10195: Order relation child is not set during edit operation

Author: RomaKis

app/code/Magento/Sales/Model/AdminOrder/Create.php

@@ -1907,6 +1907,7 @@ public function createOrder()
             $oldOrder = $this->getSession()->getOrder();
             $oldOrder->setRelationChildId($order->getId());
             $oldOrder->setRelationChildRealId($order->getIncrementId());
+            $oldOrder->save();
             $this->orderManagement->cancel($oldOrder->getEntityId());
             $order->save();
         }

dev/tests/integration/testsuite/Magento/Sales/Model/AdminOrder/CreateTest.php

@@ -104,6 +104,10 @@ public function testInitFromOrderAndCreateOrderFromQuoteWithAdditionalOptions()
 
         $this->assertEquals(1, $newOrderItems->count());
 
+        $order->loadByIncrementId('100000001');
+        $this->assertEquals($newOrder->getRealOrderId(), $order->getRelationChildRealId());
+        $this->assertEquals($newOrder->getId(), $order->getRelationChildId());
+
         $newOrderItem = $newOrderItems->getFirstItem();
 
         $this->assertEquals(