diff --git a/lib/Doctrine/DBAL/Connection.php b/lib/Doctrine/DBAL/Connection.php
index 06ebae21944..4d79fb739b6 100644
--- a/lib/Doctrine/DBAL/Connection.php
+++ b/lib/Doctrine/DBAL/Connection.php
@@ -22,7 +22,6 @@
 use Exception;
 use Throwable;
 use function array_key_exists;
-use function array_merge;
 use function assert;
 use function func_get_args;
 use function implode;
@@ -599,24 +598,26 @@ public function isTransactionActive()
     }
 
     /**
-     * Gathers conditions for an update or delete call.
+     * Adds identifier condition to the query components
      *
-     * @param mixed[] $identifiers Input array of columns to values
+     * @param mixed[]  $identifier Map of key columns to their values
+     * @param string[] $columns    Column names
+     * @param mixed[]  $values     Column values
+     * @param string[] $conditions Key conditions
      *
-     * @return string[][] a triplet with:
-     *                    - the first key being the columns
-     *                    - the second key being the values
-     *                    - the third key being the conditions
+     * @throws DBALException
      */
-    private function gatherConditions(array $identifiers)
-    {
-        $columns    = [];
-        $values     = [];
-        $conditions = [];
+    private function addIdentifierCondition(
+        array $identifier,
+        array &$columns,
+        array &$values,
+        array &$conditions
+    ) : void {
+        $platform = $this->getDatabasePlatform();
 
-        foreach ($identifiers as $columnName => $value) {
+        foreach ($identifier as $columnName => $value) {
             if ($value === null) {
-                $conditions[] = $this->getDatabasePlatform()->getIsNullExpression($columnName);
+                $conditions[] = $platform->getIsNullExpression($columnName);
                 continue;
             }
 
@@ -624,8 +625,6 @@ private function gatherConditions(array $identifiers)
             $values[]     = $value;
             $conditions[] = $columnName . ' = ?';
         }
-
-        return [$columns, $values, $conditions];
     }
 
     /**
@@ -648,7 +647,9 @@ public function delete($tableExpression, array $identifier, array $types = [])
             throw InvalidArgumentException::fromEmptyCriteria();
         }
 
-        [$columns, $values, $conditions] = $this->gatherConditions($identifier);
+        $columns = $values = $conditions = [];
+
+        $this->addIdentifierCondition($identifier, $columns, $values, $conditions);
 
         return $this->executeUpdate(
             'DELETE FROM ' . $tableExpression . ' WHERE ' . implode(' AND ', $conditions),
@@ -713,19 +714,15 @@ public function getTransactionIsolation()
      */
     public function update($tableExpression, array $data, array $identifier, array $types = [])
     {
-        $setColumns = [];
-        $setValues  = [];
-        $set        = [];
+        $columns = $values = $conditions = $set = [];
 
         foreach ($data as $columnName => $value) {
-            $setColumns[] = $columnName;
-            $setValues[]  = $value;
-            $set[]        = $columnName . ' = ?';
+            $columns[] = $columnName;
+            $values[]  = $value;
+            $set[]     = $columnName . ' = ?';
         }
 
-        [$conditionColumns, $conditionValues, $conditions] = $this->gatherConditions($identifier);
-        $columns                                           = array_merge($setColumns, $conditionColumns);
-        $values                                            = array_merge($setValues, $conditionValues);
+        $this->addIdentifierCondition($identifier, $columns, $values, $conditions);
 
         if (is_string(key($types))) {
             $types = $this->extractTypeValues($columns, $types);
@@ -777,7 +774,7 @@ public function insert($tableExpression, array $data, array $types = [])
     /**
      * Extract ordered type list from an ordered column list and type map.
      *
-     * @param string[]       $columnList
+     * @param int[]|string[] $columnList
      * @param int[]|string[] $types
      *
      * @return int[]|string[]
diff --git a/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Connection.php b/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Connection.php
index bd80e6e49a7..cb1e6018f3e 100644
--- a/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Connection.php
+++ b/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Connection.php
@@ -42,13 +42,16 @@ public function __construct(array $params, $username, $password, $driverOptions
         $isPersistent = (isset($params['persistent']) && $params['persistent'] === true);
 
         if ($isPersistent) {
-            $this->conn = db2_pconnect($params['dbname'], $username, $password, $driverOptions);
+            $conn = db2_pconnect($params['dbname'], $username, $password, $driverOptions);
         } else {
-            $this->conn = db2_connect($params['dbname'], $username, $password, $driverOptions);
+            $conn = db2_connect($params['dbname'], $username, $password, $driverOptions);
         }
-        if (! $this->conn) {
+
+        if ($conn === false) {
             throw new DB2Exception(db2_conn_errormsg());
         }
+
+        $this->conn = $conn;
     }
 
     /**
diff --git a/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Statement.php b/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Statement.php
index 4244b256414..af6e852bc43 100644
--- a/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Statement.php
+++ b/lib/Doctrine/DBAL/Driver/IBMDB2/DB2Statement.php
@@ -127,16 +127,16 @@ public function bindParam($column, &$variable, $type = ParameterType::STRING, $l
     }
 
     /**
-     * @param int|string $parameter Parameter position or name
-     * @param mixed      $variable
+     * @param int   $position Parameter position
+     * @param mixed $variable
      *
      * @throws DB2Exception
      */
-    private function bind($parameter, &$variable, int $parameterType, int $dataType) : void
+    private function bind($position, &$variable, int $parameterType, int $dataType) : void
     {
-        $this->bindParam[$parameter] =& $variable;
+        $this->bindParam[$position] =& $variable;
 
-        if (! db2_bind_param($this->stmt, $parameter, 'variable', $parameterType, $dataType)) {
+        if (! db2_bind_param($this->stmt, $position, 'variable', $parameterType, $dataType)) {
             throw new DB2Exception(db2_stmt_errormsg());
         }
     }
diff --git a/lib/Doctrine/DBAL/Driver/Mysqli/MysqliStatement.php b/lib/Doctrine/DBAL/Driver/Mysqli/MysqliStatement.php
index e7600d92296..85a88f33401 100644
--- a/lib/Doctrine/DBAL/Driver/Mysqli/MysqliStatement.php
+++ b/lib/Doctrine/DBAL/Driver/Mysqli/MysqliStatement.php
@@ -19,6 +19,7 @@
 use function fread;
 use function get_resource_type;
 use function is_array;
+use function is_int;
 use function is_resource;
 use function sprintf;
 use function str_repeat;
@@ -41,7 +42,7 @@ class MysqliStatement implements IteratorAggregate, Statement
     /** @var mysqli_stmt */
     protected $_stmt;
 
-    /** @var string[]|bool|null */
+    /** @var string[]|false|null */
     protected $_columnNames;
 
     /** @var mixed[]|null */
@@ -78,11 +79,15 @@ class MysqliStatement implements IteratorAggregate, Statement
     public function __construct(mysqli $conn, $prepareString)
     {
         $this->_conn = $conn;
-        $this->_stmt = $conn->prepare($prepareString);
-        if ($this->_stmt === false) {
+
+        $stmt = $conn->prepare($prepareString);
+
+        if ($stmt === false) {
             throw new MysqliException($this->_conn->error, $this->_conn->sqlstate, $this->_conn->errno);
         }
 
+        $this->_stmt = $stmt;
+
         $paramCount = $this->_stmt->param_count;
         if (0 >= $paramCount) {
             return;
@@ -97,14 +102,14 @@ public function __construct(mysqli $conn, $prepareString)
      */
     public function bindParam($column, &$variable, $type = ParameterType::STRING, $length = null)
     {
+        assert(is_int($column));
+
         if (! isset(self::$_paramTypeMap[$type])) {
             throw new MysqliException(sprintf("Unknown type: '%s'", $type));
         }
 
