Wrong pagination for a filtered product collection

Question

Hello

I used this event to exclude products with the same variation_group_id value from my product collection. it is showing the correct items, but the wrong way.

Any idea how to correct the following:

• show correct items count (256 is the wrong items count for this filtered collection)
• show correct pagination (it shows 1-9 pages for 256. 30 items/page) but we only have 22 in our case.

public function execute(
            \Magento\Framework\Event\Observer $observer
        ) {
            $collection  = $observer->getEvent()
                ->getCollection();
            $variations = [];
            foreach ($collection as $_product) {
                $variationGroupId = $_product->getVariationGroupId();
                if (!empty($variationGroupId)) {
                    if (in_array($variationGroupId, $variations)) {
                        $collection->removeItemByKey($_product->getId());
                    }
                    $variations[] =  $variationGroupId;
                }
            }
            return $collection;
        }

Answer 1

you should customize the collection in the same way that it was made - SQL. Because in this case, you're removing the item of the array only.

I suppose variation_group_id it's a product attribute And in this case the possible solution might be next:

All items will be grouped by some attribute that must be unique for all items in the collection

$collection  = $observer->getEvent()
                ->getCollection();
$collection->groupByAttribute('variation_group_id');

Note The attribute must be in the float table (listed in the catalog) If it doesn't you need to join this attribute using this

$collection->joinAttribute('variation_group_id', "catalog_product/variation_group_id", 'entity_id');

Example, \Magento\CatalogWidget\Model\Rule\Condition\Product::addToCollection()

Another important thing I think you should use a plugin instead event

as an example, you can consider this one \Magento\CatalogInventory\Model\AddStockStatusToCollection::beforeLoad();

I hope this information helps you.