Database.php

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<?php
namespace Wikimedia\Rdbms;
 
use InvalidArgumentException;
use LogicException;
use Psr\Log\LoggerAwareInterface;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;
use RuntimeException;
use Stringable;
use Throwable;
use Wikimedia\AtEase\AtEase;
use Wikimedia\Rdbms\Database\DatabaseFlags;
use Wikimedia\Rdbms\Platform\SQLPlatform;
use Wikimedia\Rdbms\Replication\ReplicationReporter;
use Wikimedia\RequestTimeout\CriticalSectionProvider;
use Wikimedia\RequestTimeout\CriticalSectionScope;
use Wikimedia\ScopedCallback;
use Wikimedia\Telemetry\NoopTracer;
use Wikimedia\Telemetry\SpanInterface;
use Wikimedia\Telemetry\TracerInterface;
 
abstract class Database implements Stringable, IDatabaseForOwner, IMaintainableDatabase, LoggerAwareInterface {
    protected $csProvider;
    protected $logger;
    protected $errorLogger;
    protected $deprecationLogger;
    protected $profiler;
    private $tracer;
    private $transactionManager;
 
    protected $currentDomain;
    protected $flagsHolder;
 
    // phpcs:ignore MediaWiki.Commenting.PropertyDocumentation.ObjectTypeHintVar
    protected $conn;
 
    protected $serverName;
    protected $cliMode;
    protected $connectTimeout;
    protected $receiveTimeout;
    protected $agent;
    protected $connectionParams;
    protected $connectionVariables;
    protected $nonNativeInsertSelectBatchSize;
 
    protected $ssl;
    protected $strictWarnings;
    protected $lbInfo = [];
    protected $delimiter = ';';
 
    private $htmlErrors;
 
    protected $sessionNamedLocks = [];
    protected $sessionTempTables = [];
 
    protected $lastQueryAffectedRows = 0;
    protected $lastQueryInsertId;
 
    protected $lastEmulatedAffectedRows;
    protected $lastEmulatedInsertId;
 
    protected $lastConnectError = '';
 
    private $lastPing = 0.0;
    private $lastWriteTime;
    private $lastPhpError = false;
 
    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 PING_TTL = 1.0;
    private const PING_QUERY = 'SELECT 1 AS ping';
 
    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;
 
    protected $replicationReporter;
 
    public function __construct( array $params ) {
        $this->logger = $params['logger'] ?? new NullLogger();
        $this->transactionManager = new TransactionManager(
            $this->logger,
            $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->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'];
        }
        $flags = (int)$params['flags'];
        $this->flagsHolder = new DatabaseFlags( $flags );
        $this->ssl = $params['ssl'] ?? (bool)( $flags & self::DBO_SSL );
        $this->connectTimeout = $params['connectTimeout'] ?? null;
        $this->receiveTimeout = $params['receiveTimeout'] ?? null;
        $this->cliMode = (bool)$params['cliMode'];
        $this->agent = (string)$params['agent'];
        $this->serverName = $params['serverName'];
        $this->nonNativeInsertSelectBatchSize = $params['nonNativeInsertSelectBatchSize'] ?? 10000;
        $this->strictWarnings = !empty( $params['strictWarnings'] );
 
        $this->profiler = is_callable( $params['profiler'] ) ? $params['profiler'] : null;
        $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,
            $this->logger,
            $this->currentDomain,
            $this->errorLogger
        );
        $this->tracer = $params['tracer'] ?? new NoopTracer();
        // Children classes must set $this->replicationReporter.
    }
 
    final public function initConnection() {
        if ( $this->isOpen() ) {
            throw new LogicException( __METHOD__ . ': already connected' );
        }
        // Establish the connection
        $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]
        );
        $this->lastPing = microtime( true );
    }
 
    abstract protected function open( $server, $user, $password, $db, $schema, $tablePrefix );
 
    public static function getAttributes() {
        return [];
    }
 
    public function setLogger( LoggerInterface $logger ) {
        $this->logger = $logger;
    }
 
    public function getServerInfo() {
        return $this->getServerVersion();
    }
 
    public function tablePrefix( $prefix = null ) {
        $old = $this->currentDomain->getTablePrefix();
 
        if ( $prefix !== null ) {
            $this->currentDomain = new DatabaseDomain(
                $this->currentDomain->getDatabase(),
                $this->currentDomain->getSchema(),
                $prefix
            );
            $this->platform->setCurrentDomain( $this->currentDomain );
        }
 
        return $old;
    }
 
    public function dbSchema( $schema = null ) {
        $old = $this->currentDomain->getSchema();
 
        if ( $schema !== null ) {
            if ( $schema !== '' && $this->getDBname() === null ) {
                throw new DBUnexpectedError(
                    $this,
                    "Cannot set schema to '$schema'; no database set"
                );
            }
 
            $this->currentDomain = new DatabaseDomain(
                $this->currentDomain->getDatabase(),
                // DatabaseDomain uses null for unspecified schemas
                ( $schema !== '' ) ? $schema : null,
                $this->currentDomain->getTablePrefix()
            );
            $this->platform->setCurrentDomain( $this->currentDomain );
        }
 
        return (string)$old;
    }
 
    public function getLBInfo( $name = null ) {
        if ( $name === null ) {
            return $this->lbInfo;
        }
 
        if ( array_key_exists( $name, $this->lbInfo ) ) {
            return $this->lbInfo[$name];
        }
 
        return null;
    }
 
    public function setLBInfo( $nameOrArray, $value = null ) {
        if ( is_array( $nameOrArray ) ) {
            $this->lbInfo = $nameOrArray;
        } elseif ( is_string( $nameOrArray ) ) {
            if ( $value !== null ) {
                $this->lbInfo[$nameOrArray] = $value;
            } else {
                unset( $this->lbInfo[$nameOrArray] );
            }
        } else {
            throw new InvalidArgumentException( "Got non-string key" );
        }
    }
 
    public function lastDoneWrites() {
        return $this->lastWriteTime;
    }
 
    public function sessionLocksPending() {
        return (bool)$this->sessionNamedLocks;
    }
 
    final protected function getTransactionRoundFname() {
        if ( $this->flagsHolder->hasImplicitTrxFlag() ) {
            // LoadBalancer transaction round participation is enabled for this DB handle;
            // get the owner of the active explicit transaction round (if any)
            return $this->getLBInfo( self::LB_TRX_ROUND_FNAME );
        }
 
        return null;
    }
 
    public function isOpen() {
        return (bool)$this->conn;
    }
 
    public function getDomainID() {
        return $this->currentDomain->getId();
    }
 
