Update TableBuilder.php

Set 'row_id' as primary key because joins are made on it. Without this change product flat reindex can get practically stuck while making insert-from-select query in Magento\Catalog\Model\Indexer\Product\Flat\FlatTableBuilder::_fillTemporaryFlatTable.

Author: jarnooravainen

app/code/Magento/Catalog/Model/Indexer/Product/Flat/TableBuilder.php

@@ -101,11 +101,11 @@ public function build($storeId, $changedIds, $valueFieldSuffix)
             $temporaryTableName = $this->_getTemporaryTableName($tableName);
 
             //Add primary key to temporary table for increase speed of joins in future
-            $this->_addPrimaryKeyToTable($temporaryTableName);
+            $this->_addPrimaryKeyToTable($temporaryTableName, 'row_id');
 
             //Create temporary table for composite attributes
             if (isset($valueTables[$temporaryTableName . $valueFieldSuffix])) {
-                $this->_addPrimaryKeyToTable($temporaryTableName . $valueFieldSuffix);
+                $this->_addPrimaryKeyToTable($temporaryTableName . $valueFieldSuffix, 'row_id');
             }
 
             //Fill temporary tables with attributes grouped by it type