MAGETWO-44449: Quote_id_mask table is a bottleneck under high load

Author: Stanislav Idolov

app/code/Magento/Quote/Setup/UpgradeSchema.php

@@ -0,0 +1,34 @@
+<?php
+/**
+ * Copyright © 2015 Magento. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+namespace Magento\Quote\Setup;
+
+use Magento\Framework\Setup\UpgradeSchemaInterface;
+use Magento\Framework\Setup\ModuleContextInterface;
+use Magento\Framework\Setup\SchemaSetupInterface;
+
+/**
+ * Upgrade the Catalog module DB scheme
+ */
+class UpgradeSchema implements UpgradeSchemaInterface
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function upgrade(SchemaSetupInterface $setup, ModuleContextInterface $context)
+    {
+        $setup->startSetup();
+
+        if (version_compare($context->getVersion(), '2.0.1', '<')) {
+            $setup->getConnection()->addIndex(
+                $setup->getTable('quote_id_mask'),
+                $setup->getIdxName('quote_id_mask', ['masked_id']),
+                ['masked_id']
+            );
+        }
+
+        $setup->endSetup();
+    }
+}

app/code/Magento/Quote/etc/module.xml

@@ -6,6 +6,6 @@
  */
 -->
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
-    <module name="Magento_Quote" setup_version="2.0.0">
+    <module name="Magento_Quote" setup_version="2.0.1">
     </module>
 </config>