Database.php

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<?php
namespace Wikimedia\Rdbms;
 
use BagOStuff;
use HashBagOStuff;
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;
 
abstract class Database implements IDatabase, IMaintainableDatabase, LoggerAwareInterface {
    protected $srvCache;
    protected $csProvider;
    protected $connLogger;
    protected $queryLogger;
    protected $replLogger;
    protected $errorLogger;
    protected $deprecationLogger;
    protected $profiler;
    private $transactionManager;
 
    protected $currentDomain;
 
    // phpcs:ignore MediaWiki.Commenting.PropertyDocumentation.ObjectTypeHintVar
    protected $conn;
 
    private $lazyMasterHandle;
 
    protected $server;
    protected $user;
    protected $password;
    protected $serverName;
    protected $cliMode;
    protected $agent;
    protected $topologyRole;
    protected $topologyRootMaster;
    protected $connectionParams;
    protected $connectionVariables;
    protected $nonNativeInsertSelectBatchSize;
 
    protected $flags;
    protected $ssl;
    protected $lbInfo = [];
    protected $delimiter = ';';
    protected $schemaVars;
 
    private $htmlErrors;
    private $priorFlags = [];
 
    protected $sessionNamedLocks = [];
    protected $sessionTempTables = [];
 
    private $trxReplicaLagStatus = null;
 
    protected $affectedRowCount;
 
    private $lastPing = 0.0;
    private $lastQuery = '';
    private $lastWriteTime = false;
    private $lastPhpError = false;
    private $lastRoundTripEstimate = 0.0;
 
    private $csmId;
    private $csmFname;
    private $csmError;
 
    public const ATTR_DB_IS_FILE = 'db-is-file';
    public const ATTR_DB_LEVEL_LOCKING = 'db-level-locking';
    public const ATTR_SCHEMAS_AS_TABLE_GROUPS = 'supports-schemas';
 
    public const NEW_UNCONNECTED = 0;
    public const NEW_CONNECTED = 1;
 
    protected const ERR_NONE = 0;
    protected const ERR_RETRY_QUERY = 1;
    protected const ERR_ABORT_QUERY = 2;
    protected const ERR_ABORT_TRX = 4;
    protected const ERR_ABORT_SESSION = 8;
 
    protected const DROPPED_CONN_BLAME_THRESHOLD_SEC = 3.0;
 
    private const NOT_APPLICABLE = 'n/a';
 
    private const TEMP_NORMAL = 1;
    private const TEMP_PSEUDO_PERMANENT = 2;
 
    private const DEADLOCK_TRIES = 4;
    private const DEADLOCK_DELAY_MIN = 500000;
    private const DEADLOCK_DELAY_MAX = 1500000;
 
    private const PING_TTL = 1.0;
    private const PING_QUERY = 'SELECT 1 AS ping';
 
    protected const MUTABLE_FLAGS = [
        'DBO_DEBUG',
        'DBO_NOBUFFER',
        'DBO_TRX',
        'DBO_DDLMODE',
    ];
    protected const DBO_MUTABLE = (
        self::DBO_DEBUG | self::DBO_NOBUFFER | self::DBO_TRX | self::DBO_DDLMODE
    );
 
    protected const CONN_HOST = 'host';
    protected const CONN_USER = 'user';
    protected const CONN_PASSWORD = 'password';
    protected const CONN_INITIAL_DB = 'dbname';
    protected const CONN_INITIAL_SCHEMA = 'schema';
    protected const CONN_INITIAL_TABLE_PREFIX = 'tablePrefix';
 
    protected $platform;
 
    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->lazyMasterHandle = $params['lazyMasterHandle'] ?? 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->topologyRootMaster = $params['topologicalMaster'];
        $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->getSchema(),
            $this->currentDomain->getTablePrefix()
        );
    }
 
    final public function initConnection() {
        if ( $this->isOpen() ) {
            throw new LogicException( __METHOD__ . ': already connected' );
        }
        // Establish the connection
        $this->doInitConnection();
    }
 
    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]
        );
    }
 
    abstract protected function open( $server, $user, $password, $db, $schema, $tablePrefix );
 
    final public static function factory( $type, $params = [], $connect = self::NEW_CONNECTED ) {
        $class = self::getClass( $type, $params['driver'] ?? null );
 
        if ( class_exists( $class ) && is_subclass_of( $class, IDatabase::class ) ) {
            $params += [
                // Default configuration
                'host' => null,
                'user' => null,
                'password' => null,
                'dbname' => null,
                'schema' => null,
                'tablePrefix' => '',
                'flags' => 0,
                'variables' => [],
                'lbInfo' => [],
                'cliMode' => ( PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg' ),
                'agent' => '',
                'serverName' => null,
                'topologyRole' => null,
                'topologicalMaster' => null,
                // Objects and callbacks
                'lazyMasterHandle' => $params['lazyMasterHandle'] ?? null,
                'srvCache' => $params['srvCache'] ?? new HashBagOStuff(),
                'profiler' => $params['profiler'] ?? null,
                'trxProfiler' => $params['trxProfiler'] ?? new TransactionProfiler(),
                'connLogger' => $params['connLogger'] ?? new NullLogger(),
                'queryLogger' => $params['queryLogger'] ?? new NullLogger(),
                'replLogger' => $params['replLogger'] ?? new NullLogger(),
                'errorLogger' => $params['errorLogger'] ?? static function ( Throwable $e ) {
                    trigger_error( get_class( $e ) . ': ' . $e->getMessage(), E_USER_WARNING );
                },
                'deprecationLogger' => $params['deprecationLogger'] ?? static function ( $msg ) {
                    trigger_error( $msg, E_USER_DEPRECATED );
                }
            ];
 
