Magento 2 – How to Get Order ID from Order Item ID

You can use plugin to add custom attribute to sales_order_item when order is placed. create a di.xml on under etc/di.xml.

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd" >
    <type name='Magento\Quote\Model\Quote\Item\ToOrderItem'>
        <plugin name='AddOrderItemPlugin' type='Vendorname\Module\Plugin\Model\Quote\Item\ToOrderItem' sortOrder='99'/>
    </type>
</config>

Now add a file Vendorname\Module\Plugin\Model\Quote\Item\ToOrderItem.php

<?php 
namespace Vendorname\Modulename\Plugin\Model\Quote\Item;

    class ToOrderItem {

        /**
         *
         * @var type \Magento\Catalog\Model\Product
         */
        protected $productRepository;

        /**
         * @param \Magento\Catalog\Model\Product $productRepository 
         */
        public function __construct(
        \Magento\Catalog\Model\Product $productRepository 
        ) {
            $this->productRepository = $productRepository;
        }

        /**
         * 
         * @param \Magento\Quote\Model\Quote\Item\ToOrderItem $subject
         * @param \Vendorname\Modulename\Plugin\Model\Quote\Item\callable $proceed
         * @param \Magento\Quote\Model\Quote\Item\AbstractItem $item
         * @param type $additional
         * @return type
         */
        public function aroundConvert(
        \Magento\Quote\Model\Quote\Item\ToOrderItem $subject, callable $proceed, \Magento\Quote\Model\Quote\Item\AbstractItem $item, $additional = []
        ) {

            $orderItem = $proceed($item, $additional);
            $productId = $item->getProduct()->getId();
            $product = $this->productRepository->load($productId);
            $supplier = $product->getSuppliers();//my custom product attribute
            $orderItem->setSupplierId($supplier);//saving into orde item in `supplier_id` column
            return $orderItem;
        }

    }

In file vendor/magento/module-sales/Model/ResourceModel/Order/Plugin/Authorization.php below code is throwing the error.

public function aroundLoad(
    \Magento\Sales\Model\ResourceModel\Order $subject,
    \Closure $proceed,
    \Magento\Framework\Model\AbstractModel $order,
    $value,
    $field = null
) {
    $result = $proceed($order, $value, $field);
    if (!$this->isAllowed($order)) {
        throw NoSuchEntityException::singleField('orderId', $order->getId());
    }
    return $result;
}

$this->isAllowed method checks against USER_TYPE_CUSTOMER. As I am passing the different customer token which is need of my project, it's throwing the error.