Remove product relation foreign key

app/code/Magento/Catalog/Plugin/Model/Product/Relation/RemoveRelations.php

@@ -0,0 +1,86 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Catalog\Plugin\Model\Product\Relation;
+
+use Magento\Catalog\Api\Data\ProductInterface;
+use Magento\Catalog\Model\ResourceModel\Product as ProductResource;
+use Magento\Framework\App\ResourceConnection;
+use Magento\Framework\EntityManager\MetadataPool;
+use Psr\Log\LoggerInterface;
+
+/**
+ * Plugin for removing entries from catalog_product_relation after product is deleted
+ */
+class RemoveRelations
+{
+    /**
+     * @var MetadataPool
+     */
+    private $metadataPool;
+
+    /**
+     * @var ResourceConnection
+     */
+    private $resourceConnection;
+
+    /**
+     * @var LoggerInterface
+     */
+    private $logger;
+
+    /**
+     * @param MetadataPool $metadataPool
+     * @param ResourceConnection $resourceConnection
+     * @param LoggerInterface $logger
+     */
+    public function __construct(
+        MetadataPool $metadataPool,
+        ResourceConnection $resourceConnection,
+        LoggerInterface $logger
+    ) {
+        $this->metadataPool = $metadataPool;
+        $this->resourceConnection = $resourceConnection;
+        $this->logger = $logger;
+    }
+
+    /**
+     * Delete related product relations
+     *
+     * @param ProductResource $subject
+     * @param ProductResource $result
+     * @param ProductInterface $product
+     * @return ProductResource
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     * @throws \Exception
+     */
+    public function afterDelete(
+        ProductResource $subject,
+        ProductResource $result,
+        ProductInterface $product
+    ): ProductResource {
+        $linkField = $this->metadataPool->getMetadata(ProductInterface::class)->getLinkField();
+        $connection = $this->resourceConnection->getConnection();
+        try {
+            $connection->beginTransaction();
+            $relationTable = $this->resourceConnection->getTableName('catalog_product_relation');
+            $whereCondition = $connection->quoteInto('child_id = ?', $product->getId())
+                . " OR "
+                . $connection->quoteInto('parent_id = ?', $product->getData($linkField));
+            $connection->delete($relationTable, $whereCondition);
+            $connection->commit();
+        } catch (\Exception $e) {
+            $connection->rollBack();
+            $this->logger->error(\sprintf(
+                'Could not delete product relations for product %1$s. %2$s',
+                $product->getId(),
+                $e
+            ));
+        }
+        return $result;
+    }
+}

app/code/Magento/Catalog/etc/db_schema.xml

@@ -1069,12 +1069,6 @@
             <column name="parent_id"/>
             <column name="child_id"/>
         </constraint>
-        <constraint xsi:type="foreign" referenceId="CAT_PRD_RELATION_CHILD_ID_CAT_PRD_ENTT_ENTT_ID"
-                    table="catalog_product_relation" column="child_id" referenceTable="catalog_product_entity"
-                    referenceColumn="entity_id" onDelete="CASCADE"/>
-        <constraint xsi:type="foreign" referenceId="CAT_PRD_RELATION_PARENT_ID_CAT_PRD_ENTT_ENTT_ID"
-                    table="catalog_product_relation" column="parent_id" referenceTable="catalog_product_entity"
-                    referenceColumn="entity_id" onDelete="CASCADE"/>
         <index referenceId="CATALOG_PRODUCT_RELATION_CHILD_ID" indexType="btree">
             <column name="child_id"/>
         </index>

app/code/Magento/Catalog/etc/db_schema_whitelist.json

@@ -644,9 +644,7 @@
             "CATALOG_PRODUCT_RELATION_CHILD_ID": true
         },
         "constraint": {
-            "PRIMARY": true,
-            "CAT_PRD_RELATION_CHILD_ID_CAT_PRD_ENTT_ENTT_ID": true,
-            "CAT_PRD_RELATION_PARENT_ID_CAT_PRD_ENTT_ENTT_ID": true
+            "PRIMARY": true
         }
     },
     "catalog_product_index_eav": {

app/code/Magento/Catalog/etc/di.xml

@@ -253,6 +253,9 @@
             <argument name="storage" xsi:type="object">Magento\Catalog\Model\Session\Storage</argument>
         </arguments>
     </type>
+    <type name="Magento\Catalog\Model\ResourceModel\Product">
+        <plugin name="removeProductRelationAfterDelete" type="\Magento\Catalog\Plugin\Model\Product\Relation\RemoveRelations"/>
+    </type>
     <type name="Magento\Store\Model\ResourceModel\Website">
         <plugin name="invalidatePriceIndexerOnWebsite" type="Magento\Catalog\Model\Indexer\Product\Price\Plugin\Website"/>
         <plugin name="categoryProductWebsiteAfterDelete" type="\Magento\Catalog\Model\Indexer\Category\Product\Plugin\Website"/>