            $conn = new $class( $params );
            if ( $connect === self::NEW_CONNECTED ) {
                $conn->initConnection();
            }
        } else {
            $conn = null;
        }
 
        return $conn;
    }
 
    final public static function attributesFromType( $dbType, $driver = null ) {
        static $defaults = [
            self::ATTR_DB_IS_FILE => false,
            self::ATTR_DB_LEVEL_LOCKING => false,
            self::ATTR_SCHEMAS_AS_TABLE_GROUPS => false
        ];
 
        $class = self::getClass( $dbType, $driver );
        if ( class_exists( $class ) ) {
            return call_user_func( [ $class, 'getAttributes' ] ) + $defaults;
        } else {
            throw new DBUnexpectedError( null, "$dbType is not a supported database type." );
        }
    }
 
    private static function getClass( $dbType, $driver = null ) {
        // For database types with built-in support, the below maps type to IDatabase
        // implementations. For types with multiple driver implementations (PHP extensions),
        // an array can be used, keyed by extension name. In case of an array, the
        // optional 'driver' parameter can be used to force a specific driver. Otherwise,
        // we auto-detect the first available driver. For types without built-in support,
        // an class named "Database<Type>" us used, eg. DatabaseFoo for type 'foo'.
        static $builtinTypes = [
            'mysql' => [ 'mysqli' => DatabaseMysqli::class ],
            'sqlite' => DatabaseSqlite::class,
            'postgres' => DatabasePostgres::class,
        ];
 
        $dbType = strtolower( $dbType );
 
        if ( !isset( $builtinTypes[$dbType] ) ) {
            // Not a built in type, assume standard naming scheme
            return 'Database' . ucfirst( $dbType );
        }
 
        $class = false;
        $possibleDrivers = $builtinTypes[$dbType];
        if ( is_string( $possibleDrivers ) ) {
            $class = $possibleDrivers;
        } elseif ( (string)$driver !== '' ) {
            if ( !isset( $possibleDrivers[$driver] ) ) {
                throw new InvalidArgumentException( __METHOD__ .
                    " type '$dbType' does not support driver '{$driver}'" );
            }
 
            $class = $possibleDrivers[$driver];
        } else {
            foreach ( $possibleDrivers as $posDriver => $possibleClass ) {
                if ( extension_loaded( $posDriver ) ) {
                    $class = $possibleClass;
                    break;
                }
            }
        }
 
        if ( $class === false ) {
            throw new InvalidArgumentException( __METHOD__ .
                " no viable database extension found for type '$dbType'" );
        }
 
        return $class;
    }
 
    protected static function getAttributes() {
        return [];
    }
 
    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;
    }
 
    public function getTopologyRootPrimary() {
        return $this->topologyRootMaster;
    }
 
    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();
    }
 
    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->setPrefix( $prefix );
        }
 
        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->setSchema( $this->currentDomain->getSchema() );
        }
 
        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" );
        }
    }
 
    protected function getLazyMasterHandle() {
        return $this->lazyMasterHandle;
    }
 
    public function lastQuery() {
        return $this->lastQuery;
    }
 
    public function lastDoneWrites() {
        return $this->lastWriteTime ?: false;
    }
 
    public function writesPending() {
        return $this->transactionManager->writesPending();
    }
 
    public function writesOrCallbacksPending() {
        return $this->transactionManager->writesOrCallbacksPending();
    }
 
    public function sessionLocksPending() {
        return (bool)$this->sessionNamedLocks;
    }
 
    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 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 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();
    }
 
    abstract public function indexInfo( $table, $index, $fname = __METHOD__ );
 
    abstract public function strencode( $s );
 
    protected function installErrorHandler() {
        $this->lastPhpError = false;
        $this->htmlErrors = ini_set( 'html_errors', '0' );
        set_error_handler( [ $this, 'connectionErrorLogger' ] );
    }
 
    protected function restoreErrorHandler() {
        restore_error_handler();
        if ( $this->htmlErrors !== false ) {
            ini_set( 'html_errors', $this->htmlErrors );
        }
 
        return $this->getLastPHPError();
    }
 
    protected function getLastPHPError() {
        if ( $this->lastPhpError ) {
            $error = preg_replace( '!\[<a.*</a>\]!', '', $this->lastPhpError );
            $error = preg_replace( '!^.*?:\s?(.*)$!', '$1', $error );
 
            return $error;
        }
 
        return false;
    }
 
    public function connectionErrorLogger( $errno, $errstr ) {
        $this->lastPhpError = $errstr;
    }
 