-        $type = self::$_paramTypeMap[$type];
-
         $this->_bindedValues[$column] =& $variable;
-        $this->types[$column - 1]     = $type;
+        $this->types[$column - 1]     = self::$_paramTypeMap[$type];
 
         return true;
     }
@@ -114,15 +119,15 @@ public function bindParam($column, &$variable, $type = ParameterType::STRING, $l
      */
     public function bindValue($param, $value, $type = ParameterType::STRING)
     {
+        assert(is_int($param));
+
         if (! isset(self::$_paramTypeMap[$type])) {
             throw new MysqliException(sprintf("Unknown type: '%s'", $type));
         }
 
-        $type = self::$_paramTypeMap[$type];
-
         $this->_values[$param]       = $value;
         $this->_bindedValues[$param] =& $this->_values[$param];
-        $this->types[$param - 1]     = $type;
+        $this->types[$param - 1]     = self::$_paramTypeMap[$type];
 
         return true;
     }
@@ -134,15 +139,11 @@ public function execute($params = null)
     {
         if ($this->_bindedValues !== null) {
             if ($params !== null) {
-                if (! $this->_bindValues($params)) {
+                if (! $this->bindUntypedValues($params)) {
                     throw new MysqliException($this->_stmt->error, $this->_stmt->errno);
                 }
             } else {
-                [$types, $values, $streams] = $this->separateBoundValues();
-                if (! $this->_stmt->bind_param($types, ...$values)) {
-                    throw new MysqliException($this->_stmt->error, $this->_stmt->sqlstate, $this->_stmt->errno);
-                }
-                $this->sendLongData($streams);
+                $this->bindTypedParameters();
             }
         }
 
@@ -153,10 +154,14 @@ public function execute($params = null)
         if ($this->_columnNames === null) {
             $meta = $this->_stmt->result_metadata();
             if ($meta !== false) {
+                $fields = $meta->fetch_fields();
+                assert(is_array($fields));
+
                 $columnNames = [];
-                foreach ($meta->fetch_fields() as $col) {
+                foreach ($fields as $col) {
                     $columnNames[] = $col->name;
                 }
+
                 $meta->free();
 
                 $this->_columnNames = $columnNames;
@@ -200,12 +205,9 @@ public function execute($params = null)
     }
 
     /**
-     * Split $this->_bindedValues into those values that need to be sent using mysqli::send_long_data()
-     * and those that can be bound the usual way.
-     *
-     * @return array<int, array<int|string, mixed>|string>
+     * Binds parameters with known types previously bound to the statement
      */
-    private function separateBoundValues()
+    private function bindTypedParameters()
     {
         $streams = $values = [];
         $types   = $this->types;
@@ -231,7 +233,11 @@ private function separateBoundValues()
             $values[$parameter] = $value;
         }
 
-        return [$types, $values, $streams];
+        if (! $this->_stmt->bind_param($types, ...$values)) {
+            throw new MysqliException($this->_stmt->error, $this->_stmt->sqlstate, $this->_stmt->errno);
+        }
+
+        $this->sendLongData($streams);
     }
 
     /**
@@ -263,7 +269,7 @@ private function sendLongData($streams)
      *
      * @return bool
      */
-    private function _bindValues($values)
+    private function bindUntypedValues(array $values)
     {
         $params = [];
         $types  = str_repeat('s', count($values));
diff --git a/lib/Doctrine/DBAL/Driver/OCI8/OCI8Connection.php b/lib/Doctrine/DBAL/Driver/OCI8/OCI8Connection.php
index 5ebc877a898..35333e8d2d7 100644
--- a/lib/Doctrine/DBAL/Driver/OCI8/OCI8Connection.php
+++ b/lib/Doctrine/DBAL/Driver/OCI8/OCI8Connection.php
@@ -54,13 +54,15 @@ public function __construct($username, $password, $db, $charset = null, $session
             define('OCI_NO_AUTO_COMMIT', 0);
         }
 
-        $this->dbh = $persistent
+        $dbh = $persistent
             ? @oci_pconnect($username, $password, $db, $charset, $sessionMode)
             : @oci_connect($username, $password, $db, $charset, $sessionMode);
 
-        if (! $this->dbh) {
+        if ($dbh === false) {
             throw OCI8Exception::fromErrorInfo(oci_error());
         }
+
+        $this->dbh = $dbh;
     }
 
     /**
@@ -71,17 +73,23 @@ public function __construct($username, $password, $db, $charset = null, $session
      */
     public function getServerVersion()
     {
-        if (! preg_match('/\s+(\d+\.\d+\.\d+\.\d+\.\d+)\s+/', oci_server_version($this->dbh), $version)) {
+        $version = oci_server_version($this->dbh);
+
+        if ($version === false) {
+            throw OCI8Exception::fromErrorInfo(oci_error($this->dbh));
+        }
+
+        if (! preg_match('/\s+(\d+\.\d+\.\d+\.\d+\.\d+)\s+/', $version, $matches)) {
             throw new UnexpectedValueException(
                 sprintf(
                     'Unexpected database version string "%s". Cannot parse an appropriate version number from it. ' .
                     'Please report this database version string to the Doctrine team.',
-                    oci_server_version($this->dbh)
+                    $version
                 )
             );
         }
 
-        return $version[1];
+        return $matches[1];
     }
 
     /**
@@ -222,6 +230,12 @@ public function errorCode()
      */
     public function errorInfo()
     {
-        return oci_error($this->dbh);
+        $error = oci_error($this->dbh);
+
+        if ($error === false) {
+            return [];
+        }
+
+        return $error;
     }
 }
diff --git a/lib/Doctrine/DBAL/Driver/OCI8/OCI8Exception.php b/lib/Doctrine/DBAL/Driver/OCI8/OCI8Exception.php
index 9d61ad42d08..af3a9d1a7a9 100644
--- a/lib/Doctrine/DBAL/Driver/OCI8/OCI8Exception.php
+++ b/lib/Doctrine/DBAL/Driver/OCI8/OCI8Exception.php
@@ -7,12 +7,16 @@
 class OCI8Exception extends AbstractDriverException
 {
     /**
-     * @param mixed[] $error
+     * @param mixed[]|false $error
      *
      * @return \Doctrine\DBAL\Driver\OCI8\OCI8Exception
      */
     public static function fromErrorInfo($error)
     {
+        if ($error === false) {
+            return new self('Database error occurred but no error information was retrieved from the driver.');
+        }
+
         return new self($error['message'], null, $error['code']);
     }
 }
diff --git a/lib/Doctrine/DBAL/Driver/OCI8/OCI8Statement.php b/lib/Doctrine/DBAL/Driver/OCI8/OCI8Statement.php
index 568f3713b5a..32feaef93e3 100644
--- a/lib/Doctrine/DBAL/Driver/OCI8/OCI8Statement.php
+++ b/lib/Doctrine/DBAL/Driver/OCI8/OCI8Statement.php
@@ -23,9 +23,11 @@
 use const PREG_OFFSET_CAPTURE;
 use const SQLT_CHR;
 use function array_key_exists;
+use function assert;
 use function count;
 use function implode;
-use function is_numeric;
+use function is_int;
+use function is_resource;
 use function oci_bind_by_name;
 use function oci_cancel;
 use function oci_error;
@@ -92,16 +94,20 @@ class OCI8Statement implements IteratorAggregate, Statement
     /**
      * Creates a new OCI8Statement that uses the given connection handle and SQL statement.
      *
-     * @param resource $dbh       The connection handle.
-     * @param string   $statement The SQL statement.
+     * @param resource $dbh   The connection handle.
+     * @param string   $query The SQL query.
      */
-    public function __construct($dbh, $statement, OCI8Connection $conn)
+    public function __construct($dbh, $query, OCI8Connection $conn)
     {
-        [$statement, $paramMap] = self::convertPositionalToNamedPlaceholders($statement);
-        $this->_sth             = oci_parse($dbh, $statement);
-        $this->_dbh             = $dbh;
-        $this->_paramMap        = $paramMap;
-        $this->_conn            = $conn;
+        [$query, $paramMap] = self::convertPositionalToNamedPlaceholders($query);
+
+        $stmt = oci_parse($dbh, $query);
+        assert(is_resource($stmt));
+
+        $this->_sth      = $stmt;
+        $this->_dbh      = $dbh;
+        $this->_paramMap = $paramMap;
+        $this->_conn     = $conn;
     }
 
