MAGETWO-70667: Updated EAV Attribute code max lenght #10225

Author: Oleksii Korshenko

app/code/Magento/Eav/Model/Entity/Attribute.php

@@ -21,9 +21,12 @@ class Attribute extends \Magento\Eav\Model\Entity\Attribute\AbstractAttribute im
     \Magento\Framework\DataObject\IdentityInterface
 {
     /**
-     * Attribute code max length
+     * Attribute code max length.
+     *
+     * The value is defined as 60 because in the flat mode attribute code will be transformed into column name.
+     * MySQL allows only 64 symbols in column name.
      */
-    const ATTRIBUTE_CODE_MAX_LENGTH = 255;
+    const ATTRIBUTE_CODE_MAX_LENGTH = 60;
 
     /**
      * Cache tag