    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;
    }
 
    final protected function assertHasConnectionHandle() {
        if ( !$this->isOpen() ) {
            throw new DBUnexpectedError( $this, "DB connection was already closed" );
        }
    }
 
    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" );
            }
        }
    }
 
    abstract protected function closeConnection();
 
    abstract protected function doSingleStatementQuery( string $sql ): QueryStatus;
 
    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;
    }
 
    protected function isWriteQuery( $sql, $flags ) {
        // Check if a SQL wrapper method already flagged the query as a write
        if (
            $this->fieldHasBit( $flags, self::QUERY_CHANGE_ROWS ) ||
            $this->fieldHasBit( $flags, self::QUERY_CHANGE_SCHEMA )
        ) {
            return true;
        }
        // Check if a SQL wrapper method already flagged the query as a non-write
        if (
            $this->fieldHasBit( $flags, self::QUERY_CHANGE_NONE ) ||
            $this->fieldHasBit( $flags, self::QUERY_CHANGE_TRX ) ||
            $this->fieldHasBit( $flags, self::QUERY_CHANGE_LOCKS )
        ) {
            return false;
        }
        // Treat SELECT queries without FOR UPDATE queries as non-writes. This matches
        // how MySQL enforces read_only (FOR SHARE and LOCK IN SHADE MODE are allowed).
        // Handle (SELECT ...) UNION (SELECT ...) queries in a similar fashion.
        if ( preg_match( '/^\s*\‍(?SELECT\b/i', $sql ) ) {
            return (bool)preg_match( '/\bFOR\s+UPDATE\‍)?\s*$/i', $sql );
        }
        // BEGIN and COMMIT queries are considered non-write queries here.
        // Database backends and drivers (MySQL, MariaDB, php-mysqli) generally
        // treat these as write queries, in that their results have "affected rows"
        // as meta data as from writes, instead of "num rows" as from reads.
        // But, we treat them as non-write queries because when reading data (from
        // either replica or primary DB) we use transactions to enable repeatable-read
        // snapshots, which ensures we get consistent results from the same snapshot
        // for all queries within a request. Use cases:
        // - Treating these as writes would trigger ChronologyProtector (see method doc).
        // - We use this method to reject writes to replicas, but we need to allow
        //   use of transactions on replicas for read snapshots. This is fine given
        //   that transactions by themselves don't make changes, only actual writes
        //   within the transaction matter, which we still detect.
        return !preg_match(
            '/^\s*(BEGIN|ROLLBACK|COMMIT|SAVEPOINT|RELEASE|SET|SHOW|EXPLAIN|USE)\b/i',
            $sql
        );
    }
 
    protected function getQueryVerb( $sql ) {
        // Distinguish ROLLBACK from ROLLBACK TO SAVEPOINT
        return preg_match(
            '/^\s*(rollback\s+to\s+savepoint|[a-z]+)/i',
            $sql,
            $m
        ) ? strtoupper( $m[1] ) : null;
    }
 
    protected function isTransactableQuery( $sql ) {
        return !in_array(
            $this->getQueryVerb( $sql ),
            [
                'BEGIN',
                'ROLLBACK',
                'ROLLBACK TO SAVEPOINT',
                'COMMIT',
                'SET',
                'SHOW',
                'CREATE',
                'ALTER',
                'USE',
                'SHOW'
            ],
            true
        );
    }
 
    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;
    }
 
    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;
            }
        }
    }
 
    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
        $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;
    }
 
    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;
    }
 
    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->isWriteQuery( $sql, $flags ) ) {
                $verb = $this->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['*'];
    }
 
    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 ) ? 'query-m: ' : 'query: ';
        $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;
    }
 
    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 );
    }
 
    private function beginIfImplied( $sql, $fname, $flags ) {
        if (
            !$this->fieldHasBit( $flags, self::QUERY_IGNORE_DBO_TRX ) &&
            !$this->trxLevel() &&
            $this->getFlag( self::DBO_TRX ) &&
            $this->isTransactableQuery( $sql )
        ) {
            $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
            $this->transactionManager->turnOnAutomatic();
 
            return true;
        }
 
        return false;
    }
 
    private function assertQueryIsCurrentlyAllowed( string $sql, string $fname ) {
        $verb = $this->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
            );
        }
    }
 
    private function assessConnectionLoss(
        string $sql,
        float $walltime,
        CriticalSessionInfo $priorSessInfo
    ) {
        $verb = $this->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;
    }
 
