update getNextAutoincrement

update getNextAutoincrement to not use showTableStatus for performants reasons. See also OpenMage#1712

Author: jonashrem

app/code/core/Mage/ImportExport/Model/Resource/Helper/Mysql4.php

@@ -61,12 +61,21 @@ public function getMaxDataSize()
      */
     public function getNextAutoincrement($tableName)
     {
-        $adapter = $this->_getReadAdapter();
-        $entityStatus = $adapter->showTableStatus($tableName);
+        $connection = $this->getConnection();
+        $entityStatus = $connection->showTableStatus($tableName);
 
         if (empty($entityStatus['Auto_increment'])) {
-            Mage::throwException(Mage::helper('importexport')->__('Cannot get autoincrement value'));
+        $sql = sprintf(
+            'SELECT AUTO_INCREMENT FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = %s AND TABLE_SCHEMA = DATABASE()',
+            $this->quote($tableName)
+        );
+        $entityStatus = $connection->fetchRow($sql);
+        if (empty($entityStatus['AUTO_INCREMENT']))
+        {
+            throw new \Magento\Framework\Exception\LocalizedException(__('Cannot get autoincrement value'));
         }
-        return $entityStatus['Auto_increment'];
+
+        return $entityStatus['AUTO_INCREMENT'];
+
     }
 }