    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->logger->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" );
        }
    }
 
    abstract protected function closeConnection();
 
    abstract protected function doSingleStatementQuery( string $sql ): QueryStatus;
 
    private function hasPermanentTable( Query $query ) {
        if ( $query->getVerb() === 'CREATE TEMPORARY' ) {
            // Temporary table creation is allowed
            return false;
        }
        $table = $query->getWriteTable();
        if ( $table === null ) {
            // Parse error? Assume permanent.
            return true;
        }
        [ $db, $pt ] = $this->platform->getDatabaseAndTableIdentifier( $table );
        $tempInfo = $this->sessionTempTables[$db][$pt] ?? null;
        return !$tempInfo || $tempInfo->pseudoPermanent;
    }
 
    protected function registerTempTables( Query $query ) {
        $table = $query->getWriteTable();
        if ( $table === null ) {
            return;
        }
        switch ( $query->getVerb() ) {
            case 'CREATE TEMPORARY':
                [ $db, $pt ] = $this->platform->getDatabaseAndTableIdentifier( $table );
                $this->sessionTempTables[$db][$pt] = new TempTableInfo(
                    $this->transactionManager->getTrxId(),
                    (bool)( $query->getFlags() & self::QUERY_PSEUDO_PERMANENT )
                );
                break;
 
            case 'DROP':
                [ $db, $pt ] = $this->platform->getDatabaseAndTableIdentifier( $table );
                unset( $this->sessionTempTables[$db][$pt] );
        }
    }
 
    public function query( $sql, $fname = __METHOD__, $flags = 0 ) {
        if ( !( $sql instanceof Query ) ) {
            $flags = (int)$flags; // b/c; this field used to be a bool
            $sql = QueryBuilderFromRawSql::buildQuery( $sql, $flags, $this->currentDomain->getTablePrefix() );
        } else {
            $flags = $sql->getFlags();
        }
 
        // Make sure that this caller is allowed to issue this query statement
        $this->assertQueryIsCurrentlyAllowed( $sql->getVerb(), $fname );
 
        // Send the query to the server and fetch any corresponding errors
        $status = $this->executeQuery( $sql, $fname, $flags );
        if ( $status->res === false ) {
            // An error occurred; log, and, if needed, report an exception.
            // Errors that corrupt the transaction/session state cannot be silenced.
            $ignore = (
                $this->flagsHolder::contains( $flags, self::QUERY_SILENCE_ERRORS ) &&
                !$this->flagsHolder::contains( $status->flags, self::ERR_ABORT_SESSION ) &&
                !$this->flagsHolder::contains( $status->flags, self::ERR_ABORT_TRX )
            );
            $this->reportQueryError( $status->message, $status->code, $sql->getSQL(), $fname, $ignore );
        }
 
        return $status->res;
    }
 
    final protected function executeQuery( $sql, $fname, $flags ) {
        $this->assertHasConnectionHandle();
 
        $isPermWrite = false;
        $isWrite = $sql->isWriteQuery();
        if ( $isWrite ) {
            ChangedTablesTracker::recordQuery( $this->currentDomain, $sql );
            // Permit temporary table writes on replica connections, but require a writable
            // master connection for writes to persistent tables.
            if ( $this->hasPermanentTable( $sql ) ) {
                $isPermWrite = true;
                $info = $this->getReadOnlyReason();
                if ( $info ) {
                    [ $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" );
                    }
                }
                // DBConnRef uses QUERY_REPLICA_ROLE to enforce replica roles during query()
                if ( $this->flagsHolder::contains( $sql->getFlags(), self::QUERY_REPLICA_ROLE ) ) {
                    throw new DBReadOnlyRoleError(
                        $this,
                        "Cannot write; target role is DB_REPLICA"
                    );
                }
            }
        }
 
        // Whether a silent retry attempt is left for recoverable connection loss errors
        $retryLeft = !$this->flagsHolder::contains( $flags, self::QUERY_NO_RETRY );
 
        $cs = $this->commenceCriticalSection( __METHOD__ );
 
        do {
            // Start a DBO_TRX wrapper transaction as needed (throw an error on failure)
            if ( $this->beginIfImplied( $sql, $fname, $flags ) ) {
                // Since begin() was called, any connection loss was already handled
                $retryLeft = false;
            }
            // Send the query statement to the server and fetch any results.
            $status = $this->attemptQuery( $sql, $fname, $isPermWrite );
        } while (
            // An error occurred that can be recovered from via query retry
            $this->flagsHolder::contains( $status->flags, self::ERR_RETRY_QUERY ) &&
            // The retry has not been exhausted (consume it now)
            // phpcs:ignore Generic.CodeAnalysis.AssignmentInCondition.FoundInWhileCondition
            $retryLeft && !( $retryLeft = false )
        );
 
        // Register creation and dropping of temporary tables
        if ( $status->res ) {
            $this->registerTempTables( $sql );
        }
        $this->completeCriticalSection( __METHOD__, $cs );
 
        return $status;
    }
 
    private function attemptQuery(
        $sql,
        string $fname,
        bool $isPermWrite
    ) {
        // Transaction attributes before issuing this query
        $priorSessInfo = new CriticalSessionInfo(
            $this->transactionManager->getTrxId(),
            $this->transactionManager->explicitTrxActive(),
            $this->transactionManager->pendingWriteCallers(),
            $this->transactionManager->pendingPreCommitCallbackCallers(),
            $this->sessionNamedLocks,
            $this->sessionTempTables
        );
        // Get the transaction-aware SQL string used for profiling
        $generalizedSql = GeneralizedSql::newFromQuery(
            $sql,
            ( $this->replicationReporter->getTopologyRole() === self::ROLE_STREAMING_MASTER )
                ? 'role-primary: '
                : ''
        );
        // Add agent and calling method comments to the SQL
        $cStatement = $this->makeCommentedSql( $sql->getSQL(), $fname );
        // Start profile section
        $ps = $this->profiler ? ( $this->profiler )( $generalizedSql->stringify() ) : null;
        $startTime = microtime( true );
 
        // Clear any overrides from a prior "query method". Note that this does not affect
        // any such methods that are currently invoking query() itself since those query
        // methods set these fields before returning.
        $this->lastEmulatedAffectedRows = null;
        $this->lastEmulatedInsertId = null;
 
        // Record an OTEL span for this query.
        $writeTableName = $sql->getWriteTable();
        $spanName = $writeTableName ?
            "{$sql->getVerb()} {$this->getDBname()}.{$writeTableName}" :
            "{$sql->getVerb()} {$this->getDBname()}";
        $span = $this->tracer->createSpan( $spanName )
            ->setSpanKind( SpanInterface::SPAN_KIND_CLIENT )
            ->start();
        if ( $span->getContext()->isSampled() ) {
            $span->setAttributes( [
                'code.function' => $fname,
                'db.namespace' => $this->getDBname(),
                'db.operation.name' => $sql->getVerb(),
                'db.query.text' => $generalizedSql->stringify(),
                'db.system' => $this->getType(),
                'server.address' => $this->getServerName(),
            ] );
        }
 
        if ( $writeTableName !== null ) {
            $span->setAttributes( [ 'db.collection.name' => $writeTableName ] );
        }
 