    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 );
    }
 
    protected function doHandleSessionLossPreconnect() {
        // no-op
    }
 
    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 );
    }
 
    protected function isQueryTimeoutError( $errno ) {
        return false;
    }
 
    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 );
        }
    }
 
    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 );
    }
 
    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 );
        }
    }
 
    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 );
    }
 
    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->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->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();
    }
 
    public function estimateRowCount(
        $tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
    ) {
        $conds = $this->normalizeConditions( $conds, $fname );
        $column = $this->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->normalizeConditions( $conds, $fname );
        $column = $this->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;
    }
 
    final protected function normalizeRowArray( array $rowOrRows ) {
        if ( !$rowOrRows ) {
            $rows = [];
        } elseif ( isset( $rowOrRows[0] ) ) {
            $rows = $rowOrRows;
        } else {
            $rows = [ $rowOrRows ];
        }
 
        foreach ( $rows as $row ) {
            if ( !is_array( $row ) ) {
                throw new DBUnexpectedError( $this, "Got non-array in row array" );
            } elseif ( !$row ) {
                throw new DBUnexpectedError( $this, "Got empty array in row array" );
            }
        }
 
        return $rows;
    }
 
    final protected function normalizeConditions( $conds, $fname ) {
        if ( $conds === null || $conds === false ) {
            $this->queryLogger->warning(
                __METHOD__
                . ' called from '
                . $fname
                . ' with incorrect parameters: $conds must be a string or an array',
                [ 'db_log_category' => 'sql' ]
            );
            return [];
        } elseif ( $conds === '' ) {
            return [];
        }
 
        return is_array( $conds ) ? $conds : [ $conds ];
    }
 
    final protected function normalizeUpsertParams( $uniqueKeys, &$rows ) {
        $rows = $this->normalizeRowArray( $rows );
        if ( !$rows ) {
            return null;
        }
        if ( !$uniqueKeys ) {
            // For backwards compatibility, allow insertion of rows with no applicable key
            $this->queryLogger->warning(
                "upsert/replace called with no unique key",
                [
                    'exception' => new RuntimeException(),
                    'db_log_category' => 'sql',
                ]
            );
            return null;
        }
        $identityKey = $this->normalizeUpsertKeys( $uniqueKeys );
        if ( $identityKey ) {
            $allDefaultKeyValues = $this->assertValidUpsertRowArray( $rows, $identityKey );
            if ( $allDefaultKeyValues ) {
                // For backwards compatibility, allow insertion of rows with all-NULL
                // values for the unique columns (e.g. for an AUTOINCREMENT column)
                $this->queryLogger->warning(
                    "upsert/replace called with all-null values for unique key",
                    [
                        'exception' => new RuntimeException(),
                        'db_log_category' => 'sql',
                    ]
                );
                return null;
            }
        }
        return $identityKey;
    }
 
    private function normalizeUpsertKeys( $uniqueKeys ) {
        if ( is_string( $uniqueKeys ) ) {
            return [ $uniqueKeys ];
        } elseif ( !is_array( $uniqueKeys ) ) {
            throw new DBUnexpectedError( $this, 'Invalid unique key array' );
        } else {
            if ( count( $uniqueKeys ) !== 1 || !isset( $uniqueKeys[0] ) ) {
                throw new DBUnexpectedError( $this,
                    "The unique key array should contain a single unique index" );
            }
 
            $uniqueKey = $uniqueKeys[0];
            if ( is_string( $uniqueKey ) ) {
                // Passing a list of strings for single-column unique keys is too
                // easily confused with passing the columns of composite unique key
                $this->queryLogger->warning( __METHOD__ .
                    " called with deprecated parameter style: " .
                    "the unique key array should be a string or array of string arrays",
                    [
                        'exception' => new RuntimeException(),
                        'db_log_category' => 'sql',
                    ] );
                return $uniqueKeys;
            } elseif ( is_array( $uniqueKey ) ) {
                return $uniqueKey;
            } else {
                throw new DBUnexpectedError( $this, 'Invalid unique key array entry' );
            }
        }
    }
 
    final protected function normalizeOptions( $options ) {
        if ( is_array( $options ) ) {
            return $options;
        } elseif ( is_string( $options ) ) {
            return ( $options === '' ) ? [] : [ $options ];
        } else {
            throw new DBUnexpectedError( $this, __METHOD__ . ': expected string or array' );
        }
    }
 
    final protected function assertValidUpsertRowArray( array $rows, array $identityKey ) {
        $numNulls = 0;
        foreach ( $rows as $row ) {
            foreach ( $identityKey as $column ) {
                $numNulls += ( isset( $row[$column] ) ? 0 : 1 );
            }
        }
 
        if (
            $numNulls &&
            $numNulls !== ( count( $rows ) * count( $identityKey ) )
        ) {
            throw new DBUnexpectedError(
                $this,
                "NULL/absent values for unique key (" . implode( ',', $identityKey ) . ")"
            );
        }
 
