how to use the collection walk iterator in magento2

Question

I have 50k products in my website and want to update tier price. I have existing tier prices for products, but based on the existing product price, I need to update customer price.

I have created an external root file and created one function. Like in Magento 1 I did:

$products = Mage::getModel('catalog/product')
    ->getCollection()
    ->addAttributeToSelect('id')
    ->addAttributeToFilter('status', 1)
    ->addAttributeToFilter('visibility', 4)
    ->addAttributeToSort('created_at', 'desc'); 

Mage::getSingleton('core/resource_iterator')
    ->walk(
        $products->getSelect(), 
        array(array($this, '_Callback')),
        array()        
    );

I want to do the same thing in Magento 2m using a collection. I want to only call _Callback function with Magento 2 product collection so that it can work collection walk iteratively.

$productCollection = $objectManager
    ->create('Magento\Catalog\Model\ResourceModel\Product\Collection');

$productcollection = $productCollection
    ->addAttributeToSelect('name')
    ->addAttributeToSelect('price')
    ->addAttributeToSelect('entity_id')
    ->setOrder('entity_id','ASC')
    ->load();

Please give me solution.

Answer 1

This is just an example code, please inject correct repositories and models

<?php

use Magento\Framework\Model\ResourceModel\Iterator;
use Magento\Framework\Model\ResourceModel\IteratorFactory;
use Magento\Sales\Model\ResourceModel\Order\CollectionFactoryInterface;
use Zend_Db_Select;

class RunSomeLongTask
{
    public const ORDER_STATE_VALUE = 'example';

    /** @var CollectionFactoryInterface  */
    private $orderCollectionFactory;

    /** @var IteratorFactory */
    private $iteratorFactory;

    /** @var SomeTask */
    private $someTask;

    /**
     * constructor.
     * @param CollectionFactoryInterface $orderCollectionFactory
     * @param IteratorFactory $iteratorFactory
     * @param SomeTask $someTask
     */
    public function __construct(
        CollectionFactoryInterface $orderCollectionFactory,
        IteratorFactory $iteratorFactory,
        SomeTask $someTask
    ) {
        $this->orderCollectionFactory = $orderCollectionFactory;
        $this->iteratorFactory = $iteratorFactory;
        $this->someTask = $someTask; // "important: remember create this class"
    }

    public function process(): void
    {
        $orderCollection = $this->orderCollectionFactory->create();

        $orderCollection
            ->getSelect()
            ->reset(Zend_Db_Select::COLUMNS)
            ->columns(['entity_id', 'state', 'status'])
            ->where('state=?', self::ORDER_STATE_VALUE);

        /** @var Iterator $iterator */
        $iterator = $this->iteratorFactory->create();

        $iterator->walk($orderCollection->getSelect(), [[
            $this->someTask, // instance of class SomeTask
            'run' // the function in your class "SomeTask"
        ]]);
    }
}

class SomeTask
{
    public function run(array $args): void
    {
        // you will receive the row data here
        
        $orderId = $args['row']['entity_id'];

        // do your task here on individual row
    }
}