        $status = $this->doSingleStatementQuery( $cStatement );
 
        // End profile section
        $endTime = microtime( true );
        $queryRuntime = max( $endTime - $startTime, 0.0 );
        unset( $ps );
        $span->end();
 
        if ( $status->res !== false ) {
            $this->lastPing = $endTime;
        } else {
            $span->setAttributes( [
                'db.response.status_code' => $status->code,
                'exception.message' => $status->message,
            ] );
        }
 
        $affectedRowCount = $status->rowsAffected;
        $returnedRowCount = $status->rowsReturned;
        $this->lastQueryAffectedRows = $affectedRowCount;
 
        if ( $status->res !== false ) {
            if ( $isPermWrite ) {
                if ( $this->trxLevel() ) {
                    $this->transactionManager->transactionWritingIn(
                        $this->getServerName(),
                        $this->getDomainID(),
                        $startTime
                    );
                    $this->transactionManager->updateTrxWriteQueryReport(
                        $sql->getSQL(),
                        $queryRuntime,
                        $affectedRowCount,
                        $fname
                    );
                } else {
                    $this->lastWriteTime = $endTime;
                }
            }
        }
 
        $this->transactionManager->recordQueryCompletion(
            $generalizedSql,
            $startTime,
            $isPermWrite,
            $isPermWrite ? $affectedRowCount : $returnedRowCount,
            $this->getServerName()
        );
 
        // Check if the query failed...
        $status->flags = $this->handleErroredQuery( $status, $sql, $fname, $queryRuntime, $priorSessInfo );
        // Avoid the overhead of logging calls unless debug mode is enabled
        if ( $this->flagsHolder->getFlag( self::DBO_DEBUG ) ) {
            $this->logger->debug(
                "{method} [{runtime_ms}ms] {db_server}: {sql}",
                $this->getLogContext( [
                    'method' => $fname,
                    'sql' => $sql->getSQL(),
                    'domain' => $this->getDomainID(),
                    'runtime_ms' => round( $queryRuntime * 1000, 3 ),
                    'db_log_category' => 'query'
                ] )
            );
        }
 
        return $status;
    }
 
    private function handleErroredQuery( QueryStatus $status, $sql, $fname, $queryRuntime, $priorSessInfo ) {
        $errflags = self::ERR_NONE;
        $error = $status->message;
        $errno = $status->code;
        if ( $status->res !== false ) {
            // Statement succeeded
            return $errflags;
        }
        if ( $this->isConnectionError( $errno ) ) {
            // Connection lost before or during the query...
            // Determine how to proceed given the lost session state
            $connLossFlag = $this->assessConnectionLoss(
                $sql->getVerb(),
                $queryRuntime,
                $priorSessInfo
            );
            // Update session state tracking and try to reestablish a connection
            $reconnected = $this->replaceLostConnection( $errno, __METHOD__ );
            // Check if important server-side session-level state was lost
            if ( $connLossFlag >= self::ERR_ABORT_SESSION ) {
                $ex = $this->getQueryException( $error, $errno, $sql->getSQL(), $fname );
                $this->transactionManager->setSessionError( $ex );
            }
            // Check if important server-side transaction-level state was lost
            if ( $connLossFlag >= self::ERR_ABORT_TRX ) {
                $ex = $this->getQueryException( $error, $errno, $sql->getSQL(), $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( $errno ) ) {
            // 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 = [ $error, $errno, $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( $error, $errno, $sql->getSQL(), $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;
        }
 
        return $errflags;
    }
 
    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->trxLevel() && $this->flagsHolder->hasApplicableImplicitTrxFlag( $flags ) ) {
            if ( $this->platform->isTransactableQuery( $sql ) ) {
                $this->begin( __METHOD__ . " ($fname)", self::TRANSACTION_INTERNAL );
                $this->transactionManager->turnOnAutomatic();
 
                return true;
            }
        }
 
        return false;
    }
 
    private function assertQueryIsCurrentlyAllowed( string $verb, string $fname ) {
        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 $verb,
        float $walltime,
        CriticalSessionInfo $priorSessInfo
    ) {
        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 $domainTempTables ) {
            foreach ( $domainTempTables 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' && $verb !== 'COMMIT' ) {
            // Transaction automatically rolled back, breaking the expectations of callers
            // relying on the continued existence of that transaction for things like atomic
            // writes, serializability, or reads from the same point-in-time snapshot. If the
            // connection loss occured on ROLLBACK (non-SAVEPOINT) or COMMIT, then we do not
            // need to mark the transaction state as corrupt, since no transaction would still
            // be open even if the query did succeed (T127428).
            $res = max( $res, self::ERR_ABORT_TRX );
            $blockers[] = 'explicit transaction';
        }
 
        if ( $blockers ) {
            $this->logger->warning(
                "cannot reconnect to {db_server} silently: {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://mariadb.com/kb/en/create-table/#create-temporary-table
        // https://www.postgresql.org/docs/9.2/static/sql-createtable.html (ignoring ON COMMIT)
        $this->sessionTempTables = [];
        // https://mariadb.com/kb/en/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->onSessionLoss( $this );
        // Clear additional subclass fields
        $this->doHandleSessionLossPreconnect();
    }
 
    protected function doHandleSessionLossPreconnect() {
        // no-op
    }
 
    protected function isQueryTimeoutError( $errno ) {
        return false;
    }
 
    public function reportQueryError( $error, $errno, $sql, $fname, $ignore = false ) {
        if ( $ignore ) {
            $this->logger->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->logger->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.
        // Stash any error associated with the handle before destroying it.
        $this->lastConnectError = $error;
        $this->conn = null;
 
        $this->logger->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 newUnionQueryBuilder(): UnionQueryBuilder {
        return new UnionQueryBuilder( $this );
    }
 
    public function newUpdateQueryBuilder(): UpdateQueryBuilder {
        return new UpdateQueryBuilder( $this );
    }
 
    public function newDeleteQueryBuilder(): DeleteQueryBuilder {
        return new DeleteQueryBuilder( $this );
    }
 
    public function newInsertQueryBuilder(): InsertQueryBuilder {
        return new InsertQueryBuilder( $this );
    }
 
    public function newReplaceQueryBuilder(): ReplaceQueryBuilder {
        return new ReplaceQueryBuilder( $this );
    }
 
    public function selectField(
        $tables, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
    ) {
        if ( $var === '*' ) {
            throw new DBUnexpectedError( $this, "Cannot use a * field" );
        } elseif ( is_array( $var ) && count( $var ) !== 1 ) {
            throw new DBUnexpectedError( $this, 'Cannot use more than one field' );
        }
 
