string( $reason ) ) {
	return [ $reason, 'lb' ];
	}

	return false;
	}

	/**
	* @param int $flags A bitfield of flags
	* @param int $bit Bit flag constant
	* @return bool Whether the bit field has the specified bit flag set
	* @since 1.34
	*/
	final protected function fieldHasBit( int $flags, int $bit ) {
	return ( ( $flags & $bit ) === $bit );
	}

	/**
	* Get the underlying binding connection handle
	*
	* Makes sure the connection resource is set (disconnects and ping() failure can unset it).
	* This catches broken callers than catch and ignore disconnection exceptions.
	* Unlike checking isOpen(), this is safe to call inside of open().
	*
	* @stable to override
	* @return mixed
	* @throws DBUnexpectedError
	* @since 1.26
	*/
	protected function getBindingHandle() {
	if ( !$this->conn ) {
	throw new DBUnexpectedError(
	$this,
	'DB connection was already closed or the connection dropped'
	);
	}

	return $this->conn;
	}

	/**
	* Demark the start of a critical section of session/transaction state changes
	*
	* Use this to disable potentially DB handles due to corruption from highly unexpected
	* exceptions (e.g. from zend timers or coding errors) preempting execution of methods.
	*
	* Callers must demark completion of the critical section with completeCriticalSection().
	* Callers should handle DBError exceptions that do not cause object state corruption by
	* catching them, calling completeCriticalSection(), and then rethrowing them.
	*
	* @code
	* $cs = $this->commenceCriticalSection( __METHOD__ );
	* try {
	* //...send a query that changes the session/transaction state...
	* } catch ( DBError $e ) {
	* $this->completeCriticalSection( __METHOD__, $cs );
	* throw $expectedException;
	* }
	* try {
	* //...send another query that changes the session/transaction state...
	* } catch ( DBError $trxError ) {
	* // Require ROLLBACK before allowing any other queries from outside callers
	* $this->completeCriticalSection( __METHOD__, $cs, $trxError );
	* throw $expectedException;
	* }
	* // ...update session state fields of $this...
	* $this->completeCriticalSection( __METHOD__, $cs );
	* @endcode
	*
	* @see Database::completeCriticalSection()
	*
	* @since 1.36
	* @param string $fname Caller name
	* @return CriticalSectionScope\|null RAII-style monitor (topmost sections only)
	* @throws DBUnexpectedError If an unresolved critical section error already exists
	*/
	protected function commenceCriticalSection( string $fname ) {
	if ( $this->csmError ) {
	throw new DBUnexpectedError(
	$this,
	"Cannot execute $fname critical section while session state is out of sync.\n\n" .
	$this->csmError->getMessage() . "\n" .
	$this->csmError->getTraceAsString()
	);
	}

	if ( $this->csmId ) {
	$csm = null; // fold into the outer critical section
	} elseif ( $this->csProvider ) {
	$csm = $this->csProvider->scopedEnter(
	$fname,
	null, // emergency limit (default)
	null, // emergency callback (default)
	function () use ( $fname ) {
	// Mark a critical section as having been aborted by an error
	$e = new RuntimeException( "A critical section from {$fname} has failed" );
	$this->csmError = $e;
	$this->csmId = null;
	}
	);
	$this->csmId = $csm->getId();
	$this->csmFname = $fname;
	} else {
	$csm = null; // not supported
	}

	return $csm;
	}

	/**
	* Demark the completion of a critical section of session/transaction state changes
	*
	* @see Database::commenceCriticalSection()
	*
	* @since 1.36
	* @param string $fname Caller name
	* @param CriticalSectionScope\|null $csm RAII-style monitor (topmost sections only)
	* @param Throwable\|null $trxError Error that requires setting STATUS_TRX_ERROR (if any)
	*/
	protected function completeCriticalSection(
	string $fname,
	?CriticalSectionScope $csm,
	Throwable $trxError = null
	) {
	if ( $csm !== null ) {
	if ( $this->csmId === null ) {
	throw new LogicException( "$fname critical section is not active" );
	} elseif ( $csm->getId() !== $this->csmId ) {
	throw new LogicException(
	"$fname critical section is not the active ({$this->csmFname}) one"
	);
	}

	$csm->exit();
	$this->csmId = null;
	}

	if ( $trxError ) {
	$this->transactionManager->setTransactionError( $trxError );
	}
	}

	public function __toString() {
	// spl_object_id is PHP >= 7.2
	$id = function_exists( 'spl_object_id' )
	? spl_object_id( $this )
	: spl_object_hash( $this );