     /**
@@ -272,6 +278,10 @@ public function bindParam($column, &$variable, $type = ParameterType::STRING, $l
 
         if ($type === ParameterType::LARGE_OBJECT) {
             $lob = oci_new_descriptor($this->_dbh, OCI_D_LOB);
+
+            $class = 'OCI-Lob';
+            assert($lob instanceof $class);
+
             $lob->writeTemporary($variable, OCI_TEMP_BLOB);
 
             $variable =& $lob;
@@ -327,7 +337,7 @@ public function closeCursor()
      */
     public function columnCount()
     {
-        return oci_num_fields($this->_sth);
+        return oci_num_fields($this->_sth) ?: 0;
     }
 
     /**
@@ -348,7 +358,13 @@ public function errorCode()
      */
     public function errorInfo()
     {
-        return oci_error($this->_sth);
+        $error = oci_error($this->_sth);
+
+        if ($error === false) {
+            return [];
+        }
+
+        return $error;
     }
 
     /**
@@ -358,8 +374,9 @@ public function execute($params = null)
     {
         if ($params) {
             $hasZeroIndex = array_key_exists(0, $params);
+
             foreach ($params as $key => $val) {
-                if ($hasZeroIndex && is_numeric($key)) {
+                if ($hasZeroIndex && is_int($key)) {
                     $this->bindValue($key + 1, $val);
                 } else {
                     $this->bindValue($key, $val);
@@ -505,6 +522,6 @@ public function fetchColumn($columnIndex = 0)
      */
     public function rowCount()
     {
-        return oci_num_rows($this->_sth);
+        return oci_num_rows($this->_sth) ?: 0;
     }
 }
diff --git a/lib/Doctrine/DBAL/Driver/PDOConnection.php b/lib/Doctrine/DBAL/Driver/PDOConnection.php
index 2155140b2a8..11f5febc87b 100644
--- a/lib/Doctrine/DBAL/Driver/PDOConnection.php
+++ b/lib/Doctrine/DBAL/Driver/PDOConnection.php
@@ -4,7 +4,7 @@
 
 use Doctrine\DBAL\ParameterType;
 use PDO;
-use function count;
+use function assert;
 use function func_get_args;
 
 /**
@@ -69,23 +69,13 @@ public function prepare($prepareString, $driverOptions = [])
      */
     public function query()
     {
-        $args      = func_get_args();
-        $argsCount = count($args);
+        $args = func_get_args();
 
         try {
-            if ($argsCount === 4) {
-                return parent::query($args[0], $args[1], $args[2], $args[3]);
-            }
+            $stmt = parent::query(...$args);
+            assert($stmt instanceof \PDOStatement);
 
-            if ($argsCount === 3) {
-                return parent::query($args[0], $args[1], $args[2]);
-            }
-
-            if ($argsCount === 2) {
-                return parent::query($args[0], $args[1]);
-            }
-
-            return parent::query($args[0]);
+            return $stmt;
         } catch (\PDOException $exception) {
             throw new PDOException($exception);
         }
diff --git a/lib/Doctrine/DBAL/Driver/PDOSqlsrv/Driver.php b/lib/Doctrine/DBAL/Driver/PDOSqlsrv/Driver.php
index 6543e32392e..8bc8671620f 100644
--- a/lib/Doctrine/DBAL/Driver/PDOSqlsrv/Driver.php
+++ b/lib/Doctrine/DBAL/Driver/PDOSqlsrv/Driver.php
@@ -16,13 +16,21 @@ class Driver extends AbstractSQLServerDriver
      */
     public function connect(array $params, $username = null, $password = null, array $driverOptions = [])
     {
-        [$driverOptions, $connectionOptions] = $this->splitOptions($driverOptions);
+        $pdoOptions = $dsnOptions = [];
+
+        foreach ($driverOptions as $option => $value) {
+            if (is_int($option)) {
+                $pdoOptions[$option] = $value;
+            } else {
+                $dsnOptions[$option] = $value;
+            }
+        }
 
         return new Connection(
-            $this->_constructPdoDsn($params, $connectionOptions),
+            $this->_constructPdoDsn($params, $dsnOptions),
             $username,
             $password,
-            $driverOptions
+            $pdoOptions
         );
     }
 
@@ -57,29 +65,6 @@ private function _constructPdoDsn(array $params, array $connectionOptions)
         return $dsn . $this->getConnectionOptionsDsn($connectionOptions);
     }
 
-    /**
-     * Separates a connection options from a driver options
-     *
-     * @param int[]|string[] $options
-     *
-     * @return int[][]|string[][]
-     */
-    private function splitOptions(array $options) : array
-    {
-        $driverOptions     = [];
-        $connectionOptions = [];
-
-        foreach ($options as $optionKey => $optionValue) {
-            if (is_int($optionKey)) {
-                $driverOptions[$optionKey] = $optionValue;
-            } else {
-                $connectionOptions[$optionKey] = $optionValue;
-            }
-        }
-
-        return [$driverOptions, $connectionOptions];
-    }
-
     /**
      * Converts a connection options array to the DSN
      *
diff --git a/lib/Doctrine/DBAL/Driver/PDOStatement.php b/lib/Doctrine/DBAL/Driver/PDOStatement.php
index 2aed89fbf07..f734659c2b7 100644
--- a/lib/Doctrine/DBAL/Driver/PDOStatement.php
+++ b/lib/Doctrine/DBAL/Driver/PDOStatement.php
@@ -6,6 +6,8 @@
 use Doctrine\DBAL\ParameterType;
 use PDO;
 use const E_USER_DEPRECATED;
+use function assert;
+use function is_array;
 use function sprintf;
 use function trigger_error;
 
@@ -153,20 +155,21 @@ public function fetchAll($fetchMode = null, $fetchArgument = null, $ctorArgs = n
     {
         $fetchMode = $this->convertFetchMode($fetchMode);
 
-        try {
-            if ($fetchMode === null && $fetchArgument === null && $ctorArgs === null) {
-                return parent::fetchAll();
-            }
-
-            if ($fetchArgument === null && $ctorArgs === null) {
-                return parent::fetchAll($fetchMode);
-            }
+        if ($fetchMode === null && $fetchArgument === null && $ctorArgs === null) {
+            $args = [];
+        } elseif ($fetchArgument === null && $ctorArgs === null) {
+            $args = [$fetchMode];
+        } elseif ($ctorArgs === null) {
+            $args = [$fetchMode, $fetchArgument];
+        } else {
+            $args = [$fetchMode, $fetchArgument, $ctorArgs];
+        }
 
-            if ($ctorArgs === null) {
-                return parent::fetchAll($fetchMode, $fetchArgument);
-            }
+        try {
+            $data = parent::fetchAll(...$args);
+            assert(is_array($data));
 
-            return parent::fetchAll($fetchMode, $fetchArgument, $ctorArgs);
+            return $data;
         } catch (\PDOException $exception) {
             throw new PDOException($exception);
         }
diff --git a/lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereStatement.php b/lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereStatement.php
index 6354836a478..886bb245873 100644
--- a/lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereStatement.php
+++ b/lib/Doctrine/DBAL/Driver/SQLAnywhere/SQLAnywhereStatement.php
@@ -17,7 +17,7 @@
 use function func_num_args;
 use function gettype;
 use function is_array;
-use function is_numeric;
+use function is_int;
 use function is_object;
 use function is_resource;
 use function is_string;
@@ -177,9 +177,11 @@ public function execute($params = null)
             $hasZeroIndex = array_key_exists(0, $params);
 
             foreach ($params as $key => $val) {
-                $key = $hasZeroIndex && is_numeric($key) ? $key + 1 : $key;
-
-                $this->bindValue($key, $val);
+                if ($hasZeroIndex && is_int($key)) {
+                    $this->bindValue($key + 1, $val);
+                } else {
+                    $this->bindValue($key, $val);
+                }
             }
         }
 
diff --git a/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php b/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php
index f1f9ddd1d79..dbda962006a 100644
--- a/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php
+++ b/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvConnection.php
@@ -44,10 +44,13 @@ public function __construct($serverName, $connectionOptions)
             throw SQLSrvException::fromSqlSrvErrors();
         }
 