        $options = $this->platform->normalizeOptions( $options );
        $options['LIMIT'] = 1;
 
        $res = $this->select( $tables, $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(
        $tables, $var, $cond = '', $fname = __METHOD__, $options = [], $join_conds = []
    ): array {
        if ( $var === '*' ) {
            throw new DBUnexpectedError( $this, "Cannot use a * field" );
        } elseif ( !is_string( $var ) ) {
            throw new DBUnexpectedError( $this, "Cannot use an array of fields" );
        }
 
        $options = $this->platform->normalizeOptions( $options );
        $res = $this->select( $tables, [ '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(
        $tables, $vars, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
    ) {
        $options = (array)$options;
        // Don't turn this into using platform directly, DatabaseMySQL overrides this.
        $sql = $this->selectSQLText( $tables, $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;
 
        $query = new Query( $sql, $flags, 'SELECT' );
        return $this->query( $query, $fname );
    }
 
    public function selectRow( $tables, $vars, $conds, $fname = __METHOD__,
        $options = [], $join_conds = []
    ) {
        $options = (array)$options;
        $options['LIMIT'] = 1;
 
        $res = $this->select( $tables, $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 = []
    ): int {
        $conds = $this->platform->normalizeConditions( $conds, $fname );
        $column = $this->platform->extractSingleFieldFromList( $var );
        if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
            $conds[] = "$column IS NOT NULL";
        }
 
        $res = $this->select(
            $tables, [ 'rowcount' => 'COUNT(*)' ], $conds, $fname, $options, $join_conds
        );
        $row = $res ? $res->fetchRow() : [];
 
        return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
    }
 
    public function selectRowCount(
        $tables, $var = '*', $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
    ): int {
        $conds = $this->platform->normalizeConditions( $conds, $fname );
        $column = $this->platform->extractSingleFieldFromList( $var );
        if ( is_string( $column ) && !in_array( $column, [ '*', '1' ] ) ) {
            $conds[] = "$column IS NOT NULL";
        }
        if ( in_array( 'DISTINCT', (array)$options ) ) {
            if ( $column === null ) {
                throw new DBUnexpectedError( $this,
                    '$var cannot be empty when the DISTINCT option is given' );
            }
            $innerVar = $column;
        } else {
            $innerVar = '1';
        }
 
        $res = $this->select(
            [
                'tmp_count' => $this->platform->buildSelectSubquery(
                    $tables,
                    $innerVar,
                    $conds,
                    $fname,
                    $options,
                    $join_conds
                )
            ],
            [ 'rowcount' => 'COUNT(*)' ],
            [],
            $fname
        );
        $row = $res ? $res->fetchRow() : [];
 
        return isset( $row['rowcount'] ) ? (int)$row['rowcount'] : 0;
    }
 
    public function lockForUpdate(
        $table, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
    ) {
        if ( !$this->trxLevel() && !$this->flagsHolder->hasImplicitTrxFlag() ) {
            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;
    }
 
    abstract public function tableExists( $table, $fname = __METHOD__ );
 
    public function indexExists( $table, $index, $fname = __METHOD__ ) {
        $info = $this->indexInfo( $table, $index, $fname );
 
        return (bool)$info;
    }
 
    public function indexUnique( $table, $index, $fname = __METHOD__ ) {
        $info = $this->indexInfo( $table, $index, $fname );
 
        return $info ? $info['unique'] : null;
    }
 
    abstract public function indexInfo( $table, $index, $fname = __METHOD__ );
 
    public function insert( $table, $rows, $fname = __METHOD__, $options = [] ) {
        $query = $this->platform->dispatchingInsertSqlText( $table, $rows, $options );
        if ( !$query ) {
            return true;
        }
        $this->query( $query, $fname );
        if ( $this->strictWarnings ) {
            $this->checkInsertWarnings( $query, $fname );
        }
        return true;
    }
 
    protected function checkInsertWarnings( Query $query, $fname ) {
    }
 
    public function update( $table, $set, $conds, $fname = __METHOD__, $options = [] ) {
        $query = $this->platform->updateSqlText( $table, $set, $conds, $options );
        $this->query( $query, $fname );
 
        return true;
    }
 
    public function databasesAreIndependent() {
        return false;
    }
 
    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->setCurrentDomain( $this->currentDomain );
    }
 
    public function getDBname() {
        return $this->currentDomain->getDatabase();
    }
 
    public function getServer() {
        return $this->connectionParams[self::CONN_HOST] ?? null;
    }
 
    public function getServerName() {
        return $this->serverName ?? $this->getServer() ?? 'unknown';
    }
 
    public function addQuotes( $s ) {
        if ( $s instanceof RawSQLValue ) {
            return $s->toSql();
        }
        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 expr( string $field, string $op, $value ): Expression {
        return new Expression( $field, $op, $value );
    }
 
    public function andExpr( array $conds ): AndExpressionGroup {
        return AndExpressionGroup::newFromArray( $conds );
    }
 
    public function orExpr( array $conds ): OrExpressionGroup {
        return OrExpressionGroup::newFromArray( $conds );
    }
 
    public function replace( $table, $uniqueKeys, $rows, $fname = __METHOD__ ) {
        $uniqueKey = $this->platform->normalizeUpsertParams( $uniqueKeys, $rows );
        if ( !$rows ) {
            return;
        }
        $affectedRowCount = 0;
        $insertId = null;
        $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
        try {
            foreach ( $rows as $row ) {
                // Delete any conflicting rows (including ones inserted from $rows)
                $query = $this->platform->deleteSqlText(
                    $table,
                    [ $this->platform->makeKeyCollisionCondition( [ $row ], $uniqueKey ) ]
                );
                $this->query( $query, $fname );
                // Insert the new row
                $query = $this->platform->dispatchingInsertSqlText( $table, $row, [] );
                $this->query( $query, $fname );
                $affectedRowCount += $this->lastQueryAffectedRows;
                $insertId = $insertId ?: $this->lastQueryInsertId;
            }
            $this->endAtomic( $fname );
        } catch ( DBError $e ) {
            $this->cancelAtomic( $fname );
            throw $e;
        }
        $this->lastEmulatedAffectedRows = $affectedRowCount;
        $this->lastEmulatedInsertId = $insertId;
    }
 
    public function upsert( $table, array $rows, $uniqueKeys, array $set, $fname = __METHOD__ ) {
        $uniqueKey = $this->platform->normalizeUpsertParams( $uniqueKeys, $rows );
        if ( !$rows ) {
            return true;
        }
        $this->platform->assertValidUpsertSetArray( $set, $uniqueKey, $rows );
 
