MC-37630: Updating Design Configuration runs full reindex which generates DDL statement DROP Table

Author: thiaramus

app/code/Magento/Theme/Model/Indexer/Design/Config.php

@@ -5,6 +5,7 @@
  */
 namespace Magento\Theme\Model\Indexer\Design;
 
+use Magento\Framework\App\ObjectManager;
 use Magento\Framework\Indexer\ActionInterface;
 use Magento\Framework\Indexer\FieldsetPool;
 use Magento\Framework\Indexer\HandlerPool;
@@ -93,13 +94,30 @@ protected function execute(array $ids = [])
         /** @var \Magento\Theme\Model\ResourceModel\Design\Config\Scope\Collection $collection */
         $collection = $this->collectionFactory->create();
         $this->prepareFields();
-        if (!count($ids)) {
+
+        $tmp = $this->isFlatTableExists();
+
+        if (!$this->isFlatTableExists()) {
+            // instead of clean index check if table exists and create it if not
             $this->getSaveHandler()->cleanIndex([]);
         }
         $this->getSaveHandler()->deleteIndex([], new \ArrayObject($ids));
         $this->getSaveHandler()->saveIndex([], $collection);
     }
 
+    private function isFlatTableExists()
+    {
+        /** @var \Magento\Framework\App\ResourceConnection $resource */
+        $resource = ObjectManager::getInstance()->get(\Magento\Framework\App\ResourceConnection::class);
+
+        /** @var \Magento\Framework\DB\Adapter\AdapterInterface $connection */
+        $connection = ObjectManager::getInstance()->get(\Magento\Framework\App\ResourceConnection::class)->getConnection();
+
+        $tableName = $resource->getTableName('design_config_grid_flat');
+
+        return $connection->isTableExists($tableName);
+    }
+
     /**
      * Execute full indexation
      *

app/code/Magento/Theme/etc/indexer.xml

@@ -17,7 +17,7 @@
             <field name="store_group_id" xsi:type="filterable" dataType="int"/>
             <field name="store_id" xsi:type="filterable" dataType="int"/>
         </fieldset>
-        <saveHandler class="Magento\Theme\Model\Indexer\Design\IndexerHandler"/>
+        <saveHandler class="Magento\Framework\Indexer\SaveHandler\Grid"/>
         <structure class="Magento\Framework\Indexer\GridStructure"/>
     </indexer>
 </config>

lib/internal/Magento/Framework/Indexer/SaveHandler/Grid.php

@@ -69,10 +69,16 @@ protected function prepareFilterableFields(array $documents)
      */
     public function deleteIndex($dimensions, \Traversable $ids)
     {
-        foreach ($this->batch->getItems($ids, $this->batchSize) as $batchIds) {
-            $this->connection->delete(
-                $this->getTableName('filterable', $dimensions),
-                ['entity_id IN(?)' => $batchIds]
+        if (!empty(iterator_to_array($ids))) {
+            foreach ($this->batch->getItems($ids, $this->batchSize) as $batchIds) {
+                $this->connection->delete(
+                    $this->getTableName('filterable', $dimensions),
+                    ['entity_id IN(?)' => $batchIds]
+                );
+            }
+        } else {
+            $this->connection->truncateTable(
+                $this->getTableName('filterable', $dimensions)
             );
         }
     }