-        $this->conn = sqlsrv_connect($serverName, $connectionOptions);
-        if (! $this->conn) {
+        $conn = sqlsrv_connect($serverName, $connectionOptions);
+
+        if ($conn === false) {
             throw SQLSrvException::fromSqlSrvErrors();
         }
+
+        $this->conn         = $conn;
         $this->lastInsertId = new LastInsertId();
     }
 
@@ -115,7 +118,13 @@ public function exec($statement)
             throw SQLSrvException::fromSqlSrvErrors();
         }
 
-        return sqlsrv_rows_affected($stmt);
+        $rowsAffected = sqlsrv_rows_affected($stmt);
+
+        if ($rowsAffected === false) {
+            throw SQLSrvException::fromSqlSrvErrors();
+        }
+
+        return $rowsAffected;
     }
 
     /**
diff --git a/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvStatement.php b/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvStatement.php
index 147ef76e1a0..49ca2567845 100644
--- a/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvStatement.php
+++ b/lib/Doctrine/DBAL/Driver/SQLSrv/SQLSrvStatement.php
@@ -18,6 +18,7 @@
 use function count;
 use function func_get_args;
 use function in_array;
+use function is_int;
 use function is_numeric;
 use function sqlsrv_errors;
 use function sqlsrv_execute;
@@ -200,7 +201,11 @@ public function closeCursor()
      */
     public function columnCount()
     {
-        return sqlsrv_num_fields($this->stmt);
+        if ($this->stmt === null) {
+            return 0;
+        }
+
+        return sqlsrv_num_fields($this->stmt) ?: 0;
     }
 
     /**
@@ -231,9 +236,13 @@ public function execute($params = null)
     {
         if ($params) {
             $hasZeroIndex = array_key_exists(0, $params);
+
             foreach ($params as $key => $val) {
-                $key = $hasZeroIndex && is_numeric($key) ? $key + 1 : $key;
-                $this->bindValue($key, $val);
+                if ($hasZeroIndex && is_int($key)) {
+                    $this->bindValue($key + 1, $val);
+                } else {
+                    $this->bindValue($key, $val);
+                }
             }
         }
 
@@ -406,6 +415,10 @@ public function fetchColumn($columnIndex = 0)
      */
     public function rowCount()
     {
-        return sqlsrv_rows_affected($this->stmt);
+        if ($this->stmt === null) {
+            return 0;
+        }
+
+        return sqlsrv_rows_affected($this->stmt) ?: 0;
     }
 }
diff --git a/lib/Doctrine/DBAL/DriverManager.php b/lib/Doctrine/DBAL/DriverManager.php
index 658123199c0..cb9db2c0221 100644
--- a/lib/Doctrine/DBAL/DriverManager.php
+++ b/lib/Doctrine/DBAL/DriverManager.php
@@ -18,8 +18,10 @@
 use function array_keys;
 use function array_map;
 use function array_merge;
+use function assert;
 use function class_implements;
 use function in_array;
+use function is_string;
 use function is_subclass_of;
 use function parse_str;
 use function parse_url;
@@ -263,6 +265,8 @@ private static function parseDatabaseUrl(array $params) : array
 
         // (pdo_)?sqlite3?:///... => (pdo_)?sqlite3?://localhost/... or else the URL will be invalid
         $url = preg_replace('#^((?:pdo_)?sqlite3?):///#', '$1://localhost/', $params['url']);
+        assert(is_string($url));
+
         $url = parse_url($url);
 
         if ($url === false) {
@@ -414,6 +418,7 @@ private static function parseDatabaseUrlScheme(array $url, array $params) : arra
 
             // URL schemes must not contain underscores, but dashes are ok
             $driver = str_replace('-', '_', $url['scheme']);
+            assert(is_string($driver));
 
             // The requested driver from the URL scheme takes precedence over the
             // default driver from the connection parameters. If the driver is
diff --git a/lib/Doctrine/DBAL/Platforms/AbstractPlatform.php b/lib/Doctrine/DBAL/Platforms/AbstractPlatform.php
index 68994846864..439f6f541d2 100644
--- a/lib/Doctrine/DBAL/Platforms/AbstractPlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/AbstractPlatform.php
@@ -864,9 +864,9 @@ public function getLowerExpression($str)
     /**
      * Returns the SQL snippet to get the position of the first occurrence of substring $substr in string $str.
      *
-     * @param string   $str      Literal string.
-     * @param string   $substr   Literal string to find.
-     * @param int|bool $startPos Position to start at, beginning of string by default.
+     * @param string    $str      Literal string.
+     * @param string    $substr   Literal string to find.
+     * @param int|false $startPos Position to start at, beginning of string by default.
      *
      * @return string
      *
@@ -1832,6 +1832,10 @@ protected function getCreateIndexSQLFlags(Index $index)
      */
     public function getCreatePrimaryKeySQL(Index $index, $table)
     {
+        if ($table instanceof Table) {
+            $table = $table->getQuotedName($this);
+        }
+
         return 'ALTER TABLE ' . $table . ' ADD PRIMARY KEY (' . $this->getIndexFieldDeclarationListSQL($index) . ')';
     }
 
@@ -2066,11 +2070,14 @@ protected function getPreAlterTableIndexForeignKeySQL(TableDiff $diff)
      */
     protected function getPostAlterTableIndexForeignKeySQL(TableDiff $diff)
     {
-        $tableName = $diff->newName !== false
-            ? $diff->getNewName()->getQuotedName($this)
-            : $diff->getName($this)->getQuotedName($this);
+        $sql     = [];
+        $newName = $diff->getNewName();
 
-        $sql = [];
+        if ($newName !== false) {
+            $tableName = $newName->getQuotedName($this);
+        } else {
+            $tableName = $diff->getName($this)->getQuotedName($this);
+        }
 
         if ($this->supportsForeignKeyConstraints()) {
             foreach ($diff->addedForeignKeys as $foreignKey) {
diff --git a/lib/Doctrine/DBAL/Platforms/DB2Platform.php b/lib/Doctrine/DBAL/Platforms/DB2Platform.php
index 605122115d4..bfe2790e30c 100644
--- a/lib/Doctrine/DBAL/Platforms/DB2Platform.php
+++ b/lib/Doctrine/DBAL/Platforms/DB2Platform.php
@@ -599,8 +599,14 @@ public function getAlterTableSQL(TableDiff $diff)
 
             $sql = array_merge($sql, $commentsSQL);
 
-            if ($diff->newName !== false) {
-                $sql[] =  'RENAME TABLE ' . $diff->getName($this)->getQuotedName($this) . ' TO ' . $diff->getNewName()->getQuotedName($this);
+            $newName = $diff->getNewName();
+
+            if ($newName !== false) {
+                $sql[] = sprintf(
+                    'RENAME TABLE %s TO %s',
+                    $diff->getName($this)->getQuotedName($this),
+                    $newName->getQuotedName($this)
+                );
             }
 
             $sql = array_merge(
diff --git a/lib/Doctrine/DBAL/Platforms/DrizzlePlatform.php b/lib/Doctrine/DBAL/Platforms/DrizzlePlatform.php
index 27aacf42286..bb5b5cad36d 100644
--- a/lib/Doctrine/DBAL/Platforms/DrizzlePlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/DrizzlePlatform.php
@@ -480,8 +480,10 @@ public function getAlterTableSQL(TableDiff $diff)
         $columnSql  = [];
         $queryParts = [];
 