        $encTable = $this->tableName( $table );
        $sqlColumnAssignments = $this->makeList( $set, self::LIST_SET );
        // Get any AUTO_INCREMENT/SERIAL column for this table so we can set insertId()
        $autoIncrementColumn = $this->getInsertIdColumnForUpsert( $table );
        // Check if there is a SQL assignment expression in $set (as generated by SQLPlatform::buildExcludedValue)
        $useWith = (bool)array_filter(
            $set,
            static function ( $v, $k ) {
                return $v instanceof RawSQLValue || is_int( $k );
            },
            ARRAY_FILTER_USE_BOTH
        );
        // Subclasses might need explicit type casting within "WITH...AS (VALUES ...)"
        // so that these CTE rows can be referenced within the SET clause assigments.
        $typeByColumn = $useWith ? $this->getValueTypesForWithClause( $table ) : [];
 
        $first = true;
        $affectedRowCount = 0;
        $insertId = null;
        $this->startAtomic( $fname, self::ATOMIC_CANCELABLE );
        try {
            foreach ( $rows as $row ) {
                // Update any existing conflicting row (including ones inserted from $rows)
                [ $sqlColumns, $sqlTuples, $sqlVals ] = $this->platform->makeInsertLists(
                    [ $row ],
                    '__',
                    $typeByColumn
                );
                $sqlConditions = $this->platform->makeKeyCollisionCondition(
                    [ $row ],
                    $uniqueKey
                );
                $query = new Query(
                    ( $useWith ? "WITH __VALS ($sqlVals) AS (VALUES $sqlTuples) " : "" ) .
                        "UPDATE $encTable SET $sqlColumnAssignments " .
                        "WHERE ($sqlConditions)",
                    self::QUERY_CHANGE_ROWS,
                    'UPDATE',
                    $table
                );
                $this->query( $query, $fname );
                $rowsUpdated = $this->lastQueryAffectedRows;
                $affectedRowCount += $rowsUpdated;
                if ( $rowsUpdated > 0 ) {
                    // Conflicting row found and updated
                    if ( $first && $autoIncrementColumn !== null ) {
                        // @TODO: use "RETURNING" instead (when supported by SQLite)
                        $query = new Query(
                            "SELECT $autoIncrementColumn AS id FROM $encTable " .
                            "WHERE ($sqlConditions)",
                            self::QUERY_CHANGE_NONE,
                            'SELECT'
                        );
                        $sRes = $this->query( $query, $fname, self::QUERY_CHANGE_ROWS );
                        $insertId = (int)$sRes->fetchRow()['id'];
                    }
                } else {
                    // No conflicting row found
                    $query = new Query(
                        "INSERT INTO $encTable ($sqlColumns) VALUES $sqlTuples",
                        self::QUERY_CHANGE_ROWS,
                        'INSERT',
                        $table
                    );
                    $this->query( $query, $fname );
                    $affectedRowCount += $this->lastQueryAffectedRows;
                }
                $first = false;
            }
            $this->endAtomic( $fname );
        } catch ( DBError $e ) {
            $this->cancelAtomic( $fname );
            throw $e;
        }
        $this->lastEmulatedAffectedRows = $affectedRowCount;
        $this->lastEmulatedInsertId = $insertId;
        return true;
    }
 
    protected function getInsertIdColumnForUpsert( $table ) {
        return null;
    }
 
    protected function getValueTypesForWithClause( $table ) {
        return [];
    }
 
    public function deleteJoin(
        $delTable,
        $joinTable,
        $delVar,
        $joinVar,
        $conds,
        $fname = __METHOD__
    ) {
        $sql = $this->platform->deleteJoinSqlText( $delTable, $joinTable, $delVar, $joinVar, $conds );
        $query = new Query( $sql, self::QUERY_CHANGE_ROWS, 'DELETE', $delTable );
        $this->query( $query, $fname );
    }
 
    public function delete( $table, $conds, $fname = __METHOD__ ) {
        $this->query( $this->platform->deleteSqlText( $table, $conds ), $fname );
 
        return true;
    }
 
    final public function insertSelect(
        $destTable,
        $srcTable,
        $varMap,
        $conds,
        $fname = __METHOD__,
        $insertOptions = [],
        $selectOptions = [],
        $selectJoinConds = []
    ) {
        static $hints = [ 'NO_AUTO_COLUMNS' ];
 
        $insertOptions = $this->platform->normalizeOptions( $insertOptions );
        $selectOptions = $this->platform->normalizeOptions( $selectOptions );
 
        if ( $this->cliMode && $this->isInsertSelectSafe( $insertOptions, $selectOptions, $fname ) ) {
            // 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, $fname ) {
        return true;
    }
 
    private function doInsertSelectGeneric(
        $destTable,
        $srcTable,
        array $varMap,
        $conds,
        $fname,
        array $insertOptions,
        array $selectOptions,
        $selectJoinConds
    ) {
        // For web requests, do a locking SELECT and then INSERT. This puts the SELECT burden
        // on only the primary DB (without needing row-based-replication). It also makes it easy to
        // know how big the INSERT is going to be.
        $fields = [];
        foreach ( $varMap as $dstColumn => $sourceColumnOrSql ) {
            $fields[] = $this->platform->fieldNameWithAlias( $sourceColumnOrSql, $dstColumn );
        }
        $res = $this->select(
            $srcTable,
            implode( ',', $fields ),
            $conds,
            $fname,
            array_merge( $selectOptions, [ 'FOR UPDATE' ] ),
            $selectJoinConds
        );
 
        $affectedRowCount = 0;
        $insertId = null;
        if ( $res ) {
            $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 ) {
                    $query = $this->platform->dispatchingInsertSqlText( $destTable, $rows, $insertOptions );
                    $this->query( $query, $fname );
                    $affectedRowCount += $this->lastQueryAffectedRows;
                    $insertId = $insertId ?: $this->lastQueryInsertId;
                }
                $this->endAtomic( $fname );
            } catch ( DBError $e ) {
                $this->cancelAtomic( $fname );
                throw $e;
            }
        }
        $this->lastEmulatedAffectedRows = $affectedRowCount;
        $this->lastEmulatedInsertId = $insertId;
    }
 
    protected function doInsertSelectNative(
        $destTable,
        $srcTable,
        array $varMap,
        $conds,
        $fname,
        array $insertOptions,
        array $selectOptions,
        $selectJoinConds
    ) {
        $sql = $this->platform->insertSelectNativeSqlText(
            $destTable,
            $srcTable,
            $varMap,
            $conds,
            $fname,
            $insertOptions,
            $selectOptions,
            $selectJoinConds
        );
        $query = new Query(
            $sql,
            self::QUERY_CHANGE_ROWS,
            'INSERT',
            $destTable
        );
        $this->query( $query, $fname );
    }
 
    protected function isConnectionError( $errno ) {
        return false;
    }
 
    protected function isKnownStatementRollbackError( $errno ) {
        return false; // don't know; it could have caused a transaction rollback
    }
 