        return (bool)$numNulls;
    }
 
    final protected function assertValidUpsertSetArray(
        array $set,
        array $identityKey,
        array $rows
    ) {
        // Sloppy callers might construct the SET array using the ROW array, leaving redundant
        // column definitions for identity key columns. Detect this for backwards compatibility.
        $soleRow = ( count( $rows ) == 1 ) ? reset( $rows ) : null;
        // Disallow value changes for any columns in the identity key. This avoids additional
        // insertion order dependencies that are unwieldy and difficult to implement efficiently
        // in PostgreSQL.
        foreach ( $set as $k => $v ) {
            if ( is_string( $k ) ) {
                // Key is a column name and value is a literal (e.g. string, int, null, ...)
                if ( in_array( $k, $identityKey, true ) ) {
                    if ( $soleRow && array_key_exists( $k, $soleRow ) && $soleRow[$k] === $v ) {
                        $this->queryLogger->warning(
                            __METHOD__ . " called with redundant assignment to column '$k'",
                            [
                                'exception' => new RuntimeException(),
                                'db_log_category' => 'sql',
                            ]
                        );
                    } else {
                        throw new DBUnexpectedError(
                            $this,
                            "Cannot reassign column '$k' since it belongs to identity key"
                        );
                    }
                }
            } elseif ( preg_match( '/^([a-zA-Z0-9_]+)\s*=/', $v, $m ) ) {
                // Value is of the form "<unquoted alphanumeric column> = <SQL expression>"
                if ( in_array( $m[1], $identityKey, true ) ) {
                    throw new DBUnexpectedError(
                        $this,
                        "Cannot reassign column '{$m[1]}' since it belongs to identity key"
                    );
                }
            }
        }
    }
 
    final protected function isFlagInOptions( $option, array $options ) {
        foreach ( array_keys( $options, $option, true ) as $k ) {
            if ( is_int( $k ) ) {
                return true;
            }
        }
 
        return false;
    }
 
    final protected function extractSingleFieldFromList( $var ) {
        if ( is_array( $var ) ) {
            if ( !$var ) {
                $column = null;
            } elseif ( count( $var ) == 1 ) {
                $column = $var[0] ?? reset( $var );
            } else {
                throw new DBUnexpectedError( $this, __METHOD__ . ': got multiple columns' );
            }
        } else {
            $column = $var;
        }
 
        return $column;
    }
 
    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__ );
 
    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 = [] ) {
        $rows = $this->normalizeRowArray( $rows );
        if ( !$rows ) {
            return true;
        }
 
        $options = $this->normalizeOptions( $options );
        if ( $this->isFlagInOptions( 'IGNORE', $options ) ) {
            $this->doInsertNonConflicting( $table, $rows, $fname );
        } else {
            $this->doInsert( $table, $rows, $fname );
        }
 
        return true;
    }
 
    protected function doInsert( $table, array $rows, $fname ) {
        $encTable = $this->tableName( $table );
        list( $sqlColumns, $sqlTuples ) = $this->makeInsertLists( $rows );
 
        $sql = "INSERT INTO $encTable ($sqlColumns) VALUES $sqlTuples";
 
        $this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
    }
 
    protected function doInsertNonConflicting( $table, array $rows, $fname ) {
        $encTable = $this->tableName( $table );
        list( $sqlColumns, $sqlTuples ) = $this->makeInsertLists( $rows );
        list( $sqlVerb, $sqlOpts ) = $this->makeInsertNonConflictingVerbAndOptions();
 
        $sql = rtrim( "$sqlVerb $encTable ($sqlColumns) VALUES $sqlTuples $sqlOpts" );
 
        $this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
    }
 
    protected function makeInsertNonConflictingVerbAndOptions() {
        return [ 'INSERT IGNORE INTO', '' ];
    }
 
    protected function makeInsertLists( array $rows, $aliasPrefix = '' ) {
        $firstRow = $rows[0];
        if ( !is_array( $firstRow ) || !$firstRow ) {
            throw new DBUnexpectedError( $this, 'Got an empty row list or empty row' );
        }
        // List of columns that define the value tuple ordering
        $tupleColumns = array_keys( $firstRow );
 
        $valueTuples = [];
        foreach ( $rows as $row ) {
            $rowColumns = array_keys( $row );
            // VALUES(...) requires a uniform correspondence of (column => value)
            if ( $rowColumns !== $tupleColumns ) {
                throw new DBUnexpectedError(
                    $this,
                    'Got row columns (' . implode( ', ', $rowColumns ) . ') ' .
                    'instead of expected (' . implode( ', ', $tupleColumns ) . ')'
                );
            }
            // Make the value tuple that defines this row
            $valueTuples[] = '(' . $this->makeList( $row, self::LIST_COMMA ) . ')';
        }
 
        $magicAliasFields = [];
        foreach ( $tupleColumns as $column ) {
            $magicAliasFields[] = $aliasPrefix . $column;
        }
 
        return [
            $this->makeList( $tupleColumns, self::LIST_NAMES ),
            implode( ',', $valueTuples ),
            $this->makeList( $magicAliasFields, self::LIST_NAMES )
        ];
    }
 
    protected function makeUpdateOptionsArray( $options ) {
        $options = $this->normalizeOptions( $options );
 
        $opts = [];
 
        if ( in_array( 'IGNORE', $options ) ) {
            $opts[] = 'IGNORE';
        }
 
        return $opts;
    }
 
    protected function makeUpdateOptions( $options ) {
        $opts = $this->makeUpdateOptionsArray( $options );
 
        return implode( ' ', $opts );
    }
 
    public function update( $table, $set, $conds, $fname = __METHOD__, $options = [] ) {
        $this->assertConditionIsNotEmpty( $conds, __METHOD__, true );
        $table = $this->tableName( $table );
        $opts = $this->makeUpdateOptions( $options );
        $sql = "UPDATE $opts $table SET " . $this->makeList( $set, self::LIST_SET );
 
        if ( $conds && $conds !== IDatabase::ALL_ROWS ) {
            if ( is_array( $conds ) ) {
                $conds = $this->makeList( $conds, self::LIST_AND );
            }
            $sql .= ' WHERE ' . $conds;
        }
 