-        if ($diff->newName !== false) {
-            $queryParts[] =  'RENAME TO ' . $diff->getNewName()->getQuotedName($this);
+        $newName = $diff->getNewName();
+
+        if ($newName !== false) {
+            $queryParts[] = 'RENAME TO ' . $newName->getQuotedName($this);
         }
 
         foreach ($diff->addedColumns as $column) {
diff --git a/lib/Doctrine/DBAL/Platforms/MySqlPlatform.php b/lib/Doctrine/DBAL/Platforms/MySqlPlatform.php
index 289dca9e7d7..9679a8447e7 100644
--- a/lib/Doctrine/DBAL/Platforms/MySqlPlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/MySqlPlatform.php
@@ -553,8 +553,10 @@ public function getAlterTableSQL(TableDiff $diff)
     {
         $columnSql  = [];
         $queryParts = [];
-        if ($diff->newName !== false) {
-            $queryParts[] = 'RENAME TO ' . $diff->getNewName()->getQuotedName($this);
+        $newName    = $diff->getNewName();
+
+        if ($newName !== false) {
+            $queryParts[] = 'RENAME TO ' . $newName->getQuotedName($this);
         }
 
         foreach ($diff->addedColumns as $column) {
@@ -855,10 +857,14 @@ protected function getPostAlterTableIndexForeignKeySQL(TableDiff $diff)
      */
     protected function getPostAlterTableRenameIndexForeignKeySQL(TableDiff $diff)
     {
-        $sql       = [];
-        $tableName = $diff->newName !== false
-            ? $diff->getNewName()->getQuotedName($this)
-            : $diff->getName($this)->getQuotedName($this);
+        $sql     = [];
+        $newName = $diff->getNewName();
+
+        if ($newName !== false) {
+            $tableName = $newName->getQuotedName($this);
+        } else {
+            $tableName = $diff->getName($this)->getQuotedName($this);
+        }
 
         foreach ($this->getRemainingForeignKeyConstraintsRequiringRenamedIndexes($diff) as $foreignKey) {
             if (in_array($foreignKey, $diff->changedForeignKeys, true)) {
diff --git a/lib/Doctrine/DBAL/Platforms/OraclePlatform.php b/lib/Doctrine/DBAL/Platforms/OraclePlatform.php
index 537a566bada..711fbccbd53 100644
--- a/lib/Doctrine/DBAL/Platforms/OraclePlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/OraclePlatform.php
@@ -869,8 +869,14 @@ public function getAlterTableSQL(TableDiff $diff)
         if (! $this->onSchemaAlterTable($diff, $tableSql)) {
             $sql = array_merge($sql, $commentsSQL);
 
-            if ($diff->newName !== false) {
-                $sql[] = 'ALTER TABLE ' . $diff->getName($this)->getQuotedName($this) . ' RENAME TO ' . $diff->getNewName()->getQuotedName($this);
+            $newName = $diff->getNewName();
+
+            if ($newName !== false) {
+                $sql[] = sprintf(
+                    'ALTER TABLE %s RENAME TO %s',
+                    $diff->getName($this)->getQuotedName($this),
+                    $newName->getQuotedName($this)
+                );
             }
 
             $sql = array_merge(
diff --git a/lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php b/lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php
index 3c9984f95e6..806d59e6c97 100644
--- a/lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/PostgreSqlPlatform.php
@@ -614,8 +614,14 @@ public function getAlterTableSQL(TableDiff $diff)
         if (! $this->onSchemaAlterTable($diff, $tableSql)) {
             $sql = array_merge($sql, $commentsSQL);
 
-            if ($diff->newName !== false) {
-                $sql[] = 'ALTER TABLE ' . $diff->getName($this)->getQuotedName($this) . ' RENAME TO ' . $diff->getNewName()->getQuotedName($this);
+            $newName = $diff->getNewName();
+
+            if ($newName !== false) {
+                $sql[] = sprintf(
+                    'ALTER TABLE %s RENAME TO %s',
+                    $diff->getName($this)->getQuotedName($this),
+                    $newName->getQuotedName($this)
+                );
             }
 
             $sql = array_merge(
diff --git a/lib/Doctrine/DBAL/Platforms/SQLAnywherePlatform.php b/lib/Doctrine/DBAL/Platforms/SQLAnywherePlatform.php
index ec3ef933441..0f097de601b 100644
--- a/lib/Doctrine/DBAL/Platforms/SQLAnywherePlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/SQLAnywherePlatform.php
@@ -184,9 +184,11 @@ public function getAlterTableSQL(TableDiff $diff)
 
             $sql = array_merge($sql, $commentsSQL);
 
-            if ($diff->newName !== false) {
+            $newName = $diff->getNewName();
+
+            if ($newName !== false) {
                 $sql[] = $this->getAlterTableClause($diff->getName($this)) . ' ' .
-                    $this->getAlterTableRenameTableClause($diff->getNewName());
+                    $this->getAlterTableRenameTableClause($newName);
             }
 
             $sql = array_merge(
diff --git a/lib/Doctrine/DBAL/Platforms/SQLServerPlatform.php b/lib/Doctrine/DBAL/Platforms/SQLServerPlatform.php
index dc8775e61ab..5ce17aae36b 100644
--- a/lib/Doctrine/DBAL/Platforms/SQLServerPlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/SQLServerPlatform.php
@@ -315,12 +315,19 @@ protected function _getCreateTableSQL($tableName, array $columns, array $options
      */
     public function getCreatePrimaryKeySQL(Index $index, $table)
     {
-        $flags = '';
+        if ($table instanceof Table) {
+            $identifier = $table->getQuotedName($this);
+        } else {
+            $identifier = $table;
+        }
+
+        $sql = 'ALTER TABLE ' . $identifier . ' ADD PRIMARY KEY';
+
         if ($index->hasFlag('nonclustered')) {
-            $flags = ' NONCLUSTERED';
+            $sql .= ' NONCLUSTERED';
         }
 
-        return 'ALTER TABLE ' . $table . ' ADD PRIMARY KEY' . $flags . ' (' . $this->getIndexFieldDeclarationListSQL($index) . ')';
+        return $sql . ' (' . $this->getIndexFieldDeclarationListSQL($index) . ')';
     }
 
     /**
@@ -584,8 +591,10 @@ public function getAlterTableSQL(TableDiff $diff)
 
         $sql = array_merge($sql, $commentsSql);
 
-        if ($diff->newName !== false) {
-            $sql[] = "sp_RENAME '" . $diff->getName($this)->getQuotedName($this) . "', '" . $diff->getNewName()->getName() . "'";
+        $newName = $diff->getNewName();
+
+        if ($newName !== false) {
+            $sql[] = "sp_RENAME '" . $diff->getName($this)->getQuotedName($this) . "', '" . $newName->getName() . "'";
 
             /**
              * Rename table's default constraints names
@@ -598,10 +607,10 @@ public function getAlterTableSQL(TableDiff $diff)
             $sql[] = "DECLARE @sql NVARCHAR(MAX) = N''; " .
                 "SELECT @sql += N'EXEC sp_rename N''' + dc.name + ''', N''' " .
                 "+ REPLACE(dc.name, '" . $this->generateIdentifierName($diff->name) . "', " .
-                "'" . $this->generateIdentifierName($diff->newName) . "') + ''', ''OBJECT'';' " .
+                "'" . $this->generateIdentifierName($newName->getName()) . "') + ''', ''OBJECT'';' " .
                 'FROM sys.default_constraints dc ' .
                 'JOIN sys.tables tbl ON dc.parent_object_id = tbl.object_id ' .
-                "WHERE tbl.name = '" . $diff->getNewName()->getName() . "';" .
+                "WHERE tbl.name = '" . $newName->getName() . "';" .
                 'EXEC sp_executesql @sql';
         }
 
diff --git a/lib/Doctrine/DBAL/Platforms/SqlitePlatform.php b/lib/Doctrine/DBAL/Platforms/SqlitePlatform.php
index 6eff6b88d79..009a8f23df4 100644
--- a/lib/Doctrine/DBAL/Platforms/SqlitePlatform.php
+++ b/lib/Doctrine/DBAL/Platforms/SqlitePlatform.php
@@ -685,7 +685,12 @@ protected function getPostAlterTableIndexForeignKeySQL(TableDiff $diff)
         }
 