    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->getTransactionRoundFname() !== null ) {
            // 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->getTransactionRoundFname() !== null ) {
            // 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 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->flagsHolder->hasImplicitTrxFlag(); // automatic begin() enabled?
        // Drain the queues of transaction "idle" and "end" callbacks until they are empty
        do {
            $callbackEntries = $this->transactionManager->consumeEndCallbacks();
            $count += count( $callbackEntries );
            foreach ( $callbackEntries as $entry ) {
                $this->flagsHolder->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->flagsHolder->setFlag( self::DBO_TRX ); // restore automatic begin()
                    } else {
                        $this->flagsHolder->clearFlag( self::DBO_TRX ); // restore auto-commit
                    }
                }
            }
        } while ( $this->transactionManager->countPostCommitOrIdleCallbacks() );
 
        $this->completeCriticalSection( __METHOD__, $cs );
 
        return $count;
    }
 
    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->lastEmulatedAffectedRows = 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->lastEmulatedAffectedRows = 0; // for the sake of consistency
    }
 
    final public function startAtomic(
        $fname = __METHOD__,
        $cancelable = self::ATOMIC_NOT_CANCELABLE
    ) {
        $cs = $this->commenceCriticalSection( __METHOD__ );
 
        if ( $this->trxLevel() ) {
            // This atomic section is only one part of a larger transaction
            $sectionOwnsTrx = false;
        } else {
            // Start an implicit transaction (sets trxAutomatic)
            try {
                $this->begin( $fname, self::TRANSACTION_INTERNAL );
            } catch ( DBError $e ) {
                $this->completeCriticalSection( __METHOD__, $cs );
                throw $e;
            }
            if ( $this->flagsHolder->hasImplicitTrxFlag() ) {
                // 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->transactionManager->nextSavePointId( $this, $fname );
                    $sql = $this->platform->savepointSqlText( $savepointId );
                    $query = new Query( $sql, self::QUERY_CHANGE_TRX, 'SAVEPOINT' );
                    $this->query( $query, $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__ ) {
        [ $savepointId, $sectionId ] = $this->transactionManager->onEndAtomic( $this, $fname );
 
        $runPostCommitCallbacks = false;
 
        $cs = $this->commenceCriticalSection( __METHOD__ );
 
        // Remove the last section (no need to re-index the array)
        $finalLevelOfImplicitTrxPopped = $this->transactionManager->popAtomicLevel();
 
        try {
            if ( $finalLevelOfImplicitTrxPopped ) {
                $this->commit( $fname, self::FLUSHING_INTERNAL );
                $runPostCommitCallbacks = true;
            } elseif ( $savepointId !== null && $savepointId !== self::NOT_APPLICABLE ) {
                $sql = $this->platform->releaseSavepointSqlText( $savepointId );
                $query = new Query( $sql, self::QUERY_CHANGE_TRX, 'RELEASE SAVEPOINT' );
                $this->query( $query, $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;
        [ $savedFname, $excisedSectionIds, $newTopSectionId, $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();
            $excisedSectionIds[] = $savedSectionId;
            $newTopSectionId = $this->transactionManager->currentAtomicSectionId();
 
            if ( $savepointId !== null ) {
                // Rollback the transaction changes proposed within this atomic section
                if ( $savepointId === self::NOT_APPLICABLE ) {
                    // Atomic section started the transaction; rollback the whole transaction
                    // and trigger cancellation callbacks for all active atomic sections
                    $this->rollback( $fname, self::FLUSHING_INTERNAL );
                    $runPostRollbackCallbacks = true;
                } else {
                    // Atomic section nested within the transaction; rollback the transaction
                    // to the state prior to this section and trigger its cancellation callbacks
                    $sql = $this->platform->rollbackToSavepointSqlText( $savepointId );
                    $query = new Query( $sql, self::QUERY_CHANGE_TRX, 'ROLLBACK TO SAVEPOINT' );
                    $this->query( $query, $fname );
                    $this->transactionManager->setTrxStatusToOk(); // no exception; recovered
                }
            } 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(
                $excisedSectionIds,
                $newTopSectionId
            );
        }
 
        $this->lastEmulatedAffectedRows = 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'" );
        }
 
        $this->transactionManager->onBegin( $this, $fname );
 
        if ( $this->flagsHolder->hasImplicitTrxFlag() && $mode !== self::TRANSACTION_INTERNAL ) {
            $msg = "$fname: implicit transaction expected (DBO_TRX set)";
            throw new DBUnexpectedError( $this, $msg );
        }
 
        $this->assertHasConnectionHandle();
 
        $cs = $this->commenceCriticalSection( __METHOD__ );
        $timeStart = microtime( true );
        try {
            $this->doBegin( $fname );
        } catch ( DBError $e ) {
            $this->completeCriticalSection( __METHOD__, $cs );
            throw $e;
        }
        $timeEnd = microtime( true );
        // Treat "BEGIN" as a trivial query to gauge the RTT delay
        $rtt = max( $timeEnd - $timeStart, 0.0 );
        $this->transactionManager->onBeginInCriticalSection( $mode, $fname, $rtt );
        $this->replicationReporter->resetReplicationLagStatus( $this );
        $this->completeCriticalSection( __METHOD__, $cs );
    }
 
    protected function doBegin( $fname ) {
        $query = new Query( 'BEGIN', self::QUERY_CHANGE_TRX, 'BEGIN' );
        $this->query( $query, $fname );
    }
 
