The issue is related to the new way of URL rewrites generator in Magento2. In Magento2, URL rewrites are generated (in url_rewrite table) when user save the category. If you have a complex category structure and assign a category as child of multiple parents or using categories across different store_views , it tries to generate the URL for all combinations and hence get out of memory.
Here are some links I'd recommend you to go through so you might found a solution for your problem.
https://github.com/magento/magento2/issues/9706
https://github.com/magento/magento2/issues/10242
This is not a solution but a workaround.
I had also face the same issue with after migrating a huge Magento1 site. Here is the hack down there that is not a solution but it can confirm the issue for you. Update the following core file for instance and then try to update the category name.
M2\vendor\magento\module-catalog-url-rewrite\Observer\CategoryProcessUrlRewriteSavingObserver.php
<?php /** * Copyright © 2013-2017 Magento, Inc. All rights reserved. * See COPYING.txt for license details. */ namespace Magento\CatalogUrlRewrite\Observer; use Magento\Catalog\Model\Category; use Magento\CatalogUrlRewrite\Model\CategoryUrlRewriteGenerator; use Magento\UrlRewrite\Model\UrlPersistInterface; use Magento\Framework\Event\ObserverInterface; class CategoryProcessUrlRewriteSavingObserver implements ObserverInterface { /** @var CategoryUrlRewriteGenerator */ protected $categoryUrlRewriteGenerator; /** @var UrlPersistInterface */ protected $urlPersist; /** @var UrlRewriteHandler */ protected $urlRewriteHandler; /** * @param CategoryUrlRewriteGenerator $categoryUrlRewriteGenerator * @param UrlPersistInterface $urlPersist * @param UrlRewriteHandler $urlRewriteHandler */ public function __construct( CategoryUrlRewriteGenerator $categoryUrlRewriteGenerator, UrlPersistInterface $urlPersist, UrlRewriteHandler $urlRewriteHandler ) { $this->categoryUrlRewriteGenerator = $categoryUrlRewriteGenerator; $this->urlPersist = $urlPersist; $this->urlRewriteHandler = $urlPersist; } /** * Generate urls for UrlRewrite and save it in storage * * @param \Magento\Framework\Event\Observer $observer * @return void */ public function execute(\Magento\Framework\Event\Observer $observer) { /** @var Category $category */ /* $category = $observer->getEvent()->getCategory(); if ($category->getParentId() == Category::TREE_ROOT_ID) { return; } if ($category->dataHasChangedFor('url_key') || $category->dataHasChangedFor('is_anchor') || $category->getIsChangedProductList() ) { $urlRewrites = array_merge( $this->categoryUrlRewriteGenerator->generate($category), $this->urlRewriteHandler->generateProductUrlRewrites($category) ); $this->urlPersist->replace($urlRewrites); } */ } }
