Patch-Amasty_Shopby-category-es-performance2.patch

diff --git a/Model/Layer/Filter/Category.php b/Model/Layer/Filter/Category.php
index 855d80e..4d9bf20 100644
--- a/Model/Layer/Filter/Category.php
+++ b/Model/Layer/Filter/Category.php
@@ -610,6 +610,13 @@ class Category extends \Magento\Catalog\Model\Layer\Filter\AbstractFilter
         $requestBuilder->removePlaceholder(CategoryHelper::ATTRIBUTE_CODE);
         $requestBuilder->bind(CategoryHelper::ATTRIBUTE_CODE, $categoryId);
         $requestBuilder->setAggregationsOnly(CategoryHelper::ATTRIBUTE_CODE);
+
+        /** @var \Magento\Search\Model\EngineResolver $searchEngine */
+        $searchEngine = \Magento\Framework\App\ObjectManager::getInstance()->get(\Magento\Search\Model\EngineResolver::class);
+        if (\in_array($searchEngine->getCurrentSearchEngine(), ['elasticsearch', 'elasticsearch5', 'elasticsearch6'])) {
+            $requestBuilder->setSize(0); // fix for ES aggregation performance
+        }
+
         $queryRequest = $requestBuilder->create();
 
         return $queryRequest;