    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 {
            if ( $this->trxLevel() ) {
                $query = new Query( 'COMMIT', self::QUERY_CHANGE_TRX, 'COMMIT' );
                $this->query( $query, $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 );
    }
 
    final public function rollback( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
        if (
            $flush !== self::FLUSHING_INTERNAL &&
            $flush !== self::FLUSHING_ALL_PEERS &&
            $this->flagsHolder->hasImplicitTrxFlag()
        ) {
            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 ) {
                $this->logger->info(
                    "$fname: acknowledged server-side transaction loss on {db_server}",
                    $this->getLogContext()
                );
            }
 
            return;
        }
 
        $this->assertHasConnectionHandle();
 
        if ( $this->csmError ) {
            // Since the session state is corrupt, we cannot just rollback the transaction
            // while preserving the non-transaction session state. The handle will remain
            // marked as corrupt until flushSession() is called to reset the connection
            // and deal with any remaining callbacks.
            $this->logger->info(
                "$fname: acknowledged client-side transaction loss on {db_server}",
                $this->getLogContext()
            );
 
            return;
        }
 
        $cs = $this->commenceCriticalSection( __METHOD__ );
        if ( $this->trxLevel() ) {
            // Disconnects cause rollback anyway, so ignore those errors
            $query = new Query(
                $this->platform->rollbackSqlText(),
                self::QUERY_SILENCE_ERRORS | self::QUERY_CHANGE_TRX,
                'ROLLBACK'
            );
            $this->query( $query, $fname );
        }
        $this->transactionManager->onRollbackInCriticalSection( $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 );
    }
 
    public function setTransactionManager( TransactionManager $transactionManager ) {
        $this->transactionManager = $transactionManager;
    }
 
    public function flushSession( $fname = __METHOD__, $flush = self::FLUSHING_ONE ) {
        if (
            $flush !== self::FLUSHING_INTERNAL &&
            $flush !== self::FLUSHING_ALL_PEERS &&
            $this->flagsHolder->hasImplicitTrxFlag()
        ) {
            throw new DBUnexpectedError(
                $this,
                "$fname: Expected mass flush of all peer connections (DBO_TRX set)"
            );
        }
 
        if ( $this->csmError ) {
            // If a critical section error occurred, such as Excimer timeout exceptions raised
            // before a query response was marshalled, destroy the connection handle and reset
            // the session state tracking variables. The value of trxLevel() is irrelevant here,
            // and, in fact, might be 1 due to rollback() deferring critical section recovery.
            $this->logger->info(
                "$fname: acknowledged client-side session loss on {db_server}",
                $this->getLogContext()
            );
            $this->csmError = null;
            $this->csmFname = null;
            $this->replaceLostConnection( 2048, __METHOD__ );
 
            return;
        }
 
        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 ( $this->transactionManager->sessionStatus() === TransactionManager::STATUS_SESS_ERROR ) {
            // 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 in such cases, even temporary tables
            // and server-side config variables are lost (invocation of this method is assumed
            // to imply that such losses are tolerable).
            $this->logger->info(
                "$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->getTransactionRoundFname()
        );
        if (
            $this->transactionManager->sessionStatus() === TransactionManager::STATUS_SESS_ERROR ||
            $this->transactionManager->trxStatus() === TransactionManager::STATUS_TRX_ERROR
        ) {
            $this->rollback( $fname, self::FLUSHING_INTERNAL );
        } else {
            $this->commit( $fname, self::FLUSHING_INTERNAL );
        }
    }
 
    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 affectedRows() {
        $this->lastEmulatedAffectedRows ??= $this->lastQueryAffectedRows;
 
        return $this->lastEmulatedAffectedRows;
    }
 
    public function insertId() {
        if ( $this->lastEmulatedInsertId === null ) {
            // Guard against misuse of this method by checking affectedRows(). Note that calls
            // to insert() with "IGNORE" and calls to insertSelect() might not add any rows.
            if ( $this->affectedRows() ) {
                $this->lastEmulatedInsertId = $this->lastInsertId();
            } else {
                $this->lastEmulatedInsertId = 0;
            }
        }
 
        return $this->lastEmulatedInsertId;
    }
 
    abstract protected function lastInsertId();
 
    public function ping() {
        if ( $this->isOpen() ) {
            // If the connection was recently used, assume that it is still good
            if ( ( microtime( true ) - $this->lastPing ) < self::PING_TTL ) {
                return true;
            }
            // Send a trivial query to test the connection, triggering an automatic
            // reconnection attempt if the connection was lost
            $query = new Query(
                self::PING_QUERY,
                self::QUERY_IGNORE_DBO_TRX | self::QUERY_SILENCE_ERRORS | self::QUERY_CHANGE_NONE,
                'SELECT'
            );
            $res = $this->query( $query, __METHOD__ );
            $ok = ( $res !== false );
        } else {
            // Try to re-establish a connection
            $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->logger->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->logger->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()
                ] )
            );
        }
 
        // 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 );
 
        return $ok;
    }
 
    public static function getCacheSetOptions( ?IReadableDatabase ...$dbs ) {
        $res = [ 'lag' => 0, 'since' => INF, 'pending' => false ];
 
        foreach ( func_get_args() as $db ) {
            if ( $db instanceof IReadableDatabase ) {
                $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'] );
            }
 
            if ( $db instanceof IDatabaseForOwner ) {
                $res['pending'] = $res['pending'] ?: $db->writesPending();
            }
        }
 
        return $res;
    }
 
    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 sourceStream(
        $fp,
        ?callable $lineCallback = null,
        ?callable $resultCallback = null,
        $fname = __METHOD__,
        ?callable $inputCallback = null
    ) {
        $delimiterReset = new ScopedCallback(
            function ( $delimiter ) {
                $this->delimiter = $delimiter;
            },
            [ $this->delimiter ]
        );
        $cmd = '';
 
        while ( !feof( $fp ) ) {
            if ( $lineCallback ) {
                call_user_func( $lineCallback );
            }
 
            $line = trim( fgets( $fp ) );
 
            if ( $line == '' ) {
                continue;
            }
 
            if ( $line[0] == '-' && $line[1] == '-' ) {
                continue;
            }
 
            if ( $cmd != '' ) {
                $cmd .= ' ';
            }
 
            $done = $this->streamStatementEnd( $cmd, $line );
 
            $cmd .= "$line\n";
 
            if ( $done || feof( $fp ) ) {
                $cmd = $this->platform->replaceVars( $cmd );
 
                if ( $inputCallback ) {
                    $callbackResult = $inputCallback( $cmd );
 
                    if ( is_string( $callbackResult ) || !$callbackResult ) {
                        $cmd = $callbackResult;
                    }
                }
 
                if ( $cmd ) {
                    $res = $this->query( $cmd, $fname );
 
                    if ( $resultCallback ) {
                        $resultCallback( $res, $this );
                    }
 
                    if ( $res === false ) {
                        $err = $this->lastError();
 
                        return "Query \"{$cmd}\" failed with error code \"$err\".\n";
                    }
                }
                $cmd = '';
            }
        }
 