         $sql       = [];
-        $tableName = $diff->newName ? $diff->getNewName(): $diff->getName($this);
+        $tableName = $diff->getNewName();
+
+        if ($tableName === false) {
+            $tableName = $diff->getName($this);
+        }
+
         foreach ($this->getIndexesInAlteredTable($diff) as $index) {
             if ($index->isPrimary()) {
                 continue;
@@ -908,9 +913,14 @@ public function getAlterTableSQL(TableDiff $diff)
             $sql[] = sprintf('INSERT INTO %s (%s) SELECT %s FROM %s', $newTable->getQuotedName($this), implode(', ', $newColumnNames), implode(', ', $oldColumnNames), $dataTable->getQuotedName($this));
             $sql[] = $this->getDropTableSQL($dataTable);
 
-            if ($diff->newName && $diff->newName !== $diff->name) {
-                $renamedTable = $diff->getNewName();
-                $sql[]        = 'ALTER TABLE ' . $newTable->getQuotedName($this) . ' RENAME TO ' . $renamedTable->getQuotedName($this);
+            $newName = $diff->getNewName();
+
+            if ($newName !== false) {
+                $sql[] = sprintf(
+                    'ALTER TABLE %s RENAME TO %s',
+                    $newTable->getQuotedName($this),
+                    $newName->getQuotedName($this)
+                );
             }
 
             $sql = array_merge($sql, $this->getPostAlterTableIndexForeignKeySQL($diff));
@@ -1028,7 +1038,8 @@ private function getColumnNamesInAlteredTable(TableDiff $diff)
             $columns[strtolower($columnName)]    = $columnName;
         }
 
-        foreach ($diff->addedColumns as $columnName => $column) {
+        foreach ($diff->addedColumns as $column) {
+            $columnName                       = $column->getName();
             $columns[strtolower($columnName)] = $columnName;
         }
 
@@ -1127,6 +1138,10 @@ private function getForeignKeysInAlteredTable(TableDiff $diff)
         }
 
         foreach ($diff->removedForeignKeys as $constraint) {
+            if (! $constraint instanceof ForeignKeyConstraint) {
+                $constraint = new Identifier($constraint);
+            }
+
             $constraintName = strtolower($constraint->getName());
             if (! strlen($constraintName) || ! isset($foreignKeys[$constraintName])) {
                 continue;
diff --git a/lib/Doctrine/DBAL/SQLParserUtils.php b/lib/Doctrine/DBAL/SQLParserUtils.php
index 7dc63884a51..0ff0456a00e 100644
--- a/lib/Doctrine/DBAL/SQLParserUtils.php
+++ b/lib/Doctrine/DBAL/SQLParserUtils.php
@@ -24,8 +24,13 @@
  */
 class SQLParserUtils
 {
+    /**#@+
+     *
+     * @deprecated Will be removed as internal implementation details.
+     */
     public const POSITIONAL_TOKEN = '\?';
     public const NAMED_TOKEN      = '(?<!:):[a-zA-Z_][a-zA-Z0-9_]*';
+    /**#@-*/
 
     // Quote characters within string literals can be preceded by a backslash.
     public const ESCAPED_SINGLE_QUOTED_TEXT   = "(?:'(?:\\\\\\\\)+'|'(?:[^'\\\\]|\\\\'?|'')*')";
@@ -39,6 +44,8 @@ class SQLParserUtils
      * For a statement with positional parameters, returns a zero-indexed list of placeholder position.
      * For a statement with named parameters, returns a map of placeholder positions to their parameter names.
      *
+     * @deprecated Will be removed as internal implementation detail.
+     *
      * @param string $statement
      * @param bool   $isPositional
      *
@@ -46,27 +53,64 @@ class SQLParserUtils
      */
     public static function getPlaceholderPositions($statement, $isPositional = true)
     {
-        $match = $isPositional ? '?' : ':';
+        return $isPositional
+            ? self::getPositionalPlaceholderPositions($statement)
+            : self::getNamedPlaceholderPositions($statement);
+    }
+
+    /**
+     * Returns a zero-indexed list of placeholder position.
+     *
+     * @return int[]
+     */
+    private static function getPositionalPlaceholderPositions(string $statement) : array
+    {
+        return self::collectPlaceholders(
+            $statement,
+            '?',
+            self::POSITIONAL_TOKEN,
+            static function (string $_, int $placeholderPosition, int $fragmentPosition, array &$carry) : void {
+                $carry[] = $placeholderPosition + $fragmentPosition;
+            }
+        );
+    }
+
+    /**
+     * Returns a map of placeholder positions to their parameter names.
+     *
+     * @return string[]
+     */
+    private static function getNamedPlaceholderPositions(string $statement) : array
+    {
+        return self::collectPlaceholders(
+            $statement,
+            ':',
+            self::NAMED_TOKEN,
+            static function (string $placeholder, int $placeholderPosition, int $fragmentPosition, array &$carry) : void {
+                $carry[$placeholderPosition + $fragmentPosition] = substr($placeholder, 1);
+            }
+        );
+    }
+
+    /**
+     * @return mixed[]
+     */
+    private static function collectPlaceholders(string $statement, string $match, string $token, callable $collector) : array
+    {
         if (strpos($statement, $match) === false) {
             return [];
         }
 
-        $token    = $isPositional ? self::POSITIONAL_TOKEN : self::NAMED_TOKEN;
-        $paramMap = [];
+        $carry = [];
 
         foreach (self::getUnquotedStatementFragments($statement) as $fragment) {
             preg_match_all('/' . $token . '/', $fragment[0], $matches, PREG_OFFSET_CAPTURE);
             foreach ($matches[0] as $placeholder) {
-                if ($isPositional) {
-                    $paramMap[] = $placeholder[1] + $fragment[1];
-                } else {
-                    $pos            = $placeholder[1] + $fragment[1];
-                    $paramMap[$pos] = substr($placeholder[0], 1, strlen($placeholder[0]));
-                }
+                $collector($placeholder[0], $placeholder[1], $fragment[1], $carry);
             }
         }
 
-        return $paramMap;
+        return $carry;
     }
 
     /**
@@ -109,14 +153,14 @@ public static function expandListParameters($query, $params, $types)
             return [$query, $params, $types];
         }
 
-        $paramPos = self::getPlaceholderPositions($query, $isPositional);
-
         if ($isPositional) {
             $paramOffset = 0;
             $queryOffset = 0;
             $params      = array_values($params);
             $types       = array_values($types);
 
+            $paramPos = self::getPositionalPlaceholderPositions($query);
+
             foreach ($paramPos as $needle => $needlePos) {
                 if (! isset($arrayPositions[$needle])) {
                     continue;
@@ -156,6 +200,8 @@ public static function expandListParameters($query, $params, $types)
         $typesOrd    = [];
         $paramsOrd   = [];
 
+        $paramPos = self::getNamedPlaceholderPositions($query);
+
         foreach ($paramPos as $pos => $paramName) {
             $paramLen = strlen($paramName) + 1;
             $value    = static::extractParam($paramName, $params, true);
diff --git a/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php b/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php
index bf278e6e78a..d1db70c4c25 100644
--- a/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php
+++ b/lib/Doctrine/DBAL/Schema/AbstractSchemaManager.php
@@ -14,10 +14,12 @@
 use function array_intersect;
 use function array_map;
 use function array_values;
+use function assert;
 use function call_user_func_array;
 use function count;
 use function func_get_args;
 use function is_array;
+use function is_callable;
 use function preg_match;
 use function str_replace;
 use function strtolower;
@@ -80,8 +82,11 @@ public function tryMethod()
         unset($args[0]);
         $args = array_values($args);
 
+        $callback = [$this, $method];
+        assert(is_callable($callback));
+
         try {
-            return call_user_func_array([$this, $method], $args);
+            return call_user_func_array($callback, $args);
         } catch (Throwable $e) {
             return false;
         }
diff --git a/lib/Doctrine/DBAL/Schema/Comparator.php b/lib/Doctrine/DBAL/Schema/Comparator.php
index 1d8a7275d98..585732d7dff 100644
--- a/lib/Doctrine/DBAL/Schema/Comparator.php
+++ b/lib/Doctrine/DBAL/Schema/Comparator.php
@@ -10,6 +10,7 @@
 use function array_merge;
 use function array_shift;
 use function array_unique;
+use function assert;
 use function count;
 use function strtolower;
 