        $this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
 
        return true;
    }
 
    protected function assertConditionIsNotEmpty( $conds, string $fname, bool $deprecate ) {
        $isCondValid = ( is_string( $conds ) || is_array( $conds ) ) && $conds;
        if ( !$isCondValid ) {
            if ( $deprecate ) {
                wfDeprecated( $fname . ' called with empty $conds', '1.35', false, 3 );
            } else {
                throw new DBUnexpectedError( $this, $fname . ' called with empty conditions' );
            }
        }
    }
 
    public function buildExcludedValue( $column ) {
        /* @see Database::doUpsert() */
        // This can be treated like a single value since __VALS is a single row table
        return "(SELECT __$column FROM __VALS)";
    }
 
    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 );
    }
 
    protected function doSelectDomain( DatabaseDomain $domain ) {
        $this->currentDomain = $domain;
        $this->platform->setSchema( $domain->getSchema() );
        $this->platform->setPrefix( $domain->getTablePrefix() );
    }
 
    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';
    }
 
    protected function fieldNameWithAlias( $name, $alias = false ) {
        if ( !$alias || (string)$alias === (string)$name ) {
            return $name;
        } else {
            return $name . ' AS ' . $this->addIdentifierQuotes( $alias ); // PostgreSQL needs AS
        }
    }
 
    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->normalizeUpsertParams( $uniqueKeys, $rows );
        if ( !$rows ) {
            return;
        }
        if ( $identityKey ) {
            $this->doReplace( $table, $identityKey, $rows, $fname );
        } else {
            $this->doInsert( $table, $rows, $fname );
        }
    }
 
    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->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;
    }
 
    protected function makeKeyCollisionCondition( array $rows, array $uniqueKey ) {
        if ( !$rows ) {
            throw new DBUnexpectedError( $this, "Empty row array" );
        } elseif ( !$uniqueKey ) {
            throw new DBUnexpectedError( $this, "Empty unique key array" );
        }
 
        if ( count( $uniqueKey ) == 1 ) {
            // Use a simple IN(...) clause
            $column = reset( $uniqueKey );
            $values = array_column( $rows, $column );
            if ( count( $values ) !== count( $rows ) ) {
                throw new DBUnexpectedError( $this, "Missing values for unique key ($column)" );
            }
 
            return $this->makeList( [ $column => $values ], self::LIST_AND );
        }
 
        $nullByUniqueKeyColumn = array_fill_keys( $uniqueKey, null );
 
        $orConds = [];
        foreach ( $rows as $row ) {
            $rowKeyMap = array_intersect_key( $row, $nullByUniqueKeyColumn );
            if ( count( $rowKeyMap ) != count( $uniqueKey ) ) {
                throw new DBUnexpectedError(
                    $this,
                    "Missing values for unique key (" . implode( ',', $uniqueKey ) . ")"
                );
            }
            $orConds[] = $this->makeList( $rowKeyMap, self::LIST_AND );
        }
 
        return count( $orConds ) > 1
            ? $this->makeList( $orConds, self::LIST_OR )
            : $orConds[0];
    }
 
    public function upsert( $table, array $rows, $uniqueKeys, array $set, $fname = __METHOD__ ) {
        $identityKey = $this->normalizeUpsertParams( $uniqueKeys, $rows );
        if ( !$rows ) {
            return true;
        }
        if ( $identityKey ) {
            $this->assertValidUpsertSetArray( $set, $identityKey, $rows );
            $this->doUpsert( $table, $rows, $identityKey, $set, $fname );
        } else {
            $this->doInsert( $table, $rows, $fname );
        }
 
        return true;
    }
 
    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->makeInsertLists( [ $row ], '__' );
                $sqlConditions = $this->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;
    }
 
    public function deleteJoin(
        $delTable,
        $joinTable,
        $delVar,
        $joinVar,
        $conds,
        $fname = __METHOD__
    ) {
        if ( !$conds ) {
            throw new DBUnexpectedError( $this, __METHOD__ . ' called with empty $conds' );
        }
 
        $delTable = $this->tableName( $delTable );
        $joinTable = $this->tableName( $joinTable );
        $sql = "DELETE FROM $delTable WHERE $delVar IN (SELECT $joinVar FROM $joinTable ";
        if ( $conds != '*' ) {
            $sql .= 'WHERE ' . $this->makeList( $conds, self::LIST_AND );
        }
        $sql .= ')';
 
        $this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
    }
 
    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__ ) {
        $this->assertConditionIsNotEmpty( $conds, __METHOD__, false );
 