        ScopedCallback::consume( $delimiterReset );
        return true;
    }
 
    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;
    }
 
    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->logger->info(
                __METHOD__ . ": failed to acquire lock '{lockname}'",
                [
                    'lockname' => $lockName,
                    'db_log_category' => 'locking'
                ]
            );
        }
 
        return $this->flagsHolder::contains( $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 ) {
        if ( !isset( $this->sessionNamedLocks[$lockName] ) ) {
            $released = false;
            $this->logger->warning(
                __METHOD__ . ": trying to release unheld lock '$lockName'\n",
                [ 'db_log_category' => 'locking' ]
            );
        } else {
            $released = $this->doUnlock( $lockName, $method );
            if ( $released ) {
                unset( $this->sessionNamedLocks[$lockName] );
            } else {
                $this->logger->warning(
                    __METHOD__ . ": failed to release lock '$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 ) {
            // Note that the callback can be reached due to an exception making the calling
            // function end early. If the transaction/session is in an error state, avoid log
            // spam and confusing replacement of an original DBError with one about unlock().
            // Unlock query will fail anyway; avoid possibly triggering errors in rollback()
            if (
                $this->transactionManager->sessionStatus() === TransactionManager::STATUS_SESS_ERROR ||
                $this->transactionManager->trxStatus() === TransactionManager::STATUS_TRX_ERROR
            ) {
                return;
            }
            if ( $this->trxLevel() ) {
                $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 dropTable( $table, $fname = __METHOD__ ) {
        if ( !$this->tableExists( $table, $fname ) ) {
            return false;
        }
 
        $query = new Query(
            $this->platform->dropTableSqlText( $table ),
            self::QUERY_CHANGE_SCHEMA,
            'DROP',
            $table
        );
        $this->query( $query, $fname );
 
        return true;
    }
 
    public function truncateTable( $table, $fname = __METHOD__ ) {
        $sql = "TRUNCATE TABLE " . $this->tableName( $table );
        $query = new Query( $sql, self::QUERY_CHANGE_SCHEMA, 'TRUNCATE', $table );
        $this->query( $query, $fname );
    }
 
    public function isReadOnly() {
        return ( $this->getReadOnlyReason() !== null );
    }
 
    protected function getReadOnlyReason() {
        $reason = $this->replicationReporter->getTopologyBasedReadOnlyReason();
        if ( $reason ) {
            return $reason;
        }
 
        $reason = $this->getLBInfo( self::LB_READ_ONLY_REASON );
        if ( is_string( $reason ) ) {
            return [ $reason, 'lb' ];
        }
 
        return null;
    }
 
    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() {
        $id = spl_object_id( $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 ) ) {
            $handleId = spl_object_id( $this->conn );
            $description .= " (handle id #$handleId)";
        }
 
        return $description;
    }
 
    public function __clone() {
        $this->logger->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 DatabaseFlags. Avoid using them outside of rdbms library */
 
    public function setFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
        $this->flagsHolder->setFlag( $flag, $remember );
    }
 
    public function clearFlag( $flag, $remember = self::REMEMBER_NOTHING ) {
        $this->flagsHolder->clearFlag( $flag, $remember );
    }
 
    public function restoreFlags( $state = self::RESTORE_PRIOR ) {
        $this->flagsHolder->restoreFlags( $state );
    }
 
    public function getFlag( $flag ) {
        return $this->flagsHolder->getFlag( $flag );
    }
 
    /* End of methods delegated to DatabaseFlags. */
 
    /* Start of methods delegated to TransactionManager. Avoid using them outside of rdbms library */
 
    final public function trxLevel() {
        // FIXME: A lot of tests disable constructor leading to trx manager being
        // null and breaking, this is unacceptable but hopefully this should
        // happen less by moving these functions to the transaction manager class.
        if ( !$this->transactionManager ) {
            $this->transactionManager = new TransactionManager( new NullLogger() );
        }
        return $this->transactionManager->trxLevel();
    }
 
    public function trxTimestamp() {
        return $this->transactionManager->trxTimestamp();
    }
 
    public function trxStatus() {
        return $this->transactionManager->trxStatus();
    }
 
    public function writesPending() {
        return $this->transactionManager->writesPending();
    }
 
    public function writesOrCallbacksPending() {
        return $this->transactionManager->writesOrCallbacksPending();
    }
 
    public function pendingWriteQueryDuration( $type = self::ESTIMATE_TOTAL ) {
        return $this->transactionManager->pendingWriteQueryDuration( $type );
    }
 
    public function pendingWriteCallers() {
        if ( !$this->transactionManager ) {
            return [];
        }
        return $this->transactionManager->pendingWriteCallers();
    }
 
    public function pendingWriteAndCallbackCallers() {
        if ( !$this->transactionManager ) {
            return [];
        }
        return $this->transactionManager->pendingWriteAndCallbackCallers();
    }
 
    public function runOnTransactionPreCommitCallbacks() {
        return $this->transactionManager->runOnTransactionPreCommitCallbacks( $this );
    }
 
    public function explicitTrxActive() {
        return $this->transactionManager->explicitTrxActive();
    }
 
    /* End of methods delegated to TransactionManager. */
 
    /* Start of methods delegated to SQLPlatform. Avoid using them outside of rdbms library */
 
    public function implicitOrderby() {
        return $this->platform->implicitOrderby();
    }
 
    public function selectSQLText(
        $tables, $vars, $conds = '', $fname = __METHOD__, $options = [], $join_conds = []
    ) {
        return $this->platform->selectSQLText( $tables, $vars, $conds, $fname, $options, $join_conds );
    }
 
    public function buildComparison( string $op, array $conds ): string {
        return $this->platform->buildComparison( $op, $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( string $name, $format = 'quoted' ) {
        return $this->platform->tableName( $name, $format );
    }
 
    public function tableNamesN( ...$tables ) {
        return $this->platform->tableNamesN( ...$tables );
    }
 
    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, $options = [] ) {
        return $this->platform->unionQueries( $sqls, $all, $options );
    }
 
    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, $tables, $field, $conds = '', $join_conds = []
    ) {
        return $this->platform->buildGroupConcatField( $delim, $tables, $field, $conds, $join_conds );
    }
 
    public function buildSelectSubquery(
        $tables, $vars, $conds = '', $fname = __METHOD__,
        $options = [], $join_conds = []
    ) {
        return $this->platform->buildSelectSubquery( $tables, $vars, $conds, $fname, $options, $join_conds );
    }
 
    public function buildExcludedValue( $column ) {
        return $this->platform->buildExcludedValue( $column );
    }
 
    public function setSchemaVars( $vars ) {
        $this->platform->setSchemaVars( $vars );
    }
 
    /* End of methods delegated to SQLPlatform. */
 
    /* Start of methods delegated to ReplicationReporter. */
    public function primaryPosWait( DBPrimaryPos $pos, $timeout ) {
        return $this->replicationReporter->primaryPosWait( $this, $pos, $timeout );
    }
 
    public function getPrimaryPos() {
        return $this->replicationReporter->getPrimaryPos( $this );
    }
 
    public function getLag() {
        return $this->replicationReporter->getLag( $this );
    }
 
    public function getSessionLagStatus() {
        return $this->replicationReporter->getSessionLagStatus( $this );
    }
 
    /* End of methods delegated to ReplicationReporter. */
}