protected function checkCategoryIDField()
    {
        //Check "category_id" field
        if (!$this->isFieldChanged('category_id')) {
            return;
        }

        //Update product ID cache list for category
        ProductListStore::instance()->category->clear($this->obElement->category_id);
        ProductListStore::instance()->category->clear((int) $this->obElement->getOriginal('category_id'));

        BrandListStore::instance()->category->clear($this->obElement->category_id);
        BrandListStore::instance()->category->clear((int) $this->obElement->getOriginal('category_id'));

        $this->clearCategoryProductCount($this->obElement->category_id);
        $this->clearCategoryProductCount((int) $this->obElement->getOriginal('category_id'));
    }