Magento 2.3.2: Sort by Bestselling Minimal results

Question

I am using custom code to implement sort by Best selling on the category page, I have created an around plugin for

<type name="Magento\Catalog\Block\Product\ProductList\Toolbar">
    <plugin name="Vnu_Catalog::addPriceDecendingFilterInToolbar" type="Vnu\Catalog\Plugin\Product\ProductList\Toolbar"/>
</type>

Toolbar.php

   /**
     * Plugin
     *
     * @param \Magento\Catalog\Block\Product\ProductList\Toolbar $subject
     * @param \Closure $proceed
     * @param \Magento\Framework\Data\Collection $collection
     * @return \Magento\Catalog\Block\Product\ProductList\Toolbar
     */
    public function aroundSetCollection(
        \Magento\Catalog\Block\Product\ProductList\Toolbar $subject,
        \Closure $proceed,
        $collection
    ) {
        $currentOrder = $subject->getCurrentOrder();
        $currentDirection = $subject->getCurrentDirection();
        $result = $proceed($collection);
        $subject->getCollection()->addAttributeToSelect('manufacturer');

        if ($currentOrder) {
            switch ($currentOrder) {
                case 'best_selling':
                    $subject->getCollection()->getSelect()->joinLeft(
                        'sales_order_item',
                        'e.entity_id = sales_order_item.product_id',
                        ['qty_ordered'=>'SUM(sales_order_item.qty_ordered)'])
                        ->group('e.entity_id')
                        ->order('qty_ordered desc');
                    //echo $subject->getCollection()->getSelect();die;


                    break;
                case 'price_desc':
                    $subject->getCollection()
                        ->setOrder('price', 'desc');
                    break;
                case 'price':
                    $subject->getCollection()
                        ->setOrder('price', 'asc');
                    break;
                case 'brand_asc':
                    $subject->getCollection()
                        ->addAttributeToFilter(
                            'manufacturer_value',
                            ['neq' => 'NULL']
                        )
                        ->setOrder('manufacturer_value', 'asc');
                    break;
                case 'brand_desc':
                    $subject->getCollection()
                        ->addAttributeToFilter(
                            'manufacturer_value',
                            ['neq' => 'NULL']
                        )
                        ->setOrder('manufacturer_value', 'desc');
                    break;
                case 'on_sale';
                    $subject->getCollection()
                        ->setOrder('special_price', 'desc');
                    break;

                default:
                    $subject->getCollection()->setOrder($currentOrder, $currentDirection);
                    break;

            }
        }
        //echo $subject->getCollection()->getSelect();die;
        return $result;
    }

When I print query I am able to see the correct results, but while rendering on category page, I am seeing some irrelevant results without pagination. Can anyone help on this issue?

Answer 1

I have found solution with below query,

$subject->getCollection()->getSelect()->joinLeft(
'sales_order_item',
'e.entity_id = sales_order_item.product_id',
array('qty_ordered'=>'(select sum(soi.qty_ordered) from sales_order_item soi where soi.product_id = e.entity_id)'))->distinct(true)
->order('qty_ordered '.$currentDirection);

Answer 2

You can get it by creating before plugin (following the below steps)

di.xml

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <type name="Magento\Catalog\Block\Product\ProductList\Toolbar">
        <plugin name="bestseller_before_set_collection"
                type="Vendor\Module\Plugin\Catalog\Product\Sorting\Bestsellers" />
    </type>
</config>

Bestsellers.php

<?php

namespace Vendor\Magento\Plugin\Catalog\Product\Sorting;

use Magento\Framework\Data\Collection;

class Bestsellers
{
    /**
     * Bestsellers sorting attribute
     */
    const BESTSELLERS_SORT_BY = 'bestsellers';

    /**
     * @param Toolbar $subject
     * @param Collection $collection
     */
    public function beforeSetCollection(Toolbar $subject, Collection $collection)
    {
        if ($subject->getCurrentOrder() == self::BESTSELLERS_SORT_BY) {
            $collection->getSelect()->joinLeft(['soi' => $collection->getTable('sales_order_item')],
                'e.entity_id = soi.product_id',
                array('qty_ordered' => 'SUM(soi.qty_ordered)'))
                ->group('e.entity_id')
                ->order('qty_ordered DESC');
        }
    }
}

Hope it helps!