@@ -108,6 +109,8 @@ public function compare(Schema $fromSchema, Schema $toSchema)
                 }
 
                 foreach ($diff->changedTables[$localTableName]->removedForeignKeys as $key => $removedForeignKey) {
+                    assert($removedForeignKey instanceof ForeignKeyConstraint);
+
                     // We check if the key is from the removed table if not we skip.
                     if ($tableName !== strtolower($removedForeignKey->getForeignTableName())) {
                         continue;
diff --git a/lib/Doctrine/DBAL/Schema/ForeignKeyConstraint.php b/lib/Doctrine/DBAL/Schema/ForeignKeyConstraint.php
index 31850d7f23e..0a0977a4027 100644
--- a/lib/Doctrine/DBAL/Schema/ForeignKeyConstraint.php
+++ b/lib/Doctrine/DBAL/Schema/ForeignKeyConstraint.php
@@ -3,14 +3,13 @@
 namespace Doctrine\DBAL\Schema;
 
 use Doctrine\DBAL\Platforms\AbstractPlatform;
-use function array_combine;
 use function array_keys;
 use function array_map;
-use function end;
-use function explode;
 use function in_array;
+use function strrpos;
 use function strtolower;
 use function strtoupper;
+use function substr;
 
 /**
  * An abstraction class for a foreign key constraint.
@@ -66,12 +65,8 @@ class ForeignKeyConstraint extends AbstractAsset implements Constraint
     public function __construct(array $localColumnNames, $foreignTableName, array $foreignColumnNames, $name = null, array $options = [])
     {
         $this->_setName($name);
-        $identifierConstructorCallback = static function ($column) {
-            return new Identifier($column);
-        };
-        $this->_localColumnNames       = $localColumnNames
-            ? array_combine($localColumnNames, array_map($identifierConstructorCallback, $localColumnNames))
-            : [];
+
+        $this->_localColumnNames = $this->createIdentifierMap($localColumnNames);
 
         if ($foreignTableName instanceof Table) {
             $this->_foreignTableName = $foreignTableName;
@@ -79,12 +74,26 @@ public function __construct(array $localColumnNames, $foreignTableName, array $f
             $this->_foreignTableName = new Identifier($foreignTableName);
         }
 
-        $this->_foreignColumnNames = $foreignColumnNames
-            ? array_combine($foreignColumnNames, array_map($identifierConstructorCallback, $foreignColumnNames))
-            : [];
+        $this->_foreignColumnNames = $this->createIdentifierMap($foreignColumnNames);
         $this->_options            = $options;
     }
 
+    /**
+     * @param string[] $names
+     *
+     * @return Identifier[]
+     */
+    private function createIdentifierMap(array $names) : array
+    {
+        $identifiers = [];
+
+        foreach ($names as $name) {
+            $identifiers[$name] = new Identifier($name);
+        }
+
+        return $identifiers;
+    }
+
     /**
      * Returns the name of the referencing table
      * the foreign key constraint is associated with.
@@ -218,9 +227,14 @@ public function getForeignTableName()
      */
     public function getUnqualifiedForeignTableName()
     {
-        $parts = explode('.', $this->_foreignTableName->getName());
+        $name     = $this->_foreignTableName->getName();
+        $position = strrpos($name, '.');
+
+        if ($position !== false) {
+            $name = substr($name, $position);
+        }
 
-        return strtolower(end($parts));
+        return strtolower($name);
     }
 
     /**
diff --git a/lib/Doctrine/DBAL/Schema/MySqlSchemaManager.php b/lib/Doctrine/DBAL/Schema/MySqlSchemaManager.php
index 9f50517e1d4..f442f54d116 100644
--- a/lib/Doctrine/DBAL/Schema/MySqlSchemaManager.php
+++ b/lib/Doctrine/DBAL/Schema/MySqlSchemaManager.php
@@ -9,8 +9,10 @@
 use function array_change_key_case;
 use function array_shift;
 use function array_values;
+use function assert;
 use function end;
 use function explode;
+use function is_string;
 use function preg_match;
 use function preg_replace;
 use function str_replace;
@@ -101,6 +103,8 @@ protected function _getPortableTableColumnDefinition($tableColumn)
 
         $dbType = strtolower($tableColumn['type']);
         $dbType = strtok($dbType, '(), ');
+        assert(is_string($dbType));
+
         $length = $tableColumn['length'] ?? strtok('(), ');
 
         $fixed = null;
diff --git a/lib/Doctrine/DBAL/Schema/SQLAnywhereSchemaManager.php b/lib/Doctrine/DBAL/Schema/SQLAnywhereSchemaManager.php
index 62d5fa88e89..c169a6e0708 100644
--- a/lib/Doctrine/DBAL/Schema/SQLAnywhereSchemaManager.php
+++ b/lib/Doctrine/DBAL/Schema/SQLAnywhereSchemaManager.php
@@ -5,6 +5,7 @@
 use Doctrine\DBAL\Platforms\SQLAnywherePlatform;
 use Doctrine\DBAL\Types\Type;
 use function assert;
+use function is_string;
 use function preg_replace;
 
 /**
@@ -222,9 +223,9 @@ protected function _getPortableTableIndexesList($tableIndexRows, $tableName = nu
      */
     protected function _getPortableViewDefinition($view)
     {
-        return new View(
-            $view['table_name'],
-            preg_replace('/^.*\s+as\s+SELECT(.*)/i', 'SELECT$1', $view['view_def'])
-        );
+        $definition = preg_replace('/^.*\s+as\s+SELECT(.*)/i', 'SELECT$1', $view['view_def']);
+        assert(is_string($definition));
+
+        return new View($view['table_name'], $definition);
     }
 }
diff --git a/lib/Doctrine/DBAL/Schema/SQLServerSchemaManager.php b/lib/Doctrine/DBAL/Schema/SQLServerSchemaManager.php
index 763074e7d27..ce3e403ae77 100644
--- a/lib/Doctrine/DBAL/Schema/SQLServerSchemaManager.php
+++ b/lib/Doctrine/DBAL/Schema/SQLServerSchemaManager.php
@@ -6,9 +6,11 @@
 use Doctrine\DBAL\Driver\DriverException;
 use Doctrine\DBAL\Types\Type;
 use PDOException;
+use function assert;
 use function count;
 use function in_array;
-use function preg_replace;
+use function is_string;
+use function preg_match;
 use function sprintf;
 use function str_replace;
 use function strpos;
@@ -61,7 +63,9 @@ protected function _getPortableSequenceDefinition($sequence)
      */
     protected function _getPortableTableColumnDefinition($tableColumn)
     {
-        $dbType  = strtok($tableColumn['type'], '(), ');
+        $dbType = strtok($tableColumn['type'], '(), ');
+        assert(is_string($dbType));
+
         $fixed   = null;
         $length  = (int) $tableColumn['length'];
         $default = $tableColumn['default'];
@@ -71,15 +75,7 @@ protected function _getPortableTableColumnDefinition($tableColumn)
         }
 
         if ($default !== null) {
-            while ($default !== ($default2 = preg_replace('/^\((.*)\)$/', '$1', $default))) {
-                $default = trim($default2, "'");
-
-                if ($default !== 'getdate()') {
-                    continue;
-                }
-
-                $default = $this->_platform->getCurrentTimestampSQL();
-            }
+            $default = $this->parseDefaultExpression($default);
         }
 
         switch ($dbType) {
@@ -126,6 +122,19 @@ protected function _getPortableTableColumnDefinition($tableColumn)
         return $column;
     }
 
+    private function parseDefaultExpression(string $value) : string
+    {
+        while (preg_match('/^\((.*)\)$/', $value, $matches)) {
+            $value = trim($matches[1], "'");
+        }
+
+        if ($value === 'getdate()') {
+            return $this->_platform->getCurrentTimestampSQL();
+        }
+
+        return $value;
+    }
+
     /**
      * {@inheritdoc}
      */
diff --git a/lib/Doctrine/DBAL/Schema/Table.php b/lib/Doctrine/DBAL/Schema/Table.php
index 09ae27f0590..5659e578636 100644
--- a/lib/Doctrine/DBAL/Schema/Table.php
+++ b/lib/Doctrine/DBAL/Schema/Table.php
@@ -18,9 +18,6 @@
  */
 class Table extends AbstractAsset
 {
-    /** @var string */
-    protected $_name = null;
-
     /** @var Column[] */
     protected $_columns = [];
 