        $table = $this->tableName( $table );
        $sql = "DELETE FROM $table";
 
        if ( $conds !== IDatabase::ALL_ROWS ) {
            if ( is_array( $conds ) ) {
                $conds = $this->makeList( $conds, self::LIST_AND );
            }
            $sql .= ' WHERE ' . $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->normalizeOptions( $insertOptions );
        $selectOptions = $this->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;
    }
 
    protected function isInsertSelectSafe( array $insertOptions, array $selectOptions ) {
        return true;
    }
 
    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->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;
    }
 
    protected function doInsertSelectNative(
        $destTable,
        $srcTable,
        array $varMap,
        $conds,
        $fname,
        array $insertOptions,
        array $selectOptions,
        $selectJoinConds
    ) {
        list( $sqlVerb, $sqlOpts ) = $this->isFlagInOptions( 'IGNORE', $insertOptions )
            ? $this->makeInsertNonConflictingVerbAndOptions()
            : [ 'INSERT INTO', '' ];
        $encDstTable = $this->tableName( $destTable );
        $sqlDstColumns = implode( ',', array_keys( $varMap ) );
        $selectSql = $this->selectSQLText(
            $srcTable,
            array_values( $varMap ),
            $conds,
            $fname,
            $selectOptions,
            $selectJoinConds
        );
 
        $sql = rtrim( "$sqlVerb $encDstTable ($sqlDstColumns) $selectSql $sqlOpts" );
 
        $this->query( $sql, $fname, self::QUERY_CHANGE_ROWS );
    }
 
    public function wasDeadlock() {
        return false;
    }
 
    public function wasLockTimeout() {
        return false;
    }
 
    public function wasConnectionLoss() {
        return $this->isConnectionError( $this->lastErrno() );
    }
 
    public function wasReadOnlyError() {
        return false;
    }
 
    public function wasErrorReissuable() {
        return (
            $this->wasDeadlock() ||
            $this->wasLockTimeout() ||
            $this->wasConnectionLoss()
        );
    }
 
    protected function isConnectionError( $errno ) {
        return false;
    }
 
    protected function isKnownStatementRollbackError( $errno ) {
        return false; // don't know; it could have caused a transaction rollback
    }
 
    public function deadlockLoop( ...$args ) {
        $function = array_shift( $args );
        $tries = self::DEADLOCK_TRIES;
 
        $this->begin( __METHOD__ );
 
        $retVal = null;
        $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;
        }
    }
 
    public function primaryPosWait( DBPrimaryPos $pos, $timeout ) {
        # Real waits are implemented in the subclass.
        return 0;
    }
 
    public function getReplicaPos() {
        # Stub
        return false;
    }
 
    public function getPrimaryPos() {
        # Stub
        return false;
    }
 
    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 );
    }
 
    final public function setTrxEndCallbackSuppression( $suppress ) {
        $this->transactionManager->setTrxEndCallbackSuppression( $suppress );
    }
 
    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;
    }
 
    public function runOnTransactionPreCommitCallbacks() {
        return $this->transactionManager->runOnTransactionPreCommitCallbacks( $this );
    }
 
    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;
            }
        }
    }
 
    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];
        }
    }
 
    private function runTransactionPostRollbackCallbacks() {
        $this->runOnTransactionIdleCallbacks( self::TRIGGER_ROLLBACK );
        $this->runTransactionListenerCallbacks( self::TRIGGER_ROLLBACK );
        $this->affectedRowCount = 0; // for the sake of consistency
    }
 
    protected function doSavepoint( $identifier, $fname ) {
        $sql = 'SAVEPOINT ' . $this->addIdentifierQuotes( $identifier );
        $this->query( $sql, $fname, self::QUERY_CHANGE_TRX );
    }
 
    protected function doReleaseSavepoint( $identifier, $fname ) {
        $sql = 'RELEASE SAVEPOINT ' . $this->addIdentifierQuotes( $identifier );
        $this->query( $sql, $fname, self::QUERY_CHANGE_TRX );
    }
 
    protected function doRollbackToSavepoint( $identifier, $fname ) {
        $sql = 'ROLLBACK TO SAVEPOINT ' . $this->addIdentifierQuotes( $identifier );
        $this->query( $sql, $fname, self::QUERY_CHANGE_TRX );
    }
 
    private function nextSavepointId( $fname ) {
        return $this->transactionManager->nextSavePointId( $this, $fname );
    }
 
    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 );
                    $this->doSavepoint( $savepointId, $fname );
                } 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 ) {
                $this->doReleaseSavepoint( $savepointId, $fname );
            }
        } 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
                    $this->doRollbackToSavepoint( $savepointId, $fname );
                    $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 );
    }
 
    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 );
    }
 
    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__ );
        $this->doRollback( $fname );
        $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 );
    }
 
    protected function doRollback( $fname ) {
        if ( $this->trxLevel() ) {
            # Disconnects cause rollback anyway, so ignore those errors
            $this->query( 'ROLLBACK', $fname, self::QUERY_SILENCE_ERRORS | self::QUERY_CHANGE_TRX );
        }
    }
 
