MCP-85: Optimize order creation scenario [admin area]

Author: vzabaznov

app/code/Magento/Catalog/Ui/DataProvider/Product/ProductCollection.php

@@ -25,4 +25,58 @@ protected function _productLimitationJoinPrice()
         $this->_productLimitationFilters->setUsePriceIndex(false);
         return $this->_productLimitationPrice(true);
     }
+
+    /**
+     * Return approximately amount if too much entities.
+     *
+     * @return int|mixed
+     */
+    public function getSize()
+    {
+        $sql = $this->getSelectCountSql();
+        $possibleCount = $this->analyzeCount($sql);
+
+        if ($possibleCount > 20000) {
+            return $possibleCount;
+        }
+
+        return parent::getSize();
+    }
+
+    /**
+     * Analyze amount of entities in DB.
+     *
+     * @param $sql
+     * @return int|mixed
+     * @throws \Zend_Db_Statement_Exception
+     */
+    private function analyzeCount($sql)
+    {
+        $results = $this->getConnection()->query('EXPLAIN ' . $sql)->fetchAll();
+        $alias = $this->getMainTableAlias();
+
+        foreach ($results as $result) {
+            if ($result['table'] == $alias) {
+                return $result['rows'];
+            }
+        }
+
+        return 0;
+    }
+
+    /**
+     * Identify main table alias or its name if alias is not defined.
+     *
+     * @return string
+     * @throws \LogicException
+     */
+    private function getMainTableAlias()
+    {
+        foreach ($this->getSelect()->getPart(\Magento\Framework\DB\Select::FROM) as $tableAlias => $tableMetadata) {
+            if ($tableMetadata['joinType'] == 'from') {
+                return $tableAlias;
+            }
+        }
+        throw new \LogicException("Main table cannot be identified.");
+    }
 }

app/code/Magento/Sales/etc/adminhtml/di.xml

@@ -48,4 +48,9 @@
             </argument>
         </arguments>
     </type>
+    <type name="Magento\Sales\Block\Adminhtml\Order\Create\Search\Grid\DataProvider\ProductCollection">
+        <arguments>
+            <argument name="collectionFactory" xsi:type="object">\Magento\Catalog\Ui\DataProvider\Product\ProductCollectionFactory</argument>
+        </arguments>
+    </type>
 </config>