@@ -98,8 +95,8 @@ protected function _getMaxIdentifierLength()
     /**
      * Sets the Primary Key.
      *
-     * @param string[]    $columnNames
-     * @param string|bool $indexName
+     * @param string[]     $columnNames
+     * @param string|false $indexName
      *
      * @return self
      */
diff --git a/lib/Doctrine/DBAL/Tools/Console/Command/ImportCommand.php b/lib/Doctrine/DBAL/Tools/Console/Command/ImportCommand.php
index 0e815663786..22bce134061 100644
--- a/lib/Doctrine/DBAL/Tools/Console/Command/ImportCommand.php
+++ b/lib/Doctrine/DBAL/Tools/Console/Command/ImportCommand.php
@@ -13,6 +13,7 @@
 use Symfony\Component\Console\Output\OutputInterface;
 use const PHP_EOL;
 use function assert;
+use function error_get_last;
 use function file_exists;
 use function file_get_contents;
 use function is_readable;
@@ -79,7 +80,13 @@ protected function execute(InputInterface $input, OutputInterface $output)
             }
 
             $output->write(sprintf("Processing file '<info>%s</info>'... ", $filePath));
-            $sql = file_get_contents($filePath);
+            $sql = @file_get_contents($filePath);
+
+            if ($sql === false) {
+                throw new RuntimeException(
+                    sprintf("Unable to read SQL file '<info>%s</info>': %s", $filePath, error_get_last()['message'])
+                );
+            }
 
             if ($conn instanceof PDOConnection) {
                 // PDO Drivers
diff --git a/lib/Doctrine/DBAL/Tools/Console/Command/RunSqlCommand.php b/lib/Doctrine/DBAL/Tools/Console/Command/RunSqlCommand.php
index 8361219ad08..8aeb0ea2fba 100644
--- a/lib/Doctrine/DBAL/Tools/Console/Command/RunSqlCommand.php
+++ b/lib/Doctrine/DBAL/Tools/Console/Command/RunSqlCommand.php
@@ -10,7 +10,9 @@
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
+use function assert;
 use function is_numeric;
+use function is_string;
 use function stripos;
 
 /**
@@ -51,6 +53,8 @@ protected function execute(InputInterface $input, OutputInterface $output)
             throw new RuntimeException("Argument 'SQL' is required in order to execute this command correctly.");
         }
 
+        assert(is_string($sql));
+
         $depth = $input->getOption('depth');
 
         if (! is_numeric($depth)) {
diff --git a/lib/Doctrine/DBAL/Tools/Dumper.php b/lib/Doctrine/DBAL/Tools/Dumper.php
index d5086adee81..6174b7ad865 100644
--- a/lib/Doctrine/DBAL/Tools/Dumper.php
+++ b/lib/Doctrine/DBAL/Tools/Dumper.php
@@ -9,6 +9,7 @@
 use Doctrine\Common\Persistence\Proxy;
 use stdClass;
 use function array_keys;
+use function assert;
 use function class_exists;
 use function count;
 use function end;
@@ -20,9 +21,11 @@
 use function ini_set;
 use function is_array;
 use function is_object;
+use function is_string;
 use function ob_get_clean;
 use function ob_start;
 use function strip_tags;
+use function strlen;
 use function strrpos;
 use function substr;
 use function var_dump;
@@ -68,7 +71,9 @@ public static function dump($var, int $maxDepth = 2) : string
         var_dump($var);
 
         try {
-            return strip_tags(html_entity_decode(ob_get_clean()));
+            $output = ob_get_clean();
+            assert(is_string($output));
+            return strip_tags(html_entity_decode($output));
         } finally {
             ini_set('html_errors', $html);
         }
@@ -171,6 +176,6 @@ private static function getClass($object) : string
             return $class;
         }
 
-        return substr($class, $pos + Proxy::MARKER_LENGTH + 2);
+        return substr($class, $pos + strlen(Proxy::MARKER) + 2);
     }
 }
diff --git a/lib/Doctrine/DBAL/Types/BinaryType.php b/lib/Doctrine/DBAL/Types/BinaryType.php
index 14362e840ae..2894f8c864d 100644
--- a/lib/Doctrine/DBAL/Types/BinaryType.php
+++ b/lib/Doctrine/DBAL/Types/BinaryType.php
@@ -4,6 +4,7 @@
 
 use Doctrine\DBAL\ParameterType;
 use Doctrine\DBAL\Platforms\AbstractPlatform;
+use function assert;
 use function fopen;
 use function fseek;
 use function fwrite;
@@ -34,6 +35,7 @@ public function convertToPHPValue($value, AbstractPlatform $platform)
 
         if (is_string($value)) {
             $fp = fopen('php://temp', 'rb+');
+            assert(is_resource($fp));
             fwrite($fp, $value);
             fseek($fp, 0);
             $value = $fp;
diff --git a/lib/Doctrine/DBAL/Types/BlobType.php b/lib/Doctrine/DBAL/Types/BlobType.php
index c309f0f0637..c9c8d88ec1c 100644
--- a/lib/Doctrine/DBAL/Types/BlobType.php
+++ b/lib/Doctrine/DBAL/Types/BlobType.php
@@ -4,6 +4,7 @@
 
 use Doctrine\DBAL\ParameterType;
 use Doctrine\DBAL\Platforms\AbstractPlatform;
+use function assert;
 use function fopen;
 use function fseek;
 use function fwrite;
@@ -34,6 +35,7 @@ public function convertToPHPValue($value, AbstractPlatform $platform)
 
         if (is_string($value)) {
             $fp = fopen('php://temp', 'rb+');
+            assert(is_resource($fp));
             fwrite($fp, $value);
             fseek($fp, 0);
             $value = $fp;
diff --git a/lib/Doctrine/DBAL/Types/Type.php b/lib/Doctrine/DBAL/Types/Type.php
index ec1ab681356..025eb14cbda 100644
--- a/lib/Doctrine/DBAL/Types/Type.php
+++ b/lib/Doctrine/DBAL/Types/Type.php
@@ -5,9 +5,9 @@
 use Doctrine\DBAL\DBALException;
 use Doctrine\DBAL\ParameterType;
 use Doctrine\DBAL\Platforms\AbstractPlatform;
-use function end;
-use function explode;
 use function str_replace;
+use function strrpos;
+use function substr;
 
 /**
  * The base class for so-called Doctrine mapping types.
@@ -255,9 +255,14 @@ public static function getTypesMap()
      */
     public function __toString()
     {
-        $e = explode('\\', static::class);
+        $type     = static::class;
+        $position = strrpos($type, '\\');
 
-        return str_replace('Type', '', end($e));
+        if ($position !== false) {
+            $type = substr($type, $position);
+        }
+
+        return str_replace('Type', '', $type);
     }
 
     /**
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 4bedf0cd776..22f53630b64 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -1,5 +1,5 @@
 parameters:
-    level: 5
+    level: 6
     paths:
         - %currentWorkingDirectory%/lib
     autoload_files:
@@ -29,6 +29,10 @@ parameters:
         # https://github.com/JetBrains/phpstorm-stubs/pull/488
         - '~^Parameter #1 \$byteCount of function SQLSRV_SQLTYPE_VARBINARY expects int, string given\.\z~'
 
+        # https://github.com/phpstan/phpstan/issues/1847
+        - '~^Parameter #2 \$registeredAliases of static method Doctrine\\DBAL\\Query\\QueryException::unknownAlias\(\) expects array<string>, array<int, int|string> given\.\z~'
+        - '~^Parameter #2 \$registeredAliases of static method Doctrine\\DBAL\\Query\\QueryException::nonUniqueAlias\(\) expects array<string>, array<int, int|string> given\.\z~'
+
         # legacy variadic-like signature
         - '~^Method Doctrine\\DBAL\\Driver\\Connection::query\(\) invoked with \d+ parameters?, 0 required\.\z~'