	$description = $this->getType() . ' object #' . $id;
	// phpcs:ignore MediaWiki.Usage.ForbiddenFunctions.is_resource
	if ( is_resource( $this->conn ) ) {
	$description .= ' (' . (string)$this->conn . ')'; // "resource id #<ID>"
	} elseif ( is_object( $this->conn ) ) {
	// spl_object_id is PHP >= 7.2
	$handleId = function_exists( 'spl_object_id' )
	? spl_object_id( $this->conn )
	: spl_object_hash( $this->conn );
	$description .= " (handle id #$handleId)";
	}

	return $description;
	}

	/**
	* Make sure that copies do not share the same client binding handle
	* @throws DBConnectionError
	*/
	public function __clone() {
	$this->connLogger->warning(
	"Cloning " . static::class . " is not recommended; forking connection",
	[
	'exception' => new RuntimeException(),
	'db_log_category' => 'connection'
	]
	);

	if ( $this->isOpen() ) {
	// Open a new connection resource without messing with the old one
	$this->conn = null;
	$this->transactionManager->clearEndCallbacks();
	$this->handleSessionLossPreconnect(); // no trx or locks anymore
	$this->open(
	$this->connectionParams[self::CONN_HOST],
	$this->connectionParams[self::CONN_USER],
	$this->connectionParams[self::CONN_PASSWORD],
	$this->currentDomain->getDatabase(),
	$this->currentDomain->getSchema(),
	$this->tablePrefix()
	);
	$this->lastPing = microtime( true );
	}
	}

	/**
	* Called by serialize. Throw an exception when DB connection is serialized.
	* This causes problems on some database engines because the connection is
	* not restored on unserialize.
	* @return never
	*/
	public function __sleep() {
	throw new RuntimeException( 'Database serialization may cause problems, since ' .
	'the connection is not restored on wakeup' );
	}

	/**
	* Run a few simple checks and close dangling connections
	*/
	public function __destruct() {
	if ( $this->transactionManager ) {
	// Tests mock this class and disable constructor.
	$this->transactionManager->onDestruct();
	}

	$danglingWriters = $this->pendingWriteAndCallbackCallers();
	if ( $danglingWriters ) {
	$fnames = implode( ', ', $danglingWriters );
	trigger_error( "DB transaction writes or callbacks still pending ($fnames)" );
	}

	if ( $this->conn ) {
	// Avoid connection leaks. Normally, resources close at script completion.
	// The connection might already be closed in PHP by now, so suppress warnings.
	AtEase::suppressWarnings();
	$this->closeConnection();
	AtEase::restoreWarnings();
	$this->conn = null;
	}
	}

	/* Start of methods delegated to TransactionManager. Avoid using them outside of rdbms library */

	final public function trxLevel() {
	// FIXME: A lot of tests disable constructor leading to trx manager being
	// null and breaking, this is unacceptable but hopefully this should
	// happen less by moving these functions to the transaction manager class.
	if ( !$this->transactionManager ) {
	$this->transactionManager = new TransactionManager( new NullLogger() );
	}
	return $this->transactionManager->trxLevel();
	}

	public function trxTimestamp() {
	return $this->transactionManager->trxTimestamp();
	}

	public function trxStatus() {
	return $this->transactionManager->trxStatus();
	}

	public function writesPending() {
	return $this->transactionManager->writesPending();
	}

	public function writesOrCallbacksPending() {
	return $this->transactionManager->writesOrCallbacksPending();
	}

	public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
	return $this->transactionManager->pendingWriteQueryDuration( $this, $type );
	}

	public function pendingWriteCallers() {
	if ( !$this->transactionManager ) {
	return [];
	}
	return $this->transactionManager->pendingWriteCallers();
	}

	public function pendingWriteAndCallbackCallers() {
	if ( !$this->transactionManager ) {
	return [];
	}
	return $this->transactionManager->pendingWriteAndCallbackCallers();
	}

	public function runOnTransactionPreCommitCallbacks() {
	return $this->transactionManager->runOnTransactionPreCommitCallbacks( $this );
	}

	private function nextSavepointId( $fname ) {
	return $this->transactionManager->nextSavePointId( $this, $fname );
	}

	public function explicitTrxActive() {
	return $this->transactionManager->explicitTrxActive();
	}

	/* End of methods delegated to TransactionManager. */

	/* Start of methods delegated to SQLPlatform. Avoid using them outside of rdbms library */

	public function implicitOrderby() {
	return $this->platform->implicitOrderby();
	}

	public function selectSQLText(
	$table, $vars, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
	) {
	return $this->platform->selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
	}

	public function makeList( array $a, $mode = self::LIST_COMMA ) {
	return $this->platform->makeList( $a, $mode );
	}

	public function makeWhereFrom2d( $data, $baseKey, $subKey ) {
	return $this->platform->makeWhereFrom2d( $data, $baseKey, $subKey );
	}

	public function factorConds( $condsArray ) {
	return $this->platform->factorConds( $condsArray );
	}