    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();
    }
 
    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 );
    }
 
    public function explicitTrxActive() {
        return $this->transactionManager->explicitTrxActive();
    }
 
    public function duplicateTableStructure(
        $oldName,
        $newName,
        $temporary = false,
        $fname = __METHOD__
    ) {
        throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
    }
 
    public function listTables( $prefix = null, $fname = __METHOD__ ) {
        throw new RuntimeException( __METHOD__ . ' is not implemented in descendant class' );
    }
 
    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();
    }
 
    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;
    }
 
    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();
    }
 
    final protected function getRecordedTransactionLagStatus() {
        return $this->trxLevel() ? $this->trxReplicaLagStatus : null;
    }
 
    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 ) ];
    }
 
    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();
    }
 
    protected function doGetLag() {
        return 0;
    }
 
    public function encodeBlob( $b ) {
        return $b;
    }
 
    public function decodeBlob( $b ) {
        if ( $b instanceof Blob ) {
            $b = $b->fetch();
        }
        return $b;
    }
 
    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 setSchemaVars( $vars ) {
        $this->schemaVars = is_array( $vars ) ? $vars : null;
    }
 
    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->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;
    }
 
    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;
    }
 
    protected function replaceVars( $ins ) {
        $vars = $this->getSchemaVars();
        return preg_replace_callback(
            '!
                /\* (\$wgDBprefix|[_i]) \*/ (\w*) | # 1-2. tableName, indexName
                \'\{\$ (\w+) }\'                  | # 3. addQuotes
                `\{\$ (\w+) }`                    | # 4. addIdentifierQuotes
                /\*\$ (\w+) \*/                     # 5. leave unencoded
            !x',
            function ( $m ) use ( $vars ) {
                // Note: Because of <https://bugs.php.net/bug.php?id=51881>,
                // check for both nonexistent keys *and* the empty string.
                if ( isset( $m[1] ) && $m[1] !== '' ) {
                    if ( $m[1] === 'i' ) {
                        return $this->indexName( $m[2] );
                    } else {
                        return $this->tableName( $m[2] );
                    }
                } elseif ( isset( $m[3] ) && $m[3] !== '' && array_key_exists( $m[3], $vars ) ) {
                    return $this->addQuotes( $vars[$m[3]] );
                } elseif ( isset( $m[4] ) && $m[4] !== '' && array_key_exists( $m[4], $vars ) ) {
                    return $this->addIdentifierQuotes( $vars[$m[4]] );
                } elseif ( isset( $m[5] ) && $m[5] !== '' && array_key_exists( $m[5], $vars ) ) {
                    return $vars[$m[5]];
                } else {
                    return $m[0];
                }
            },
            $ins
        );
    }
 
    protected function getSchemaVars() {
        return $this->schemaVars ?? $this->getDefaultSchemaVars();
    }
 
    protected function getDefaultSchemaVars() {
        return [];
    }
 
    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;
    }
 
    protected function doLockIsFree( string $lockName, string $method ) {
        return true; // not implemented
    }
 
    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;
    }
 
    protected function doLock( string $lockName, string $method, int $timeout ) {
        return microtime( true ); // not implemented
    }
 
    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;
    }
 
    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;
    }
 
    public function namedLocksEnqueue() {
        return false;
    }
 
    public function dropTable( $table, $fname = __METHOD__ ) {
        if ( !$this->tableExists( $table, $fname ) ) {
            return false;
        }
 
        $this->doDropTable( $table, $fname );
 
        return true;
    }
 
    protected function doDropTable( $table, $fname ) {
        // https://mariadb.com/kb/en/drop-table/
        // https://dev.mysql.com/doc/refman/8.0/en/drop-table.html
        // https://www.postgresql.org/docs/9.2/sql-truncate.html
        $sql = "DROP TABLE " . $this->tableName( $table ) . " CASCADE";
        $this->query( $sql, $fname, self::QUERY_CHANGE_SCHEMA );
    }
 
    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 );
        }
    }
 
    protected function doTruncate( array $tables, $fname ) {
        foreach ( $tables as $table ) {
            $sql = "TRUNCATE TABLE " . $this->tableName( $table );
            $this->query( $sql, $fname, self::QUERY_CHANGE_SCHEMA );
        }
    }
 
    public function setBigSelects( $value = true ) {
        // no-op
    }
 
    public function isReadOnly() {
        return ( $this->getReadOnlyReason() !== false );
    }
 
    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;
    }
 
    final protected function fieldHasBit( int $flags, int $bit ) {
        return ( ( $flags & $bit ) === $bit );
    }
 
    protected function getBindingHandle() {
        if ( !$this->conn ) {
            throw new DBUnexpectedError(
                $this,
                'DB connection was already closed or the connection dropped'
            );
        }
 
        return $this->conn;
    }
 
    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;
    }
 
    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;
    }
 
    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 );
        }
    }
 
    public function __sleep() {
        throw new RuntimeException( 'Database serialization may cause problems, since ' .
            'the connection is not restored on wakeup' );
    }
 
    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 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 );
    }
 
    /* End of methods delegated to SQLPlatform. */
}
 
class_alias( Database::class, 'DatabaseBase' );
 
class_alias( Database::class, 'Database' );