Make internal use of driver consistent.

src/Database/Connection.php

@@ -294,7 +294,7 @@ class Connection implements ConnectionInterface
      */
     public function compileQuery(Query $query, ValueBinder $generator)
     {
-        return $this->getDriver()->compileQuery($query, $generator)[1];
+        return $this->_driver->compileQuery($query, $generator)[1];
     }
 
     /**
@@ -843,7 +843,7 @@ class Connection implements ConnectionInterface
      */
     protected function _newLogger(StatementInterface $statement)
     {
-        $log = new LoggingStatement($statement, $this->getDriver());
+        $log = new LoggingStatement($statement, $this->_driver);
         $log->logger($this->logger());
 
         return $log;

src/Database/Query.php

@@ -211,10 +211,10 @@ class Query implements ExpressionInterface, IteratorAggregate
     public function execute()
     {
         $statement = $this->_connection->run($this);
-        $driver = $this->_connection->driver();
         $typeMap = $this->getSelectTypeMap();
 
         if ($typeMap->toArray() && $this->_typeCastAttached === false) {
+            $driver = $this->_connection->getDriver();
             $this->decorateResults(new FieldTypeConverter($typeMap, $driver));
             $this->_typeCastAttached = true;
         }