	public function bitNot( $field ) {
	return $this->platform->bitNot( $field );
	}

	public function bitAnd( $fieldLeft, $fieldRight ) {
	return $this->platform->bitAnd( $fieldLeft, $fieldRight );
	}

	public function bitOr( $fieldLeft, $fieldRight ) {
	return $this->platform->bitOr( $fieldLeft, $fieldRight );
	}

	public function buildConcat( $stringList ) {
	return $this->platform->buildConcat( $stringList );
	}

	public function buildGreatest( $fields, $values ) {
	return $this->platform->buildGreatest( $fields, $values );
	}

	public function buildLeast( $fields, $values ) {
	return $this->platform->buildLeast( $fields, $values );
	}

	public function buildSubstring( $input, $startPosition, $length = null ) {
	return $this->platform->buildSubstring( $input, $startPosition, $length );
	}

	public function buildStringCast( $field ) {
	return $this->platform->buildStringCast( $field );
	}

	public function buildIntegerCast( $field ) {
	return $this->platform->buildIntegerCast( $field );
	}

	public function tableName( $name, $format = 'quoted' ) {
	return $this->platform->tableName( $name, $format );
	}

	public function tableNames( ...$tables ) {
	return $this->platform->tableNames( ...$tables );
	}

	public function tableNamesN( ...$tables ) {
	return $this->platform->tableNamesN( ...$tables );
	}

	protected function indexName( $index ) {
	return $this->platform->indexName( $index );
	}

	public function addIdentifierQuotes( $s ) {
	return $this->platform->addIdentifierQuotes( $s );
	}

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

	public function buildLike( $param, ...$params ) {
	return $this->platform->buildLike( $param, ...$params );
	}

	public function anyChar() {
	return $this->platform->anyChar();
	}

	public function anyString() {
	return $this->platform->anyString();
	}

	public function limitResult( $sql, $limit, $offset = false ) {
	return $this->platform->limitResult( $sql, $limit, $offset );
	}

	public function unionSupportsOrderAndLimit() {
	return $this->platform->unionSupportsOrderAndLimit();
	}

	public function unionQueries( $sqls, $all ) {
	return $this->platform->unionQueries( $sqls, $all );
	}

	public function unionConditionPermutations(
	$table,
	$vars,
	array $permute_conds,
	$extra_conds = '',
	$fname = __METHOD__,
	$options = [],
	$join_conds = []
	) {
	return $this->platform->unionConditionPermutations(
	$table,
	$vars,
	$permute_conds,
	$extra_conds,
	$fname,
	$options,
	$join_conds
	);
	}

	public function conditional( $cond, $caseTrueExpression, $caseFalseExpression ) {
	return $this->platform->conditional( $cond, $caseTrueExpression, $caseFalseExpression );
	}

	public function strreplace( $orig, $old, $new ) {
	return $this->platform->strreplace( $orig, $old, $new );
	}

	public function timestamp( $ts = 0 ) {
	return $this->platform->timestamp( $ts );
	}

	public function timestampOrNull( $ts = null ) {
	return $this->platform->timestampOrNull( $ts );
	}

	public function getInfinity() {
	return $this->platform->getInfinity();
	}

	public function encodeExpiry( $expiry ) {
	return $this->platform->encodeExpiry( $expiry );
	}

	public function decodeExpiry( $expiry, $format = TS_MW ) {
	return $this->platform->decodeExpiry( $expiry, $format );
	}

	public function setTableAliases( array $aliases ) {
	$this->platform->setTableAliases( $aliases );
	}

	public function getTableAliases() {
	return $this->platform->getTableAliases();
	}

	public function setIndexAliases( array $aliases ) {
	$this->platform->setIndexAliases( $aliases );
	}

	public function buildGroupConcatField(
	$delim, $table, $field, $conds = '', $join_conds = []
	) {
	return $this->platform->buildGroupConcatField( $delim, $table, $field, $conds, $join_conds );
	}

	public function buildSelectSubquery(
	$table, $vars, $conds = '', $fname = __METHOD__,
	$options = [], $join_conds = []
	) {
	return $this->platform->buildSelectSubquery( $table, $vars, $conds, $fname, $options, $join_conds );
	}

	public function buildExcludedValue( $column ) {
	return $this->platform->buildExcludedValue( $column );
	}

	public function setSchemaVars( $vars ) {
	$this->platform->setSchemaVars( $vars );
	}

	/* End of methods delegated to SQLPlatform. */
	}

	/**
	* @deprecated since 1.28
	*/
	class_alias( Database::class, 'DatabaseBase' );

	/**
	* @deprecated since 1.29
	*/
	class_alias( Database::class, 'Database' );

mediawiki/includes/libs/rdbms/database/Database.php80546c718a04REL1_39

Database.phpView Options

mediawiki/includes/libs/rdbms/database/Database.php
80546c718a04REL1_39

Database.php
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